Differential Diagnosis for Flank Pain with Foul Smelling Urine and Normal Retroperitoneal US
- Single Most Likely Diagnosis
- Pyelonephritis: This is a likely diagnosis given the symptoms of flank pain and foul-smelling urine, which suggest an upper urinary tract infection. The normal retroperitoneal ultrasound does not rule out pyelonephritis, as it primarily affects the renal parenchyma and collecting system, which may not be visible on ultrasound.
- Other Likely Diagnoses
- Urinary Tract Infection (UTI) with urethritis or cystitis: While the flank pain might suggest upper urinary tract involvement, the foul-smelling urine could also be due to a lower urinary tract infection. The normal ultrasound does not exclude this possibility.
- Kidney Stone (with or without infection): Although the ultrasound is normal, small stones or those not causing significant obstruction might not be visible. The presence of infection could explain the foul-smelling urine.
- Do Not Miss Diagnoses
- Septic Pyelonephritis or Urosepsis: These conditions are life-threatening and require immediate intervention. The presence of flank pain and foul-smelling urine, even with a normal ultrasound, necessitates consideration of these diagnoses, especially if the patient shows signs of sepsis.
- Emphysematous Pyelonephritis: A rare but serious condition, especially in diabetic patients, characterized by gas formation in the kidney due to infection. It can be life-threatening and requires prompt diagnosis and treatment.
- Rare Diagnoses
- Xanthogranulomatous Pyelonephritis: A rare form of chronic pyelonephritis that can cause flank pain and foul-smelling urine. It is often associated with long-standing urinary tract obstruction and infection.
- Malacoplakia: A rare inflammatory condition that can affect the urinary tract and cause symptoms similar to those of a urinary tract infection, including foul-smelling urine.