Abdomen / Pelvis for Friday, April 11th, 2025

History

8 year old boy with several years of intermittent left sided abdominal pain, comes to ER with nausea, vomiting.

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Question

What is the diagnosis?

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Correct answer

left UPJ obstruction

Discussion

This is a case of left ureteropelvic junction obstruction, evident as enlarged left renal shadow on KUB and marked pelvicaliectasis on renal ultrasound.  There is disproportionate enlargement of the renal pelvis and no hydroureter (not shown). The degree of dilation may wax and wane over time, causing intermittent symptoms that may resolve spontaneously.  The obstruction may be caused by a crossing vessel at the UPJ or be due to intrinsic stricture, abnormal muscular anatomy, or abnormal innervation.  Patient went on to have a Tc 99m MAG3 Lasix scan which showed obstructive physiology and left renal function of 28%.  An intra-op retrograde ureterogram showed tortuous proximal ureter and abrupt caliber change at the UPJ, likely due to crossing vessel.  Patient had robotic assisted UPJ repair with dismembered pyeloplasty circumventing the crossing vessel.

Differential diagnosis

Multicystic dysplastic kidney would not typically have this uniform rind of cortex.  The remaining renal parenchyma is typically echogenic and the kidney usually involutes over time, becoming small/unrecognizable by 8 years of age.  Cysts in MCDK are non-communicating and the largest cyst is seldom in the expected position of the renal pelvis. The spleen is not enlarged on the ultrasound, though the KUB report did include splenomegaly in the differential. Pancreatic cysts may have an intermittent clinical course, but these ultrasound images do not show a pancreatic origin. 

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References

• https://app.statdx.com/document/ureteropelvic-junction-obstruction/47c0e8be-a45e-452f-854b-05e7aa58ba3d?term=UPJO%20pediatric&searchType=documents&category=All&documentTypeFilters=all