People with Crohn's disease are at risk of developing a number of complications.  

The two most common problems associated with Crohn's disease are discussed in more detail below.

Intestinal stricture

The inflammation of the bowel (intestines) in Crohn's disease can cause scar tissue to form, leading to the affected areas becoming narrowed. This is known as stricture.

If this happens, there's a risk of digestive waste causing an obstruction. This means you won't be able to pass any stools or you'll only be able to pass watery stools.

Other symptoms of bowel obstruction include:

• abdominal pain and cramping
• being sick (vomiting)
• bloating
• an uncomfortable feeling of fullness in your abdomen

Left untreated, there's a risk the bowel could split (perforate). This creates a hole that the contents of the bowel can leak from. You should contact your GP as soon as possible if you suspect your bowel is obstructed. If this isn't possible, call NHS 111.

Intestinal stricture is usually treated with surgery to widen the affected section of intestine. In some cases this may be achieved without surgery, using a procedure called balloon dilation, which is performed during colonoscopy.

During balloon dilation, a colonoscope is passed up your back passage (rectum) and a balloon is inserted through the colonoscope. This is then inflated to open up the affected area.

Read diagnosing Crohn's disease for more information on colonoscopy.

If this doesn't work or is unsuitable, a surgical procedure known as a stricturoplasty may be needed to widen the affected area. During this operation, the surgeon widens the narrowed part of the intestine by opening it, reshaping it and sewing it back together.

Fistulas

If your digestive system becomes scarred as a result of excessive inflammation, ulcers can develop.

Over time, the ulcers develop into tunnels that run from one part of your digestive system to another or, in some cases, to the bladder, vagina, anus or skin. These passageways are known as fistulas.

Small fistulas don't usually cause symptoms. However, larger fistulas can become infected and cause symptoms, such as:

• a constant, throbbing pain
• a high temperature (fever) of 38C (100F) or above
• blood or pus in your stools
• leakage of stools or mucus into your underwear

If a fistula develops on your skin (usually on or near the anus) it may release a foul-smelling discharge.

Biological medication is usually used to treat fistulas. Surgery is usually required if these aren't effective.

Read more about treating a fistula.

Other complications

People with Crohn's disease are also at an increased risk of other complications, such as:

• osteoporosis – weakening of the bones caused by the intestines not absorbing nutrients and the use of steroid medication to treat Crohn's disease
• iron deficiency anaemia – a condition that can occur in people with Crohn's disease because of bleeding in the digestive tract; common symptoms include tiredness, shortness of breath and a pale complexion
• vitamin B12 or folate deficiency anaemia – a condition caused by a lack of vitamin B12 or folate being absorbed by the body; common symptoms include tiredness and lack of energy
• pyoderma gangrenosum – a rare skin reaction that causes painful skin ulcers

Children with Crohn's disease may also experience problems with their growth and development because their bodies aren't absorbing enough nutrients.

Colorectal cancer

Some people with Crohn's disease have a slightly increased risk of developing colorectal cancer in later life.

You should be offered regular check-ups to look for colon cancer if your healthcare team feels you may be at an increased risk.

This usually involves a colonoscopy and a biopsy. See diagnosing Crohn's disease for more information about these tests.