Pelviureteric junction (PUJ) obstruction/stenosis, also known as ureteropelvic junction (UPJ) obstruction/stenosis, can be one of the causes of obstructive uropathy. It can be congenital or acquired with a congenital PUJ obstruction being one of the commonest causes of antenatal hydronephrosis.
It may present in both pediatric and adult populations although they tend to have differing etiology. The estimated incidence in pediatric populations is ~1 per 1000-2000 newborns, and there is a male predominance (M:F = 2:1).
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. They are also at high risk of renal injury even by minor trauma.
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.
PUJ obstruction is most commonly unilateral but is reported to be bilateral in ~30% (range 10-49%) of cases 10. There is a recognized predilection towards the left side (~67% of cases).
During embryogenesis, the pelviureteric junction forms usually around the fifth week and the initial tubular lumen of the ureteric bud become recanalized 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.
- idiopathic and often unknown; proposed causes include
- abnormal muscle arrangement at the PUJ
- anomalous collagen collar at PUJ
- ischemic insult to PUJ region
- urothelial ureteral fold
- extrinsic ureter compression or encasement
- crossing vessel (at PUJ)
- idiopathic and often unknown; proposed causes include
- in congenital cases, some renal tract abnormalities are recognized
- 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
Traditionally intravenous urography/pyelography (IVP/IVU) has been performed for assessing for PUJ obstruction. The administration of furosemide may be used to assist in confirming the diagnosis, in particular, to exclude a dilated non-obstructed upper collecting system (so-called 'baggy pelvis').
- will often show a dilated renal pelvis with a collapsed proximal ureter
- Doppler sonography: the obstructed kidneys may show higher resistive indices
May show evidence of hydronephrosis +/- caliectasis with collapsed ureters. Useful for assessing crossing vessels at the PUJ, especially when surgical intervention is planned 5,7.
Renal scintigraphy can quantitate the degree of obstruction:
- 99mTc-MAG3: Agent of choice due to a high extraction rate, which may be necessary for an obstructed system. Diuretic (furosemide) renogram is performed to evaluate between obstructive vs. nonobstructive hydronephrosis. The non-obstructive hydronephrosis will demonstrate excretion (downward slope on renogram) after administration of diuretic from the collecting system. Whereas mechanical obstructive hydronephrosis will show no downward slope on renogram, with retained tracer in the collecting system.
- 99mTc-DTPA: Not the agent of choice because of predominantly glomerular filtration of 99mTc-DTPA. Glomerular function declines earlier and more rapidly than does tubular function in obstructive uropathy. 99mTc-DTPA may be used if the kidney is known to have a good renal function.
Treatment and prognosis
Treatment depends on the underlying cause. In a majority of congenital cases, the condition is benign, and usually, no intervention is required. However, when there is a definitive structural obstruction (commonly adult cases), surgical intervention with pyeloplasty or stenting may be necessary.
General imaging differential considerations include:
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- 5. Quillin SP, Brink JA, Heiken JP et-al. Helical (spiral) CT angiography for identification of crossing vessels at the ureteropelvic junction. AJR Am J Roentgenol. 1996;166 (5): 1125-30. AJR Am J Roentgenol (abstract) - Pubmed citation
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- 7. Rouvière O, Lyonnet D, Berger P et-al. Ureteropelvic junction obstruction: use of helical CT for preoperative assessment--comparison with intraarterial angiography. Radiology. 1999;213 (3): 668-73. Radiology (full text) - Pubmed citation
- 8. Lawler LP, Jarret TW, Corl FM et-al. Adult ureteropelvic junction obstruction: insights with three-dimensional multi-detector row CT. Radiographics. 25 (1): 121-34. doi:10.1148/rg.251045510 - Pubmed citation
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- 11. Wolfgang Dähnert. Radiology Review Manual. (2011) ISBN: 9781609139438