Definition of Pyelonephritis

Pyelonephritis: Bacterial infection of the kidney. Pyelonephritis can be acute (sudden) or chronic (slow, subtle, and stubborn). It is most often due to the ascent of bacteria from the bladder up the ureters to infect the kidneys.

The symptoms of pyelonephritis include flank (side) pain, fever, shaking chills, sometimes foul-smelling urine, urgency (to urinate), frequency (urinating), and general malaise. Tenderness is elicited on gently tapping over the kidney with a fist (percussion).

The laboratory examination of the urine (the urinalysis) reveals white blood cells (pyuria, i.e. pus in the urine) and bacteria in the urine (bacteriuria). There is usually also an increase in circulating white cells in the blood (leucocytosis).

Treatment involves appropriate antibiotics.