Costovertebral angle tenderness is a term used to describe having pain and tenderness in a region of the lower back adjacent to the spine. Often doctors check for the presence of tenderness in this area by tapping patients on their backs. Having pain in this region of the body could signify the presence of diseases such as pyelonephritis, perinephric abscesses, or kidney stones.

In order to fully understand what having costovertebral angle tenderness represents, it helps to understand some of the basic anatomy underlying this area of the body. The ribs, which wrap around the human body, protecting important structures such as the heart and lungs, originate in the spinal column and end in the sternum at the front of the body. Where the ribs and the vertebral column intersect in the region of the lower ribs is known as the costovertebral angle. It is an important area because it marks the spot where the kidneys are typically found.

Doctors often check for costovertebral angle tenderness by tapping their fists on this region of the body. This maneuver was originated by John Benjamin Murphy, an American physician. The test is sometimes referred to as the "kidney punch." If the maneuver elicits pain, positive costovertebral angle tenderness is said to be present. Typically, a doctor would check for tenderness both on the right and left sides of the body.

The presence of costovertebral angle tenderness is most closely associated with the presence of pyelonephritis, an infection of the kidneys. Renal stones, a condition also known as pyelonephritis, can also cause this type of pain. Having an infection or abscess in the area surrounding the kidney could also cause pain or soreness in this region. Other causes of costovertebral angle tenderness could include rib fracture, rashes in the skin overlying the region, or bruising in the area secondary to previous trauma.

One of the most important reasons to check for tenderness at the costovertebral angle is to distinguish between pyelonephritis and urinary tract infections. Pyelonephritis, which involves inflammation and infection of the kidney itself, is often caused by the spread of bacteria from outside the body up the urinary tract through the bladder into the kidneys. Therefore, a simple urinary tract infection affecting the bladder could eventually cause pyelonephritis if not treated. Whereas having a urinary tract infection does not cause costovertebral angle tenderness, pyelonephritis does. The presence of costovertebral angle tenderness therefore helps identify sicker patients who have developed more advanced infections and might require more aggressive treatment.