Congenital Disorders and Diseases Secondarily Involving the Urinary Tract

Introduction

Serious congenital disorders of the kidneys and urinary tract nearly all present at birth or in early childhood (see Ch. 51 ). The exception is polycystic kidney , which presents more commonly in adulthood. Less common abnormalities of the upper tract may interfere with normal flow dynamics and predispose to infection, for example, duplex systems or medullary sponge kidney. Asymptomatic abnormalities, such as unilateral renal agenesis, renal cysts or horseshoe kidney, may be discovered incidentally during investigation or during surgery. With advancing age, a large proportion of the population develops benign renal cysts; these are usually of no clinical consequence. A summary of congenital disorders that present after childhood is given in Table 39.1 .

Polycystic Kidneys

Adult polycystic kidney disease is characterised by bilateral multiple cysts of renal parenchyma ( Fig. 39.1 ). The cysts slowly expand, compressing the parenchyma, and may disrupt local control of blood pressure and eventually impair renal function. Polycystic kidneys have four main variants:

• A rare infantile form also affecting the liver; affected children often die young (autosomal recessive polycystic kidney disease).

• A serious adult form manifesting in middle age with hypertension or progressive renal failure (autosomal dominant polycystic kidney disease or ADPKD). It is the commonest cause of inherited renal failure. Kidneys can appear normal on ultrasound scanning up to about the age of 20 years.

• A less serious adult form usually found incidentally in later life, with almost normal renal function. Patients are usually hypertensive.

• Acquired disease seen in patients with end-stage renal failure undergoing dialysis.

Thus adult (autosomal dominant) polycystic kidney may present with hypertension or progressive chronic renal failure . The enlarged kidneys may cause loin pain or be discovered incidentally on abdominal examination. These kidneys are vulnerable to even minor trauma, and haematuria and urinary tract infections are common presentations. Patients can also have multiple cysts in the liver and sometimes in the pancreas. They present with massive abdominal swelling caused by gross liver enlargement. In addition, there is a risk of cerebral Circle of Willis berry aneurysms, which can result in subarachnoid haemorrhage, and also renal tumours (adenomas). There is no specific treatment for polycystic kidney disease, and despite good conservative management, about 50% will eventually require dialysis or renal transplantation.

Medullary Sponge Kidney

This is caused by cyst-like dilatation ( ectasia ) of the renal medulla collecting ducts and may affect one or both kidneys. Cysts tend to calcify, giving a characteristic radiographic appearance of streaky linear calcification of renal papillae (see Fig. 39.2 ). On excretion pyelography (intravenous urogram [IVU]), tubular ectasia can be demonstrated as a ‘flare’ in the renal papilla (like ‘bristles on a brush’). Most are asymptomatic, however marked degrees of medullary sponge kidney predispose to recurrent infection, haematuria and stone formation because of intrarenal urinary stasis and ureteric colic. Patients rarely present before adulthood. Minor degrees are often discovered on IVU or computed tomography (CT), but are not causing symptoms. Up to half of patients will have excessive urinary excretion of calcium (hypercalciuria), which should be managed with good fluid intake, a diet low in salt and animal protein, plus thiazide diuretics, if needed.

Case History