Inflammation of the kidney (see KIDNEYS), usually the result of bacterial infection. The inflammation may be acute or chronic. Acute pyelonephritis comes on suddenly, is commoner in women, and tends to occur when they are pregnant. Infection usually spreads up the URETER from the URINARY BLADDER which has become infected (CYSTITIS). Fevers, chills and backache are the usual presenting symptoms. SEPTICAEMIA is an occasional complication. ANTIBIOTICS are prescribed according to the causative organism's sensitivity.

Chronic pyelonephritis may start in childhood, and is often associated with backflow of urine from the bladder into one of the ureters – perhaps because of a congenital deformity of the valve where the ureter drains into the bladder. Constant urine reflux results in recurrent infection of the kidney and damage to its tissue. Full investigation of the urinary tract is essential and, if an abnormality is detected, surgery may well be required to remedy it. HYPERTENSION and renal failure may be serious complications of pyelonephritis (KIDNEYS, DISEASES OF).