What Is Ulcerative Colitis?

Table of Contents
View All
Table of Contents

Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) that primarily affects the large intestine (colon). It may also cause signs and symptoms in other body systems, which are called extra-intestinal manifestations. There is currently no cure for this disease though medications and lifestyle adjustments can make it more manageable.

Person sitting on couch with hands on abdomen

Vichuda Sirisarakarn / EyeEm / Getty Images

Types of Ulcerative Colitis

Ulcerative colitis affects the large intestine in various ways. The inflammation the disease causes begins in the rectum. It may then spread up into the other parts of the colon. The types of ulcerative colitis are usually divided into four buckets: proctitis, proctosigmoiditis, left-sided colitis, and pancolitis (also called extensive colitis).

  • Proctitis: The inflammation the disease causes affects the last part of the large intestine, the rectum.
  • Proctosigmoiditis: This affects the last section of the colon (sigmoid colon) and the rectum.
  • Left-sided colitis: This affects the rectum, the sigmoid colon, and the transverse colon. All these sections are after what is called the splenic flexure, where the transverse colon meets the descending colon.
  • Pancolitis: Inflammation goes up all the way from the rectum through the large intestine to beyond the splenic flexure and into the transverse colon and ascending colon.

One study showed that of people with ulcerative colitis, 18% had proctitis, 22% had proctosigmoiditis, 28% had left-sided colitis, and 32% had pancolitis.

Ulcerative Colitis vs. Crohn’s Disease

Crohn's disease is another common form of IBD. The biggest difference between Crohn's disease and ulcerative colitis is that Crohn's disease can affect the digestive system beyond the large intestine. This includes but is not limited to the small intestine, stomach, esophagus, and mouth.

Some of the other differences include:

  • Bleeding from the rectum is more common in ulcerative colitis than in Crohn's disease.
  • Crohn's disease affects all layers of the walls of the intestines, while ulcerative colitis affects only the inner layer.
  • Inflammation is continuous in ulcerative colitis and patchy in Crohn's disease.
  • Pain in ulcerative colitis is more common in the lower left abdomen and more common in the lower right abdomen in Crohn's disease.

What Causes Ulcerative Colitis?

What causes ulcerative colitis is not yet well understood. There are several theories as to what might start the inflammatory process. One of the most common is that there are probably several things (including genetics and environmental triggers) that work together to lead to the development of the disease.

Genetics: There is some inheritability to ulcerative colitis, but it doesn't pass directly from parent to child. Genetics may play a role in 20–25% of cases of IBD, meaning that most people do not have a family history of the disease. Hundreds of genes have been identified as associated with one or more forms of IBD.

Environmental factors: Other factors besides genetics are involved in IBD. These are not yet completely understood. However, as more is discovered about IBD, the list continues to improve in terms of definition and support. 

Some of the environmental risk factors that studies show may play a part in developing IBD include:

Microbiome: The microbiome is the community of microbes that naturally live in the intestinal tract, including bacteria, viruses, and fungi. Studies show that people with IBD have changes in their microbiome compared to those without IBD. However, whether that happens before IBD develops or because of the IBD is not yet determined.

Immune system changes: IBD is an immune-mediated condition, meaning that it disrupts the immune system. The immune system may respond inappropriately, which could lead to a series of events that results in inflammation.

What Triggers UC to Flare Up?

Ulcerative colitis goes through periods when it is less active and more active. It’s not always clear why the disease begins to pick up activity again and why it subsides.

Many people with ulcerative colitis will learn what triggers their disease over time. There has been some study to understand what might cause a flare-up, but it’s not settled science. These include:    

  • Antibiotics: Treatment with antibiotics can cause an imbalance in the microbiome of the digestive tract. Antibiotics may trigger a flare-up of ulcerative colitis in some people.
  • Diet: Diet doesn’t cause ulcerative colitis or other forms of IBD, but some people find it affects their symptoms. Most people learn over time what foods may they have more difficulty eating during a flare-up or can tolerate better during remission.
  • Heat waves: Some data from patient registries shows that heat waves may be associated with disease flare-ups.
  • International travel: Traveling by plane internationally may be associated with flare-ups. The effect might be increased in people with higher fecal calprotectin levels (a protein in stool found in higher levels in people with IBD) and other health conditions.
  • Low vitamin D levels: People with ulcerative colitis are at risk for low vitamin D levels. Low vitamin D has been associated with an increased risk of flare-ups and the development of colorectal cancer.
  • Non-steroidal anti-inflammatory drugs (NSAIDs): Some studies show a connection between NSAIDs leading to flare-ups of ulcerative colitis, but others show there is none.
  • Stopping medications: Probably the most consistent factor in causing a flare-up is stopping medications or not taking them as prescribed.
  • Stress: Stressful events don’t cause ulcerative colitis. However, some people find that stress can lead to disease flare-ups.

