The trachea and esophagus are derived from the primitive foregut. Initially, they appear as a common ventral diverticulum at about the nineteenth day of gestation. Beginning several days later, elongation and separation of the diverticulum into the airway and esophagus occurs in a caudal to cephalad direction. Errors in this process result in esophageal atresia, tracheoesophageal fistula, and their variants (Figure 43–8).
A: Pure (long gap) esophageal atresia. B: Esophageal atresia with proximal tracheoesophageal fistula. C: Esophageal atresia with distal tracheoesophageal fistula. D: Esophageal atresia with proximal and distal fistulas. E: Tracheoesophageal fistula without esophageal atresia. (Reproduced, with permission, from Grosfeld JL: Pediatric surgery. In: Sabiston DC, ed. Textbook of Surgery. Philadelphia, PA: Saunders; 1991.)
A. With Esophageal Atresia
There is a blind proximal pouch and a fistula between the distal end of the esophagus and the distal one-third of the trachea (type C, 85% of cases).
There is a blind proximal esophageal pouch, no tracheoesophageal fistula, and a blind, short distal esophagus (type A, 10% of cases). This is referred to as “pure or long gap” atresia.
There are fistulas between both proximal and distal esophageal segments and the trachea (type D, 2% of cases).
There is a fistula between the proximal esophagus and the trachea and a blind distal esophagus without fistula (type B, 1% of cases).
B. Without Esophageal Atresia
There is an “H”-type tracheoesophageal fistula that is usually present in the low cervical region (type E, 4%-5% of cases).
There is esophageal stenosis consisting of a membranous occlusion (often containing cartilage) between the mid and distal third of the esophagus (rare).
There is a laryngotracheoesophageal cleft of varying length, consisting of a linear communication between these structures (very rare).
Shortly after birth, the infant with esophageal atresia is noted to have excessive salivation and repeated episodes of coughing, choking, and cyanosis. Attempts at feeding result in choking, gagging, and regurgitation. Infants with tracheoesophageal fistula in addition to esophageal atresia will have reflux of gastric secretions into the tracheobronchial tree, with resulting pneumonia. Pulmonary infiltrates are usually noted first in the right upper lobe. Diagnosis may be delayed (several months) in cases of H-type tracheoesophageal fistula who are able to feed but may present with recurrent upper respiratory infections due to aspiration.
A size 10F catheter should be passed into the esophagus by way of the nose or mouth; if esophageal atresia is present, the tube will not go down the expected distance to the stomach and will coil in the upper esophageal pouch. If a tracheoesophageal fistula connects to the lower esophageal segment, air will be present in the stomach and bowel on plain radiographs. Absence of air below the diaphragm usually means that a distal tracheoesophageal fistula is not present.
Abdominal distention is a prominent finding because the Valsalva effect of coughing and crying forces air through a fistula into the stomach and bowel. The presence and position of the fistula can be determined by bronchoscopy.
Laryngotracheoesophageal cleft produces symptoms similar to those of tracheoesophageal fistula but of much greater severity. Laryngoscopy may show the cleft between the arytenoids extending down the larynx. Bronchoscopy is the best means of outlining the cleft.
There is a 50% incidence of associated anomalies: cardiac (patent ductus arteriosus, septal defects), GI (imperforate anus, duodenal atresia), genitourinary, and skeletal. The VACTERL association (vertebral, anorectal, cardiac, tracheoesophageal, renal, and limb anomalies) is present in 25% of cases. Isolated esophageal atresia has been associated with various genetic abnormalities, including trisomy 18 and trisomy 21. Echocardiogram, renal ultrasound, anorectal exam and genetic testing should be considered in the workup of all patients with TEF.
A sump suction catheter should be placed in the upper esophageal pouch and the head of the bed elevated. An echocardiogram is required to determine the position of the aortic arch since a right-sided arch makes the standard right thoracotomy (or thoracoscopic) repair difficult and is present in 5% of infants. If possible, aspiration pneumonia is treated before repair.
The goal of operative therapy is to divide and ligate the fistula and repair the atresia in one stage, if possible. This is usually performed using a right posterolateral thoracotomy with an extrapleural dissection, although a transpleural thoracoscopic approach is gaining popularity for those stable, full-term infants. Also, thoracoscopic approaches are gaining acceptance as minimal invasive techniques continue to evolve. In those with an H-type tracheoesophageal fistula, the fistula is located above the thoracic inlet in two-thirds of cases. These fistulas may be divided through a left transverse cervical incision. A feeding gastrostomy tube is no longer routinely inserted except when the esophageal repair is under extreme tension, when there is long gap atresia not amenable to single-stage repair, and when there are severe associated anomalies (eg, congenital heart disease). A transanastomotic feeding tube is placed for postoperative feeding pending demonstration of a leak-free anastomosis by esophagogram obtained 7 days after surgery.
Staged operations are reserved for extremely premature babies, those who have severe aspiration pneumonitis, and those with severe anomalies or long gaps between the esophageal pouches. There are several strategies for repairing these defects. These include cervical esophagostomy, division of the fistula, and insertion of a gastrostomy tube. Several months later a staged reconstruction by esophageal replacement with colon or stomach interposition can be undertaken. Another alternative is a gastrostomy tube alone with intermittent bougienage and stretching of the upper esophageal pouch, followed by primary esophageal anastomosis and immediate interposition grafting.
Esophageal narrowing or webs in the distal esophageal segment readily respond to esophageal dilation. This is usually accomplished with Hurst or Maloney bougies. Dilations are repeated until healing occurs without recurrence of the web. Esophagoscopy and excision of portions of a tough or thick web, using biopsy forceps or the endoscopic laser, may be required in addition to dilation. A lower esophageal stricture containing cartilage requires excision and anastomosis.
The survival rate for a full-term infant without associated anomalies is excellent. However, deaths occur as a result of pulmonary complications, severe associated anomalies, prematurity, and sepsis due to anastomotic disruption. Anastomotic leaks occur because of tension or poor blood supply. In performing the anastomosis, the extrapleural approach prevents the development of empyema and confines a leak and possible infection to a small localized area.
Swallowing is a reflex response that must be reinforced early in infancy. If establishment of esophageal continuity is delayed for more than 4-6 weeks, it may take many months to overcome oral aversion and learn to swallow. Babies with cervical esophagostomies should be encouraged to suck, eat, and swallow during gastrostomy feedings.
Dysphagia may occur for months or years following successful repair of esophageal atresia and is multifactorial. An anastomotic stricture is not uncommon and may require one or more dilations under anesthesia. Swallowed foreign bodies will lodge at the site of anastomosis and require removal with esophagoscopy. Another cause of dysphagia is poor peristalsis of the distal esophageal segment. This frequent problem improves with age.
