Adult polycystic kidney disease is an autosomal dominant hereditary condition and almost always bilateral (95% of cases). The disease encountered in infants is different from that seen in adults, although the literature reports a small number of infants with the adult type. The former is an autosomal recessive disease in which life expectancy is short, whereas that diagnosed in adulthood is autosomal dominant; symptoms ordinarily do not appear until after age 40. Cysts of the liver, spleen, and pancreas may be noted in association with both forms. The kidneys are larger than normal and are studded with cysts of various sizes.
Etiology and Pathogenesis
The evidence suggests that the cysts occur because of defects in the development of the collecting and uriniferous tubules and in the mechanism of their joining. Blind secretory tubules that are connected to functioning glomeruli become cystic. As the cysts enlarge, they compress adjacent parenchyma, destroy it by ischemia, and occlude normal tubules. The result is progressive functional impairment.
Grossly, the kidneys are usually much enlarged. Their surfaces are studded with cysts of various sizes (Figure 32–1). On section, the cysts are found to be scattered throughout the parenchyma. Calcification is rare. The fluid in the cyst is usually amber colored but may be hemorrhagic.
Polycystic kidney. Multiple cysts deep in the parenchyma and on the surface. Note distortion of the calyces by the cysts.
Microscopically, the lining of the cysts consists of a single layer of cells. The renal parenchyma may show peritubular fibrosis and evidence of secondary infection. There appears to be a reduction in the number of glomeruli, some of which may be hyalinized. Renal arteriolar thickening is a prominent finding in adults.
Pain over one or both kidneys may occur because of the drag on the vascular pedicles by the heavy kidneys, from obstruction or infection, or from hemorrhage into a cyst. Gross or microscopic total hematuria is not uncommon and may be severe; the cause for this is not clear. Colic may occur if blood clots or stones are passed. The patient may notice an abdominal mass.
Infection (chills, fever, renal pain) commonly complicates polycystic disease. Symptoms of vesical irritability may be the first complaint. When renal insufficiency ensues, headache, nausea and vomiting, weakness, and loss of weight occur.
One or both kidneys are usually palpable. They may feel nodular. If infected, they may be tender. Hypertension is found in 60–70% of these patients. Evidence of cardiac enlargement is then noted.
Fever may be present if pyelonephritis exists or if cysts have become infected. In the stage of uremia, anemia and loss of weight may be evident. Ophthalmoscopic examination may show changes typical of moderate or severe hypertension.
Anemia may be noted, caused either by chronic loss of blood or, more commonly, by the hematopoietic depression accompanying uremia. Proteinuria and microscopic (if not gross) hematuria are the rule. Pyuria and bacteriuria are common.
Progressive loss of concentrating power occurs. Renal clearance tests show varying degrees of renal impairment. About one-third of patients with polycystic kidney disease are uremic when first seen.
Both renal shadows are usually enlarged on a plain film of the abdomen, even as much as five times normal size. Kidneys >16 cm in length are suspect.
The renal masses are usually enlarged and the calyceal pattern is quite bizarre (spider deformity). The calyces are broadened and flattened, enlarged, and often curved, as they tend to hug the periphery of adjacent cysts. Often, the changes are only slight or may even be absent on one side, leading to the erroneous diagnosis of tumor of the other kidney. If cysts are infected, perinephritis may obscure the renal and even the psoas shadows.
CT is an excellent noninvasive technique used to establish the diagnosis of polycystic disease. The multiple thin-walled cysts filled with fluid and the large renal size make this imaging method extremely accurate (95%) for diagnosis.
Photoscans reveal multiple “cold” avascular spots in large renal shadows.
Sonography appears to be superior to both excretory urography and isotope scanning in diagnosis of polycystic disorders.
Cystoscopy may show evidence of cystitis, in which case the urine will contain abnormal elements. Bleeding from a ureteral orifice may be noted. Ureteral catheterization and retrograde urograms are rarely indicated.
Bilateral hydronephrosis (on the basis of congenital or acquired ureteral obstruction) may present bilateral flank masses and signs of impairment of renal function, but ultrasonography shows changes quite different from those of the polycystic kidney.
Bilateral renal tumor is rare but may mimic polycystic kidney disease perfectly on urography. Tumors are usually localized to one portion of the kidney, whereas cysts are quite diffusely distributed. The total renal function should be normal with unilateral tumor but is usually depressed in patients with polycystic kidney disease. CT scan may be needed at times to differentiate between the two conditions.
In von Hippel-Lindau disease (angiomatous cerebellar cyst, angiomatosis of the retina, and tumors or cysts of the pancreas), multiple bilateral cysts or adenocarcinomas of both kidneys may develop. The presence of other stigmas should make the diagnosis. CT, angiography, sonography, or scintiphotography should be definitive.
Tuberous sclerosis (convulsive seizures, mental retardation, and adenoma sebaceum) is typified by hamartomatous tumors often involving the skin, brain, retinas, bones, liver, heart, and kidneys (see Chapter 21). The renal lesions are usually multiple and bilateral and microscopically are angiomyolipomas. The presence of other stigmas and use of CT or sonography should make the differentiation.
A simple cyst (see section following) is usually unilateral and single; total renal function should be normal. Urograms usually show a single lesion (Figure 32–2), whereas polycystic kidney disease is bilateral and has multiple filling defects.
Simple cyst. Upper left: Large cyst displacing lower pole laterally. Upper right: Section of kidney showing one large and a few small cysts. Lower left: Excretory urogram showing soft-tissue mass in upper pole of right kidney. Elongation and distortion of upper calyces by cyst. Lower right: Infusion nephrotomogram showing large cyst in upper renal pole distorting upper calyces and dislocating upper portion of kidney laterally.
For reasons that are not clear, pyelonephritis is a common complication of polycystic kidney disease. It may be asymptomatic; pus cells in the urine may be few or absent. Stained smears or quantitative cultures make the diagnosis. A gallium-67 citrate scan will definitely reveal the sites of infection, including abscess.
Infection of cysts is associated with pain and tenderness over the kidney and a febrile response. The differential diagnosis between infection of cysts and pyelonephritis may be difficult, but here again a gallium scan will prove helpful. In rare instances, gross hematuria may be so brisk and persistent as to endanger life.
Except for unusual complications, the treatment is conservative and supportive.
The patient should be put on a low-protein diet (0.5–0.75 g/kg/day of protein) and fluids forced to 3000 mL or more per day. Physical activity may be permitted within reason, but strenuous exercise is contraindicated. When the patient is in the state of absolute renal insufficiency, one should treat as for uremia from any cause. Hypertension should be controlled. Hemodialysis may be indicated.
There is no evidence that excision or decompression of cysts improves renal function. If a large cyst is found to be compressing the upper ureter, causing obstruction and further embarrassing renal function, it should be resected or aspirated. When the degree of renal insufficiency becomes life threatening, chronic dialysis or renal transplantation should be considered.
Treatment of Complications
Pyelonephritis must be rigorously treated to prevent further renal damage. Infection of cysts requires surgical drainage. If bleeding from one kidney is so severe that exsanguination is possible, nephrectomy or embolization of the renal or, preferably, the segmental artery must be considered as a life-saving measure. Concomitant diseases (eg, tumor, obstructing stone) may require definitive surgical treatment.
When the disease affects children, it has a very poor prognosis. The large group presenting clinical signs and symptoms after age 35–40 has a somewhat more favorable prognosis. Although there is wide variation, these patients usually do not live longer than 5 or 10 years after the diagnosis is made, unless dialysis is made available or renal transplantation is done.