Pyelonephritis describes inflammation of which part of the body?

Pyelonephritis specifically refers to the inflammation of the renal pelvis and the kidney itself. This condition is typically caused by a bacterial infection that ascends the urinary tract, impacting both the kidney tissue and the collecting system (the renal pelvis). When an infection occurs in this area, it can lead to symptoms such as fever, flank pain, and urinary changes, which are characteristic of renal involvement.

The other options represent different physiological systems or organs that are not related to pyelonephritis. The uterus and bladder are part of the reproductive and urinary systems, respectively, but do not pertain to kidney inflammation. The lungs and bronchi are associated with respiratory conditions, while the heart and arteries are involved in cardiovascular health. Therefore, understanding the specific organ systems involved clarifies why B is the correct answer in the context of pyelonephritis.