The diagnosis and management of patients with sphincter of Oddi dysfunction remains a challenge and a controversy for gastroenterologists. Principle to that challenge is determining which patient population may benefit from endosocopic sphincterotomy. In addition to classification systems based on objective data, randomized studies have suggested that SOM is beneficial in the identification of true sphincter hypertension and thus potential benefit from sphincterotomy [1
]. Studying sphincterotomy versus sham procedure, Geenen et al. showed a 91% of patients classified as type II SOD with sphincter hypertension benefitted symptomatically from sphincterotomy [1
]. Toouli et al. showed a benefit of sphincterotomy only in patients with sphincter hypertension [2
]. Despite the promising data in these randomized studies, skepticism remains regarding the accuracy and reproducibility of these data. Several nonrandomized studies have called into question the utility of SOM in identifying patients that benefit from sphincterotomy and in the need for manometry in all suspected Type II and III patients [12
]. In addition, research regarding SOM primarily occurs in centers with extensive experience and interest in the performance and interpretation of SOM. For example, in a recently published paper from a single center, 5352 patients had ERCP with SOM over a 13-year period, averaging over 400 manometry cases per year [14
]. Similarly, in a recent paper from Cotton et al., over a 12-year period performed over 1300 biliary SOM were performed at one institution, corresponding to over 100 SOM cases per year [11
]. It is unknown if ERCP with SOM can and should be performed outside of such large SOM centers.
In this study, we examined the outcomes and safety of SOM in the diagnosis and treatment of SOD at a center where SOM is performed far less frequently. In general, about 7 patients in our institution undergo SOM annually. Despite these small numbers, our data is similar to previously published data. In our study, those patients classified as type II SOD with manometric evidence of sphincter hypertension seemed to benefit from sphincterotomy (). Additionally, patients with type II SOD without sphincter hypertension and patients with type III SOD demonstrated less demonstrable benefit from sphincterotomy. This data is in agreement with published guidelines that sphincter of Oddi manometry is best performed in type II and Type III SOD with sphincterotomy reserved for those with documented sphincter hypertension [1
]. We also found that even when rarely performed SOM can be used to predict who will have a benefit from endoscopic sphincterotomy.
The overall complication rate of 16% in this study fell well within expected values with no major complications. Acute pancreatitis, the most feared complication of SOM, occured in only 11% of patients and all of the cases were mild being hospitalized for less than 5 days with no sequelae. This value also falls within previously published rates [9
]. It is important to note however that while our center is a low-volume SOM center, it is a tertiary referral ERCP center. All of the ERCPs in this study were performed by an experienced biliary endoscopist that performs in excess of 400 ERCPs per year. Previous studies have documented that low ERCP volume is associated with an increased risk of postprocedural complications [15
]. Therefore, it should be reinforced that although abundant experience in the performance of SOM may not be a necessary prerequisite for SOM safety, whether SOM effectiveness and safety can be reproduced in any center particularly those with overall low volume ERCPs cannot be definitively stated.
There are several weaknesses to this study. First is the nature of the study with a small patient population. We performed this study with the purpose to see if SOM could be performed successfully in small numbers but this made true statistical comparison difficult. While the data trended toward statistical significance, the total population was small and the data did not reach significance. In addition, no patient followup was available for twelve patients. The main reason for lack of patient followup is that these patients often were from geographic areas that were significantly far from our center and were referred for SOM. Finally, outcomes were based on patient perception of symptom improvement. Scoring systems to assess symptom and quality of life improvement were not used. In addition, as with all functional intestinal disorders, the impact of placebo effect cannot be underestimated.
In conclusion, SOM is perhaps the most technically challenging ERCP procedure in a challenging patient population. Most research on SOM has been performed in large volume centers with highly experienced gastroenterologists in the performance and interpretation of SOM. There has been little research published on SOM in a “real world” scenario outside of larger research studies and SOM centers. This study reflects that SOM can be performed safely with acceptable risk in centers that perform SOM infrequently. In addition, it did reproduce previously published data suggesting that manometry studied patients with sphincter hypertension are the most likely population to benefit from sphincterotomy, and SOM when done in low numbers can also be effective in the treatment of suspected SOD patients.