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Pelviureteric junction (PUJ) obstruction
Patient Data

AGE: Child

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Coronal Heavily-weighted T2 sequence

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Grade III left hydronephrosis, with ballooned renal pelvis and abrupt narrowing at pelviureteric junction. The left ureter is not dilated.

Case Discussion
This child was found to have a left sided pelviureteric junction obstruction. 

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 pelviureteric junction 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 1,000-2,000 newborns, and there is a male predominance (M:F = 2:1).

in congenital cases, some renal tract abnormalities are recognized
renal duplication
multicystic dysplastic kidneys
horseshoe kidney or 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
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. They are also at high risk of renal injury even by minor trauma.

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

Pelviureteric junction obstruction is most commonly unilateral but is reported to be bilateral in ~30% (range 10-49%) of cases . 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 pelviureteric junction area is the last to recanalize. Inadequate canalization is thought to be the main embryological explanation of a pelviureteric junction obstruction. Extrinsic obstructions secondary to bands, kinks, and aberrant vessels also are commonly encountered.

Interestingly, research has failed to identify any anatomically-discrete pelviureteric junction although physiologically there is evidence of a sphincter-like action in this region .

1. Esteves FP, Taylor A, Manatunga A et-al. 99mTc-MAG3 renography: normal values for MAG3 clearance and curve parameters, excretory parameters, and residual urine volume. AJR Am J Roentgenol. 2006;187 (6): W610-7. doi:10.2214/AJR.05.1550 - Pubmed citation
2. Senac MO, Miller JH, Stanley P. Evaluation of obstructive uropathy in children: radionuclide renography vs. the Whitaker test. AJR Am J Roentgenol. 1984;143 (1): 11-5. AJR Am J Roentgenol (abstract) - Pubmed citation
3. Neri E, Boraschi P, Caramella D et-al. MR virtual endoscopy of the upper urinary tract. AJR Am J Roentgenol. 2000;175 (6): 1697-702. AJR Am J Roentgenol (full text) - Pubmed citation

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