Kidney infection is a general term used to describe infection of the kidney by bacteria, fungi, or viruses. The infecting microbe may have invaded the kidney from the urinary bladder or from the bloodstream. The disease is characterized by fever, chills, back pain, and, often, the symptoms associated with bladder infection.
As the principle part of the urinary system, the kidneys process the fluid component of blood (called plasma) to maintain appropriate water volume and concentrations of chemicals. The waste product formed from this process is called urine. Urine travels from the kidney, through tubes called ureters, to the urinary bladder, and is eliminated from the body through a tube called the urethra. The kidneys and ureters comprise the upper urinary tract, and the bladder and urethra comprise the lower urinary tract.
Kidney infection, also called pyelonephritis and upper urinary tract infection, occurs when microbes, usually bacteria, invade the tissues of the kidney and multiply. One or both kidneys may be infected. Infection originating directly from the bladder is called an ascending infection.
Inflammation occurs in response to the infection. As a result of the infection and inflammation, scarring and other tissue damage may occur. Most cases of acute kidney infection resolve without any permanent kidney damage. In severe cases, kidney damage is so extensive that the kidneys can no longer function, a state called renal failure.
Types of kidney infections:
- Acute pyelonephritis: uncomplicated kidney infection that has a short and relatively severe course.
- Chronic pyelonephritis: long-standing disease associated with either active or inactive (healed) kidney infection.
- Emphysematous pyelonephritis: acute infection associated with gas in and around the kidney. This type almost always occurs in persons with diabetes.
- Pyonephrosis: acute or chronic pyelonephritis associated with blockage of the ureter.
- Renal and perinephric abscesses: abscesses (pockets of pus) in and around the kidney.
Kidney infections occur most often in adult females who are otherwise healthy. Urinary tract infections are uncommon in males until old age, when bladder catheterization and other urinary procedures are more commonly performed.
Causes & symptoms
Kidney infection is usually caused by bacteria, although infection by fungi (yeasts and molds) or viruses does occur. The bacteria Escherichia coli (E. coli) is responsible for about 85% of the cases of acute pyelonephritis. Other common causes include Klebsiella, Enterobacter, Proteus, Enterococcus, and Pseudomonas species. Infection by Proteus species can lead to the formation of stones. E. coli causes only 60% of the acute pyelonephritis cases in the elderly. Kidney infection may also be caused
Certain women are inherently more susceptible to urinary tract infections. Researchers have found that women who have recurrent infections possess certain markers on their blood cells. Also, the bacteria which commonly cause urinary tract infections stick more readily to the vaginal cells of women who have recurrent infections. Other risk factors for kidney disease include:
- bladder catheterization or instrumentation
- urinary calculi (stones)
- urinary tract abnormalities
- urinary tract obstruction
The symptoms of kidney infection include fever, shaking chills, nausea, vomiting, and middle to lower back pain which may travel to the abdomen and groin. This pain may be severe. These symptoms may be preceded or accompanied by those associated with bladder infection—frequent, painful urination.
Infants and young children may show fever, irritability, straining on urination, and urine odor. Fewer than half of newborns have fever associated with kidney infection, which makes diagnosis difficult.
In more than 20% of elderly patients with kidney infection, the presenting symptoms are gastrointestinal or pulmonary (lung). Also, one-third of elderly patients do not develop fever.
Kidney infections can be diagnosed by family doctors, OB/GYN doctors, and urologists (doctors who specialize in the urinary system). The diagnosis of kidney infection is based primarily on symptoms, urinalysis, and urine cultures. Blood tests may also be performed. Approximately 20% of patients have bacteria in the bloodstream, a condition called bacteremia. Urine dipsticks that detect signs of infection are often used right in the doctor's office. Urine would be examined with a microscope for the presence of bacteria and leukocytes (white blood cells). Urine culture would identify which microbe is causing the infection and may also be used to determine which antibiotic would be effective.
Other routine diagnostic procedures to look for signs of infection in the kidney may be used. An x ray of the abdomen may be taken. Ultrasound, which uses sound waves to visualize internal organs, may be used to examine the bladder and kidney. Less routinely performed are intravenous urograms, computerized tomography (CT scan), and scintillation scans.
Delays in the diagnosis and treatment of kidney infection can lead to permanent kidney damage. Anyone who suspects kidney infection should seek professional care immediately. Alternative medicine may be used as an adjunct to the appropriate antibiotic treatment.
Dietary changes which may help to control and prevent kidney infection include:
- Drinking eight to 12 glasses of water daily helps to wash out bacteria (although this may also dilute antibacterial factors in the urine).
- Acidifying the urine by eating few alkaline foods (dairy and soda).