Most of these infants have an alarming, barking cough and rattling sound on respiration from tracheomalacia. This results from in utero compression of the trachea by the dilated proximal esophageal pouch. This frequently improves with age and is rare after 5 years of age. GER is common after successful repair and may result in recurrent aspiration pneumonitia, dysphagia, failure to thrive, and recurrent anastomotic stricture. Medical therapy with an H2-blocker or proton pump inhibitor should be instituted in all patients after repair and a surgical antireflux procedure may be necessary if medical therapy fails.
L Surgical outcomes of esophageal atresia without fistula for 24 years at a single institution. J Pediatr Surg 2009 Oct;44(10):1928–1932.
INTESTINAL OBSTRUCTION IN THE NEWBORN
Since fetuses continually swallow amniotic fluid into their GI tracts and excrete it in their urine, intestinal obstruction may be noted on prenatal ultrasound by the presence of polyhydramnios (increased amniotic fluid level). The presence of polyhydramnios correlates with the level of the obstruction; it is most common with proximal GI tract obstruction (eg, esophageal and duodenal atresia), is rarely noted with ileal atresia, and is never noted in association with anorectal obstruction.
After birth, vomiting is the principal symptom, and it is bile stained if the obstruction is distal to the ampulla of Vater. It is important to note that bilious vomiting in the newborn is pathologic until proved otherwise. On physical examination, the presence and degree of abdominal distention depends on the level of the obstruction and should be noted. For example, there is no significant distention with duodenal obstruction versus massive distention with colonic obstruction (eg, Hirschsprung disease). A careful perineal examination should be performed to determine whether the anus is present, patent, and in the normal location. Meconium, the first newborn stool, passes in the first 24 hours of life in 94% of normal full-term infants and by 48 hours in 98%. Failure to pass meconium may be indicative of lower GI tract obstruction. However, 30%-50% of newborn infants with intestinal obstruction will pass meconium.
Depending on the pathology, the plain abdominal radiograph may demonstrate dilated bowel loops, air-fluid levels, calcifications (if in utero perforation occurred), or a gasless abdomen. Unlike in adult patients, one cannot differentiate small from large bowel by their usual markings on a plain radiograph of the newborn’s abdomen. If a lower GI tract obstruction is suspected, a contrast (usually water-soluble contrast) enema is the most useful study since it can be both diagnostic and therapeutic in the majority of cases (see below). An upper GI series is rarely indicated unless malrotation is to be ruled out. The CT, MRI, or ultrasound scans are virtually never indicated in the workup of newborn intestinal obstruction.
HYPERTROPHIC PYLORIC STENOSIS
Pyloric stenosis is the most common surgical disorder producing emesis in infancy. It results from hypertrophy of the circular and longitudinal muscularis of the pylorus and the distal antrum of the stomach with progressive narrowing of the pyloric canal (Figure 43–9). The cause is not known. The male:female incidence is 4:1. The disorder is more common in firstborn infants and occurs four times more often in the offspring of mothers who had the disease as infants than in those whose fathers had the disease. If one monozygotic twin is affected, the other will also have the disorder in two-thirds of cases. A seasonal variation is noted in the occurrence of symptoms, with peaks in spring and fall.
Hypertrophic pyloric stenosis. Note that the distal end of the hypertrophic muscle protrudes into the duodenum (arrow), accounting for the ease of perforation into the duodenum during pyloromyotomy.
Typically, the affected infant is full term when born and feeds and grows well until 2-4 weeks after birth, at which time occasional regurgitation of some of the feedings occurs. Several days later, however, the vomiting becomes more frequent and forceful. The vomitus contains the previous feeding and no bile. Blood may be seen in the vomitus in 5% of cases, and coffee grounds or occult blood is frequently present. Shortly after vomiting, the infant acts starved and will feed again. The stools become infrequent and firm in consistency as dehydration occurs. With dehydration, infants often have sunken fontanelles, dry mucous membranes, and poor skin turgor. Weight loss follows progressive feeding intolerance. Jaundice with indirect hyperbilirubinemia occurs in fewer than 10% of cases. Gastric peristaltic waves can usually be seen moving from the left costal margin to the area of the pylorus. In over 90% of cases, the pyloric “tumor,” or “olive,” can be palpated when the infant is relaxed. Abdominal relaxation may be accomplished by sedating the infant or by feeding clear fluids and simultaneously aspirating the stomach contents with a gastric tube.
An imaging study is indicated when the pyloric tumor cannot be palpated. Abdominal ultrasound, the most sensitive and specific test, will identify hypertrophic pyloric stenosis when the muscle thickness is greater than 4 mm and the length of the pylorus is greater than 16 mm. A dynamic ultrasound may also show no passage of ingested fluid. A contrast upper GI series is indicated if an experienced ultrasonographer is unavailable or if there is a reasonable chance that the patient’s symptoms are not due to pyloric stenosis (eg, a premature, 1-week-old baby) since this examination can demonstrate other entities in the differential. A positive upper GI series can include the following diagnostic signs: (1) outlining of the narrow pyloric channel by a single “string sign” or “double track” owing to folds of mucosa; (2) a pyloric “beak” where the pyloric entrance from the antrum occurs; (3) the “shoulder” sign, in which the pyloric mass bulges into the antrum; and (4) complete obstruction of the pylorus.
Repeated nonbilious vomiting in early infancy may be due to overfeeding, intracranial lesions, pylorospasm, antral web, GER, pyloric duplication, duodenal stenosis, malrotation of the bowel, or adrenal insufficiency.
Repeated vomiting with inadequate intake of formula results in hypokalemic hypochloremic alkalosis, dehydration, and starvation. Gastritis and reflux esophagitis occur frequently. Aspiration of vomitus may produce pneumonia.
The operative treatment is the Fredet-Ramstedt pyloromyotomy, in which the pylorus is incised along its entire length, spread widely exposing but not breaching the underlying mucosa. Surgery should be undertaken only after dehydration and the hypokalemic hypochloremic alkalosis have been corrected, heralded by a normal serum chloride (which is a proxy for a normal serum bicarbonate) as well as a urine output greater than 1 cc/kg/h. There are three approaches to the pyloromyotomy: a right upper quadrant transverse skin incision, a circumumbilical or intraumbilical skin incision, or a laparoscopic approach with the telescope in the umbilicus and the two working instruments placed directly through the abdominal wall. The laparoscopic approach offers advantages in postoperative recovery with equivalent outcomes in experienced hands. Successful myotomy is evident when the submucosa is seen to herniate out of the myotomy site. If, during the pyloromyotomy, the mucosa is inadvertently entered (usually on the duodenal side), it is closed with fine nonabsorbable sutures and an omental patch is placed. Large perforations are managed by closing the pyloromyotomy, rotating the pylorus 90 degrees, and repeating the myotomy.
