Chapter 69. Hydronephrosis

A 74-year-old man presented with a 2-day history of severe, steady pain radiating down to the lower abdomen and left testicle. He has had urinary frequency, nocturia, hesitancy, and urinary dribbling for several years with slight worsening with time. CT scan revealed left-sided hydronephrosis (Figure 69-1). In this patient, an irregular mass was seen at the left ureterovesical junction compressing the bladder. Prostate cancer was found on biopsy.

Hydronephrosis refers to distention of the renal calyces and pelvis of one or both kidneys by urine. Hydronephrosis is not a disease but a physical result of urinary blockage that may occur at the level of the kidney, ureters, bladder, or urethra. The condition may be physiologic (e.g., occurring in up to 80% of pregnant women) or pathologic.

• The most common cause of congenital bilateral hydronephrosis is posterior urethral valves (in males). Other causes include narrowing of the ureteropelvic or ureterovesicular junction.
• Using a large European database for surveillance of congenital malformations (EUROCAT), authors found a prevalence of congenital hydronephrosis of 11.5 cases per 10,000 births; the majority (72%) was in males.1
• Ureteropelvic junction obstruction is one of the most common congenital abnormalities of the urinary tract causing hydronephrosis, occurring in approximately 1 in 5000 to 8000 live births.2
• Authors of one systematic review reported a mean prevalence of 15% for postnatal primary vesicoureteral reflux (VUR) in children after prenatally detected hydronephrosis.3 Of the remaining cases, 53% had no postnatal anomalies and 29% had other anomalies (e.g., duplicate collecting systems; Figure 69-2).
• Among acquired causes in adults, pelvic tumors, renal calculi, and urethral stricture predominate.4 If renal colic is present, renal stone is likely present (90% in one study).5
• Hydronephrosis is common in pregnancy because of the compression from the enlarging uterus and functional effects of progesterone.

• Bilateral hydronephrosis is caused by a blockage to urine flow occurring at or below the level of the bladder or urethra.
• Unilateral hydronephrosis is caused by a blockage to urine flow occurring above the level of the bladder.
• Multiple causes result in this condition including congenital (e.g., VUR), acquired intrinsic (e.g., calculi, inflammation, and trauma), and acquired extrinsic (e.g., pregnancy or uterine leiomyoma, retroperitoneal fibrosis). Within these groupings, obstruction may be a result of mechanical (e.g., benign prostatic hypertrophy) or functional (e.g., neurogenic bladder) defects.
• Urinary obstruction causes a rise in ureteral pressure leading to declines in glomerular filtration, tubular function (e.g., ability to transport sodium and potassium or adjust urine concentration), and renal blood flow.
• If obstruction persists, tubular atrophy and permanent nephron loss can occur.

• In children, the diagnosis of hydronephrosis or megaureter is often made by a routine ultrasound.
• A work-up for hydronephrosis in adults is often triggered by the discovery of azotemia (caused by impaired excretory function of sodium, urea, and water). Sudden or new onset of hypertension (because of the increased renin release with unilateral obstruction) may also trigger an investigation. A first step in the evaluation is to perform bladder catheterization. If diuresis occurs, the obstruction is below the bladder neck.

Clinical Features

• Pain is the symptom that most commonly leads an adult patient to seek medical attention. This is caused by distention of the collecting system or renal capsule. The pain is often described as severe, steady, and radiating down to the lower abdomen, testicles, or labia. Flank pain with urination is pathognomonic for VUR.
• Disturbed excretory function or difficulty in voiding: Oliguria and anuria are symptoms of complete obstruction whereas polyuria and nocturia occur with partial obstruction (impaired concentrating ability causes osmotic diuresis).
• Fever or dysuria can occur with associated urinary tract infection (UTI).
• The physical examination may reveal distention of the kidney or bladder. Rectal exam may show an enlarged prostate or rectal/pelvic mass and pelvic examination may reveal an enlarged uterus or pelvic mass.

Laboratory Testing

• Urinalysis may show hematuria, pyuria, proteinuria, or bacteruria but the sediment is often normal.3
• Assess renal function (blood urea nitrogen [BUN], creatinine).
• Urodynamic testing may be indicated for patients with neurogenic bladder or other suspected bladder causes of hydronephrosis.

Imaging

• Ultrasound imaging has a sensitivity and specificity of 90% for identifying the presence of hydronephrosis if no diuresis occurs following bladder catheterization.4
• If a source remains unidentified, an IV urogram (Figures 69-1 and 69-3) and/or CT scan (Figure 69-4) should be obtained to diagnose intraabdominal or retroperitoneal causes.
• One study of magnetic resonance (MR) pyelography (vs. ultrasound and urography) reported a sensitivity in detecting stones, strictures, and congenital ureteropelvic junction obstructions of 68.9%, 98.5%, and 100%, respectively, with a specificity of 98%.6 Accuracy regarding the level of obstruction was high (100%).
• Antegrade urography (percutaneous placement of ureteral catheter) or retrograde urography (cystoscopic placement of ureteral catheter) may be needed in patients with azotemia and poor excretory function or in those at high risk of acute renal failure from IV contrast (i.e., diabetes, multiple myeloma).
• A voiding cystourethrogram is useful in the diagnosis of VUR and bladder neck and urethral obstructions.
• For children identified in the prenatal period with hydronephrosis, the American Urologic Association (AUA) recommends a voiding cystourethrogram if there is high-grade hydronephrosis, hydroureter, or an abnormal bladder on ultrasound (late-term prenatal or postnatal), or for children who develop a UTI on observation.7 SOR C Given the unproven value in diagnosing and treating VUR, an observational approach without screening may be taken for children with lesser grades of prenatally detected hydronephrosis (Society for Fetal Urology [SFU] grade 1 or 2).

