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Internal Hernia after Gastric Bypass: Seven CT Signs
Abstract & Commentary
By Namir Katkhouda, MD, FACS, Professor of Surgery, Chief, Minimally Invasive Surgery, University of Southern California (USC)-Los Angeles, CA. Dr. Katkhouda is a consultant for Baxter, Ethicon, Storz, and Gore.
Synopsis: Mesenteric swirl is the best indicator of internal hernia after laparoscopic Roux-en-Y gastric bypass, and even minor degrees of swirl should be considered suspicious.
Source: Lockhart ME, et al. Internal hernia after gastric bypass: Sensitivity and specificity of seven CT signs with surgical correlation and controls. AJR Am J Roentgenol. 2007;188:745-750.
Objective: The purpose of this study was to evaluate the sensitivity and specificity of 7 CT signs in the diagnosis of internal hernia after laparoscopic Roux-en-Y gastric bypass.
Materials and methods: With institutional review board approval, the CT scans of 18 patients (17 women, one man) with surgically proven internal hernia after laparoscopic Roux-en-Y gastric bypass were retrieved, as were CT studies of a control group of 18 women who had undergone gastric bypass but did not have internal hernia at reoperation. The scans were reviewed by 3 radiologists for the presence of 7 CT signs of internal hernia: swirled appearance of mesenteric fat or vessels, mushroom shape of hernia, tubular distal mesenteric fat surrounded by bowel loops, small-bowel obstruction, clustered loops of small bowel, small bowel other than duodenum posterior to the superior mesenteric artery, and right-sided location of the distal jejunal anastomosis. Sensitivity and specificity were calculated for each sign. Stepwise logistic regression was performed to ascertain an independent set of variables predictive of the presence of internal hernia.
Results: Mesenteric swirl was the best single predictor of hernia; sensitivity was 61%, 78%, and 83%, and specificity was 94%, 89%, and 67% for the 3 reviewers. The combination of swirled mesentery and mushroom shape of the mesentery was better than swirled mesentery alone, sensitivity being 78%, 83%, and 83%, and specificity being 83%, 89%, and 67%, but the difference was not statistically significant.
Conclusion: Mesenteric swirl is the best indicator of internal hernia after laparoscopic Roux-en-Y gastric bypass, and even minor degrees of swirl should be considered suspicious
This study defined in a very elegant way the sensitivity and specificity of 7 radiological signs that correlate best with postoperative internal hernias following laparoscopic gastric bypass.
The diagnosis of internal hernias is a real problem following gastric bypass. Most patients will present with vague abdominal symptoms such as intermittent pain, distension, and sometimes postprandial vomiting. There are many possible explanations for these symptoms, not limited to, anastomotic strictures, dumping, extra small size of the pouch, and ulcers. Internal hernias should be recognized as early as possible, as the delay of diagnosis can lead to possible massive strangulation of the small bowel and possible mortality.
Most workup include an upper GI endoscopy to rule out ulcers and anastomotic strictures, and until now, a CT was done and reported to be negative in the majority of the cases, as subtle radiological signs of small internal hernias were not previously described.
With this study, Lockhart and colleagues insist on several signs, the most important one being the mesenteric swirl sign, which should prompt the diagnosis of internal hernia and an operation.
We would like to propose that all patients presenting with persistent vague pain and vomiting undergo an upper GI endoscopy and a CT scan. The detected lesions should be treated, and internal hernias be repaired laparoscopically. If the CT is negative, patients should still be suspect of an internal hernia, given the gravity of a missed diagnosis, and we have offered this approach to 4 patients, 3 of whom had internal hernias.
The best method is prevention by a rigorous closure of all hernia spaces created during a laparoscopic gastric bypass, namely the jejunojejunostomy site, the space of Petersen behind the Roux en Y loop, and the transmesocolic space in the event of a transmesocolic Roux-en-Y.