Kidney (Renal) Infection (Pyelonephritis)
Infection of one or both kidneys by bacteria is the condition called pyelonephritis.
What happens under normal conditions?
The kidneys function to remove waste products from your body as urine. Urine travels from the kidneys to the bladder where it is excreted via the urethra. The kidneys in their healthy state are sterile, that is they are not infected with bacteria. However, bacteria can infect the kidneys, usually by entering the urethra and ascending into the bladder (causing cystitis or urinary tract infection) and from the bladder continuing their ascent into the kidneys.
Cystitis is very common in females, occurring in 1-3% of adult women per year. Extension of a bladder infection to the kidneys to cause pyelonephritis is less common (about 1 in every 30 cases of urinary tract infection) but more severe. Pyelonephritis risk is increased during pregnancy, with obstruction of the urinary system (from a kidney stone for example), with abnormalities of the urinary system (seen in young girls but also in adults due to diverticula and other abnormalities), with diabetes, and with a weakened immune system.
What are the signs of pyelonephritis?
The symptoms of pyelonephritis are pain and tenderness in the flank (the part of the back between the ribs and the hip) with fever, and usually with frequent, urgent and/or painful urination. Nausea and vomiting are common. Much less common are lightheadedness, confusion or loss of consciousness due to sepsis and shock (this can occur if bacteria enter the bloodstream from the kidney) in the most severe form of pyelonephritis.
Because it can be life threatening it is important for you to seek immediate medical care should you have symptoms that suggest pyelonephritis. Many other problems in the pelvis and abdomen can cause symptoms that mimic pyelonephritis, such as kidney stones or appendicitis for example; so one of the first steps that your health care provider will take is to determine if your urine is infected.
Why does pyelonephritis happen?
Pyelonephritis usually happens because bacteria enter the urethra where they travel to the bladder to cause cystitis and from there into the kidney. Cystitis is very common in females, occurring in 1-3% of adult women per year. Extension of a bladder infection to the kidneys to cause pyelonephritis is less common (about 1 in every 30 cases of urinary tract infection) but more severe. Pyelonephritis risk is increased during pregnancy, with obstruction of the urinary system (from a kidney stone for example), with abnormalities of the urinary system (seen in young girls but also in adults due to diverticula and other abnormalities), with diabetes, and with a weakened immune system.
What are treatment options for pyelonephritis?
Pyelonephritis is treated with antibiotics. In many cases orally administered antibiotics will suffice, but with severe infection and/or with nausea and vomiting that precludes taking medicines by mouth hospitalization and intravenous antibiotics may be required until the patient recovers enough to take oral antibiotics. In order to eradicate the infection and prevent relapse a prolonged treatment course is required, usually a total of 2 weeks or more of antibiotics. Surgery may be needed if an obstruction in the urinary track is discovered (most patients when admitted to the hospital for pyelonephritis will receive an ultrasound examination of the kidneys to look for obstruction).
What can be expected after treatment for Pyelonephritis?
Improvement in the symptoms is seen within one to several days with effective antibiotic therapy in the absence of obstruction. If there is obstruction then a urologic procedure to relieve the obstruction (due to a stone or a structural abnormality in the urinary tract) is usually required for treatment. Even though the symptoms are gone within several days, completion of the entire two or more week treatment with antibiotics is required to prevent the infection from relapsing.
In the case of frequent recurrences of pyelonephritis a small dose of antibiotic may be administered every day to prevent recurrences.
Frequently asked questions:
Will pyelonephritis damage the kidneys? Yes untreated pyelonephritis can damage the kidneys and lead to renal insufficiency or less commonly complete renal failure. This can occur both due to direct infection-related damage of the kidney as well as secondary damage from inadequate blood flow to the kidney if sepsis occurs.
Are the bacteria that cause pyelonephritis resistant to antibiotics? Yes the bacteria can be resistant to some antibiotics, but it would be very unusual for it to be resistant to all antibiotics. Both urine and blood cultures are taken prior to starting antibiotics; these can help the health care provider to change the therapy based on the sensitivity of the infecting bacteria to different antibiotics.
What can I do to avoid getting pyelonephritis? Women should wipe from the front to the back after having a bowel movement, as this will help to prevent the introduction of the bacteria that cause cystitis and pyelonephritis into the urethra. Urinating after sexual intercourse may help to flush out any bacteria introduced into the urethra. The use of forms of contraception other than diaphragms and spermicidal foam may help, as these kinds of contraception can cause more frequent urinary tract infection.
What if I am pregnant? Urinary tract infections during pregnancy are dangerous for both the mother and baby and should be treated immediately. There are many antibiotics that are safe to use even during pregnancy that can cure the infection.
Reviewed: January 2011
Last updated: April 2013