Hydronephrosis is usually found during an investigation for symptoms such as flank pain or renal failure. Following are other causes of flank pain:

• Pyelonephritis—Fever, chills, nausea, vomiting, and diarrhea often occurring with or without symptoms of cystitis.
• Cholelithiasis—Pain is more typical in the epigastrium and right upper quadrant (biliary colic) and often nausea and vomiting occurs (see Chapter 62, Gallstones).
• Other urologic disorders include ureteropelvic junction obstruction, renal subcapsular hematoma, and renal cell carcinoma (see Chapter 71, Renal Cell Carcinoma).

Causes of unexplained renal failure in adults:

• Hypoperfusion (prerenal failure).
• Acute tubular necrosis (ATN), interstitial, glomerular, or small vessel disease (intrarenal failure).
• Hypoperfusion and ATN account for the majority of cases of acute renal failure.

Nonpharmacologic

• Spontaneous resolution or decrease in urinary tract dilation is expected for most cases of neonatal hydronephrosis and primary megaureter diagnosed prenatally.8,9
• Functional causes may be treated by frequent voiding or catheterization (intermittent preferred).10 SOR B

Medications

• Children younger than 1 year of age with VUR complicated by a history of febrile UTI or higher grades of VUR (grades III to V) should be placed on prophylactic antibiotics (sulfamethoxazole/trimethoprim or nitrofurantoin).11 SOR B
• Adult patients with hydronephrosis, complicated by infection, should be treated with appropriate antibiotics for 3 to 4 weeks. Chronic or recurrent unilateral infections may require nephrectomy. SOR A
• Anticholinergic drugs (e.g., oxybutynin, tolterodine) are recommended for patients with neurogenic bladder.10 SOR B
• α-Adrenergic blockade in children with neurogenic bladder can also be considered, but studies are lacking.10 SOR C

Procedures and Surgery

• Hydronephrosis with infection is a urologic emergency that can be treated by prompt drainage using retrograde stent insertion or percutaneous nephrostomy.12
• Pyeloplasty is a surgical technique for repairing an obstruction between the ureter and kidney that involves excising the obstructing segment with reanastomosis of the ureter. For children with ureteropelvic junction obstruction, three basic procedures (open pyeloplasty [OP], endopyelotomy, and laparoscopic pyeloplasty [LP]) can be used for treatment; early surgery is only needed in approximately 15% to 20% of patients.13 In one review of largely retrospective data, OP and LP had higher success rates than endopyelotomy (94.1% and 95.9% to 97.2% vs. 62% to 83%, respectively).14
• Treatment for VUR includes surgical repair (ureteral reimplantation or ureteroneocystostomy) or endoscopic injection of a bulking agent. Surgical repair reduces rates of pyelonephritis compared to medical treatment, but not UTI or renal scarring.15
• Stenting (conventional and metallic) is also used for bypassing ureteral obstruction to alleviate hydronephrosis.16 The American College of Radiology (ACR) recommends percutaneous antegrade ureteral stenting or percutaneous nephrostomy for afebrile nonanuric patients with acute hydronephrosis.17 In a septic patient with acute obstruction, ACR recommends urgent percutaneous nephrostomy (preferred) or urgent retrograde ureteral stenting.17
• Patients with renal failure can be treated with dialysis. SOR A
• Elective surgery for drainage is performed for persistent pain or progressive loss of renal function. SOR C

• The prevalence of VUR in siblings of an index case is 27.4% and in offspring 35.7%; severe reflux is identified in approximately 10% of screened patients.18 Because of the lack of randomized controlled trials of treated versus untreated screened siblings with VUR regarding health outcomes, the best screening strategy is not known. One cost analysis estimated that it would require screening 30 to 430 asymptomatic siblings 1 year of age to prevent 1 febrile UTI at a cost of $56,000 to $820,000 per averted episode.19

Prognosis depends on the underlying etiology.

• Neonates and children with unresolved hydronephrosis or megaureter should be followed periodically with urine cultures, serum creatinine, ultrasonography, and possibly renal scan.11
• Prognosis for an adult patient depends on the duration and completeness of the obstruction and associated complications like infection; complete obstruction for 1 to 2 weeks may be followed by partial return of renal function, but after 8 weeks, recovery is unlikely.4
• Postobstructive diuresis can cause loss of sodium, potassium, and magnesium that may require replacement in the setting of hypovolemia, hypotension, or electrolyte imbalance.

• Education regarding VUR should include a discussion of the treatment rationale, treatment approaches, and likely adherence with the care plan.10

Patient Resources

• National Kidney Foundation (800-622-9010) or www.kidney.org.
• National Institutes of Health, MedlinePlus. Bilateral Hydronephrosis—http://www.nlm.nih.gov/medlineplus/ency/article/000474.htm.

Provider Resources

• Lusaya DG, Lerma EV. Hydronephrosis and Hydroureter—http://emedicine.medscape.com/article/436259-overview.
• Guideline: Screening of the neonate/infant with prenatal hydronephrosis. In: American Urologic Association Education and Research. Management and Screening of Primary Vesicoureteral Refluxin Children: AUA Guideline. Linthicum, MD: American Urologic Association Education and Research; 2010:1-12. http://www.guideline.gov/content.aspx?id=24030&search=hydronephrosis.
• Guideline: Vatakencherry G, Funaki BS, Ray CE Jr, et al; Expert Panel on Interventional Radiology. ACR Appropriateness Criteria® Treatment of Urinary Tract Obstruction. [online publication]. Reston, VA: ACR; 2010. 7 p. http://www.guideline.gov/content.aspx?id=23819&search=hydronephrosis.