Crohn's disease can lead to several different complications within the digestive tract, caused largely by the inflammation and injury to the bowel wall that characterize the disease.

But Crohn's disease — and possibly certain treatments for it — can also lead to complications in other areas of the body, which may be related either to inflammation or to malnutrition caused by the disease.

Different Types of Intestinal Complications

The following complications in the intestines can develop because of Crohn's disease:

Bowel Obstruction (Blockage) Inflammation from the disease can build up areas of scar tissue — known as strictures — that constrict an area of the intestines and block normal digestion. This is more common in the small intestine than in the large intestine (colon). (1)

Symptoms of a blockage often include a reduced appetite, severe abdominal cramps, nausea, and vomiting. Surgery may be required to remove the obstruction.

Anal Fissure This is a tear or crack in the skin lining the anus or around the anus.

Fissures can cause mild to severe rectal pain and bleeding, especially during and right after bowel movements. A fissure may become infected or develop into a perianal fistula, according to the Mayo Clinic. (1)

Fistula A fistula is an abnormal channel or connection that develops between two areas of the body. In Crohn's disease, a fistula usually develops from an ulcer, or sore, in the intestines that deepens into a tract (channel).

A fistula may connect two different areas of the intestines, or it may connect part of the intestines with the bladder, vagina, or outer skin. Fistulas can interfere with nutrient absorption and often require surgery to repair, especially if they're large or numerous.

According to the Crohn's & Colitis Foundation, about 30 percent of people with Crohn's disease develop fistulas. (2)

Abscess An abscess is a pocket of pus caused by a bacterial infection. It may develop in or around a fistula but can also occur separately from fistulas. Abscesses may cause swelling, pain, and fever.

An abscess that forms in the intestinal wall may cause it to bulge, and abscesses around the anus may be visible and look like boils. (2)

Depending on its location and severity, an abscess may be drained by using a needle or through surgery. Antibiotics are also often used to help clear up the infection.

Malnutrition A variety of factors in Crohn's disease may make it difficult to consume or absorb enough nutrients. These include difficulty eating due to pain or diarrhea, or malabsorption in the intestines due to extensive inflammation and injury, certain medication, or surgery.

Medical treatment to replace nutrients (often by IV) is usually successful at treating malnutrition, according to the Crohn’s & Colitis Foundation. (3)

Intestinal Infection Overgrowth of bacteria in the small intestine can cause abdominal pain, gas, bloating, and diarrhea.

Having Crohn's disease raises the likelihood of developing a C. difficile infection, according to the . This type of infection often causes severe diarrhea. (4)

Antibiotics are used to treat intestinal infections.

Toxic Megacolon This is a serious complication in which deep inflammation in the colon leads it to become enlarged and paralyzed.

A colon with toxic megacolon can rupture, which is a life-threatening emergency that requires surgery. (5)

Colon Cancer Having Crohn's disease increases your risk of developing colorectal cancer. This risk is highest if you've had the disease for at least eight years or have large areas of your colon affected by it, according to the Crohn’s and Colitis Foundation. (6)

Because of this increased risk, ask your doctor if you should have a colonoscopy earlier or more frequently than general guidelines recommend.

Complications Outside the Intestines

Less commonly, Crohn's disease complications can affect other areas of the body. These complications include:

Mouth Problems Both canker sores and yeast infections in your mouth are common problems in people with Crohn's disease. (1)

Joint Problems Inflammation due to Crohn's disease can also cause arthritis (stiffness in your joints). (3)

You may also be at risk for clubbing of your fingers and toes (abnormal widening at the ends of these extremities). (7)

Skin Disorders People with Crohn's disease may develop red, knot-like swellings and other skin lesions, which can spread from areas close to your colon to as far away as your arms and legs.

Having Crohn's disease also increases your risk of developing psoriasis (patches of red, itchy, scaly skin). (7)

Liver Problems For some people with Crohn’s the liver can become damaged or inflamed. While most liver damage is reversible, about 5 percent of people living with IBD have serious liver disease, according to the Crohn’s and Colitis Foundation. (8)

Anemia It’s common for Crohn’s patients to develop anemia as a result of low iron and vitamin B12 due to malnutrition. (1)

Blood Clots Having Crohn's disease increases your risk of developing blood clots in your legs, as well as developing a pulmonary embolism, in which a clot travels from your legs to your lungs. (9)

Eye Problems Corticosteroids — drugs that are sometimes used to control inflammation in Crohn's disease — can increase your risk of developing cataracts (clouding of the lens of the eye) or glaucoma (a group of conditions that damage the optic nerve). (10)

Crohn's disease itself can also lead to inflammation in the eyes. (1)

Bone Issues Both Crohn's disease and corticosteroids can contribute to osteoporosis (weakened, porous bones) and osteopenia (reduced bone density), leading to a higher risk of fractures.

According to the Crohn’s & Colitis Foundation, between 30 and 50 percent of people who take corticosteroids long term go on to develop osteoporosis. (11)

Kidney Stones and Gallstones Both these conditions are more common in people with Crohn's disease. (9,12)

Weight Issues For some people, symptoms of Crohn’s such as nausea and abdominal pain can lead to loss of appetite and weight loss. Side effects of certain medication can also lead to weight loss, while others can lead to weight gain. (13)

Delayed Growth Crohn's disease can limit physical growth and development in children. (1)

Emotional Problems Fear of pain and potentially disruptive or embarrassing symptoms can lead to social isolation and a higher risk of developing depression or anxiety. (14)