- Following a diet rich in grains, vegetables, and acidifying juices, like citrus.
- Eliminating high-sugar foods (sweet vegetables, fruits, sugar, and honey).
- Drinking unsweetened cranberry juice to acidify the urine and provide the antimicrobial agent hippuric acid. Cranberry capsules can substitute for the juice.
- Ingesting at least one clove of garlic (or up to 1,200 mg garlic as a tablet) daily for its anti-infective properties.
Magnesium may be helpful in treating renal disease. Zinc may boost the immune system. A study in rats with ascending pyelonephritis found that the addition of vitamins A and E to standard antibiotic therapy significantly reduced kidney inflammation as compared to antibiotic treatment alone.
Traditional Chinese medicine treats pyelonephritis with acupuncture, herbals, and patent medicines. The Chinese patent medicine Zhi Bai Di Huang Wan (Anemarrhena, Phellodendron, and Rehmannia Pill) is often used to treat kidney infections and disease and bladder infections. The patient can take eight pills three times daily. Treatment of urinary tract infection often uses one or more of the following herbs in doses of 30 g to 60 g taken once or twice daily (Patients should consult a traditional Chinese medical practioner for the treatment best suited for them.):
Initiating antibiotic therapy as soon as possible is critical to prevent or reduce damage to the kidneys. Historically, all pyelonephritis patients were treated in the hospital. This has been found to be unnecessary in many cases. Responsible patients who have mild kidney infection can be treated at home with antibiotics taken by mouth. Patients with high fever, vomiting, evidence of bacteria in the bloodstream, and/or dehydration would be hospitalized and treated with intravenous (IV) antibiotics and fluids. Severe illness, either with or without complications, would require hospitalization for treatment.
The recommended treatment for acute pyelonephritis is two weeks of therapy with the antibiotic combination trimethoprim/sulfamethoxazole. Fluoroquinolones (Cipro, Noroxin, NegGram), ceftriaxone (Rocephin), or gentamicin are other choices. Fluoroquinolones should not be used by pregnant women or children. With treatment, symptoms normally resolve within two to three days.
Abscesses may be resolved with percutaneous (by a needle through the skin) or surgical drainage. Emphysematous pyelonephritis may be treated with antibiotics; however, surgical removal of the kidney (nephrectomy) may be necessary. Because of the 75% death rate, nephrectomy is the treatment of choice in diabetics with emphysematous pyelonephritis. Urinary stones are eliminated by a percutaneous method which involves stone removal and shock wave treatment.
Antibacterial therapy of kidney infection has a 90% cure rate. Severe or chronic infection can lead to kidney damage and renal failure. Renal failure requires hemodialysis, a process which uses a dialysis machine (an artificial kidney) to process the patient's blood. Patients with severe kidney damage requires kidney transplantation.
Researchers are trying to develop a vaccine for UTIs, but as of early 2000, none are ready for human studies. The key to preventing kidney infection is to promptly treat bladder infection. Measures taken to prevent bladder infection may prevent subsequent kidney infection. These include:
- drinking large amounts of fluid
- reducing intake of sugar
- voiding frequently and as soon as the need arises
- proper cleansing of the area around the urethra (females), especially after sexual intercourse
- acupuncture (effective in preventing recurrent lower UTIs in women)
- avoiding use of vaginal diaphragms and spermicidal jelly (females) for contraception
The primary preventive measure specifically for males is prompt treatment of prostate infections. Chronic prostatitis may go unnoticed but can trigger recurrent UTIs. In addition, males who require temporary catheterization following surgery can be given antibiotics to lower the risk of UTIs.
Kunin, Calvin M. "Pyelonephritis and Other Infections of the Kidney." Urinary Tract Infections: Detection, Prevention, and Management, 5th edition. Baltimore: Willliams & Wilkins, 1997.
Kunin, Calvin M. "Pathogenesis of Infection — The Host Defenses." Urinary Tract Infections: Detection, Prevention, and Management, 5th edition. Baltimore: Willliams & Wilkins, 1997.
Ying, Zhou Zhong and Jin Hui De. "Genitourinary Diseases." In Clinical Manual of Chinese Herbal Medicine and Acupuncture. New York: Churchill Livingston, 1997.
Bennett, Robert T., Richard J. Mazzaccaro, Neeru Chopra, Arnold Melman, and Israel Franco. "Suppression of Renal Inflammation With Vitamins A and E in Ascending Pyelonephritis in Rats." Journal of Urology 161 (1999): 1681-1684.
Roberts, James A. "Management of Pyelonephritis and Upper Urinary Tract Infections." Urologic Clinics of North America 26 (1999): 753-763.