Kidney infection, also called pyelonephritis, is an infection that starts in the lower urinary tract--urethra or bladder--and spreads to the kidneys, according to the Mayo Clinic. Pyelonephritis may be acute--short-term--or chronic, meaning that it does not go away. The acute form causes more severe symptoms; the signs of chronic pyelonephritis are more vague. Patients with chronic pyelonephritis almost always have anatomical abnormalities that obstruct urine flow, according to the Merck Manual. Chronic pyelonephritis can cause permanent kidney damage and, rarely, blood poisoning.
Pain
Some patients with chronic pyelonephritis have a history of an acute kidney infection but most do not, according to the Merck Manual. Acute kidney infections cause a dull, aching pain in the back, abdominal, groin or flank, along with a burning sensation when urinating. The symptoms of a chronic kidney infection are vague. Some patients complain of pain in the abdomen or flank but others do not experience pain.
Malaise
Malaise--feeling generally ill--and a loss of appetite may occur in patients with chronic pyelonephritis, according to the Merck Manual. Other patients, however, do not experience these symptoms.
Fever
In contrast to the high fevers, chills or night sweats of an acute attack of pyelonephritis, chronic pyelonephritis may cause a fever that comes and goes or none at all, according to the Merck Manual. Rarely, fever is due to kidney abscesses caused by a rare form of chronic kidney infection called xanthogranulomatous pyelonephritis, or XPN. XPN is a complication of kidney obstruction due to kidney stones.
Renal Mass
XPN is a rare complication of kidney obstruction due to kidney stones, according to the Merck Manual. Most XPN patients are middle-aged women with a history of frequent urinary tract infections, but children may also have the disease. The affected kidney enlarges, becomes scarred and sometimes develops abscesses. On physical examination, a mass in the kidney can almost always be felt.
