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Acute pyelonephritis is most common in adult females but can affect people of either sex and any age. Its onset is usually sudden, with symptoms that are often mistaken as the results of straining the lower back. Pyelonephritis is often complicated by systemic infection. Left untreated or unresolved, it can progress to a chronic condition that lasts for months or years, leading to scarring and possible loss of kidney function.
The most common cause of pyelonephritis is the backward flow (reflux) of infected urine from the bladder to the upper urinary tract. Bacterial infections may also be carried to one or both kidneys through the bloodstream or lymph glands from infection that began in the bladder. Kidney infection sometimes results from urine that becomes stagnant due to obstruction of free urinary flow. A blockage or abnormality of the urinary system, such as those caused by stones, tumors, congenital deformities, or loss of bladder function from nerve disease, increases a person's risk of pyelonephritis. Other risk factors include diabetes mellitus, pregnancy, chronic bladder infections, a history of analgesic abuse, paralysis from spinal cord injury, or tumors. Catheters, tubes, or surgical procedures may also trigger a kidney infection.
The bacteria that are most likely to cause pyelonephritis are those that normally occur in the feces. Escherichia coli causes about 85% of acute bladder and kidney infections in patients with no obstruction or history of surgical procedures. Klebsiella, Enter-obacter, Proteus,or Pseudomonas are other common causes of infection. Once these organisms enter the urinary tract, they cling to the tissues that line the tract and multiply in them.
Symptoms of acute pyelonephritis typically include fever and chills, burning or frequent urination, aching pain on one or both sides of the lower back or abdomen, cloudy or bloody urine, and fatigue. The patient may also have nausea, vomiting, and diarrhea. The flank pain may be extreme. The symptoms of chronic pyelonephritis include weakness, loss of appetite, hypertension, anemia, and protein and blood in the urine.
Author Info: Kathleen D. Wright RN, The Gale Group Inc., Gale, Detroit, Gale Encyclopedia of Medicine, 2002
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