[Clinical description of acute pyelonephritis]

Acute pyelonephritis is frequent. Its usual signs and symptoms comprise renal pain, fever, inflammation, and presence of germs and leukocytes in the urine. Primary acute E. coli pyelonephritis is frequent in the young female and in most cases is a benign condition. Atypical pyelonephritis may be painless, or without high fever, or lacking bacterial growth in the urine owing to previous inappropriate treatment. Severe pyelonephritis is mainly observed in diabetic, alcoholic or immunocompromised patients. In occasional cases, a common form of pyelonephritis may develop to formation of a renal abscess requiring drainage. When secondary to urinary tract abnormalities, pyelonephritis may be complicated with septicaemia and can induce early and severe renal tissue damage. This form warrants early urological treatment. The common pyelonephritis of the young female without previous history of febrile urinary tract infection requires little imaging. Conversely, extensive uroradiological workup is mandatory in the very young and the elderly, in the male, when treatment is not rapidly effective or in case or early relapse. In some cases, pyelonephritis leads to the development of cortical scars, the long-term prognosis of which remains to be determined.