Complications of Crohn's disease may be related or unrelated to the inflammation within the intestine. Intestinal complications of Crohn's disease include obstruction and perforation of the small intestine or colon, abscesses (collections of pus), fistulae, and intestinal bleeding. Massive distention or dilatation of the colon (megacolon) and rupture (perforation) of the intestine are potentially life-threatening complications. Both may require surgery, but, fortunately, these two complications are rare. Recent data suggest that there is an increased risk of cancer of the small intestine and colon in patients with long-standing Crohn's disease, but studies are conflicting.
Other complications involve the skin, joints, spine, eyes, liver, and bile ducts. Skin involvement includes painful, red, and raised spots on the legs (erythema nodosum) and an ulcerating skin condition generally found around the ankles called pyoderma gangrenosum. Painful eye conditions (uveitis, episcleritis) can cause visual difficulties. Arthritis can cause pain, swelling, and stiffness of the joints of the extremities. Inflammation of the low back (sacroiliac joint arthritis) and of the spine (ankylosing spondylitis) can cause pain and stiffness. Inflammation of the liver (hepatitis) or bile ducts (primary sclerosing cholangitis) also can occur. Sclerosing cholangitis causes narrowing and obstruction of the ducts draining the liver and can lead to yellow skin (jaundice), recurrent bacterial infections, and liver cirrhosis with liver failure. Sclerosing cholangitis with liver failure is one of the reasons for performing a liver transplant. Sclerosing cholangitis often is complicated by the development of cancer of the bile ducts or gallbladder. People who also have cirrhosis are at increased risk of developing liver cancer.