IBD versus IBS

Posted by em on 6/12/2002, 11:51 pm

Irritable bowel syndrome (IBS)typically causes colicky abdominal pain and intermittent diarrhoea and affects at least one in four of the population at one point in there lives.

Crohn's Disease and Ulcerative Colitis each affect about one in 500 to one in 1,000. UC typically causes rectal bleeding or bloody diarrhoea so is not commonally confused with IBS but CD is less commonally associated with bleeding and the symptoms can be very similar to those of IBS.

It is no surprise therefore that patients with CD are often misdiagnosed with IBS initially. The situation is further complicated by the fact that both UC & CD are associated with an increased risk for IBS, probably as a result of transient damage to the nerve endings in the intestine as a result of inflammation. It is quite common, for example, for an attack of UC to be followed by irritable bowel symptoms that may persist for several months. The same problem occurs quite often after infective gastro-enteritis, eg. salmonella food poisoning.

IBS is incompletely understood. In affected individuals the intestine looks normal on x-rays, when endoscoped and when biopsed. There is, for example, no evedence of inflammation. This can be helpful in differentiating from active CD. Research has demonstrated a fairly consistent increased sensitivity of the intestines to distension, eg. with a balloon in IBS, but this is not a routine test and diagnosis is based on the combination of symptoms and exclusion of other conditions. Most patients with IBS do not have a previous history of IBD or recent gastroenteritis and attacks are most commonly precipitated by stress.

It is presumed that stress alters the nerve communications between the brain and the gut and that this results in the altered sensitivity of the intestine. Although a feeling of bloating is common there is evidence that this is caused by the altered sensation rather than by an actual increase in intestinal gas. In most cases explanation and reassurance leads to an improvement in symptoms.

Medical treatments are not totally effective. Anti-spasmodics such as alverine citrate (spasmonal), available without prescription, or mebervine (colofac) which requires a prescription, can help and are very safe. Very occasionally antidepressants such as amitriptyline are used even if there is no evidence for depression. They seem to work by interfering with pain pathways and reducing sensitivity but may have a relaxing effect on the intestine. Diarrhoea can be treated with a simple anti-diarrhoeal such as loperamide (imodium), available without a prescription, but if you also have IBD you should ask your dr for advice as it is not usually helpful if you have active inflammation.

Dietary therapies sometimes prove effective but the response is inconsistant. Hypnotherapy can also be effective but is not widely available on the NHS. IBS is not associated with any increase in risk for bowel cancer and, although the colicky pain can be very severe, it is never associated with perforation of the bowel or any other surgical emergency. The condition nearly always improves with time.

Professor Jonathon Rhodes,Consultant Gastroenterologist,University of Liverpool