Constipation in Crohn’s Disease

Crohn’s disease (CD) is usually associated with diarrhoea, so it often comes as a surprise that some patients suffer with constipation instead, or find that the two alternate. Constipation in CD needs a little more thought than ordinary constipation, because the usual advice to eat more fibre is not always safe.

What is constipation?

Constipation is the infrequent passage (less than 3 times per week) of a hard, dry motion, usually with discomfort, straining, abdominal pain and bloating. Some people open their bowels regularly but still feel that they have not emptied completely.

What causes constipation in Crohn’s disease?

1. Narrowing of the bowel (strictures)

Long-standing inflammation in CD can lead to scarring and narrowing of the bowel, known as a stricture. This is most common in the small intestine. A stricture slows the passage of the bowel contents and may cause crampy pain after meals, bloating, a swollen abdomen and noisy bowel sounds. These symptoms are sometimes mistaken for constipation, but the problem is a partial blockage higher up rather than hard motions in the colon. Strictures can also occur in the colon and rectum.

2. Medicines

Several medicines commonly used in CD may cause constipation:

• Drugs used to control diarrhoea, such as loperamide (Imodium) and codeine
• Painkillers, particularly codeine, tramadol and other opioids
• Iron tablets, given for anaemia
• Colestyramine, used after removal of the end of the small intestine to control diarrhoea caused by bile acids
• Some antidepressants and antispasmodics

3. Diet

People with CD often limit their diet to avoid symptoms, and a low fibre or low residue diet may be advised by doctors when there is a stricture. This reduces the bulk of the motions and can lead to constipation. During and after a liquid diet the motions become small and infrequent, which is expected and is not usually true constipation.

4. Not drinking enough

Diarrhoea, fever and avoiding drinks to reduce trips to the toilet can all lead to dehydration, making the motions harder and more difficult to pass.

5. Painful conditions around the anus

Fissures, fistulae and abscesses around the anus are common in CD. Opening the bowels can be painful and some people put off going to the toilet, which allows the motion to become harder.

6. Proximal constipation

When the inflammation is confined to the lower part of the colon or the rectum, the bowel above it may become loaded with motion, even though the patient is passing frequent small motions with blood or mucus. This is better known in ulcerative colitis and is described in our page on constipation in ulcerative colitis, but it can also occur in CD of the colon.

7. Pelvic floor problems

Some people find it difficult to empty the rectum even when the disease is in remission, because the muscles of the pelvic floor do not relax properly while straining. This is more common in people who have had perianal disease and can be helped by specialist physiotherapy known as biofeedback.

8. Irritable bowel syndrome

Some people with CD in remission have symptoms of irritable bowel syndrome, which may include constipation. A stool test (faecal calprotectin) can help to show whether the symptoms are due to active inflammation or not.

How is it treated?

The first step is to find the cause, as the treatment of a stricture is quite different from the treatment of simple constipation. Your doctor may arrange blood tests, a calprotectin test or a scan of the bowel.

Fluids

A daily fluid intake of at least 1.5-2 litres is advised. Water is best, as caffeine and alcohol have a dehydrating effect.

Fibre

If there is no stricture, a gradual increase in fibre from fruit, vegetables and wholegrain cereals may help, taken with plenty of fluid. If there is a stricture, or one is suspected, fibre should not be increased without advice from your doctor or dietitian, as large amounts of fibrous food (e.g. nuts, seeds, sweetcorn, the skins of fruit and vegetables) may block the narrowed bowel.

Reviewing medicines

It is worth asking your doctor or pharmacist whether any of your medicines may be responsible. Anti-diarrhoeal drugs may need to be reduced, and a different form of iron, or iron given by infusion, may be better tolerated.

Laxatives

1. Osmotic laxatives (e.g. macrogols such as Movicol and Laxido) draw water into the bowel to soften the motion. They are usually the first choice in CD and can be used safely for long periods.
2. Stimulant laxatives (e.g. senna and bisacodyl) make the bowel contract. They are best used for short periods only.
3. Bulking agents (e.g. Fybogel) should be avoided if there is a stricture, as they may cause a blockage.
4. Suppositories and enemas (e.g. glycerine suppositories) may be helpful when the problem is in the rectum.

Laxatives should be used with caution during a flare-up of CD of the colon and it is wise to discuss them with your IBD team first.

When to seek help urgently

A blocked bowel (bowel obstruction) is a serious complication of CD. You should seek medical help at once if you have:

• Severe, crampy abdominal pain
• A swollen, tight abdomen
• Vomiting, particularly if it is green or brown
• No bowel motion and an inability to pass wind

These symptoms should not be treated with laxatives. More information about strictures and their treatment can be found in Complications of Crohn’s Disease and Surgery in Crohn’s Disease.