Extra-intestinal manifestations are well recognized in inflammatory bowel disease (IBD). To what extent the commonly recognized extra-intestinal manifestations seen in IBD patients are attributable to IBD is, however, not clear due to the limited number of controlled studies published.
Card, T. R., Langan, S. M., & Chu, T. P. (2016). Extra-gastrointestinal manifestations of inflammatory bowel disease may be less common than previously reported. Digestive Diseases and Sciences, 61(9), https://doi.org/10.1007/s10620-016-4195-1