Bariatric surgery increases the risk of new-onset inflammatory bowel disease (IBD), according to a case series and national database study.

“A past history of bariatric surgery, but not recent surgery, was associated with both new-onset” Crohn’s disease and ulcerative colitis, wrote Ryan Ungaro, MD, assistant professor of medicine at the Icahn School of Medicine at Mount Sinai, New York. “Analyses further classifying recent bariatric surgery as preserved or altered intestinal anatomy showed no significant difference in risk … when compared to patients without a history of bariatric surgery.”

IBD and more specific conditions like ulcerative colitis (UC) and Crohn’s disease (CD) are on the rise. One environmental factor that can increase the likelihood of these disorders is surgery. To investigate how IBD may develop in response to bariatric surgery, Dr. Ungaro and his colleagues compiled descriptive case studies from six (three New York, three European) medical centers, then conducted a case-control study with a sample of patients from a large health claims database (Symphony Health Solutions Integrated Dataverse) to assess the association between prior bariatric surgery and risk of new-onset IBD. Using the information from the Symphony database, a database focusing exclusively on IBD patients was developed.

From the case studies included in the study, Dr. Ungaro and his colleagues identified 15 patients with IBD who had a prior history of bariatric surgery: 10 patients had CD, 4 had UC, and 1 had an unclassified form of IBD. Most of the patients had undergone Roux-en-Y gastroenterostomy. The average time between surgery and diagnosis of IBD was 5.7 years. Most of the cases (67%) were mild or moderate in severity and over half (53.3%) of the cases were mildly active. Only about a quarter of these patients required immunosuppressant therapy.

The database portion of the study also revealed some interesting associations between bariatric surgery and IBD. The researchers identified 8,980 patients with IBD and 43,059 controls. Ultimately, Dr. Ungaro and his colleagues found that any type of bariatric surgery increased the odds of developing IBD (adjusted odds ratio, 1.45; 95% confidence interval, 1.08-1.94). Interestingly, only past history of bariatric surgery was associated with an almost twofold increase in onset of IBD. The study also revealed that bariatric surgeries prior to 2008 were associated with an increase chance of developing IBD.

Bariatric surgery was not limited to increasing the risk of IBD, but also increased the specific risks for CD and UC. A past history of bariatric surgery was heavily associated with an increase of both CD (aOR,1.86; 95% CI,1.10-3.15; P = .066) and UC (aOR, 2.12; 95% CI, 1.26-3.57; P = .015).

The size of the sample and utilization of a large, national database strengthen the results of the study, but the use of retrospective data is a potential limitation. The deidentified nature of the data also makes it difficult to validate cases and determine whether new cases of IBD were definitely incident cases.

Regardless, there is still no clear-cut explanation why bariatric surgery would cause IBD. One of the proposed mechanisms is vitamin D deficiency caused by malabsorption, a common consequence of the Roux-en-Y procedure. Vitamin D deficiency is often linked with an increased risk of developing IBD. Additionally, bariatric surgery may alter bile acid composition, which can have inflammatory effects.

Because no direct mechanism has been identified, Dr. Ungaro stated that further research needs to be done.

“The potential association between prior bariatric surgery and new IBD highlights the need to perform a thorough work-up and have a broad differential diagnosis in postbariatric surgery patients with new gastrointestinal symptoms,” Dr. Ungaro and his colleagues wrote. “However, given the nature of administrative database studies, we cannot draw causative conclusions and further prospective studies are needed to confirm this association and delineate if certain types of bariatric surgeries have differential effects on risk of IBD.”

Multiple authors who worked on this study have worked as consultants for pharmaceutical companies. Dr. Ungaro is supported by a Crohn’s and Colitis Foundation career development award and a KL2 Scholar award.

SOURCE: Ungaro R et al. Aliment Pharmacol Ther. 2018 Mar 7;47[8]:1126-34: doi: 10.1111/apt.14569 .