Development of kidney scars after acute uncomplicated pyelonephritis: relationship with clinical, laboratory and imaging data at diagnosis

Background: Acute pyelonephritis is a potential cause of kidney scars. Aim: To evaluate the relationship between clinical, laboratory and imaging data and the development of kidney scars in acute pyelonephritis. Methods: All consecutive patients hospitalized for acute uncomplicated pyelonephritis in our nephrology unit from June 1996 to June 2004 were considered: 58 females, median age 25.6 years (16–52). Diagnosis of pyelonephritis required parenchymal lesions shown by CT or NMR scan. Results: The lesions were bilateral in 17.2% (10/58) patients, unilateral, but multifocal in 81.0% (47/58); at CT or NMR, 65.5% of the lesions were classified as simple, 19% with tendency to colliquation and 15.5% abscessual. The median interval between first symptoms and diagnosis was 5 days (1–25); at referral, only 20.7% had a positive urine culture and 94.8% (55/58) had undergone previous antibiotic treatment. The therapeutic protocol required intravenous therapy for ≥2 weeks, followed by 2–4 weeks of oral therapy. At 6–8 months, the prevalence of kidney scars was 29.3%. Their development was highly correlated with the type of lesions at diagnosis (highest risk with abscessual lesions; uni- and multivariate analysis). No other clinical or laboratory marker (age, fever, positive cultures, levels of acute phase reactants, interval between onset and diagnosis) was correlated with the outcome (scars). Conclusions: The type of lesion at diagnosis of acute uncomplicated pyelonephritis is highly correlated with the development of kidney scars. Further studies are needed to test the therapeutic schedules tailored according to the imaging data.