What defines pyelonephritis?

Pyelonephritis is specifically defined as the inflammation of the renal parenchyma, which is the functional tissue of the kidneys. This condition is typically caused by a bacterial infection that ascends from the lower urinary tract (such as the bladder) to the kidneys, leading to inflammation and potential damage to the renal structures. The signs and symptoms often include fever, flank pain, and urinary complaints, making a clear distinction from other urinary tract conditions.

In contrast, inflammation of the bladder is referred to as cystitis, and an infection of the urethra is known as urethritis. Kidney stones, while they can lead to obstruction and secondary infection, do not directly define pyelonephritis. Understanding these distinctions is crucial for diagnosing and managing urinary tract infections effectively.