Symptoms of Ulcerative Colitis

Ulcerative colitis mainly affects the large intestine. However, there can also be symptoms outside of the digestive tract, called extra-intestinal symptoms. 

Some of the signs and symptoms experienced by people with ulcerative colitis include:

  • Abdominal cramping
  • Abdominal pain
  • Anemia (a low level of healthy red blood cells)
  • Bloody stools
  • Chronic diarrhea
  • Fever
  • Mucus in the stool
  • Tenesmus (a feeling of pressure in the anus)
  • Urgent need to use the bathroom
  • Weight loss

How to Diagnose Ulcerative Colitis

Ulcerative colitis is usually suspected because of symptoms such as diarrhea, bloody stools, and abdominal pain or cramping. However, it’s important to make a clear diagnosis, which various tests can accomplish.

A colonoscopy is usually the test whose results provide the final pieces of information for the diagnosis. Other tests, including blood and stool tests, will usually monitor the effects of the disease on the body.

Some of the tests that may contribute to an ulcerative colitis diagnosis include:

  • Barium enema: Contrast dye in combination with an X-ray explores the lower part of the digestive system. This test may help rule out other conditions or to see if there is any inflammation in the area.
  • Complete blood cell (CBC) count: Because ulcerative colitis causes bleeding and inflammation, this blood test may monitor for low levels of red blood cells and high levels of white blood cells.
  • Colonoscopy: This test inserts a flexible tube into the anus in order to look at the inside of the colon and see any inflammation. Biopsies (microscopically analyzed tissue samples) can also help in making the diagnosis.
  • Electrolyte panel: Diarrhea can deplete electrolytes (essential charged compounds and minerals) and this blood test can monitor them. 
  • Fecal calprotectin: This stool test measures levels of a protein found in higher levels in the stool of people who have an IBD.
  • Liver function tests: Ulcerative colitis and other forms of IBD can be associated with liver disease. A blood test can monitor liver enzymes.
  • Sigmoidoscopy: Similar to a colonoscopy, a sigmoidoscopy uses a flexible tube to see inside the colon via the anus. In this test, only the last part of the colon can be seen, which may be enough to see inflammation in the area caused by ulcerative colitis.
  • Stool tests: A stool test can rule out infections that could cause similar symptoms.
  • X-rays: An X-ray has a limited role in ulcerative colitis, especially now in an era of better testing. A plain abdominal X-ray might aid in diagnosis under some circumstances.

Treatment for Ulcerative Colitis

Treatment for ulcerative colitis depends on the severity of the disease. Medications, changes to diet and lifestyle, and surgery might all factor into it. Though there are guidelines as to how to treat ulcerative colitis, it is usually specific to each person.


Several different types of medications treat ulcerative colitis. They include oral medications, injections, and intravenous infusions. In some cases, especially during a flare-up, two or more medications might apply at the same time.

These include:


In some cases, ulcerative colitis becomes unmanageable, life-threatening, or causes low quality of life. These cases might require surgery. There are medical reasons for surgery, but there are also emotional ones. Some people choose surgery as their form of treatment. There are a few surgical options for treating ulcerative colitis.

Colectomy with ileostomy: A colectomy is the total removal of the colon. After this surgery, the stool must leave the body by means other than through the anus. One way is through an ileostomy.

An ileostomy is when a part of the small intestine comes out through the abdomen to create a stoma. A bag is worn over the stoma to collect stool and emptied out several times a day.

After a colectomy with the placement of an ileostomy, some people go on to have another surgery called a proctectomy. In this surgery, the rectum and anus are removed. This surgery might apply for people who continue to have symptoms even after having a colectomy.

Colectomy with ileal pouch-anal anastomosis (IPAA): This surgery is more commonly known as a J-pouch. The last part of the small intestine is fashioned into a reservoir for stool. It is connected to either the anus or a rectal stump, and stool passes through the bottom.

Usually, the reservoir is made into the shape of a J, but it can take the shape of an S or a W (though these are less common).

