Significantly more women who have stress urinary incontinence benefit from a surgery that uses their own tissue to form a sling than from another common treatment that uses sutures. But the benefits of the sling approach come with more risk of side effects.

Results of the study, the largest and most rigorous U.S. trial ever to compare the oft-used Sling and Burch procedures, will be published in the New England Journal of Medicine Thursday. They were released three days early to coincide with a presentation of the results at the annual gathering of the American Urological Association Thursday by one of the main investigators, Dr. Peggy Norton of the University of Utah.

It was the study that many believed could not be done because doctors and their patients would not agree to be randomly assigned a type of surgery, revealed to them in the operating room, said Norton, an associate professor of obstetric and gynecology and part of the U.'s Division of Urogynecology. But nationwide, 655 women with stress incontinence or that combined with urge incontinence were indeed randomly assigned to one or the other procedure. The results provide the first data-based rather than anecdotal information to allow doctors and patients to discuss the benefits and risks.

The study was funded by the National Institute of Diabetes and Digestive and Kidney Disease.

The incidence of both stress and urgency incontinence increases with age, peaking around menopause and after age 65.

With stress urinary incontinence, urine may leak, prompted by sneezing, laughing, coughing, running or heavy lifting. The solution typically involves an operation to provide extra support to the bladder neck and urethra.

"Success" for the study was defined as complete dryness, not just improvement, Norton said. Researchers also measured patient satisfaction afterward.

The sling is made from the patient's own tissue and provides support around the urethra. The Burch culposuspension technique uses sutures attached to a pelvic ligament to support the urethra. The study found that two years after having the sling, 47 percent of women were dry overall, compared to 38 percent who underwent a Burch procedure, including leakage that might have resulted from urge rather than stress incontinence. For stress incontinence only, the number jumped to 66 percent for the sling, compared to 49 percent for Burch.

Patient satisfaction rates were 86 percent for women who received a sling compared to 78 percent for those who received a Burch.

But the sling created more side effects, particularly urinary tract infections, which affected 63 percent of those women, compared to 47 percent of the Burch women. The sling also created more problems with urination (14 percent vs. 2 percent). Nineteen of the women with slings needed surgery to correct problems voiding, while no one in the Burch group needed it.