Diagnosing Pyelonephritis in Patients with Perinephric Stranding and a 5mm Mobile Calculus

Clinical Features and Diagnosis

The American College of Radiology suggests that fever, typically >38°C/100.4°F, with systemic toxicity is a required clinical feature for pyelonephritis diagnosis 1, 2
Flank pain and tenderness on examination are also necessary for diagnosing pyelonephritis 1, 2
Pyuria and bacteriuria on urinalysis with positive urine culture are essential for confirming pyelonephritis 1, 2
Elevated inflammatory markers, such as leukocytosis, elevated CRP/ESR, support the diagnosis of pyelonephritis 1, 2

The American College of Radiology recommends contrast-enhanced CT abdomen and pelvis as the gold standard for detecting both the stone and parenchymal changes of acute pyelonephritis, with a sensitivity of 97% for stone detection 1, 2, 3, 4
Noncontrast CT alone can detect the stone and hydronephrosis but cannot adequately assess for pyelonephritis, as parenchymal inflammatory changes require IV contrast for visualization 1, 2, 3, 4
Ultrasound has nearly 100% sensitivity for detecting 5mm stones and hydronephrosis but has significantly lower sensitivity for detecting acute pyelonephritis and renal abscesses compared to CT 1, 2, 4

The American College of Radiology advises against assuming infection based on imaging alone, as perinephric stranding is a nonspecific finding that occurs with simple obstruction from the mobile stone without infection 1, 2
Forniceal rupture from acute obstruction and urine extravasation can also cause perinephric stranding without infection 1, 2
Delaying appropriate imaging can lead to missed diagnoses of complicated pyelonephritis, which requires urgent intervention 1, 2, 3, 4