Multiple postoperative feeding schedules have been described, ranging from immediate full feeds to delayed feeds with incremental advances in volume. This has stemmed from the observation that nearly all patients with pyloric stenosis vomit after surgery, presumably due to gastric ileus, gastritis, GER, or all of the above. An incomplete pyloromyotomy (usually on the antral side) is suspected when vomiting persists beyond 1-2 weeks postoperatively and stems from a short myotomy or incomplete division of the muscle. Incomplete myotomy should be evaluated by upper GI series as ultrasound will likely show ongoing hypertrophy.
Pyloric stenosis never recurs, and there is a uniformly excellent outcome.
et al.: Recovery after open versus laparoscopic pyloromyotomy for pyloric stenosis: a double-blind multicentre randomised controlled trial. Lancet 2009 Jan 31 ;373(9661):390–398.
K: Pyloric stenosis in pediatric surgery: an evidence-based review. Surg Clin North Am 2012 Jun;92(3):527–539.
CONGENITAL DUODENAL OBSTRUCTION
The various causes of duodenal obstruction are atresia, stenosis, mucosal web (complete or variably perforate), annular pancreas, preduodenal portal vein, and peritoneal bands (Ladd bands) from malrotation. Duodenal atresia is distinguished from more distal GI atresias since it is due to failure of recanalization of the duodenum early in gestation rather than due to mesenteric vascular abnormality late in gestation. Atresia of the duodenum is twice as common as in the jejunum or ileum. In about half of cases, multiple congenital anomalies are present, including Down syndrome in 30% and congenital heart disease in 20%. Birth weight is less than 2500 g in half of these infants. Mucosal webs or stenoses occur as often as pure atresia. Annular pancreas is almost always associated with hypoplasia of the duodenum at the level of the ampulla. The cause is a developmental defect characterized by circumferential persistence of the gland around the duodenum at the site of the embryonic ventral anlage, leading to duodenal obstruction and an accessory pancreatic duct.
In 75% of cases, duodenal obstruction occurs distal to the ampulla of Vater, causing bile to be diverted to the proximal duodenum and stomach. Bilious emesis occurs shortly after birth and during attempted feedings. The upper abdomen is rarely distended. Meconium is passed in over 50% of cases.
The plain abdominal radiograph demonstrates an air-distended stomach and duodenum (“double bubble” sign). Gas in the small and large intestine indicates incomplete obstruction. Contrast upper GI series is used to identify the presence or absence of malrotation in those cases with incomplete obstruction since obstruction from intestinal malrotation is a surgical emergency.
Surgery is performed using a right upper transverse abdominal incision or via laparoscopy. A Kocher maneuver should be performed, with complete mobilization of the third and fourth portions of the duodenum. Obstruction from Ladd bands requires simple division of the bands and correction of the malrotation (see below). Duodenoduodenostomy is performed for duodenal atresia and annular pancreas. A mucosal web can be excised if technically feasible, taking care to avoid injury to the adjacent ampulla. Commonly, the duodenum is hugely dilated above the obstruction, which results in impaired aboral progression of ingested feedings. This problem is resolved by excision or plication of a portion of the antimesenteric wall of the bowel to normalize the lumen diameter (tapered duodenoplasty). Gastrojejunostomy should not be done because the blind duodenal pouch may cause repeated vomiting. The distal bowel should be irrigated and assessed for associated intrinsic obstruction if possible. However, the rate of associated distal atresia is low (0.5%-3% incidence) and most commonly seen in conjunction with an “apple peel” deformity). Mortality is related to prematurity and associated anomalies.
S: Laparoscopic duodenoduodenostomy in the neonate. J Pediatr Surg 2009 May;44(5):906–908.
DJ: Should we be concerned about jejunoileal atresia during repair of duodenal atresia? J Laparoendosc Adv Surg Tech A 2010 Nov;20(9):773–775.
ATRESIA & STENOSIS OF THE JEJUNUM, ILEUM, & COLON
Atresia and stenosis of the jejunum, ileum, and colon are caused by a mesenteric vascular accident in utero, which may result from hernia, volvulus, or intussusception, producing aseptic necrosis and resorption of the necrotic bowel. Although atresia may occur in any portion of the intestine, most cases occur in the distal ileum or proximal jejunum. Colonic atresia is very rare, accounting for no more than 1% of all intestinal atresias. A short area of necrosis may produce only stenosis or a membranous web occluding the lumen (type I) (Figure 43–10). A more extensive infarct may leave a fibrous cord between the two bowel loops (type II), or the proximal and distal bowel may be completely separated with a V-shaped defect in the mesentery (type IIIa). Multiple atresias occur in 10% of cases (type IV). A type III variant (type IIIb) is commonly called apple-peel or Christmas tree atresia, in which there is a blind-ending proximal jejunum, absence of a long length of mid small bowel, and a terminal ileum coiled around its tenuous blood supply from an ileocolic vessel.
The anatomic spectrum of intestinal atresia. Type I is a stenosis or mucosal web. Type II, a fibrous cord between two bowel ends. Type IIIa, blind-ending proximal and distal bowel loops with a V-shaped mesenteric defect. Type IIIb (apple peel deformity, Christmas tree deformity) consists of a blind ending proximal jejunum, absence of a large portion of the midgut, and a terminal ileum that is coiled around its ileocolic blood supply. Type IV, multiple atresias of any kind. (Reproduced, with permission, from Grosfeld JL et al: Operative management of intestinal atresia based on pathologic findings. J Pediatr Surg. 1979 June;14(3):368–375.)
Vomiting of bile, abdominal distention, and failure to pass meconium indicate intestinal obstruction. The plain abdominal radiograph will give an estimate of how far along the intestine the obstruction exists. A contrast enema may be indicated to detect the level of obstruction. In obstructions that occur in the distal bowel and appear relatively early in gestation, the colon is empty of meconium and appears abnormally narrow (microcolon). When the obstruction is proximal or when it occurs late in pregnancy, meconium is passed into the colon. The contrast enema will then outline a more generous-sized colon with its contents (meconium). In older children with evidence of partial intestinal obstruction, a small bowel series may be indicated to identify intestinal stenosis.
