Pyelonephritis is a kidney infection caused by bacteria that lead to kidney inflammation. Common symptoms include severe lower back pain, frequent urination, fever, malaise, and pelvic pain.

This infection usually develops when a urinary tract infection is not treated properly and spreads through the ureters to the kidneys. It can also result from the use of a urinary catheter or the presence of kidney stones.

Treatment for pyelonephritis should begin as soon as possible with a nephrologist or primary care doctor. Treatment typically involves antibiotics to eliminate the bacteria and prevent complications such as kidney damage or even loss of kidney function.

Main symptoms

The main symptoms of pyelonephritis include:

Severe lower back, pelvic, or abdominal pain
Burning sensation when urinating
Frequent urge to urinate
Cloudy, reddish, pinkish, or foul-smelling urine
High fever, chills, and excessive sweating
Nausea and vomiting
Shaking or general malaise

As bacteria multiply in the kidneys, severe inflammation can cause progressive loss of kidney function. This may lead to kidney injury and, in more serious cases, kidney failure.

Research suggests that people with pyelonephritis and acute kidney injury are at greater risk of developing chronic kidney disease, especially when kidney damage is severe.

Confirming a diagnosis

Pyelonephritis is diagnosed by a nephrologist or primary care doctor based on symptoms, physical exam, and test results.

Tests may include a urinalysis to detect red blood cells, white blood cells, or bacteria, and a urine culture to identify the bacteria causing the infection. This helps determine the most effective antibiotic.

A CT scan may also be recommended to confirm the diagnosis, identify the cause, and check for complications such as kidney stones, renal abscesses, or ureter obstruction.

Types of pyelonephritis

Pyelonephritis can be classified into two types:

1. Acute pyelonephritis

Acute pyelonephritis develops suddenly with intense symptoms and usually improves within a few days or weeks when treated properly.

This type may temporarily impair kidney function, but the damage is often reversible if treatment is started promptly.

2. Chronic pyelonephritis

Chronic pyelonephritis is caused by recurrent bacterial infections that are not fully treated.

This leads to ongoing kidney inflammation and serious damage that can cause acute kidney injury, progress to chronic kidney disease, and eventually result in end-stage renal disease if not treated.

Possible causes

The main causes of pyelonephritis are:

Untreated urinary tract infection
Use of a urinary catheter
Bladder motility problems
Kidney stones
Enlarged prostate

Pyelonephritis can also develop after urinary tract surgery or due to vesicoureteral reflux.

It is more common in women due to the shorter distance between the urethra and the anus, which makes infections more likely. It also occurs more easily in people with weakened immune systems, such as those with diabetes, immunosuppression, or advanced age.

Treatment options

Treatment for pyelonephritis should be guided by a nephrologist or primary care doctor. The goal is to relieve symptoms and eliminate the bacteria causing the infection.

The main treatment options are:

1. Medications

Antibiotics are the primary treatment for pyelonephritis, prescribed according to the type of bacteria involved. They should be started as quickly as possible to prevent kidney damage and stop the infection from spreading into the bloodstream, which can cause sepsis.

Pain relievers may also be recommended to ease discomfort. In some cases, anti-inflammatory drugs can be used, but with caution, as they may increase the risk of acute kidney injury.

2. Surgery

If the infection is caused by an obstruction or a kidney malformation, surgery may be necessary to correct the problem.

3. Dialysis

In cases of chronic pyelonephritis with severe kidney damage leading to kidney failure, dialysis may be required in addition to antibiotics. Dialysis helps filter the blood when the kidneys are no longer functioning effectively.

Kidney function may partially or fully recover after treatment, depending on the extent of the damage.

Possible complications

If untreated, acute pyelonephritis can increase the risk of serious complications, such as:

Sepsis
Kidney abscess
Kidney failure
High blood pressure
Chronic pyelonephritis

Pyelonephritis: Symptoms, Diagnosis, Types, Causes & Treatment