What condition is characterized by an infection and inflammation of the kidneys?

Pyelonephritis is characterized by both infection and inflammation of the kidneys, specifically affecting the renal pelvis and the kidney tissues. This condition typically arises from an ascending urinary tract infection, where bacteria travel from the lower urinary tract to the kidneys. The acute form of pyelonephritis presents with symptoms such as fever, flank pain, and signs of systemic infection, while chronic pyelonephritis may result in scarring and damage to the kidney tissues over time.

In contrast, an intrarenal abscess refers to localized collections of pus within the kidney due to infection but does not encompass the generalized infection and inflammation associated with pyelonephritis. A perinephric abscess occurs outside of the kidney within the perinephric space, often a complication of serious underlying infections, and does not directly involve the kidney's parenchyma itself. Nosocomial infection refers to infections acquired in a healthcare setting, which could include pyelonephritis but is not specific to the kidneys or to kidney inflammation.

Given the specific definition and symptoms associated with pyelonephritis, it clearly stands out as the correct answer regarding the condition described in the question.