A 4-year-old girl has her first febrile UTI. DMSA scan shows an area of reduced uptake in the right upper pole. What does this finding represent acutely, and what is its clinical significance?
- A Renal scar — indicates prior permanent parenchymal damage from old infection
- B Vesicoureteral reflux — DMSA always diagnoses reflux directly
- C Acute pyelonephritis — acutely reduced uptake indicates active focal infection; if scan is repeated at 4–6 months and persists, it indicates a scar ✓
- D Renal tumor — requires MRI for characterization
Correct answer: C. Acute pyelonephritis — acutely reduced uptake indicates active focal infection; if scan is repeated at 4–6 months and persists, it indicates a scar
Explanation
DMSA (dimercaptosuccinic acid) scintigraphy is the gold standard for detecting both acute pyelonephritis and renal scarring. In the acute setting (within weeks of UTI), reduced uptake represents acute pyelonephritis/focal nephritis. The scan should be repeated after 4–6 months — persistent defects at that point confirm renal scarring (permanent). This distinction matters because acute changes are potentially reversible with appropriate antibiotic treatment. DMSA does not directly diagnose VUR (that requires MCUG/voiding cystourethrogram).
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.