A 30-year-old woman with flank pain and rigors has ultrasound showing gross hydronephrosis with echogenic debris in the collecting system of the left kidney. Blood cultures are positive for Escherichia coli. After antibiotics are started, the immediate next step is:
- A Urgent percutaneous nephrostomy to drain the infected collecting system ✓
- B Extracorporeal shock wave lithotripsy of the obstructing calculus
- C Elective ureteroscopy after two weeks of oral antibiotics
- D CT-guided aspiration of the renal cortex
Correct answer: A. Urgent percutaneous nephrostomy to drain the infected collecting system
Explanation
Obstructed infected kidney, or pyonephrosis, is a urological emergency because pressure in the collecting system prevents antibiotics reaching the pus and permits rapid septicaemia. Urgent decompression by percutaneous nephrostomy, or ureteric stenting if feasible, is required alongside parenteral antibiotics. Lithotripsy is contraindicated in active infection, and delayed instrumentation risks worsening sepsis. Aspirating cortex does not drain the collecting system.
Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.