Kidney Infection (Pyelonephritis)

The kidney. Source: Gray's Anatomy, 1918.

A kidney infection, also called pyelonephritis is a bacterial infection of the kidney and the ducts that carry urine away from the kidney (ureters). This condition usually results from a lower urinary tract infection which ascends to the kidney. Recurrent pyelonephritis can occur in the setting of anatomic abnormalities, the most common of these being vesicoureteric reflux (the persistent backflow of urine from the bladder into the ureters or pelvis of the kidney). A kidney infection is treated with antibiotics.

Types

Pyelonephritis can be further classified as either:

• Acute (sudden development of kidney infection)
• Chronic (a long-standing infection that does not clear)

Signs and Symptoms

Common symptoms of pyelonephritis include:

• Back, side, or groin pain
• An urgent need to urinate (urgency)
• Frequent urination
• Pain or burning during urination
• Fever with Chills (being a very important component)
• Nausea and vomiting
• Pus and/or blood in the urine
• Foul or strong odor to the urine

Causes

Possible causes of kidney infection include the following:

• A bladder infection which ascends to the kidney
• The use of a catheter (to drain urine from the bladder)
• A history of cystoscopy (use of a cystoscope to examine the bladder and urethra)
• Past history of surgery on the urinary tract
• Conditions such as prostate enlargement and kidney stones that prevent the efficient flow of urine from the bladder
• Defects or abnormalities in the urinary tract that block the flow of urine

Diagnosis

Localization of the infection to the kidney is often a clinical diagnosis. Patients with infection in the kidney are more likely to have fever or chills and blood in the urine. Having one or more of the risk factors for kidney infection may help to localize the infection as well.

Exams and tests

• Physical examination may reveal tenderness on palpation (pressing) over the kidney.
• A urinalysis commonly reveals white blood cells (WBCs) or red blood cells (RBCs) in the urine. This is a quick screening test for urinary tract infection.
• A urine culture from a clean catch or urine culture may reveal bacteria in the urine and identify the type of bacteria that are causing the infection. The urinalysis and urine culture do not localize the infection but can confirm that infection is present in the urinary tract.

Underlying abnormalities of the kidney that put a patient at high risk for acute pyelonephritis may be discovered by additional tests and procedures, including the following:

• Intravenous pyelogram (IVP)
• Computed tomography (CT) scan of the abdomen
• Voiding cystourethrogram
• Renal ultrasound
• Renal biopsy ( rarely) and might have to be even avoided because the risk of spreading the infection.

Treatment

The goals of treatment are control of the infection and reduction of symptoms. Acute symptoms usually disappear within 48 to 72 hours after appropriate treatment. A kidney infection is treated with an appropriate antibiotic taken for several weeks. Anatomic abnormalities may need to be surgically treated.

Severely ill patients with kidney infections may be hospitalized until they can take fluids and needed drugs on their own.

Due to the high mortality rate in the elderly population and the risk of complications, prompt treatment is recommended. The elderly, infants, and people with a compromised immune system are at increased risk for developing sepsis (a severe blood infection) and shock. Often, these people will be admitted to the hospital to receive frequent monitoring for potential problems and to receive IV antibiotics, additional IV fluids, and other medications as necessary.

After obtaining a urine culture to identify the bacteria, antibiotics are selected to treat the infection.

Medications

Commonly used oral antibiotics include the following:

• Sulfa drugs such as sulfisoxazole/trimethoprim
• Amoxicillin
• Cephalosporins
• Levofloxacin and ciprofloxacin
• Vitamin C and Mendalamine for prevention of frequent Urinary tract infections

If infections are recurrent, a complete urologic workup may be warranted to look for structural abnormalities. The workup is done by a urologist or nephrologist, doctors who specialize in diseases of the urinary tract.