There are three main goals of operation: (1) to restore the continuity of the bowel; (2) to preserve as much intestinal length as possible; and (3) to retain the ileocecal valve if possible (the minimum length of bowel needed to sustain full enteral nutrition doubles in the absence of the ileocecal valve). A transverse upper abdominal incision is preferred. Infants with jejunal or ileal atresia usually have a segment of the proximal bowel adjacent to the atresia that is dilated out of proportion to the rest of the proximal bowel. This is referred to as the “club” and it lacks normal peristaltic activity. If left in or not tapered, it may become a source of persistent functional obstruction. It is tapered when it is a very proximal bowel segment, near the ligament of Treitz; otherwise it should be resected. A great discrepancy between the diameter of the segments of intestine proximal and distal to the atresia is the rule. Atresia of the proximal colon should be treated by resection of the dilated bowel and ileocolostomy. Atresia of the distal colon may be treated by proximal end colostomy or by a side-to-side colostomy. Later, the continuity of the distal colon may be established by end-to-end anastomosis.
Infants born with extensive small bowel loss may benefit from a Bianchi procedure, where the entire greatly dilated bowel is divided longitudinally into two lengths of bowel. An alternative bowel lengthening procedure termed the STEP (serial transverse enteroplasty procedure) is quickly gaining acceptance as the procedure of choice for gaining length from dilated and shortened intestine. The end of the jejunum in continuity with the duodenum is anastomosed to the proximal end of the divided bowel.
In contrast to duodenal atresia, associated anomalies are unusual in small bowel and colon atresia. Following repair, return of GI function can be prolonged and feeds should be introduced accordingly.
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A: Comparison of intestinal lengthening procedures for patients with short bowel syndrome. Ann Surg 2007 Oct;246(4):593–601.
DISORDERS OF INTESTINAL ROTATION
The fetal intestine begins as a somewhat straight tube that grows faster than the abdominal cavity and thus herniates out into the body stalk (future umbilicus) at about 4-6 weeks’ gestation. At 10-12 weeks, the bowel returns to the abdominal cavity, rotates, and becomes fixed to the retroperitoneum along a long diagonal axis extending from the level of the left of the T12 vertebra to the level of the right of the L5 vertebra. The duodenojejunal portion of gut rotates posterior (counterclockwise) to the superior mesenteric vessels for 270 degrees and becomes fixed at the ligament of Treitz and located to the left of and cephalad to the superior mesenteric artery. The cecocolic portion of the midgut also rotates 270 degrees, but clockwise (anterior) to the superior mesenteric artery. The cecum becomes fixed in the right lower abdomen (L5 level).
Anomalies of rotation and fixation are twice as common in males as in females. They may be classified as (1) nonrotation, (2) incomplete rotation, (3) reversed rotation, and (4) anomalous fixation of the mesentery.
With nonrotation, the midgut is suspended from the superior mesenteric vessels; the small bowel is located predominantly on the right side of the abdomen and the large bowel in the left abdomen. No fixation occurs, and adhesive bands are not present. This is the fetal anatomy prior to 10 weeks’ gestation. Because its base is so short, the mesentery is narrow, which predisposes to volvulus, with clockwise twisting of the bowel about the superior mesenteric vessels. This anomaly is usually found in patients with omphalocele, gastroschisis, and CDH.
Incomplete rotation (commonly called malrotation) may affect the duodenojejunal segment, the cecocolic segment, or both. Adhesive bands (Ladd bands) are usually present. In the most common form, the cecum stops rotating and fixes near the origin of the superior mesenteric vessels, and dense peritoneal bands extend from the right flank to the cecum and obstruct the second or third portion of the duodenum or other segments of the small bowel. The duodenojejunal segment also only partially rotates, usually stopping at or to the right of the vertebral bodies. The intestinal mesentery is fixed posteriorly, but is very narrow, only extending the distance between the cecum and the duodenojejunal segment. This predisposes to volvulus (Figure 43–11).
Malrotation of the midgut with volvulus. Note cecum at the origin of the superior mesenteric vessels. Fibrous bands cross and obstruct the duodenum as they adhere to the cecum. Volvulus is untwisted in a counterclockwise direction.
In reversed rotation, the bowel rotates varying degrees in a clockwise direction about the superior mesenteric axis. The duodenojejunal loop is anterior to the superior mesenteric artery. The cecocolic loop may be prearterial or may be rotated clockwise or counterclockwise in a retroarterial position. In either case, the cecum may be right sided or left sided. The most frequent anomaly is retroarterial clockwise rotation, which causes obstruction of the right colon.
D. Anomalous Fixation of Mesentery
Anomalies of mesenteric fixation account for internal mesenteric and paraduodenal hernias, a mobile cecum, or obstructing adhesive bands in the absence of anomalous bowel rotation. Excessive rotation of the duodenojejunal junction may result in superior mesenteric artery compression of the third portion of the duodenum.
Anomalies of intestinal rotation may cause symptoms related to intestinal obstruction, peptic ulceration, or malabsorption. The majority of patients who develop intestinal obstruction are infants. Older patients may develop intermittent obstruction. The obstruction is in the duodenum or upper jejunum as a result of adhesive bands or midgut volvulus, respectively. Vomiting of bile occurs initially. Older patients may be thin and underweight because of chronic postprandial discomfort or malabsorption. Malabsorption with steatorrhea may result from partial venous and lymphatic obstruction, which is associated with coarse rugal folds in the small bowel. With duodenal obstruction from bands, abdominal distention is not prominent. Midgut volvulus, however, produces marked abdominal distention. Bloody stools and signs of peritonitis are manifestations of intestinal infarction. Peptic ulcer occurs in 20% of patients, presumably as a result of antral and duodenal stasis.
With obstructing Ladd bands, plain abdominal radiographs may show a “double bubble” sign that mimics duodenal stenosis. Distribution of gas throughout the intestines may be normal, although there may be a paucity of it. When volvulus occurs, the proximal bowel will be distended with gas early, but over time, a “gasless” abdomen may appear as the gas is resorbed in the ischemic bowel. The intestinal walls are thickened.
The identification of inverted superior mesenteric artery and superior mesenteric vein position on ultrasound is highly suggestive of malrotation and warrants further investigation; however, ultrasound can miss 10%-15% of cases. Upper GI series is the gold standard for diagnosis and demonstrates distention of the duodenum, abnormal positioning of the duodenojejunal segment (usually to the right of the midline), and narrowing at the point of obstruction. The small bowel is commonly visualized on the right side of the abdomen and the colon on the left. Contrast enema demonstrates abnormal position of the cecum, although the cecum can complete its rotation and fixation after birth, so the contrast enema is not a valuable diagnostic test for malrotation.
