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A retrospective study of more than 2,100 laparoscopic surgeries performed over 12 years confirmed what many urologists have long suspected: Overall laparoscopic conversion rates are low, and conversion rates fall toward zero as laparoscopic surgeons gain experience.
"We saw a diminution in the frequency of conversions as the case load and cumulative experience increased," said Lee Richstone, MD, director of laparoscopy and robotic surgery at the Smith Institute for Urology, North Shore-Long Island Jewish Health System, New Hyde Park, NY. "The drop-off in the rate of conversion was seen across all procedures."
Dr. Richstone was lead author of a retrospective study that tracked 2,128 laparoscopic procedures performed between 1993 and 2005. The study found that 3.2% of patients were converted to open surgery over the 12-year study period, as reported at the AUA annual meeting. Both the absolute number of conversions and the rate of conversions fell over time as surgical volume and surgeon experience grew. By the end of the study, the annual conversion rate was less than 2%.
Researchers also found major differences in blood loss between cases completed laparoscopically and those cases requiring open conversion. In the laparoscopic group, mean estimated blood loss was 255 cc, compared to 910 cc (p<.0001) for the conversion group.
While the overall incidence of conversion was low and declined for all procedures, Dr. Richstone noted that actual rates of conversion varied widely by procedure. The study covered seven common urologic procedures: radical nephrectomy, simple nephrectomy, partial nephrectomy, donor nephrectomy, pyeloplasty, nephroureterectomy, and retroperitoneal lymph node dissection. All procedures were initiated laparoscopically.
Pyeloplasty showed the lowest conversion rate at 0%, while nephroureterectomy had the highest conversion rate at 8.5%. Other procedures fell between these extremes: simple nephrectomy at 5.9%; retroperitoneal lymph node dissection at 4.7%; partial nephrectomy at 4%; radical nephrectomy at 2.9%; and donor nephrectomy at 2.5%.
What did not change over the course of the study period were the indications for conversion. Among these, vascular injuries accounted for 36.8% of conversions, followed by failure to progress (14.7%), concern over margins (8.8%), visceral injuries (8.8%), and other issues (30.9%).
What influences conversion?
On logistic regression, age emerged as the most notable risk factor for conversion. Patients over the age of 50 years were at a five-fold risk for conversion, Dr. Richstone said. Patient body mass index, type of procedure, history of prior abdominal surgery, estimated blood loss, and year of laparoscopic surgery had no significant effect on conversion.
"There is prior data on conversion for laparoscopic surgery," he said, "but the earlier data is not reflective of the cumulative experience documented here. Our data are significant due to the overall size of the cohort and the ability to look at conversions across different procedures at a single institution. If anything, our rate of conversion was somewhat lower than that in the literature."
Confirmation that surgeons have fewer conversions as they gain more experience should reassure both clinicians and their patients, Dr. Richstone said. New data can help urologists counsel their patients more appropriately in evaluating the risk of conversion for laparoscopic procedures. Physicians can also use these results to help patients judge the relative risks involved in specific laparoscopic procedures.
"The simple fact that the frequency of conversion is less than 5% is of great utility in counseling patients," Dr. Richstone said. "When experienced hands embark on laparoscopic surgery, there is a high likelihood that you will complete it."