Sonographic measurement of renal pelvis wall thickness as diagnostic criterion for acute pyelonephritis in adults.

PURPOSE: Inflammatory processes may increase the urothelial thickness of the renal pyelon. Purpose of the study was to assess sonographic measurement of pyelon wall thickness (PWT) in adult patients with acute pyelonephritis, chronic urinary tract infection (UTI) and indwelling ureteral stents. MATERIALS AND METHODS: Four study groups (acute pyelonephritis n=50, chronic UTI n=10, indwelling ureteral stents n=10, controls n=25) underwent renal ultrasonography (Acuson Seqouia, Mountain View, CA; 6 MHz Transducer). The renal pyelon was imaged in transverse and longitudinal planes. PWT measurements of patients with acute pyelonephritis were repeated after successful antibiotic treatment. RESULTS: Mean PWT in healthy controls was 1.0 mm+/-0.19. In patients with acute pyelonephritis, PWT was significantly increased to 2.9 mm+/-0.89 (p<0.001). PWT decreased significantly after antibiotic treatment to 1.4 mm+/-0.47 (p<0.001). Kidneys with indwelling stents presented with a PWT of 2.7 mm+/-0.68, kidneys with chronic UTI demonstrated a PWT of 2.8 mm+/-0.62. PWT in these patient groups was significantly greater than PWT in healthy volunteers (p<0.001). The interobserver agreement was excellent (p<0.001). CONCLUSION: PWT is a reproducible diagnostic criterion for acute pyelonephritis. Based upon our experience, we suggest a cut-off value of 2.0 mm to distinguish healthy kidneys from those with urothelium thickened by inflammation. PWT cannot be used to distinguish acute pyelonephritis from chronic inflammation of the urothelium.