Mid-urethral slings for ISD: what is the evidence?
By Kristin Jenkins

QUEBEC CITY, Que. -- In patients with incontinence, including those with previous failed surgery and no urethral mobility, TVT remains a treatment alternative, Dr. Marie-Claude Lemieux told delegates to Urogynecology Quebec 2007.

“I think that if you balance the risks of the procedure and the lower morbidity of TVT compared to other sling procedures or other surgical alternatives, it remains a treatment alternative in these patients,” said Dr. Lemieux, who is with the Female Urology Unit at Jewish General Hospital in Montreal.

She noted, however, that the success rate of TVT in the treatment of incontinence is lower in patients with ISD than for patients without ISD.  And while reported success rates appear quite variable, “The factors linked to this lower success rate may be decreased urethral mobility and obesity,” noted Dr. Lemieux.

In an interview, she said there might also be a role for periurethral injectable agents in this particular subgroup.

ISD is a concept “that is an attempt to diagnose neuromuscular failure of the internal urethral sphincter mechanism,” said Dr. Lemieux.  “The problem is how we diagnose,” she added. “There are many different ways but no consensus in the literature.”

Causes of ISD include aging, hypoestrogenism, trauma (vaginal delivery), radiation, surgical injury and neurological disease.

When gynecologists (89%) and urologists (11%) were surveyed by the IUGA about their procedure of choice for ISD, 75% indicated they favoured bulking agents, 44.6% TVT and 32.3% a suburethral sling (autologous fascia: 46.5%; Marlex mesh: 27.8%; and fascia lata: 11.6%). In the same survey, 48.8% of surgeons said the procedure of choice for stress incontinence was TVT while 44% favoured Burch.

A preoperative urodynamics survey of 946 experienced incontinence surgeons in Canada, the U.S., New Zealand, Australia and the U.K. indicates that only 70% have access to urodynamic studies prior to surgery, said Dr. Lemieux. “That means 30% do incontinence surgery without prior urodynamic studies,” she pointed out.

“Pubovaginal slings are recommended for the treatment of stress urinary incontinence with ISD,” noted Dr. Lemieux, who added that the cure rate is 83%. “Will midurethral tapes perform similarly?” she asked.

Looking at the literature as far back as 1987, results with retropubic colposuspension showed that higher failure rates were associated with patients with low MUCP or low VLPP. “There is also some data to suggest that surgical outcome is not as good in patients with a weaker urethra,” said Dr. Lemieux.

A look at the seven-year results of TVT from a three-center cohort study of 80 patients with a mean followup of 91 months indicated an 81.3% objective cure rate and an 83.4% subjective cure rate. There was an unchanged continence status in 87.5%, improved continence status in 5% and a worsened continence status in 7.5%, noted Dr. Lemieux.

A literature review of TVT in a prospective cohort of 45 women older than 65 years shows that there was a one-year cure rate of 91%. However, pointed out Dr. Lemieux, there was a 25% increased rate of voiding dysfunction.

A prospective cohort of TVT in 33 women with previous failed surgery showed that at 20.5 months, the cure rate was 90% for those with a mobile urethra and only 33% for those with a fixed urethra. “There is a significant decline in success rate in patients with failed mobility,” said Dr. Lemieux.

In a retrospective study of TVT without prop urethral mobility in 153 women, the success rate without mobility was 79%. “We see that the figures don’t jive,” Dr. Lemieux told delegates. “Because the numbers of women studied are so small, the conclusions reached in different studies may not be similar. Further studies are required.”

Other studies looking at TVT with low urethral pressure suggest that cure rate is decreased with very low mobility or very low urethral pressures, said Dr. Lemieux.

“Pooling the data, we see that isolation of urethral hypermobility is a factor affecting cure rate,” said Dr. Lemieux. “So is lower urethral closure pressure or VLPP.

“How low can you go?” she asked. “Is there a cutoff rate where you see success or disaster?” Although mid-urethral slings can be done in these patients, said Dr. Lemieux, “…caution them that they can expect lower success rates – anywhere from 30-70%.”