Through a transverse upper abdominal incision, the entire bowel should be delivered from the abdominal cavity to assess the anomalous arrangement of the intestinal loops. Volvulus should be untwisted in a counterclockwise direction. The Ladd procedure is used for incomplete rotation with obstruction of the duodenum by congenital bands. It consists of division of the bands between the proximal colon and the lateral abdominal wall that cover and compress (obstruct) the duodenum. The mesentery is often folded upon itself due to intermesenteric adhesions, and these are incised. The appendix is removed. The cecum is then placed in the left lower quadrant, and the duodenum dissected and straightened as much as possible with a final position to the right of the midline. In essence, one is creating nonrotated intestinal anatomy much like the anatomic situation in early fetal life (prior to 10 weeks’ gestation). The Ladd procedure has increasingly been performed using laparoscopic techniques for those cases without suspected volvulus.
Approximately 30% of infants treated for volvulus die of complications of midgut ischemia and gangrene. If the anomaly is corrected before irreversible bowel damage occurs, the long-term results are good. Some patients tend to form adhesions that cause recurrent intestinal obstruction. Recurrent volvulus is rare after the Ladd procedure.
D, van der Zee
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In 10%-20% of infants born with cystic fibrosis, the thick mucous secretions of the small bowel produce obstruction by inspissated meconium. This usually occurs in the terminal ileum. Although there is no clear correlation between pancreatic insufficiency and the development of inspissated meconium, meconium ileus also occurs in patients with pancreatic duct obstruction and pancreatic aplasia. Meconium obstruction with no apparent cause has also been described in newborn infants.
The infant typically has a normal birth weight and very distended abdomen. No meconium is passed, and bilious emesis occurs early. Loops of thick, distended bowel may be seen and palpated.
Plain abdominal radiographs show loops of bowel that vary greatly in diameter; the thick meconium gives a ground-glass appearance. Air mixed with the meconium produces the “soap bubble” sign, which is usually located in the right lower quadrant. Radiographs taken shortly after the infant has been placed in an upright position may fail to show air-fluid levels because the thick, viscid meconium fails to layer out rapidly. Contrast enema will show microcolon with rare meconium flecks. Reflux of contrast medium through the ileocecal valve demonstrates a small terminal ileum containing “pellets” of inspissated mucus; more proximally, the bowel is progressively distended with packed meconium. Antenatal perforation may be detected by the presence of abdominal calcifications since the meconium becomes saponified.
Meconium ileus may be complicated by a segmental (not midgut) volvulus due to the heavy, distended loops of distal ileum. If this occurs early in fetal life, the volvulus may progress to gangrene of the affected bowel segment. This can heal completely, with abdominal calcifications as the only manifestation that it occurred. Conversely, it may heal in such a way that an intestinal atresia is formed. Perforation late in gestation may lead to meconium peritonitis or a large meconium pseudocyst at birth.
Other common complications of meconium ileus are related to the almost universal presence of cystic fibrosis. These infants are susceptible to repeated pulmonary infection with chronic bronchopneumonia, bronchiectasis, atelectasis, and lung abscess. Malabsorption due to pancreatic insufficiency requires pancreatic enzyme replacement. Rectal prolapse and intussusception may be produced by strained passage of inspissated stools. Nasal polyps and chronic sinusitis are frequent. Biliary cirrhosis and bleeding varices from portal hypertension are late manifestations of bile duct obstruction by mucus.
Nonoperative treatment is successful in 60%-70% of cases. A nasogastric tube should be inserted and connected to suction. A contrast enema can be both diagnostic and therapeutic. It should be performed with a slightly hypertonic water-soluble contrast agent (never barium). The addition of N-acetylcysteine, which is mucolytic, may be necessary to disperse the meconium in uncomplicated cases. The infant must be well hydrated, and intravenous fluids must be continued during and after the procedure in order to prevent hypovolemia from the effects of the hypertonic contrast solution. If this fails to relieve the obstruction, laparotomy is indicated. The ileum is opened and, if possible, flushed clear. The bowel can be reanastomosed or brought out as a double-barrel stoma. Alternatively, a T-tube may be placed in the bowel and brought out of the anterior abdominal wall for postoperative irrigations. Compromised intestine is resected, and appendectomy is performed because of the high rate of appendicitis in patients with cystic fibrosis.
All patients should be evaluated for cystic fibrosis. Pancreatic enzyme replacement may be required. A formula low in long-chain fatty acids and high in medium-chain triglycerides may give better absorption and growth than standard formulas. The patient must be placed in an environment with high humidity to keep tracheobronchial secretions fluid. Postural drainage with cupping of the chest should be taught to the parents so that they will continue to maintain tracheobronchial toilet indefinitely. Older children and adolescents may develop a meconium ileus-like syndrome termed distal ileal obstruction syndrome. This is ileal obstruction due to inspissated stool. It can occur when patients are not compliant with their medications or become dehydrated. Most often, it is successfully treated with hypertonic contrast enemas.
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Hirschsprung disease is due to failure in the cephalocaudal migration of the parasympathetic myenteric nerve cells into the distal bowel. Therefore, the absence of ganglion cells always begins at the anus and extends a varying distance proximally. The aganglionic bowel produces functional obstruction because the bowel fails to relax in response to distention. Short-segment aganglionosis involving only the terminal rectum occurs in about 10% of cases; the disease extends to the sigmoid colon in 75%; more proximal colon in 10%; and the entire colon with small bowel involvement in 5%. Extensive involvement of the small bowel is rare.
Males are affected four times more frequently than females when the disease is limited to the rectosigmoid. Females tend to have longer aganglionic segments. A familial association occurs in 5%-10% of cases—more frequently when females are affected. The length of involvement tends to be consistent in familial cases. Down syndrome occurs in 10%-15% of patients.
The absence of ganglion cells results in a functional obstruction since the affected area fails to relax due to unopposed sympathetic tone. The symptoms vary widely in severity but almost always occur shortly after birth. The infant passes little or no meconium within 24 hours. Thereafter, chronic or intermittent constipation usually occurs. Progressive abdominal distention, bilious emesis, reluctance to feed, diarrhea, listlessness, irritability, and poor growth and development follow. A rectal examination in the infant may be followed by expulsion of stool and flatus, with remarkable decompression of abdominal distention. In older children, chronic constipation and abdominal distention are characteristic. Passage of flatus and stool requires great effort, and the stools are small in caliber. Children with constipation from Hirschsprung disease do not exhibit soiling of their diapers or undergarments, distinguishing this form of constipation from idiopathic constipation (encopresis). These children are sluggish, with wasted extremities and flared costal margins. Rectal examination in older children usually reveals a normal or contracted anus and a rectum without feces. Impacted stools in the greatly dilated and distended sigmoid colon can be palpated across the lower abdomen.
