By Christina Frangou
Surgeons from Vanderbilt University are recommending that dynamic abdominal sonography for hernia (DASH) replace computed tomography (CT) as the gold standard for the radiographic identification and characterization of incisional hernia.
“The DASH examination is an accurate alternative to the CT scan for diagnosing abdominal wall hernias, with additional benefits of no radiation exposure and instant bedside interpretation,” concluded Benjamin K. Poulose, MD, MPH, assistant professor of general surgery, Vanderbilt University Medical Center, Nashville, Tenn., and his colleagues in a report published in the March edition of the Journal of the American College of Surgeons (216:447-453).
Dr. Poulose, co-author William B. Beck and their colleagues studied 181 patients who underwent surgeon-performed DASH, as well as CT scans of the abdomen and pelvis. Surgeons and radiologists read the CT results.
Analysis showed the DASH examination accurately identified incisional hernias, with a positive predictive value of 91% and negative predictive value of 97%. Moreover, DASH exams identified clinically apparent hernias missed by surgeon-interpreted CT.
Unlike CT, DASH can be performed without exposing patients to ionizing radiation. Additionally, DASH provides real-time results available to both the surgeon and patient for clinical decision making.
Speaking at the 2013 Annual Hernia Repair Meeting in Orlando, Fla., Dr. Poulose said DASH has the potential to change clinical practice and significantly improve research in the field of hernia. Currently, no reliable, cost-effective means of detecting hernias exists.
“Using clinical exams alone, we may be missing 20% to 30% of recurrences and follow-up CT scanning is prohibitively expensive with a concomitant radiation risk. DASH could easily facilitate long-term follow-up of hernia patients,” said Dr. Poulose.
The patients studied had a prior abdominal or pelvic operation performed via incision of the anterior abdominal wall. All had a viewable CT scan of the abdomen and pelvis in the six months before enrollment in the study.
A surgeon who successfully completed the American College of Surgeons Ultrasound for Surgeons Basic Course performed DASH. DASH results were then compared with the gold standard, surgeon-interpreted CT, along with the clinical exam results and radiologist interpretations of the CTs.
DASH exams revealed 107 incisional hernias, including four missed by the surgeon-interpreted CT scans. All missed hernias were in patients with “fairly thick” hernia sacs that were difficult to distinguish radiographically from healthy adjacent fascia, although these hernias were clinically obvious. As well, DASH identified 28 incisional hernias in patients who were deemed not to have hernias based on history and physical exam alone.
The most challenging hernias to detect with DASH were small umbilical hernias in obese patients. Investigators said CT could help with diagnosis in difficult situations.
The U.S. machine varies in cost between $15,000 and $30,000, depending on its age and its features. Investigators argue that clinical practices can offset the cost through billing for the procedure itself. Surgeons also can use machines already installed in their practices by adapting the machines to evaluate the anterior abdominal wall, said investigators.
They caution, however, that practitioners need to meet the credentialing and billing requirements of their institution.
Internal data from Vanderbilt indicates that about 100 DASH exams need to be performed to recoup the initial cost of the machine and maintenance fees.
Robert J. fitzgibbons Jr., MD, professor of surgery and chief of general surgery at Creighton University in Omaha, Neb., said the DASH test appears to be a viable option but may have difficulty gaining widespread acceptance.
“There are two limitations to adoption of this technology: the large up-front outlay of cash required to purchase the hardware and the fact that ultrasonography really has not caught on with surgeons.
“I’ve thought throughout my career that ultrasonography would play a much larger role in general surgery practice. It is a natural. The surgeon has a unique perspective in that the examination can be obtained and the findings unequivocally confirmed or denied with a subsequent open procedure. … But it has never really caught on outside of breast surgery. I sometimes wonder if surgeons have trouble thinking in the two-dimensional world of ultrasound while working in the three-dimensional environment of surgery.”
DASH requires formal training via the American College of Surgeons Ultrasound for Surgeons Basic Course.
Seventeen patients in the study were evaluated to assess interrated reliability with three surgeons performing DASH and evaluating the corresponding CT images. Identical results were obtained for two surgeons with discordant results found in three patients with the third surgeon.