What is pyelonephritis?

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Pyelonephritis is a kidney infection that typically occurs suddenly and severely. It is a type of urinary tract infection that begins in the bladder and spreads to the kidneys. Pyelonephritis makes the kidneys swell and can cause permanent damage without proper treatment.

Isolated instances of pyelonephritis are called acute pyelonephritis. If someone experiences repeated attacks, they might have chronic pyelonephritis. The chronic form of pyelonephritis is most common in children or people with urinary obstructions.

What causes pyelonephritis?

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Pyelonephritis usually begins as a urinary tract infection in the lower urinary tract. Bacteria enter the urinary tract, multiply, and spread to the kidneys. A urinary tract infection can spread to any part of the urinary tract, including the urethra, bladder, ureters, and kidneys. Beyond a urinary tract infection, any severe bloodstream infection can travel to the kidneys and cause pyelonephritis.

There are several conditions that could increase risk of developing pyelonephritis. See the section below regarding risk factors and groups to learn more about which conditions might cause a kidney infection.

What are symptoms of pyelonephritis?

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Pyelonephritis comes on suddenly and severely. The symptoms listed below could develop intensely and without warning. Symptoms typically develop within two days of infection.

Pyelonephritis symptoms include:

  • Cloudy urine
  • Foul-smelling urine
  • Dark urine
  • Blood or pus in the urine
  • Frequent or urgent urination
  • Fever over 102 degrees Fahrenheit
  • Pain in the groin, side, back, or abdomen
  • Vomiting
  • Nausea
  • Fatigue
  • Brain fog
  • Chills

Pyelonephritis symptoms might present differently in adults and children. Adults are more likely than children to experience brain fog as a symptom of pyelonephritis, and it is often the only noticeable symptom. Younger children might only have a high fever.

Chronic pyelonephritis often does not present symptoms at all, and the symptoms that do develop are usually mild.

Are there any risk factors or groups for pyelonephritis?

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Any issue that might obstruct urine flow can cause pyelonephritis. The presence of urine obstructions can help determine risk factors and groups for pyelonephritis.

These risk factors and groups include:

  • Being female. Women typically have a shorter urethra than men. Shorter urethras mean that bacteria can more easily spread from outside of the body to the bladder. Additionally, women’s urethras are in close proximity to the vagina and anus. This proximity provides more chances for bacteria to pass into the bladder. From the bladder, a urinary tract infection can spread to the kidneys. Pregnancy also increases risk of pyelonephritis.
  • Having nerve damage around the bladder. Damage to the nerves or spinal cord can interfere with signals of a bladder infection. If someone is unaware of bladder pain or discomfort, an undetected urinary tract infection can travel to the kidneys and cause permanent damage without raising a red flag.
  • Having vesicoureteral reflux. This condition causes urine to flow from the bladder back into the kidneys and ureters. Vesicoureteral reflux increases risk of pyelonephritis in both children and adults.
  • Having a urinary tract blockage. Interrupting the normal flow of urine can cause pyelonephritis. A urinary tract blockage includes anything that impedes the ability to empty the bladder or reduces the flow of urine. Common urinary tract blockages include kidney stones, an enlarged prostate gland, or an abnormality in the urinary tract’s structure.
  • Having a weakened or compromised immune system. Certain conditions, including HIV and diabetes, can increase risk of pyelonephritis. These conditions impact the immune system, make it difficult to sense a full bladder, and make it difficult to empty the bladder. Neuropathy, or nerve damage, around the bladder limits the ability to sense bladder fullness.
  • Using a urinary catheter. A urinary catheter is a tube that helps move urine from the bladder. People will often use a urinary catheter for a diagnostic test or surgery, while others use urinary catheters full-time. A urinary catheter does not always empty the bladder completely, resulting in the risk of urinary tract infection and pyelonephritis.

