Transverse section, showing the relations of the capsule of the kidney.
Image of a human back
Costovertebral angle tenderness (CVAT), also known as Murphy's punch sign (Latin: succusio renalis), is a medical test in which pain is elicited by percussion of the area of the back overlying the kidney (the costovertebral angle, an angle made by the vertebral column and the costal margin). The test is positive in people with an infection around the kidney (perinephric abscess), pyelonephritis or renal stone. Because the kidney lies directly below this area, known as the costovertebral angle, tapping disturbs the inflamed tissue, causing pain.