This type of testing assesses bladder and sphincter function, including the pressure and volume of urine in the bladder, and the pressure and flow of urine from the bladder through the urethra. One test, called cystometry, measures contractions of the bladder muscle as it fills and empties by inserting a catheter through the urethra into the bladder and filling it with water. Another tiny tube is inserted into the rectum or vagina to measure pressure on your bladder when you cough or exert pressure. Urodynamic testing also may include imaging, such as X-ray or ultrasound, to examine changes in the position of the bladder and urethra during urination, coughing or straining. The use of catheters can be uncomfortable but these tests are well-tolerated. Imaging tests are generally noninvasive and do not hurt.