PELVIURETERIC JUNCTION OBSTRUCTION

Pelviureteric junction (PUJ) obstruction
Definition
A blockage of the ureter at the junction with the renal pelvis resulting in a restriction of urine flow. Boys are affected more than girls. The left side is more often affected than the right side. They are bilateral in up to 40%.

Aetiology
In children, most PUJ obstruction is congenital, due to either an intrinsic narrowing (secondary to aberrant development of ureteric/ renal pelvis muscle, abnormal collagen, or ureteral polyps) or extrinsic causes (compression of the PUJ by aberrant vessels). Coexisting vesicoureteric reflux (VUR) is found in 40%.

Presentation
PUJ obstruction is the most common cause of hydronephrosis found on prenatal and early postnatal USS (differential diagnoses include VUJ obstruction, VUR, renal abnormalities, and posterior urethral valves). Infants may also present with an abdominal mass, UTI, and haematuria. Older children present with flank or abdominal pain (exacerbated by diuresis), UTI, nausea and vomiting, and haematuria following minor trauma.

Investigation
If prenatal USS has shown a large or bilateral hydronephrosis, a follow-up renal tract ultrasound scan should be performed soon after birth. If there is a prenatal unilateral hydronephrosis (and the bladder is normal), the scan is deferred until day 3–7 (to allow normal physiological diuresis to occur, which may spontaneously improve or resolve the hydronephrosis). If upper tract obstruction persists, a micturating cystourethrogram (MCUG) is indicated (to rule out VUR and examine for posterior urethral valves), and a renogram can assess individual renal function and drainage (DTPA, MAG-3).

Treatment
Children may be observed with USS and renogram if they remain stable, with good renal function, and no other complications (such as persistent infection or stones). If children are symptomatic or have a significant hydronephrosis with impaired renal function (<40%), pyeloplasty is recommended.