Pelviureteric junction obstruction

A pelvi-ureteric junction (PUJ) obstruction can be one of the causes of an obstructive uropathy. It can be congenital or acquired with a congenital PUJ obstruction being one of the commonest causes of antenatal hydronephrosis.

Epidemiology

The estimated incidence is at ~ 1 per 1000 - 2000 newborns ⁹. The condition is commonly unilateral. It may present in both paediatric and adult populations although they tend to have differing aetiology. With neonatal cases, there is a recognised predilection towards the left side (~ 67% of cases) and a male predominance. 

Clinical presentation

Many cases are asymptomatic and identified incidentally when the renal tract is imaged for other reasons. When symptomatic, symptoms include recurrent urinary tract infections, stone formation and even a palpable flank mass.

Classically intermittent pain after drinking large volumes of fluid or fluids with a diuretic effect is described, due to the reduced outflow from the renal pelvis into the ureter ^8.

Pathology

During embryogenesis, the pelvi-ureteric junction forms usually around the fifth week and the initial tubular lumen of the ureteric bud becomes recanalised by ~ 10 - 12 weeks. The PUJ area is the last to recanalize. Inadequate canalization is thought to be the main embryological explanation of a PUJ obstruction. Extrinsic obstructions secondary to bands, kinks, and aberrant vessels also are commonly encountered. 

Causes

• congenital (neonatal)
  • idiopathic and often unknown; proposed causes include
    • abnormal muscle arrangement at the PUJ
    • anomalous collagen collar at PUJ
    • ischaemic insult to PUJ region
    • urothelial ureteral fold 
• adult
  • preceding renal pelvic trauma
  • obstructing calculus immediately distal to PUJ
  • previous pyelitis with scarring
  • intrinsic malignancy : e.g. upper tract urothelial carcinoma
  • extrinsic ureter compression of encasement
    • fibrosis
    • malignancy

Associations

• In congenital cases, a number of rental tract abnormalities are recognised, including:
  • multicystic dysplastic kidneys
  • horseshoe kidney
  • cross fused ectopia
• in ~ 40% of cases, an aberrant, accessory, or early-branching lower pole segment vessel is found and observed to compress the ureter, causing mechanical obstruction

Radiographic features

IVU

Traditionally IVU has been performed for assessing for PUJ obstruction.  The administration of frusemide is used to assist confirming the diagnosis, in particular to exclude a so called 'baggy pelvis'.

Ultrasound

• will often show a dilated renal pelvis with a collapsed proximal ureter
• with Doppler sonography the obstructed kidneys can show show higher RI's (resistive indices).

CT

May show evidence of hydronephrosis + / - calyectasis with collapsed ureters. Useful for assessing crossing vessels at the PUJ especially when surgical intervention is planned ^5,7.

Scintigraphy

Scintigraphy can quantitate the degree of obstruction

• ^99mTc diethylenetriaminepentaacetic acid (DTPA) : to be added
• ^99mTc MAG3  : to be added

Treatment and prognosis

Treatment depends on the underlying cause. In a majority of congenital cases, the condition is essentially benign and usually no intervention is required. However when there is a definitive structural obstruction (commonly adult cases), surgical intervention with pleyoplasty or stenting may be required. 

Differential diagnosis

General imaging differential considerations include

• congenital megacalyectasis : central renal pelvis tends to be relatively collapsed
• extra renal pelvis