Is my diarrhoea just due to IBS?
In my clinical practice as a gastroenterologist, I always worry a little when I see that someone’s diarrhoea is apparently ‘just’ due to irritable bowel syndrome. While diarrhoea-predominant IBS (sometimes called IBS-D) certainly exists, loose stool and diarrhoea has a much wider possible set of causes, and there are a range of conditions which need to be excluded. Unfortunately, I frequently see patients where the appropriate work up has not been completed, and sometimes treatable conditions have been missed.
Diarrhoea and loose stool are common symptoms, and can be really debilitating. In particular, urgency and frequency of defaecation can really affect people’s quality of life, affecting their ability to work, travel, and even leave the house. It is important that symptoms are carefully evaluated with a careful history, and your previous illnesses, medications, and supplements are reviewed.
There are a wide range of conditions that can cause loose stool and diarrhoea, including:
Inflammatory conditions like Crohn’s disease, ulcerative colitis, and microscopic colitis
Autoimmune conditions like coeliac disease
Food allergies and intolerances, such as lactose intolerance
Metabolic issues, like thyroid problems
Pancreatic and biliary problems, like pancreatic exocrine insufficiency or bile acid malabsorption
Medication side effects
Issues relating to food or health supplements
These problems often need a through, careful work-up. Unfortunately patients are sometimes told everything is due to IBS, or have one test which is ‘normal’, and told there is nothing else going on. There are three conditions in particular which are often missed, which I want to discuss in more detail. These conditions all have specific treatments which can hugely help control symptoms, so accurate diagnosis is key.
The first is microscopic colitis, a type of inflammatory bowel disease. Microscopic colitis is common, and comes in two subtypes, lymphocytic colitis and collagenous colitis. Microscopic colitis causes watery diarrhoea, often with severe urgency. Microscopic colitis most commonly affects women, often in their 5th decade and beyond. The problem with diagnosing microscopic colitis is that the inflammation is not easily seen with the colonoscopy camera alone, and samples (biopsies) need to be collected from several parts of the colon and examined under the microscope to make the diagnosis. The good news is that this condition responds very well to a type of steroid medication (budesonide), with 90% or more of patients having complete resolution of symptoms with the right treatment.
The second condition that is often missed is pancreatic exocrine insufficiency (PEI). The pancreas gland secretes a range of enzymes which help with digestion, including of fats and protein. If the pancreas is not working well enough, a person can have problems with malabsorption, which leads to diarrhoea. The typical description is of fatty stools which leave an oily residue and don’t flush away (called steatorrhoea), however many patients don’t notice these features. Pancreatic exocrine insufficiency (PEI) is diagnosed on a stool test, called faecal elastase. Again, treatment with supplemental enzymes (PERT) will generally settle symptoms rapidly. It is important to check for underlying causes like structural issues with the pancreas gland, and to check for vitamin and mineral deficiencies and bone thinning.
The third condition that I often diagnose in my clinic is bile acid diarrhoea, also called bile acid malabsorption. Bile acids are secreted by the liver to help with fat emulsification and digestion. They are then reabsorbed by the end of the small intestine, the terminal ileum. However, in some situations this reabsorption does not happen and they enter the colon, causing irritation and diarrhoea. Treatment with a bile acid sequestrant (cholestyramine or colesevalam) can hugely improve symptoms.
There are a range of other conditions that can cause diarrhoea and looser stool, so careful evaluation is critical. If you’re looking to obtain a specialist opinion and get to the root cause of your symptoms, do get in touch and arrange an appointment.
