Acute Pyelonephritis

Description of the Disease

Acute pyelonephritis is a bacterial infection of the kidneys. In most cases, the infection begins in the lower urinary tract, such as the bladder or urethra, and spreads upward to the kidneys (ascending infection). Less commonly, bacteria reach the kidneys through the bloodstream (hematogenous spread), which may occur in individuals with bloodstream infections, including those associated with infected prosthetic heart valves or joint prostheses.

Acute pyelonephritis is a common condition, affecting approximately 15 out of every 10,000 people each year. Women, particularly those between 15 and 30 years of age, are affected several times more often than men.

Cause of the Disease

The most common cause of acute pyelonephritis is a bacterial infection. In more than 90% of ascending infections, the causative organism is Escherichia coli. Other bacteria may also cause the disease. Viral pyelonephritis is rare.

Risk Factors

Several factors increase the risk of developing acute pyelonephritis, including:

• Female sex, due to anatomical factors that facilitate bacterial entry into the urinary tract.
• Urinary tract obstruction, such as kidney stones, which can cause urine stasis and promote bacterial growth.
• Pregnancy.
• A weakened immune system caused by certain medications or conditions such as HIV infection.
• Diagnostic or therapeutic procedures involving the urinary tract, including urinary catheterization.

Symptoms

Common symptoms of acute pyelonephritis include:

• Fever, usually above 38°C.
• Chills.
• Flank pain.
• Abdominal pain.

Additional symptoms may include nausea, vomiting, and general weakness.

Diagnosis

Diagnosis is based on the patient’s symptoms, medical history, and laboratory findings. Urinalysis typically reveals leukocytes, bacteria, erythrocytes, and small amounts of protein. A urine culture is performed to identify the causative organism and determine its antibiotic susceptibility.

Treatment

Acute pyelonephritis is a potentially serious infection because it can lead to complications such as sepsis or permanent kidney damage. Patients with severe disease often require hospitalization. Empirical antibiotic therapy should be started promptly and adjusted if necessary once urine culture results become available. Adequate fluid intake is recommended to maintain urine output and support recovery.

Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology