A patient presents with right flank pain on percussion at the costovertebral angle. Which structure is MOST likely involved?

• A. Bladder
• B. Appendix
• C. Spleen
• D. Kidney

Answer: (D)

Pain at the costovertebral angle points to kidney involvement. The CVA is the posterior angle where the 12th rib meets the spine, and the kidney sits retroperitoneally just beneath that area. Percussing there that produces flank pain suggests renal parenchymal or collecting system pathology, such as nephritis or obstruction. The other organs—bladder in the pelvis, appendix in the right lower quadrant, and spleen in the left upper quadrant—don’t lie under the CVA and would typically produce pain in different locations or with different exam findings. The kidney’s pain fibers travel with sympathetic nerves to the T10–L1 levels, so renal inflammation or infection characteristically presents as flank pain that can be elicited by percussion at the CVA. The right kidney is slightly lower due to the liver, which helps localize the finding to the right side.