Mo1635 CT Scan Is Helpful for Internal Hernia Detection Following Weight Loss Surgery

Abstract

Introduction: Radiographic imagingwith CT scan in patients presentingwith acute abdominal pain following Roux-en-Y gastric bypass (RYGB) or biliopancreatic diversion with duodenal switch (BPD/DS) is becoming commonplace. While surgical exploration remains the gold standard for diagnosing internal hernia, decisions for operative intervention are often based on CT findings. The accuracy of CT scan to reliably identify internal hernia in this subset of patients remains unknown. The purpose of this study is to evaluate the reliability of CT scan as a diagnostic tool to identify internal hernia (IH) in bariatric patients with acute abdominal pain. Methods: Following institutional review board approval, a retrospective chart review of all patients presenting with symptoms concerning for obstruction following Roux-en-Y gastric bypass or BPD/DS switch was performed. Patients without CT scans were excluded. Fifty two patients who underwent an operation for a suspected internal hernia from 2008-2013 were identified from surgeons' records at 2 institutions. CT and intraoperative findings were compared via univariate statistical analysis. Patients with incidental finding of a hernia defect were excluded. Results: Of the 52 patients, 50 had previous RYGB and 2 BPD/DS. There was a higher number of female patients in this population (Table 1). Mean time to presentation was 5 years following initial bariatric procedure (5 months to 14 years). Of the 52 patients, 27 had IH at operation. Thirty one (60%) patients had CT scans read as positive for IH and/or obstruction. Of these 31, 21(68%) were found to have IH at operation and 10 (32%) underwent negative diagnostic laparoscopy. Of the 21 patients with negative CT scans, 6 (29%) had IH at operation versus 15 (71%) who were negative. The sensitivity of CT scan to identify IH and/or obstruction is 78% with 95% CI [57% to 91%], specificity is 60% with 95% CI [39%-78%], positive predictive value is 68% with 95% CI [49%-83%], and negative predictive value is 71% with 95% CI [48%-88%]. Kappa statistics comparing the agreement between CT findings and operative findings was 0.380 with 95 CI 0.131-0.629, which was consistent with fair agreement. Conclusions: This study examined the utilization of CT scans in detection of internal hernias. Positive CT scan is highly predictive of IH, but not specific. As CT scan will not detect IH in 1:4 patients, despite negative findings surgical exploration should remain the gold standard for patients with acute abdominal pain following RYGB or BPD when IH cannot be ruled out.