Ulcerative colitis

Last updated: 1 October 2026
Reviewed by: Specialist doctors from the Elfcare quality team

Recurrent bloody diarrhoea, an urgent need to use the toilet, or lower abdominal cramping that comes and goes over weeks or months are symptoms that can occur with ulcerative colitic. The same goes for mucus or blood in your stool, increased bowel frequency, fatigue, or unexplained weight loss. Ulcerative colitis is a chronic inflammatory condition that affects the colon and rectum and can vary considerably in severity and extent.

Ulcerative colitis is frequently underdiagnosed or misattributed to irritable bowel syndrome for months to years before a structural diagnosis is made. Early identification through imaging and blood testing, followed by colonoscopic confirmation, opens the door to treatment that can achieve and maintain remission and significantly reduce the long-term risks associated with chronic colonic inflammation.

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What is ulcerative colitis?

Ulcerative colitis (UC) is a chronic autoimmune inflammatory bowel disease causing continuous mucosal inflammation confined to the inner lining of the colon and rectum. Unlike Crohn's disease, which can affect any part of the gastrointestinal tract and involves all layers of the bowel wall, UC is limited to the colonic mucosa and submucosa and always begins in the rectum, extending proximally in a continuous pattern without skip lesions. For an overview of inflammatory bowel disease as a whole, see our IBD page.

UC is classified by the anatomical extent of inflammation:

  • Proctitis inflammation limited to the rectum. It commonly causes rectal bleeding, urgency, and a feeling of needing to pass stool even when the bowel is empty.

  • Left-sided colitis inflammation extending from the rectum to the splenic flexure. Symptoms can include bloody diarrhoea, increased bowel frequency, and abdominal cramping.

  • Extensive colitis or pancolitis inflammation extending beyond the splenic flexure to involve most or all of the colon. Associated with the most severe symptoms and the highest long-term colorectal cancer risk.

Ulcerative colitis often follows a relapsing and remitting course, with periods of active inflammation followed by periods when symptoms improve or disappear. Approximately 10 to 15% of patients have a chronic continuous course without remission. Flares can range from mild to severe, and severe disease can lead to complications such as toxic megacolon, which requires urgent medical treatment.

Symptoms of ulcerative colitis

The symptoms of ulcerative colitis depend on how much of the colon is affected and how active the inflammation is. Common symptoms include:

  • Rectal bleeding or bloody diarrhoea. A common and characteristic symptom, particularly when inflammation is active

  • Increased stool frequency, often with urgency and tenesmus (a feeling of needing to pass stool even when the bowel is empty)

  • Lower abdominal cramping, typically in the left lower abdomen

  • Mucus in the stool

  • Persistent fatigue, which can be related to inflammation, anaemia, or disturbed sleep

  • Weight loss and reduced appetite during significant flares

  • Fever during moderate to severe flares

Extraintestinal manifestations affect up to 30% of UC patients:

Ulcerative colitis can also affect parts of the body outside the digestive system. These extraintestinal manifestations can include:

  • Joint pain and swelling from peripheral arthropathy or axial arthritis

  • Eye inflammation including uveitis and episcleritis

  • Skin conditions including erythema nodosum and pyoderma gangrenosum

  • Primary sclerosing cholangitis (PSC), a chronic inflammatory condition affecting the bile ducts. It occurs in a minority of people with IBD and requires separate medical assessment

Severe UC, urgent features:

  • six or more bloody stools in 24 hours

  • fever, rapid heart rate or other signs of systemic illness

  • significant anaemia or raised inflammatory markers

  • severe abdominal pain, dehydration or marked weakness

Important: Severe bloody diarrhoea with fever, tachycardia, and abdominal distension may indicate toxic megacolon, a surgical emergency. Seek immediate medical attention.

What causes ulcerative colitis?

The exact cause of ulcerative colitis is not fully understood. It is thought to develop through a combination of genetic, immune, environmental, and gut microbiome factors:

  • Immune dysregulation in people who are susceptible to UC, the immune system can respond abnormally to substances and microorganisms normally present in the intestine, resulting in persistent inflammation

  • Genetic predisposition many genetic variants are associated with IBD and can influence the intestinal immune response and the function of the intestinal barrier

  • Gut microbiome changes in the composition and function of intestinal microorganisms are associated with IBD. It remains unclear whether these changes are a cause, a consequence of inflammation, or both

  • Environmental factors diet, antibiotic exposure, smoking, stress and other environmental factors may influence the risk or course of IBD, but no single environmental factor explains why a person develops UC

  • Psychological stress does not appear to be a simple cause of UC, but stress may influence symptoms and can contribute to disease flares in some people

  • Non-steroidal anti-inflammatory drugs (NSAIDs) can trigger or worsen UC flares through prostaglandin inhibition affecting mucosal protection

How is ulcerative colitis detected?

Ulcerative colitis is diagnosed using a combination of symptoms, stool and blood tests, endoscopic assessment and biopsy. Colonoscopy with biopsies is the key diagnostic examination.

Abdominal MRI Elfcare's full body MRI images the colon directly as part of the standard abdominal sequence. It can provide information about the bowel and surrounding abdominal structures. Dedicated intestinal MRI techniques may be useful in selected patients to assess bowel inflammation or investigate complications, particularly when Crohn's disease or another structural condition is being considered.

Blood tests assess the inflammatory burden, nutritional consequences, and systemic impact of UC. Relevant markers in Elfcare's panel include:

  • CRPkey inflammatory marker that correlates with disease severity and guides treatment.

  • Full blood count and hemoglobin identifies anemia from chronic rectal bleeding and flags active flares.

