Congenital disorders and diseases secondarily involving the urinary tract
Congenital urinary tract disorders
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, e.g. 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.
Adult polycystic kidney disease (PCKD) is an autosomal dominant disorder characterised by bilateral multiple cysts of renal parenchyma (see 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 three main variants:
Fig. 39.1 Polycystic kidneys
IVU tomogram from a 52-year-old woman with hypertension and microscopic haematuria; both kidneys exhibit multiple lucent areas in the nephrogram representing cysts (arrowed) and the pelvicalyceal systems are slightly compressed
• A rare infantile form also affecting the liver; affected children often die young
• A serious adult form manifesting in middle age with hypertension or progressive renal failure. It is the commonest cause of inherited renal failure. Kidneys can appear normal on ultrasound scanning up to about the age of 20
• A less serious adult form usually found incidentally in later life with almost normal renal function. Patients are usually hypertensive
Thus, adult 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.
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 (IVU), tubular ectasia can be demonstrated as a ‘flare’ in the renal papilla. Marked degrees of medullary sponge kidney predispose to recurrent infection and stone formation because of intrarenal urine stasis but patients rarely present before adulthood. Minor degrees are often seen on IVU without causing symptoms.
