what causes diarrhoea and when can it become dangerous?

Dr Philip Woodland, Consultant Gastroenterologist at London Digestive Health, part of HCA Healthcare UK, takes us through the various causes of diarrhoea and advises on what to look out for and when there’s a need for medical advice.

What is diarrhoea?

When you frequently need to have a bowel movement, or often pass watery or loose stools, this is called diarrhoea.

Most of the time it’s nothing to be worried about and only lasts a few days, however, it can come with other unpleasant symptoms, such as nausea, cramping, bloating, dehydration, fever or even bloody stools.

Diarrhoea is considered chronic if it lasts for over four weeks.

What are the main causes of diarrhoea? 

There are several causes of diarrhoea and it happens when:

  • One of the most common causes of short-term diarrhoea is infection, where liquid secretion and absorption can both be affected.
  • Certain food is also a common culprit for loose bowel movements. This is especially common when you’re travelling and aren’t used to local cuisines, but even day-to-day things like coffee and alcohol can be triggers for many.
  • In many people, stress can be a trigger for the bowel to move more quickly and cause diarrhoea. This is why lose bowel movements can be common before exams or job interviews.

Is diarrhoea normally something that goes away on its own? 

Most of the time, diarrhoea does go away by itself and most causes (such as infections) are transient. If symptoms last more than four to six weeks then it should be checked out by a doctor, please speak to a GP or gastroenterologist if you’re concerned.

When is diarrhoea dangerous?

Diarrhoea in itself is rarely dangerous in the UK. The main danger of acute diarrhoea is dehydration. This can usually be avoided by ensuring good water intake or using oral rehydration solutions, if the diarrhoea is particularly severe. In very unusual circumstances, hospital treatment is needed.

A more frequent question is whether the diarrhoea is indicative of a serious underlying problem. Most of the time it is not, but persistent diarrhoea is an important symptom to have checked by your doctor.

Is it normal to have bloody diarrhoea?

Bloody diarrhoea is not a normal symptom. There are several causes, not all of them concerning. However, there are causes of bloody diarrhoea that are very important to diagnose and treat so it is always best to discuss with your doctor if you have this symptom.

Is it normal to have diarrhoea when pregnant?

Although it is perhaps more common to have constipation during pregnancy, diarrhoea can sometimes happen. Short spells of diarrhoea are usually nothing to worry about, however, if the diarrhoea is persistent, contains blood or wakes you up at night, then seeking medical advice is recommended.

Irritable bowel syndrome (IBS)and inflammatory bowel disease (IBD)

Diarrhoea is a symptom of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

Irritable bowel syndrome (IBS) is extremely common. The most common associated symptom is abdominal pain, often associated with a need to go to the toilet. IBS does not cause long-term harm, but, of course, can cause troublesome symptoms that your doctor can often help you with.

Any long-term change in bowel habits should be checked, but some signs are important to get looked at urgently. Particularly, if the persistent diarrhoea is associated with bleeding or if you have lost weight.

Inflammatory bowel disease (IBD) causes inflammation within the bowel, which would require medical treatment. Often simple blood tests and stool samples are sufficient to distinguish IBS from IBD. Occasionally, a camera test (colonoscopy) can provide a conclusive result very quickly, particularly if there is concern about other problems such as cancer.

Bowel cancer

For many people, diarrhoea leads to concern about bowel cancer. Most of the time this is not the cause of diarrhoea, but acting fast can mean treatment is more effective if cancer is found. This is why it’s important to seek medical attention if diarrhoea persists, or if there are concerning signs such as rectal bleeding or weight loss.

Most of the time, diarrhoea is not due to anything serious and much of the time any problems found can be dealt with fairly simply. However, it is always worth taking professional advice if you are concerned.