Plain abdominal radiographs in infants show dilated loops of bowel, but it is difficult to distinguish small and large bowel in infancy. A contrast enema should be performed. There should be no rectal examination or attempt to clean out the stool before the fluoroscopic examination, for this can dilate the rectum and obscure the change in caliber between aganglionic and ganglionic bowel. The contrast enema often demonstrates a contracted (aganglionic) segment that appears relatively narrow compared with the dilated proximal bowel. The proximal aganglionic intestine can be dilated by impacted stool or enema, giving a false impression of the level of the normal colon. Irregular, bizarre contractions (saw-toothed pattern) that do not encircle the aganglionic portion of the bowel may also be recognized. The dilated proximal bowel may have circumferential, smooth, parallel contractions (similar in appearance to those of the jejunum) that are exaggerated contraction waves. The contrast enema may not show a transition zone in the first 6 weeks after birth, since the liquid stool can pass into the aganglionic bowel and the proximal intestine may not be dilated. Lateral projection radiographs should be taken to demonstrate the rectum, the transition zone, and the irregular contractions that may otherwise be obscured by a redundant sigmoid colon on anteroposterior views. Normally, the neonatal rectum is wider than the rest of the colon (including the cecum), and when the rectum is seen to be narrower than the proximal colon, then Hirschsprung disease is suspected. Radiographs of the abdomen and lateral pelvis should be repeated after 24-48 hours. The contrast agent will be retained for prolonged periods, and saline enemas may be required to evacuate it. The delayed film may show the transition zone and the bizarre irregular contractions more clearly than the initial study.
Definitive diagnosis is made by rectal biopsy. Mucosal and submucosal biopsies may be taken from the posterior rectal wall with a suction biopsy capsule at the bedside. Serial sections may demonstrate the characteristic lack of ganglion cells and proliferation of nerve trunks in Meissner plexus. If the findings are equivocal, it is necessary to remove a 1-cm or 2-cm full-thickness strip of mucosa and muscularis from the posterior rectum proximal to the dentate line under anesthesia. A sample of this size is sufficient for the pathologist to determine the presence or absence of ganglion cells in Meissner plexus or in Auerbach plexus. Manometric studies will show a failure of relaxation of the internal sphincter following rectal distention by a balloon, although this test is rarely performed except in older children.
Low intestinal obstruction in the newborn infant may be due to rectal or colonic atresia, meconium plug syndrome (see below), or meconium ileus as well as a variety of functional causes such as hypermagnesemia, hypocalcemia, hypokalemia, and hypothyroidism. Hirschsprung disease in patients who develop enterocolitis and diarrhea may mimic other causes of diarrhea. Chronic constipation due to functional causes may suggest Hirschsprung disease. Although functional constipation may occur early in infancy, the stools are normal in caliber, soiling is frequent, and enterocolitis is rare. In functional constipation, stool is palpable in the lower rectum, and a contrast enema shows uniformly dilated bowel to the level of the anus. However, short segment Hirschsprung disease may be difficult to differentiate, and rectal biopsy may be necessary. Segmental dilation of the colon is a rare entity that causes constipation similar to that found in Hirschsprung disease.
Traditionally, the surgical treatment was staged and consisted of a leveling colostomy followed several months later by resection of the aganglionic bowel and performance of a pull-through procedure. The trend recently has been toward performing a single-stage procedure (no colostomy) in the newborn period. This paradigm is as follows: bowel obstruction and enterocolitis (if present) may be relieved by placement of a large (30F) rectal tube and repeated warmed saline irrigations in 10 mL/kg aliquots preoperatively. Infants with moderate to severe enterocolitis should be treated with a diverting colostomy. At the time of surgery, frozen section analysis of the colonic muscle is required in order to establish the correct (ganglionic) level for the stoma. Infants who are not ill may undergo any one of three effective operative procedures: Swenson operation, Duhamel operation, or Soave operation. The main operative principles for these procedures are removal of most or all of the aganglionic bowel—while preserving the surrounding nerves to the pelvic organs—and anastomosing ganglionic bowel (confirmed by frozen section analysis) to the rectum just above the dentate line. In contrast to the Swenson and Soave procedures, the Duhamel operation leaves a cuff of aganglionic rectum along which the ganglionic bowel is stapled, creating a mini-reservoir. Historically, these operations have been performed via a low transverse abdominal incision. However, the laparoscopic approach has become the method of choice. A solely transanal mucosectomy has been used for those babies with short-segment disease. In total aganglionic colon, ileostomy is necessary. Nonoperative treatment with enemas is ineffective because it fails to prevent further obstruction and enterocolitis.
The mortality for untreated aganglionic megacolon in infancy may be as high as 80%. Nonbacterial, nonviral enterocolitis is the principal cause of death. This tends to occur more frequently in infants but may appear at any age. The cause is not known but seems to be related to the high-grade partial obstruction, poor motility in the “normal” bowel, a frequently competent ileocecal valve, and hypertonic rectal sphincters. There is no correlation between the length of aganglionosis and the occurrence of enterocolitis. Perforation of the colon and appendix may result from distal bowel obstruction. Atresia of the distal small bowel or colon secondary to bowel obstruction due to Hirschsprung disease in utero has been reported.
Anastomotic leak with perirectal and pelvic abscess is the most serious complication following the pull-through procedure. This complication should be treated immediately by proximal colostomy until the anastomosis has healed. Necrosis of the pulled-through colon may occur if the bowel has not been mobilized sufficiently to prevent tension on the mesenteric blood supply.
Long-term patients who are properly treated for Hirschsprung disease do well. Incontinence and soiling may occur in a few cases despite a prompt diagnosis and a perfect operation. Episodic constipation and abdominal distention are more common, since the aganglionic internal anal sphincter is intact. Patients with these symptoms can respond to anal dilation. Occasionally, an internal sphincterotomy may be necessary. Smaller children may still develop enterocolitis after definitive treatment, and they should be treated with a large rectal tube and enemas. It is rare after age 5 years. Postoperative enterocolitis is more common in children with Down syndrome.
P: Outcome comparison among laparoscopic Duhamel, laparotomic Duhamel, and transanal endorectal pull-through: a single-center, 18-year experience. J Laparoendosc Adv Surg Tech A 2011 Nov;21(9):859–863.
