UMEM Educational Pearls


32 year-old female presents with 5 days of fever, chills, and flank pain. She is hypotensive on presentation and urinalysis shows pyuria. Click here for the non-contrast CT scan. What's the diagnosis and what type of antibiotics should be started empirically?


Answer: Staghorn caliculi secondary to struvite stone. Broad-spectrum antibiotics to cover anaerobic bacteria should be initiated.

  • Staghorn caliculi are upper urinary stones involving both the renal pelvis and at least 2 calyces.
  • Any category of renal stone can form a staghorn calculi, but most are magnesium-ammonium-phosphate stones (i.e., struvite stones); struvite stones are typically associated with urinary tract infections secondary to urease-producing bacteria (e.g., Proteus species).
  • Struvite stones may result in several types of urinary tract infections; perinephric abscess, pyelonephritis, and in severe cases, sepsis.
  • Management includes:
    • Early broad-spectrum antibiotics covering both aerobic and anaerobic bacteria until culture and sensitivities are available
    • Complete removal of stone is necessary (e.g., extracorporeal-shockwave lithotripsy, surgery, etc.)
  • The CT shown here demonstrates a left kidney struvite stone with associated air (green arrows) suggesting an anaerobic infection.


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