  • Ferritin and serum iron confirms depleted iron stores resulting from ongoing blood loss.

  • Albumin low levels signal active mucosal inflammation, protein loss, and nutritional depletion.

  • ALP and GGT evaluates liver function to screen for Primary Sclerosing Cholangitis (PSC).

  • Bilirubin detects potential bile duct blockages linked to PSC.

  • Vitamin D checks for deficiencies caused by poor absorption and flare-related lifestyle changes.

  • tTG-IgA rules out celiac disease, which presents with similar symptoms.

  • Platelet count high levels reflect systemic inflammation during active disease flares.

If symptoms, blood tests or stool tests raise concern for inflammatory bowel disease, further assessment by a gastroenterologist may be required, including colonoscopy or flexible sigmoidoscopy with biopsies.

Why early detection matters

Persistent intestinal inflammation in ulcerative colitis is associated with an increased risk of complications over time. The risk of colorectal cancer is influenced by several factors, including the duration and extent of colonic inflammation, the severity of ongoing inflammation, the presence of primary sclerosing cholangitis, family history and previous dysplasia. Modern estimates suggest that the overall colorectal cancer risk in IBD is lower than historically reported, but it remains higher than in the general population for people with colonic IBD.

Effective treatment aims to control symptoms and inflammation and to maintain long-term remission. Current treatment strategies use a treat-to-target approach, with endoscopic improvement or remission an important treatment goal. Achieving good control of inflammation can reduce the risk of hospitalisation, surgery and other complications.

People with colonic IBD may also need regular colonoscopic surveillance depending on their individual risk factors. Current guidance recommends risk assessment based on disease duration, extent, inflammatory activity and other factors rather than applying the same surveillance schedule to everyone.

How Elfcare can help

Elfcare's abdominal MRI can provide information about the abdominal organs and bowel. MRI cannot diagnose ulcerative colitis on its own, but it may provide useful information about the bowel and help identify findings that need further assessment.

Our blood panel covers CRP, haemoglobin, ferritin, albumin, ALP, GGT, bilirubin, vitamin D, and platelet count, providing a comprehensive picture of inflammatory activity, nutritional status, and the hepatic consequences most specifically associated with UC.

If our MRI or blood tests identify findings consistent with UC, we take care of further diagnostics or refer you to the appropriate specialist, typically a gastroenterologist with IBD expertise.

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Summary

Ulcerative colitis is a chronic immune-mediated inflammatory bowel disease that primarily affects the colon and rectum. Symptoms can include bloody diarrhoea, bowel urgency, increased stool frequency, abdominal cramping and fatigue. The condition can vary considerably in extent and severity and may also cause symptoms outside the digestive system.

Elfcare's abdominal MRI images the colon directly, assessing disease extent and identifying complications, while our blood panel covers CRP, haemoglobin, ferritin, albumin, liver function, and vitamin D. Early identification and effective treatment achieving mucosal healing is the most important investment in protecting long-term colonic health and reducing the colorectal cancer risk that chronic uncontrolled UC accumulates, a clear example of how early detection directly shapes long-term health.

Last updated: 1 October 2026
Reviewed by: Specialist doctors from the quality team at Elfcare

FAQ

  • Ulcerative colitis is a chronic autoimmune inflammatory bowel disease causing continuous mucosal inflammation confined to the inner lining of the colon and rectum, always beginning in the rectum and extending proximally in a continuous pattern. It is one of the two main forms of inflammatory bowel disease, distinct from Crohn's disease which can affect any part of the gastrointestinal tract and involves all bowel wall layers. It follows a relapsing and remitting course and is associated with a significantly elevated colorectal cancer risk with long-standing extensive disease.

  • Rectal bleeding or bloody diarrhoea, increased stool frequency with urgency and tenesmus, lower abdominal cramping, mucus in the stool, fatigue, and weight loss during significant flares. Extraintestinal manifestations including joint pain, eye inflammation, and skin conditions affect up to 30% of patients. Severe UC with more than six bloody stools per day, fever, and tachycardia requires urgent hospital assessment.

  • An abnormal Th2 mucosal immune response to colonic bacteria in genetically susceptible individuals. Gut microbiome disruption, westernised diet, antibiotic use, reduced microbial exposure, psychological stress, and NSAIDs all contribute. Smoking has a paradoxically protective effect in UC, the inverse of its role in Crohn's disease.

  • Abdominal MRI identifies colonic wall thickening, mucosal hyperenhancement, and disease extent, alongside complications including toxic megacolon and PSC-related biliary changes. Blood tests covering CRP, haemoglobin, ferritin, albumin, and liver function assess inflammatory activity and nutritional consequences. Faecal calprotectin distinguishes active inflammation from functional symptoms. Definitive diagnosis requires colonoscopy with biopsy.

  • Yes. Elfcare's abdominal MRI images the colon directly and our blood panel covers CRP, haemoglobin, ferritin, albumin, ALP, GGT, bilirubin, and vitamin D. If findings consistent with UC are identified, we take care of further diagnostics or refer you to the appropriate specialist.

  • Yes. UC is managed with a stepwise approach from aminosalicylates (mesalazine) for mild disease through corticosteroids for acute flares, immunomodulators including azathioprine, and biological therapies including anti-TNF agents, vedolizumab, and tofacitinib for moderate to severe disease. Colectomy is curative for UC confined to the colon and is considered for medically refractory disease or dysplasia. Early effective treatment achieving mucosal healing reduces both symptom burden and the long-term colorectal cancer risk that chronic active UC accumulates over time.