Which condition is characterized by an inflammation of the kidneys?

The condition characterized by inflammation of the kidneys is nephritis. This term specifically refers to inflammation that can affect the kidney's glomeruli, tubules, or interstitial tissues, leading to various symptoms and potential complications. Nephritis can result from infections, autoimmune diseases, or exposure to toxins, making it an important condition to recognize in clinical practice.

While other options also refer to inflammatory conditions, they involve different anatomical sites or structures. Cystitis refers to inflammation of the bladder, prostatitis involves inflammation of the prostate gland, and pyelonephritis, although related, specifically refers to inflammation of the kidney due to infection often stemming from the urinary tract. While pyelonephritis is a subset of nephritis focused on infection, "nephritis" encompasses a broader category of kidney inflammation. Therefore, nephritis is the most accurate term specifically for inflammation of the kidneys themselves.