Pyelonephritis is an infection of the kidney and the ureters, the ducts that carry urine away from the kidney.

Urinary tract infection - complicated; Infection - kidney; Complicated urinary tract infection; Kidney infection

Pyelonephritis most often occurs as a result of urinary tract infection, particularly when there is occasional or persistent backflow of urine from the bladder into the ureters or an area called the kidney pelvis. See: Vesicoureteric reflux

Pyelonephritis can be sudden (acute) or long-term (chronic).

• Acute uncomplicated pyelonephritis is the sudden development of kidney inflammation.
• Chronic pyelonephritis is a long-standing infection that does not go away.

Pyelonephritis occurs much less often than a bladder infection, although a history of such an infection increases your risk. You're also at increased risk for a kidney infection if you have any of the following conditions:

• Backflow of urine into the ureters or kidney pelvis
• Kidney stones
• Ostructive uropathy
• Renal papillary necrosis

You are also more likely to get a kidney infection if you have a history of chronic or recurrent urinary tract infection, especially if the infection is caused by a particularly aggressive type of bacteria.

Acute pyelonephritis can be severe in the elderly and in people who are immunosuppressed (for example, those with cancer or AIDS).

Images

Kidney anatomy

Kidney - blood and urine flow

Tuberculosis in the kidney

Anatomical landmarks, back view

Anatomical landmarks, side view

Review Date: 09/18/2008
Reviewed By: Linda Vorvick, MD, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)