Complications of IBD

Complications of inflammatory bowel disease (IBD) are generally separated into ones that directly affect the gut (local) and ones that affect other organs in the body (systemic). Complications may also differ between Crohn’s disease and ulcerative with some being more likely in one over the other.

Key points 

  • Inflammation of the gut can lead to different types of damage that need to be treated by medication or surgery. 
  • Keeping track of your symptoms will help you notice any changes in your health so that you can deal with any complications early. 
  • The most common types of gut complications caused by Crohn’s disease are fistulae and strictures. 
  • Some complications like perforation of the bowel and fulminant colitis will lead to emergency treatment. 

IBD complications that affect the gut 

Complications in the gut are usually caused by long-term (chronic) inflammation. Not everyone will experience these complications but finding them early is important to reach the best health outcome. Always contact your doctor if you notice a change in your symptoms. 


A fistula is a small tunnel that can form between the intestine and another part of the body. For example, a fistula can form between the gut and bladder or between the gut and skin. The most common type of fistula is called a perianal fistula, which connects the gut and the skin around the anus. 

Fistulae are more common in Crohn’s disease than in ulcerative colitis, affecting around a third of people with Crohn’s. 


Abscess – when fluid gathers inside a fistula and becomes infected.  

Urinary tract infection (UTI) – may cause a burning feeling when urinating, cloudy urine or blood in urine. 

Passing of stool and undigested food between areas connected by fistulae. 


Fistulae are connected to inflammation caused by IBD and getting the inflammation under control should decrease the chances of a fistula forming.  

Fistulae around the anus are usually monitored using careful physical examination, ultrasound, or MRI to make sure there is no infection or abscess. 

There are a few treatments that are effective for managing fistulae: 

  • Anti-TNF biologics, such as infliximab, can close fistulae, often permanently. 
  • Antibiotics, such as metronidazole or ciprofloxacin, can help to treat infection related to a fistulae. 
  • Immunosuppressants, such as azathioprine, may help but are less effective than biologics. 
  • Surgery may be required if the fistula is severe but it is generally not recommended. 
  • Research is growing around the use of stem cells to encourage healing of fistulae. 

Anal Fissures  

Anal fissures are small tears in the lining of the anus. They may cause sharp pain and bleed when passing stool and are fairly common in Crohn’s disease and rare in ulcerative colitis. 

Anal fissures usually heal by themselves over time but can return if you have constipation. They can be managed with a high-fibre diet, warm baths and nitroglycerine or diltiazem ointment. If they are very serious, Botox injections may be used. 

Fulminant colitis 

Fulminant colitis usually affects people with ulcerative colitis but less then 10% will ever experience it. This complication involves severe inflammation of the large intestine (colon) which causes the intestine to dilate (widen). This will lead to a condition call ileus where the normal movement of the intestine to pass faeces and gas through the gut will stop. 

If the ileus worsens, it can lead to a toxic megacolon. This is one of the most serious medical complications in IBD. Symptoms may include: 

  • Fever 
  • Swollen and tender belly 
  • Bloody diarrhoea more than 10 times a day 
  • Fast heartbeat 
  • Low blood pressure 


Both fulminant colitis and toxic megacolon are medical emergencies and need immediate medical attention. Medications used will usually include steroids. Surgery may mean removing the inflamed part of the large bowel and creating a pouch to hold the stool. Treating a toxic megacolon will often also include a nasogastric (through the nose) tube that will suck up the excess air in the large bowel and reduce the chances of the bowel tearing. 

Colon Cancer 

Around 5 to 8 per cent of people with ulcerative colitis will develop colon cancer as compared to the 3 to 6 per cent of the general population that will develop it. The risk of colon cancer increases the longer you have IBD and if the inflammation is severe. The link between colon cancer and Crohn’s disease is weaker and exists only when the disease is affecting the colon. 

Small intestinal bacterial overgrowth (SIBO) 

SIBO involves large amounts of bacteria being present in the small intestine. The bacteria become overachievers in digesting food leading to gas, abdominal pain, bloating and diarrhoea. SIBO usually occurs in Crohn’s disease but may also occur in ulcerative colitis. The condition is often treated successfully with antibiotics. 


Adhesions are scar tissue that sticks the intestine to the abdominal wall, to other parts of the intestine, or to another organ. Adhesions can cause the intestine to twist, causing a blockage. 

Abdominal surgery is the main cause of adhesions but can sometimes happen because of inflammation. 


Symptoms of adhesions may include: 

  • Chronic bloating 
  • Abdominal cramping
  • Changed bowel habits such as constipation 
  • Nausea 
  • Gut blockage, which may cause the above symptoms 
  • Female infertility 
  • In females, painful sexual intercourse 
  • Rectal bleeding and painful passing of stool during menstruation 


There are currently no medications that are effective in the treatment of adhesions. 

If the main symptom is abdominal cramps, it might be worthwhile to try a muscle relaxant, such as dicyclomine. 

If the adhesion is the cause of constipation, increasing fibre intake generally does not help and it could make constipation worse.  A low-fibre diet may be recommended. 

In some patients, surgery can break down the adhesions. But in around 70% of cases the surgery will cause more adhesions. 

Strictures and fibrosis

A stricture is a narrowing of part of the gut because of scar tissue (fibrosis). Inflammation damages the lining of the gut causing the scar tissue to increase and replace healthy cells. If the narrowing becomes severe it can lead to a bowel obstruction. 

Strictures are more common in Crohn’s disease than ulcerative colitis.  In Crohn’s disease, a quarter of people have had at least once stricture in their small intestine. The most common place for a stricture to form is at the end of the small intestine (ileum) but can also form in the upper part of the digestive system (mouth to beginning of small intestine), colon, rectum or anus. 


Symptoms will be different depending on where the stricture is. If the stricture has led to a bowel obstruction (blockage), symptoms may include: 

  • Nausea and vomiting 
  • Abdominal pain 
  • Bloating 
  • Inability to pass gas or stool 

Strictures can be diagnosed with either an endoscopy, CT scan, MRI or ultrasound. 


If there is still inflammation in the area, medications that reduce inflammation can decrease the swelling and open up the blockage. 

There is also a procedure called endoscopy with balloon dilation that can help. A gastroenterologist will pass a balloon at the end of a colonoscope through the narrowed area of the gut. 

Surgery may be required if the stricture has caused a significant blockage or unmanageable symptoms.  

Learn more about Surgery and IBD

Perforation of the bowel

Perforation of the intestines happens when inflammation is out of control. Inflammation can lead to ulcers (sores) forming on the intestines that weaken the intestinal wall. When the wall becomes too weak a hole can form which can lead to life threatening infections (peritonitis). 


Surgery is usually required to repair the hole in the intestines and can lead to a stoma. But sometimes doctors may prefer to wait and see if the gut can heal itself and prescribe antibiotics for the infection. 


An ostomy is a surgery to create a small opening (stoma) that allows the intestine inside your body to exit through the surface of your belly (abdomen). A bag is then fitted to the stoma to collect waste. 

For more information read our life with a stoma or Managing a high output stoma through diet page.

Other conditions connected to IBD 

It is not uncommon for people with inflammatory bowel disease (IBD) to experience health complications not only in the gut but also in other areas of the body. Nearly half of people with IBD will experience some sort of health complication related to their IBD. It can be to do with the eyes, joints, skin, bones, kidneys and/or liver. 

For more information read other conditions connected to IBD.