Water enema: a new ultrasound technique in defining pelvic anatomy.

A new technique is described for delineating pelvic structures by using a distended bladder in combination with a water enema. The distended urinary bladder, which acts as a sonic window to the pelvis, fully defines only the portion of structures that abut against the surface. With fluid in both the bladder and rectosigmoid colon, and occasionally the cecum, a 'sandwich effect' can be obtained, resulting in a more complete definition of interposed structures. Questionable masses that might be feces in the bowel can be easily distinguished from significant pathology. This new technique has the potential for increasing accuracy of diagnosis of pelvic masses and delineating tumor extension of masses arising in such pelvic organs as the bladder, prostate, and uterus.