Colonic manometry is used to study how the colon is working. A manometry catheter is placed in the colon (large intestine). The catheter is a thin, flexible tube that is used to measure how the muscles and nerves of the colon are working. The catheter is either placed by colonoscopy or in interventional radiology. The catheter is attached to a computer that records the strength and coordination of muscle contractions in the colon.