NEONATAL SMALL LEFT COLON SYNDROME (MECONIUM PLUG SYNDROME)
This problem of newborn infants consists of low intestinal obstruction associated with a left colon of narrow caliber and a dilated transverse and right colon. The infants are in most cases otherwise normal, though approximately 30%-50% are born to diabetic mothers and are large for gestational age. Most are over 36 weeks’ gestational age and have normal birth weights. Two-thirds are male. Hypermagnesemia has been occasionally associated when the mother has been treated for eclampsia by intravenous magnesium sulfate.
Rectal examination may be normal or may reveal a tight anal canal. Little or no meconium is passed, and progressive abdominal distention is followed by vomiting. After thermometer or finger stimulation of the rectum, some meconium and gas may be evacuated. Contrast enema shows a very small left colon, usually to the level of the splenic flexure. Proximal to this point, the colon and commonly the small bowel are greatly distended. In about 30% of cases, a meconium plug is present at the junction of the narrow and dilated portion of the bowel, and the enema (using water-soluble contrast) will dislodge it.
The small left colon syndrome may be confused with Hirschsprung disease or meconium ileus. These lesions rarely cause obstruction at the level of the splenic flexure, and when the colon readily decompresses without further obstruction, Hirschsprung disease is unlikely.
A nasogastric tube should be inserted and intravenous fluids started. A contrast enema is required to differentiate the various causes of low intestinal obstruction. When the left colon is narrow and contrast material refluxes into the dilated proximal colon, the diagnosis is most likely the small left colon syndrome. The contrast enema is usually followed by evacuation of copious meconium and decompression of the bowel. Incomplete evacuation of the meconium or persistent symptoms after the enema mandates a suction rectal biopsy to rule out Hirschsprung disease.
Telescoping of a segment of bowel (intussusceptum) into the adjacent segment (intussuscipiens) is the most common cause of intestinal obstruction in children between 6 months and 2 years of age (Figure 43–12). The process of intussusception may result in gangrene of the intussusceptum. The most common form is intussusception of the terminal ileum into the right colon (ileocolic intussusception). In 95% of infants and children, it is idiopathic. The disease is most common in midsummer and midwinter, and there is a correlation with adenovirus infections. In most cases, hypertrophied Peyer patches are noted on the leading edge of bowel. Mechanical factors such as Meckel diverticulum, polyps, hemangioma, enteric duplication, intramural hematoma (Henoch-Schönlein purpura), and intestinal lymphoma are present with increasing frequency in patients over 2 years old. Postoperative intussusception can occur at any age, is usually ileoileal or jejunojejunal, and is due to differential return of bowel motility, often after retroperitoneal surgery. The ratio of males to females is 3:2. The peak age is in infants 5-9 months of age; 80% of patients are under the age of 2 years.
The typical patient is a healthy child who suddenly begins crying and doubles up because of abdominal pain. The pain occurs in episodes that last for about 1 minute, alternating with intervals of apparent well being. Reflex vomiting is an early sign, but vomiting due to bowel obstruction occurs late. Blood from venous infarction and mucus produce a “currant jelly” stool. In small infants and in postoperative patients, the colicky pain may not be apparent; these babies become withdrawn, and the most prominent symptom is vomiting. Pallor and sweating are common signs during colic. Repeated vomiting and bowel obstruction will produce progressive dehydration. A mass is usually palpable along the distribution of the colon, most commonly in the right upper quadrant of the abdomen. Occasionally, intussusception is palpable on rectal examination. Prolonged intussusception produces edema and hemorrhagic or ischemic infarction of the intussusceptum.
The contrast enema is diagnostic as well as therapeutic in 60%-80% of cases (Figure 43–13). Contrast enema (using either barium or air) should not be attempted until the patient has been resuscitated enough to allow an operative procedure to be performed safely. It is contraindicated if peritonitis is present. If barium is used, the column of contrast should not stand more than 100 cm above the patient in order to minimize the risk of perforation. Air is pumped into the colon at a pressure of 60-80 mm Hg (never > 120 mm Hg). A successful study reduces the intussusceptum and demonstrates reflux of barium or air into the terminal ileum. Several attempts should be made before taking the child to surgery. A contrast enema will not reduce gangrenous bowel.
Contrast enema demonstrating obstruction to retrograde flow of barium by a filling defect (intussusceptum) in the mid transverse colon. (Reproduced, with permission, from Albanese CT. Pediatric surgery. In: Norton JA, ed. Surgery. New York, NY: Springer; 2000.)
Operation is required for unsuccessful enema reduction or signs of bowel perforation and peritonitis. The procedure may be performed either by laparotomy or laparoscopically. In the absence of gangrene, reduction is accomplished by gentle retrograde compression of the intussuscipiens, not by traction on the proximal bowel. Resection of the intussusception is indicated if the bowel cannot be reduced or if the intestine is gangrenous.
Intussusception recurs after 5% of enema reductions and 1% of operative reductions. Deaths are rare but occur if treatment of gangrenous bowel is delayed.
et al.: Intussusception in children-clinical presentation, diagnosis and management. Int J Colorectal Dis 2009;24:1187–1192.
ANORECTAL ANOMALIES (IMPERFORATE ANUS)
The normal continence mechanism for bowel control consists of an internal sphincter composed of smooth muscle and the striated muscle complex from the levator ani and external sphincter. The striated muscles assume a funnel shape, originating from the pubis, pelvic rim, and sacrum. These muscles converge at the perineum while interdigitating with the internal and external sphincters. Most of the striated muscle complex consists of horizontal muscles that contract against the wall of the rectum and anus while longitudinal muscle fibers run in a cephalocaudal direction and elevate the anus.
Anomalies of the anus result from abnormal growth and fusion of the embryonic anal hillocks. The rectum is normally developed, and the sphincter mechanism is usually intact. With proper surgical treatment, the sphincter will function normally. Anomalies of the rectum develop as a result of faulty division of the cloaca into the urogenital sinus and rectum by the urorectal septum. In these anomalies, the internal sphincter and striated muscle complex are hypoplastic. Therefore, surgical repair results in varying degrees of continence.
Physical examination of the perineum and imaging studies determine the extent of malformation of the anus or rectum. When an orifice is evident at the perineum or distal introitus, the anomaly is referred to as a low imperforate anus; the absence of an obvious orifice at the perineal level suggests a high imperforate anus (Figures 43–14, 43–15, 43–16, and 43–17) In most instances, with high imperforate anus, there is a communication (fistula) of the rectum with the urethra or bladder in the male or with the upper vagina in the female. Distinguishing between a high and low anomaly may be possible radiologically by determining the position of the rectum in relation to the levator ani or pubococcygeal line.
