Pelviureteric junction obstruction (idiopathic hydronephrosis) - Renal tract obstruction

Pelviureteric junction obstruction (idiopathic hydronephrosis)

Definition

Narrowing of the pelviureteric junction (PUJ) which is a common cause of gross hydronephrosis.

Age

Likely to be congenital but may present at any age.

Aetiology/pathophysiology

The cause is unknown. There appear to be excessive collagen fibres around the muscle cells at the PUJ, which prevent their proper relaxation, so that there is a narrowed segment of the ureter at the exit of the renal pelvis. This causes gross dilatation ‘hydronephrosis’ of the renal pelvis.

Clinical features

Usually presents as a pain or ache in the back or abdomen which may be exacerbated by drinking large amounts of fluid, for example it may become symptomatic for the first time in students who drink large quantities of beer. There may be a palpable loin mass. Occasionally the hydronephrosis is so marked that it can mimic ascites.

In some cases, it is asymptomatic and diagnosed incidentally when an ultrasound is performed for another reason. Congenital cases may be found on antenatal ultrasound scan, or in childhood during investigation of urinary tract infections.

Complications

Infection of the dilated system due to urinary stasis, renal stones and renal failure.

Investigations

An IVU shows a dilated renal pelvis (often grossly) with normal, undilated ureters. There is delayed passage of contrast, which is not overcome by administration of diuretics. If obstruction is in doubt, further investigations as for urinary tract obstruction (see above) may be needed.

Management

If the PUJ obstruction is causing symptoms or renal impairment, reconstruction of the renal pelvis (pyeloplasty) can be undertaken so that the renal pelvis drains into the ureter, by excising the narrowed segment.

Prognosis

It is not possible to predict how much function will recover and a small proportion of patients continue to have pain.