Congenital abnormalities of the renal pelvis and ureter

Duplication of a renal pelvis

Duplication of a renal pelvis (Fig. 64.8) is the most common congenital abnormality of the upper renal tract and is found in about 4 per cent of patients. It is usually unilateral and is slightly more common on the left. The upper renal pelvis is relatively small and drains the upper group of calyces; the larger lower renal pelvis drains the middle and lower groups of calyces.

Duplication of a ureter

Duplication of a ureter is found in about 3 per cent of excretion urograms. The ureters often join before they reach the bladder, usually in the lower third of their course (Fig. 64.9) and have a common ureteric orifice. Less commonly the ureters open independently into the bladder, in which case the ureter from the upper pelvis opens distal and medial to its fellow (Fig. 64.10).

Clinical features

Duplication of the renal pelvis or ureter is often a chance finding on renal imaging but infection, calculus formation and pelviureteric junction obstruction are more common than in normal kidneys. One of the moieties may be dysplas­tic and nonfunctioning. Where the two ureters open sepa­rately, the lower orifice is liable to be abnormal in function or position. Failure of the normal valvular mechanism at the ureterovesical junction may lead to urinary reflux and, if there is associated infection, damage to the parenchyma of the upper moiety. An ectopic second ureteric opening is a rarity but it may cause puzzling symptoms.

In the female an ectopic ureter opens either into the urethra below the sphincter (Fig. 64.11) or into the vagina. The diagnosis can often be made from the history alone and is confirmed by excretion orography. A girl or woman who has dribbled urine for as long as she can remember, despite the fact that she has a desire to void and indeed voids normally, probably has an ectopic oreteric orifice. The orifice is often difficult to see because it is guarded by a valve: it may help to give an intravenous injection of a dye such as indigocarmine to colour the urine leaking from it.

In the male patient the aberrant opening is above the external urethral sphincter so the patient is continent. The ureteric orifice at the apex of the trigone, the posterior urethra, in a seminal vesicle or in an ejaculatory duct is likely to be functionally abnormal and infection is the most common complication.

Treatment

Asymptomatic duplication of the kidney is a harmless variant and does not require treatment. If one moiety is severely diseased or atrophic, partial nephrectomy is usually simple and effective. An ectopic ureter in the female frequently drains hydronephrotic and chronically infected renal tissue, which is best excised. Rarely, the incontinence can be cured and renal function preserved by implanting the ectopic ureter into the bladder or by joining it to its fellow.

Congenital megaureter

Congenital megaureter is a curious and uncommon condition which may be bilateral and is often associated with other congenital anomalies. A functional obstruction at the lower end of the ureter leads to progressive dilatation and a tendency to infection. The ureteric orifice appears normal and a ureteric catheter passes easily. Reflux is not a feature of the untreated condition but is almost inevitable if the ureteric orifice is opened endoscopically to make it drain. Definitive surgical treatment involves refashioning the lower end of the affected ureter so that a tunnelled reimplantation into the bladder can be done to prevent reflux.

Postcaval ureter

The right ureter passes behind the inferior vena cava instead of lying to the right of it. If this causes obstructive symptoms, the ureter can be divided and rejoined in front of the cava using a long oblique anastomosis without tension. Unusually, the retrocaval portion of the ureter is fibrotic and must be excised.

Ureterocele

Ureterocele is a cystic enlargement of the intramural portion of the ureter thought to result from congenital atresia of the ureteric orifice. Although present from childhood, the condition is often unrecognised until adult life. The ‘adder head’ on excretory orography (Fig. 64.12) is typical. Usually the cyst wall is composed of urothelium only and the diagnosis is confirmed by the cystoscopic appearance of a translucent cyst enlarging and collapsing as urine flows in from the upper ureter (Fig. 64.13). Treatment should be avoided unless there are symptoms arising from infection and/or stone formation. Ureterocele is most common in women; occasionally the cyst may cause obstruction to the bladder outflow by prolapsing into the internal urethral opening.

Endoscopic diathermy incision is usually all that is required for treatment of a symptomatic ureterocele, although a micturating cystogram is advisable to detect postoperative urinary reflux. In advanced unilateral cases with hydronephrosis or pyonephrosis, nephrectomy may be appropriate.