Dr. Claire Smyth explains that while the symptoms of IBD and IBS may overlap,there are key differences between them
Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS) are often confused. IBD, as its name suggests, is associated with varying degrees of inflammation throughout the bowel, causing a number of distinct symptoms which will be discussed later. The incidence of IBD in the UK is 8-14 per 100,000, with UC being slightly more common than CD.
IBD is commonly divided into two main categories, namely ulcerative colitis (UC) and Crohn’s disease (CD). UC is confined to the large bowel or colon whereas CD can affect anywhere in the gastrointestinal tract, from mouth to anus. There are a number of other types of IBD such as microscopic colitis, lymphocytic colitis, ischaemic colitis and infective colitis but for the purpose of this discussion, we will refer to UC and CD.
IBS is far more common, with as many as 1 in 5 people affected. The underlying aetiology is poorly understood but inflammation and ulceration of the bowel does not occur. Some symptoms may be suggestive of IBD but with careful evaluation, these conditions can be distinguished easily. It is important to distinguish between IBS and IBD as the treatment varies considerably.
IBD and IBS symptoms
Symptoms of IBD and IBS may often overlap and co-exist but certain symptoms are most suggestive of one over the other.
IBD commonly presents with bloody diarrhoea. Bowel frequency can vary from 3 bowel motions up to close to 20 bowel motions a day during “flares”. Patients may often get up in the middle of the night to pass a bowel motion, and, during attacks of significant inflammation, may experience episodes of incontinence. Other symptoms may include fever, weight loss, fatigue and abdominal pain or cramps. In addition, patients with IBD may develop symptoms unrelated to the bowel such as joint pains, painful red eyes, and skin rashes.
IBS can present with diarrhoea (diarrhoea predominant) but classically non-bloody. Patients do not
experience nocturnal symptoms and never have incontinence unless for another reason. Other patients with IBS may present with constipation (constipation predominant) and a third subgroup have a mixed pattern, alternating between diarrhoea and constipation. Bloating, abdominal cramps and urgency are prominent. Patients with IBS however do not develop the other associated symptoms mentioned above such as fever, weight loss etc.
Diagnosing IBS and IBD
There are a number of tests and investigations to distinguish between IBD and IBS. Some of these tests can be easily done by your GP and others will necessitate seeing a specialist.
Tests used by your GP
After taking a history of your symptoms and examining you, blood tests will usually be performed. These blood tests will focus on a number of inflammatory markers, your blood count and iron stores. These tend to be abnormal in IBD but normal in IBS. A sample of your bowel motion may also be sent for analysis as infection of your bowel may often mimic both of these conditions. The combination of your history, examination and test results will help your GP determine whether you need to be referred to a Gastroenterologist for further investigations.
Tests used by specialists
Once you have symptoms such as outlined above you may often be referred to a Gastroenterologist. They may repeat a number of the tests performed by your GP but more specifically may perform a colonoscopy or sigmoidoscopy. This involves the insertion of a flexible fibre optic tube into your back passage with a camera attached, to inspect your large bowel. In the majority of patients, IBD can be diagnosed immediately with this test but in general biopsies are taken from the bowel and sent for analysis to the laboratory to confirm the findings. In the case of IBS, the bowel lining looks normal and biopsies are also normal. In some cases, particularly when dealing with CD, further investigations may need to be carried out such as specific x-ray tests e.g. barium tests and MRI scans. These would be explained to you by your Gastroenterologist.
Treatment
The treatment of IBS and IBD is very different. Patients with IBD generally require maintenance or longterm treatment. There are a variety of medications used which aim to reduce the level of inflammation in the bowel. Some patients require stronger medications which suppress the immune system which in turn reduces inflammation in the bowel. In general, while on these medications, patients will be monitored regularly in out-patient clinics and with regular blood tests. This is partly to ensure patients do not develop side-effects from these medications. Medications prescribed include anti-inflammatory agents, immunosuppressants and newer agents known as biological agents. Steroids are used on an intermittent basis to control “flares” of inflammation, these are used on a short-term basis and not on a long-term basis. Some patients may require surgery to control disease.
The treatment of IBS on the other hand is usually with dietary modifications and medications that target symptomatic relief. Anti-spasmodics are used to relieve cramps, stool bulking agents for constipation and anti-diarrhoeal agents for loose stools. Soluble fibres such as oats have occasionally been found to be beneficial. More recently, research has shown that patients with IBS have a hypersensitivity in their bowel which can respond well to medications also used to treat depression. It is thought these medications modify the pain signals sent to the brain from the gut in patients with IBS.
Tips: What to discuss with your GP?
Patients should discuss their symptoms with their GPs if they are worried that they suffer with IBS or IBD and if they require help to distinguish between the two. GPs would usually help determine whether further tests are necessary. If you are uncertain about the nature of these tests, your GP will be able to clarify the various procedures. Treatment options would differ depending on the diagnosis and your GP will be able to explain these in further detail including possible treatment side effects. If you have IBD and you are planning on becoming pregnant, it would be advisable to discuss this with your doctor beforehand so that you understand the importance and implications of being on medications during your pregnancy. Some medications may need the dosage to be modified during pregnancy. If you find out you are pregnant unexpectedly, please talk to your GP or Specialist before stopping any medications.
Summary
IBD and IBS are often mistaken but clearly are very distinct conditions. Symptoms may overlap or coexist. Careful history taking, clinical examination and investigations will easily distinguish these
conditions. Treatments are very different. Long-term follow-up with a specialist is necessary for patients with IBD but not with IBS.
Table 1: Summary of differences between IBD and IBS
Dr. Claire Smyth
Consultant Gastroenterologist
Connolly Hospital, Blanchardstown.