Differential Diagnosis for Mild Left Perinephric Fat Stranding on CT in a Patient with Flank Pain and Fever
- Single Most Likely Diagnosis
- Pyelonephritis: This is the most likely diagnosis given the patient's symptoms of flank pain and fever, along with the imaging finding of mild left perinephric fat stranding. Pyelonephritis is an infection of the kidney, and perinephric fat stranding can indicate inflammation or infection in the perinephric space.
- Other Likely Diagnoses
- Nephrolithiasis (Kidney Stones): Kidney stones can cause flank pain and may lead to secondary infection or inflammation, resulting in perinephric fat stranding.
- Urinary Tract Infection (UTI) with Extension: A UTI that extends to the upper urinary tract can cause symptoms similar to pyelonephritis and may show perinephric fat stranding on imaging.
- Do Not Miss Diagnoses
- Renal Abscess: Although less common, a renal abscess is a serious condition that requires prompt treatment. It can present with similar symptoms and imaging findings, making it crucial not to miss.
- Septic Emboli: In patients with a history of intravenous drug use or certain types of infections, septic emboli to the kidney can cause perinephric fat stranding and must be considered to avoid missing a potentially life-threatening condition.
- Rare Diagnoses
- Renal Cell Carcinoma with Secondary Infection: Although rare, a renal cell carcinoma can become secondarily infected, leading to symptoms and imaging findings that mimic more common conditions like pyelonephritis.
- Xanthogranulomatous Pyelonephritis: This is a rare form of chronic pyelonephritis that can cause perinephric fat stranding and is often associated with long-standing urinary tract obstruction and infection.
- Extramedullary Hematopoiesis: In patients with chronic anemia or myeloproliferative disorders, extramedullary hematopoiesis can occur in the perinephric fat, potentially causing stranding on CT scans.