How inflammatory bowel disease affects the body

Written by: Professor Stuart Bloom
Published: | Updated: 19/04/2023
Edited by: Cal Murphy

Inflammatory bowel disease (IBD) is a term that generally refers to two chronic digestive system conditions: ulcerative colitis and Crohn’s disease. But can these conditions have an effect on the body outside the gut? Top Doctors interviews Dr Stuart Bloom, an expert on Crohn’s and colitis, who explained how these conditions affect the body.

How does inflammatory bowel disease affect the digestive system?

The ways in which inflammatory bowel disease affects the digestive system, depends on whether the condition is ulcerative colitis or Crohn’s disease.


Ulcerative colitis tends to affect just the colon (large bowel) and therefore, in general, it presents with bleeding from the back passage and diarrhoea. It can vary in the amount of the colon that it involves, so patients can sometimes get just bleeding associated with some urgency, or some frequent visits to the bathroom without bleeding, or, if the disease affects a larger part of the bowel, there can be a rather unpleasant mixture of blood and diarrhoea, which, again, can affect the patient with frequent lavatory visits, sometimes getting them up in the middle of the night.


Crohn's disease most commonly presents with abdominal pain and diarrhoea, although in a small proportion of patients, if the large bowel is affected, it can produce bleeding, a bit like colitis. If other parts of the digestive tract are involved, like the oesophagus, the gullet, or the stomach, it can present with upper abdominal pain, indigestion-type symptoms, or problems with swallowing. Sometimes, Crohn’s can affect the bottom area – so-called perianal disease – when it can produce some discharge or some discomfort around the bottom.



How does inflammatory bowel disease affect the rest of the body?

Inflammatory bowel diseases - ulcerative colitis and Crohn’s disease - can sometimes affect other parts of the body.

  • The joints – in 15-20 per cent of cases, patients can get joint symptoms, which can sometimes mirror the activity of the inflamed intestines.
  • The liver – sometimes, for reasons that we don’t fully understand, the diseases can affect the liver and this produces a condition called primary sclerosing cholangitis (PSC) – a big medical label, but what it actually means is inflammation of the liver which goes with inflammatory bowel disease.
  • The skin can also be affected. There are various inflammatory conditions, like pyoderma and erythema nodosum – again, just sort of Latin labels, but detailing rather nasty, painful, inflammatory conditions of the skin, which are usually active when the inflammatory bowel disease is active.
  • The eyes – IBD can cause iritis and uveitis, which leads to sore, red eyes.




If you are concerned you may have Crohn's or ulcerative colitis, arrange a consultation with Dr Bloom via his Top Doctors profile

By Professor Stuart Bloom

Professor Stuart Bloom is a gastroenterologist based in London. He is an expert in inflammatory bowel disease, as well as the management of irritable bowel syndrome and food intolerance. He leads the inflammatory bowel disease clinic at University College London Hospitals, where he has worked as a consultant since 1996.

Professor Bloom is the Senior Author of the current British Society of Gastroenterology (BSG) guidelines for managing Colitis and Crohn’s disease, published in 2010. He was chair of the UK clinical research network in Gastroenterology from 2008-2013. He is currently chair of the UK IBD registry.

Professor Stuart Bloom is also an accredited bowel cancer screening colonoscopist, with a low rate of complications during colonoscopies. He has been recognised for his expertise and contributions to medicine in his field (The Leslie Parrott Prize from the National Association of Crohn’s and Colitis (1994), the President's medal from the British Society of Gastroenterology (2013)).

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