The Times article, by Dr Mark Porter, 18 October 2016: Not all of the six million Brits who think they have IBS need to hang on for the new wonder drug

Part of the challenge is that IBS is unlikely to be one disorder

At least six million people in the UK are regularly troubled by symptoms of irritable bowel syndrome (IBS), so it should come as no surprise that an effective treatment has long been the holy grail of pharmaceutical companies working in the gastrointestinal arena. They are yet to make a significant breakthrough.

The latest advance, however, comes from the US, where researchers at the prestigious Mayo Clinic have announced that pregabalin — a drug used to treat neuralgia and anxiety — eases the discomfort associated with IBS. Yet it is early days and pregabalin may go the way of other breakthroughs in this area, which have all failed to live up to early promise.

Part of the challenge is that IBS is unlikely to be one disorder. It is simply a diagnosis of exclusion — an umbrella term to explain groups of symptoms that can’t be attributed to anything else. At least that is what it is supposed to be.

In recent years it has become clear that many people with problems previously attributed to IBS may have another condition. If you have the type of IBS associated with diarrhoea/loose stools — about half of people do — your symptoms may be more manageable than you think; as many as half a million sufferers are thought to have idiopathic bile acid diarrhoea (BAD) caused by an excess of bile in the lower bowel. We all produce about eight litres of digestive juices each day, including up to a litre of bile that helps us to absorb fat. Nearly all of these juices are reabsorbed before they reach the lower part of the gut, but this process goes awry in BAD.

The volume of digestive juices is the reason why gastroenteritis can quickly lead to dehydration. If the intestinal transit time is dramatically increased by infection-induced inflammation, there is not enough time to absorb the digestive juices and you can pass litres a day, even if you have had only a cup of tea and nibbled on a biscuit. With BAD there is no infective virus or bacteria, but the unabsorbed bile has an irritant effect on the lower bowel, increasing transit time in a similar fashion.

There are some good medical reasons why the bile reabsorption mechanism is hampered in some people — ranging from inflammatory bowel disease to gall bladder removal — but for those with idiopathic BAD there appears to be a genetic glitch in the transport system responsible for collecting and recycling bile salts. The result is that too much bile reaches the colon.

As well as the characteristic bloating and discomfort you get with IBS, tell-tale signs of BAD include unusual-coloured stools (shades of green or yellow) that are difficult to flush away, and needing to go to the loo during the night. Symptoms tend to be worse after fatty meals because these induce more bile secretion.

Specialist gastroenterology clinics have access to a specific test to confirm BAD, but it is expensive and not routinely available. A more pragmatic approach is to consider a trial of therapy with a granular drink (cholestyramine) that mops up bile. If this works it suggests that your IBS is in fact BAD.

The trick is to reduce the cholestyramine (mixed with water into a rather unpleasant wallpaper paste-like drink) to the bare minimum dose that controls the symptoms — often one or two sachets a day are enough. Other tips include switching to a low-fat diet and making breakfast and lunch your main meals of the day and only snacking in the evening.

So, while we await a “cure” for IBS, our best hope remains research into other possible underlying causes. And I very much doubt BAD will be the only “new” discovery in this field as we increase our understanding of the gut and the billions of friendly bacteria that live in it.

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