Roughly 250,000 kidney infections (called pyelonephritis) occur each year in the U.S., according to an article in the "American Family Physician" journal by Kalyanakrishnan Ramakrishnan, M.D., and Dewey C. Scheid, M.D., M.P.H. In most cases, bacteria enter the urinary system through the urethra (the tube that carries urine out of the body) and travel up the urine stream to infect the kidney tissue. Bacterial abscesses in or surrounding the kidney are less common forms of kidney infection than pyelonephritis. Approximately one-third of pyelonephritis cases are subclinical--meaning they do not cause typical symptoms, states Ramakrishnan. However, most kidney infections develop rapidly over several hours and present with symptoms that point to the kidney as the source of infection. Diabetes, pregnancy and structural abnormalities of the urinary tract increase the risk for kidney infection.
Fever and Shaking Chills
Pyelonephritis usually causes a high fever and shaking chills. The typical fever is 103 Fahrenheit (39.4 Celsius) or higher. Flushing or increased redness of the skin often accompanies high fever. Elderly people with pyelonephritis may not have a fever.
Flank and Abdominal Pain
Pain is a common symptom of kidney infection and ranges from mild to severe. It is typically a dull, constant pain experienced in the side of the abdomen or the back, between the ribs and the hip. The pain is usually greater on one side, but it may be more generalized. Tenderness is commonly present on physical examination and is characteristically aggravated by tapping on the back at the junction of the spine and ribs. This is called costovertebral angle tenderness. Pain that extends into the groin or down the leg may suggest an abscess around the kidney, says MedlinePlus.
Urinary Urgency, Frequency and Pain
Pyelonephritis commonly causes urinary urgency--a sudden, overwhelming urge to urinate that is difficult to delay. This is often accompanied by increased urinary frequency and burning pain with urination. The urine may be cloudy with a strong, foul odor. It may contain blood, making the urine appear pink or brown.
Loss of Appetite, Nausea and Vomiting
Loss of appetite is common with pyelonephritis. Nausea and vomiting may also be present, ranging from mild to severe.
Malaise, Weakness and Fatigue
Pyelonephritis typically causes an overall sense of being unwell--a symptom called malaise. This is often accompanied by a profound lack of energy (fatigue) and weakness.
References
- AAFP: Diagnosis and Management of Acute Pyelonephritis in Adults
- "Harrison's Principles of Internal Medicine, 16th Edition"; Anthony S. Fauci, M.D., et al; 2004
- Cleveland Clinic: Kidney Infections
- National Kidney and Urologic Diseases Clearinghouse: Pyelonephritis (Kidney Infection) in Adults
- Mayo Clinic: Kidney Infection