Prevention

Some lifestyle changes which may decrease the risk of a kidney infection include:

• Drinking plenty of fluids (drinking cranberry juice prevents certain types of bacteria from attaching to the wall of the bladder and may lessen the chance of infection)
• Urinating frequently
• Emptying the bladder after intercourse
• Taking showers rather than bathing
• Wiping front to back (urethra to rectum)
• Avoiding feminine products, perfumed soaps or bubble baths

Chances of Developing Kidney Infection (Pyelonephritis)

Risk factors

Some of the risk factors for developing pyelonephritis are:

• Being female (women have a shorter urethra than men so the infected urine has less distance to travel to the kidney)
• Urinary tract obstruction, such as kidney stones, structural abnormalities of the urinary system and or an enlarged prostate gland (in men)
• A weakened immune system (usually resulting from diseases such as HIV/AIDS, cancer, diabetes or immunosuppressant medicines (such as those taken after organ transplantation
• Neural or spinal cord damage (may affect emptying of the bladder and may blunt the symptoms of a bladder infection and allow it to ascend to the kidneys undetected
• Prolonged use of catheters in the bladder (used for some chronic diseases or after surgery or procedures
• Vesicourethral reflux, a condition which allows urine to travel "backwards" from the bladder through the ureters to the kidneys

Related Problems

Complications

In rare cases, infection in the kidney may spread to the bloodstream. Infection of the bloodstream is a serious condition called sepsis. Sepsis may cause shock and can ultimately cause death.

Permanent kidney damage can result from kidney infections when they are chronic, when they occur in a transplanted kidney, or when multiple infections occur during infancy or childhood. Acute kidney injury (acute renal failure) may occur when an infection is severe enough to result in shock (low blood pressure). Severe episodes of acute kidney injury may result in permanent kidney damage and lead to chronic kidney disease.

Pyelonephritis during pregnancy can cause preterm delivery and low birth weight babies. Women are often hospitalized when a kidney infection occurs during pregnancy.

Expected Outcome

Most people recover from a kidney infection within a few weeks if treated with the appropriate antibiotics.

Clinical Trials

A list of ongoing clinical trials is available here

Research

• The use of thin needle aspiration biopsy of the kidneys to diagnose acute pyelonephritis is discussed. This method is shown to be an effective diagnostic tool after 24 hours of ineffective treatment. ^[1]
• A study published in Pediatrics concludes that early (within the first 24 hours) and appropriate treatment for pyelonephritis decreased the likelihood of kidney involvement but did not decrease the incidence of scarring of the kidneys. ^[2]
• A recent study from Iran found that rats treated with allopurinol and Vitamin E at the onset of fever had less renal damage with pyelonephritis. ^[3]
• The use of prophylactic antibiotics in children with vesicoureteral reflux was evaluated and was not found to decrease the incidence of kidney damage in children less than 30 months of age and with reflux grades II through IV. ^[4]

History

Etymology

The word pyelonephritis is derived from the Greek puelos (basin), nephro(kidney), and itis (disease).

References

1. ↑ No authors listed. Thin needle aspiration biopsy of the kidneys in diagnosis of acute pyelonephritis. Urologiia. 2007 Nov-Dec;(6):29-31. Abstract
2. ↑ Doganis D, Siafas K, Mavrikou M, et al. Does early treatment of urinary tract infection prevent renal damage? Pediatrics. 2007 Oct;120(4):e922-8. Epub 2007 Sep 17. Abstract | Full Text
3. ↑ Sadeghi Z, Kajbafzadeh AM, Tajik P, Monajemzadeh M, Payabvash S, Elmi A. Vitamin E administration at the onset of fever prevents renal scarring in acute pyelonephritis. Pediatr Nephrol. 2008 Sep;23(9):1503-10. Epub 2008 Jun 4. Abstract
4. ↑ Pennesi M, Travan L, Peratoner L. Is antibiotic prophylaxis in children with vesicoureteral reflux effective in preventing pyelonephritis and renal scars? A randomized, controlled trial. Pediatrics. 2008 Jun;121(6):e1489-94. Epub 2008 May 19. Abstract

External Links

American Urological Association Foundation

UrologyHealth.org