Pyelonephritis
Pyelonephritis is a kidney infection that occurs when bacteria travel from the bladder or ureters into the kidneys, causing inflammation and swelling. It can range from mild to severe and may lead to fever, flank pain, nausea, or urinary symptoms. Some cases become complicated, especially in individuals with kidney stones, urinary obstruction, diabetes, or weakened immune systems. Imaging helps determine the severity of infection and identify any underlying causes.
What is it?
Pyelonephritis develops when bacteria enter the kidneys, causing infection and inflammation. Most cases begin as a lower urinary tract infection that spreads upward. The kidneys may become swollen, and the infection can create areas of decreased blood flow or small pockets of inflammation, which may be visible on imaging.
CT imaging is highly sensitive for diagnosing pyelonephritis, showing characteristic changes such as swelling, streaky inflammation, or reduced enhancement of infected areas. Ultrasound may show swelling or obstruction but can be less sensitive for subtle infections. Urine and blood tests help confirm the diagnosis and guide treatment.
Important to Know
Most kidney infections improve with prompt treatment, but delayed or severe cases can lead to complications such as abscess formation, sepsis, or kidney damage. People with diabetes, stones, or structural kidney issues are more prone to severe or recurrent infections.
Red flag symptoms include high fever, severe flank pain, vomiting, confusion, or signs of dehydration. These may indicate a more serious infection requiring urgent medical attention. Follow-up imaging may be recommended if symptoms do not improve or if complications are suspected.