A 22-year-old woman reports recurrent episodes of severe left flank pain with vomiting, triggered by heavy fluid intake and relieved by lying down. Ultrasound shows left hydronephrosis with a normal calibre ureter. Which single investigation best confirms the functional significance of the pelviureteric junction obstruction?

• A Non-contrast CT KUB
• B Micturating cystourethrogram
• C Diuretic (frusemide) renography with Tc-99m MAG3 ✓
• D Retrograde pyelography alone

Explanation

The history of pain precipitated by a diuresis and relieved by rest is typical of Dietl crisis in intermittent pelviureteric junction obstruction. A diuretic renogram assesses differential function and washout of tracer after frusemide: impaired washout (a prolonged half-time, conventionally more than 20 minutes) confirms a functionally significant obstruction. CT defines anatomy but not function, MCUG excludes vesicoureteric reflux rather than PUJ obstruction, and retrograde pyelography alone gives anatomical detail only.

Reference: Campbell-Walsh Urology, 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.