A: Low female anomaly. Perineal fistula. B: Low female anomaly. Fourchette/vestibule fistula. (Reproduced, with permission, from Pena A: Atlas of Surgical Management of Anorectal Malformations. New York, NY: Springer-Verlag; 1990)
A: High female anatomic anomaly. Low vaginal fistula. B: High female anomaly. High vaginal fistula. (Reproduced, with permission, from Pena A: Atlas of Surgical Management of Anorectal Malformations. New York, NY: Springer-Verlag; 1990.)
A: Low male anomaly. Perineal fistula. B: Low male anomaly. Rectobulbar urethra fistula. (Reproduced, with permission, from Pena A: Atlas of Surgical Management of Anorectal Malformations. New York, NY: Springer-Verlag; 1990.)
A: High male anomaly. Rectoprostatic urethra fistula. B: High male anomaly. Rectovesical neck fistula. (Reproduced, with permission, from Pena A: Atlas of Surgical Management of Anorectal Malformations. New York, NY: Springer-Verlag; 1990.)
In low anomalies, the anus may be ectopically placed anterior to its normal position or it may be in the normal position with a narrow outlet due to stenosis or an anal membrane. There may be no opening in the perineum, but the skin at the anal area is heaped up and may extend as a band in the perineal raphe completely covering the anal opening. A small fistula usually extends from the anus anteriorly to open in the raphe of the perineum, scrotum, or penis in the male or the vulva in the female. These babies often have well-developed perineal and gluteal musculature and rarely have sacral vertebral anomalies.
In high anomalies, the rectum may end blindly (10%), but more commonly there is a fistula to the urethra or bladder in the male or the upper vagina in the female. In the female, a very high fistula may extend between the two halves of a bicornuate uterus directly to the bladder. Patients with high imperforate anus often have deficient pelvic and gluteal innervation and musculature, a high incidence of sacral anomalies (caudal regression), and a poor prognosis for continence after surgical repair. The most severe of the high deformities is a cloacal anomaly in which there is a common channel between the poorly developed pelvic structures (urogenital sinus and rectum) with a single perineal opening.
The best means of establishing the type of anorectal anomaly is by physical examination. In low anomalies, an ectopic opening from the rectum can be detected in the perineal raphe in males or in the lower vagina, vestibule, or fourchette in females. A high anomaly exists when no orifice or fistula can be seen upon examination of the perineum or when meconium is found at the urethral meatus, in the urine, or in the upper vagina. Absence of external sphincter contraction with cutaneous stimulation of the anus may also help differentiate between high and low lesions.
No single test is ideal in the evaluation of imperforate anus, so several studies are used to define the neonatal anatomy. Radiographs are sometimes useful when the clinical impression is unclear. A lateral film of the pelvis with the baby inverted (Wangensteen invertogram), once commonly used, is an inaccurate method of establishing the lower extent of the rectum because swallowed air may not have completely displaced the meconium from the rectum; or the striated muscle complex may be contracted, which obliterates the lumen and makes it look as if the gas in the rectum ends high in the pelvis. With crying or straining, the puborectalis muscle and rectum may actually descend below the ischium, giving a falsely low estimate of rectal height. Gas in the bladder clearly indicates a rectourinary fistula. Lower abdominal and perineal ultrasound, CT, and MRI have been used to define the pelvic anatomy and location in relation to the rectal musculature. Anomalies of the vertebrae and the urinary tract occur in two-thirds of all patients with high anomalies and in one-third of male patients with low anomalies. Vertebral abnormalities in females invariably indicate a high imperforate anus. Anomalies of the sacrum warrant MRI of the lumbosacral area to identify spinal cord anomalies such as a tethered filum terminale.
Associated anomalies occur in up to 70% in those with a high anomaly. Imperforate anus is associated with the VACTERL syndrome (see Esophageal Anomalies). The possible constellation of anomalies includes esophageal atresia, anomalies of the GI tract, hemivertebrae or agenesis of one or more sacral vertebrae (agenesis of S1, S2, or S3 is associated with corresponding neurologic deficits, resulting in neuropathic bladder and greatly impaired continence), genitourinary anomalies (up to 50% incidence with high imperforate anus), and anomalies of the heart and upper limbs/digits.
Delay in diagnosis of imperforate anus may result in excessively large bowel distention and perforation. The presence of a rectourinary fistula allows reflux of urine into the rectum and colon, and absorption of ammonium chloride may cause acidosis. Colon contents will reflux into the urethra, bladder, and upper tracts, producing recurrent pyelonephritis.
The three main goals of treatment are (1) to allow passage of stool (ie, relieve obstruction), (2) to place the rectal pouch on the perineum in good position, and (3) to close the fistula.
Low anomalies are usually repaired from the perineal approach in the newborn period using a muscle stimulator to precisely determine the location of the sphincter complex. The anteriorly placed anal opening is completely mobilized and transferred to the normal position. After healing, the anal opening must be dilated daily for 3-5 months to prevent stricture formation and to allow for growth.
Traditionally, a high deformity was treated by a three-stage repair consisting of colostomy and mucous fistula formation, a posterior sagittal anorectoplasty 4-6 weeks later, and closure of the colostomy several months after that. Recently, the staged approach has been challenged and a one-stage repair has been performed by both posterior sagittal and laparoscopic approaches. Because the anal sphincters are poorly developed—especially the internal sphincter—continence is most dependent upon a functioning striated muscle complex, which requires conscious voluntary contraction. Care must be taken to preserve the afferent and efferent nerves of the defecation reflex arc as well as the existing sphincter muscles. In all cases, the surgically created anus must be dilated for several months to prevent circumferential cicatrix formation.
Surgical complications include damage to the nervi erigentes, resulting in poor bladder and bowel control and failure of erection. Division of a rectourethral fistula some distance from the urethra produces a blind pouch prone to recurrent infection and stone formation, while cutting the fistula too short may result in urethral stricture. Erroneously attempting to repair a high anomaly from the perineal approach may leave a persistent rectourinary fistula. An abdominoperineal pull-through procedure performed for a low anomaly invariably produces an incontinent patient who might otherwise have had an excellent prognosis. Injury to the vas deferens and ureter is possible during repair of high anomalies.
Patients with imperforate anus tend to have varying degrees of constipation as an inherent part of the defect, believed to be due to poor inherent motility of the rectosigmoid. Patients with low anomalies usually have good sphincter function. Children with high anomalies do not have an internal sphincter that provides continuous, unconscious, and unfatiguing control against soiling. However, in the absence of a lower spine anomaly, perception of rectal fullness, ability to distinguish between flatus and stool, and conscious voluntary control of rectal discharge by contraction of the striated muscle complex can be achieved. When the stools become liquid, sphincter control is usually impaired in patients with high anomalies.
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