Chronic pyelonephritis occurs most often in people with urinary obstructions. A urinary obstruction can come from vesicoureteral reflux, anatomical anomalies, and urinary tract infections. Children are more likely than adults to develop chronic pyelonephritis.

How is pyelonephritis diagnosed?

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Initially, a doctor will assess a patient for a fever and tenderness in the abdomen. If results from those initial checks warrant suspicion of a kidney infection, then the doctor will assess for pyelonephritis using different types of testing.

Testing for pyelonephritis might include:

  • Urine tests. A urine test gives care teams the opportunity to check for blood, pus, concentration, and bacteria in the urine.
  • Imaging. An ultrasound can reveal tumors, cysts, and other potential urinary tract blockages.

How is pyelonephritis treated?

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Pyelonephritis treatment depends on severity. Treatment plans might include:

  • Antibiotics. This is the first line of defense against kidney infections. A urine test will reveal specifics about the type of bacteria found in the urine and help determine which antibiotic will work best. Antibiotics help resolve pyelonephritis symptoms within a few days, although some people will need to take the medication for a week or more. It is important to follow the treatment plan set by a medical professional. Common antibiotics for pyelonephritis include: co-trimoxazole, levofloxacin, ampicillin, and ciprofloxacin.
  • Hospitalization. Some cases of pyelonephritis are so severe that antibiotics will not work. A doctor might admit someone with a severe case of pyelonephritis to the hospital. Hospital treatments include intravenous hydration and antibiotics, typically for 1-2 days. Length of stay depends on severity of the pyelonephritis and how successfully the treatment reduces infection. Hospitalization allows a dedicated care team to track the infection by analyzing blood and urine samples.
  • Surgery. Repeated kidney infections, including cases of chronic pyelonephritis, might necessitate surgery. In extreme cases, surgery can potentially correct structural issues in the kidneys and remove urinary tract blockages. If antibiotics did not work, surgery can drain a resulting abscess.

What are lifestyle changes that could help with pyelonephritis?

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Lifestyle changes can reduce risk of pyelonephritis. Including:

  • Hydrating. Each person needs a different amount of water per day. It is important to speak with a medical professional about recommended daily water intake.
  • Emptying the bladder completely. Do not hold urine for several hours. Stay on the toilet for an extra 1-2 minutes after urinating to make sure the bladder is completely empty.
  • Urinating after sexual intercourse. Bacteria can enter the urinary tract during sex. Urinating after sex flushes out bacteria and helps keep the urinary tract clean. This is an important practice for men and women.
  • Practicing good hygiene. Prevent infections by practicing good hygiene. Wipe front to back after a bowel movement, so that bacteria has a harder time reaching the urethra. Avoid using irritating products near the urethra, including feminine sprays and douches.

Some at-home remedies can supplement a pyelonephritis treatment plan, including:

  • Taking pain medicine. Treat fever and general discomfort using acetaminophen or ibuprofen.
  • Applying heat. Use a heating pad on the back, side, or abdomen to relieve pain.


Should you see a doctor for pyelonephritis?

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Contact a doctor as soon as concerning symptoms develop. Pyelonephritis develops suddenly and intensely. The earlier someone seeks treatment, the sooner a care team can stop the infection from spreading and causing further damage.

What is the outlook for people living with pyelonephritis?

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Pyelonephritis is not necessarily life-threatening, but it can cause permanent damage or even death if left untreated. A week-long antibiotic treatment plan can resolve less severe cases, while hospitalization and surgery might be necessary to treat more severe cases. Simple lifestyle changes can prevent the majority of pyelonephritis cases.

Pregnant women are at increased risk for developing pyelonephritis. Most pregnant women with pyelonephritis will require hospitalization, as the condition impacts the health of not only the mother, but the baby, as well. Symptoms typically resolve within a few days using a hospital’s treatment plan. A urine culture in the first few months of a pregnancy will detect early symptoms of a urinary tract infection and prevent it from spreading further.