Continent ostomy: Various types of continent ostomy surgeries for ulcerative colitis have developed. The most common is the Kock pouch. This surgery involves the creation of a nipple valve on the abdomen, and stool is eliminated through the use of a catheter. An external bag is not necessary. This surgery is less common since the development of the j-pouch in the 1980s.

How Diet Impacts Ulcerative Colitis

Diet is an important and also challenging topic for people living with ulcerative colitis. Diet matters, but the specifics are on an individual basis. There are no published guidelines on diet, and study is ongoing. 

Healthcare providers (such as dietitians) that specialize in diet and IBD can help people develop a personalized nutrition plan. A Mediterranean diet is sometimes recommended as a starting point for making dietary changes.

In some cases, other established diets developed for IBD or gastrointestinal conditions may help navigate the process of trial and error. 

Some of the diets that are undergoing study or that people with ulcerative colitis have tried include:

Ulcerative Colitis in Children

Ulcerative colitis is most often diagnosed between the ages of 15 and 35, but it can also be diagnosed in younger children. Though the symptoms may be similar to those in adults, children sometimes also experience symptoms in their upper digestive system, such as gastroesophageal reflux or dyspepsia.

Ulcerative colitis may be treated differently in children than it is in adults. Special attention can ensure that children are receiving proper nutrition and are growing well. Psychological considerations are also important to make sure children can attend school and socialize with friends and peers.

The treatments may be similar to those that are for adults and will depend on the stage and severity of the disease. Other considerations will include taking lifestyle and patient and parental preferences into account (such as preferring long-acting versus daily medications or preferring oral medications to injectables).

Additionally, longstanding ulcerative colitis, pancolitis in particular, is associated with a risk of colorectal cancer. For children, the duration of disease over their lifetime will be longer, so monitoring for cancer as they age will be part of managing the disease. Colon cancer is rare in children with ulcerative colitis.

Complications of Ulcerative Colitis

Ulcerative colitis can bring some complications, both in the digestive system and outside of it. Not everyone has complications, but understanding what they are can help catch them if they occur. As many as 17% of people with ulcerative colitis may have an extra-intestinal manifestation.

Anemia: The bleeding ulcerative colitis causes may lead to significant blood loss. In addition, not absorbing enough nutrients or not eating enough of the right nutrients can lead to anemia. At the time of diagnosis, approximately 20% of people have anemia. For those with long-standing disease, the rate is closer to 10%.

Colon cancer: Ulcerative colitis is associated with a higher risk of colon cancer. It is of special concern for those who have had the disease for about eight years, have uncontrolled inflammation, and have disease throughout the colon (pancolitis).

The risk may be as much as five times higher than in people without ulcerative colitis. A yearly or biennial colonoscopy to monitor for colon cancer may be recommended. 

Primary sclerosing cholangitis (PSC): PSC is a liver disease more common in people with ulcerative colitis. It may be found in 0.6% of people who have it.

Venous thromboembolism: Thromboembolisms are blood clots in blood vessels. They are more common in people with ulcerative colitis. Having severe disease may increase the risk of blood clots. The cumulative risk is about 1%, which is still relatively rare. However, it is a serious complication.

Tips for Managing Ulcerative Colitis

Ulcerative colitis currently has no cure, but medications and lifestyle changes can help to manage it. The disease may go through periods of activity and remission. Getting proactive about treatments can help manage the disease's ups and downs.

Flare-ups may not be avoidable in some cases. But research shows that missing medication doses or stopping medication is the thing that is most often associated with a flare-up.

Getting some control over the disease may seem impossible. But there are things people with ulcerative colitis can do for better overall health:

  • Be mindful of your diet and try keeping a food journal.
  • Develop a treatment plan with a healthcare provider.
  • Drink enough water or other liquids every day.
  • Keep stress levels low.
  • Prioritize rest and sleep.
  • See a healthcare provider regularly for both routine and specialist care.
  • Seek therapy from a therapist who works with people who live with chronic diseases
  • Stay active and get low-impact exercise regularly.
  • Use meditation, journaling, or other techniques to manage mental health.

Work closely with your healthcare provider to develop a treatment plan. This includes making decisions together, so focus on making your treatment goals known. Preferences and lifestyle are important, and there are enough therapies available now that you should be able to craft a treatment plan that suits you.

The outlook for people with ulcerative colitis is good, especially as more about the disease is understood and new treatments continue to develop.

18 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Saleem A, Zeeshan M, Hazoor F, Mustafa G. Sigmoidoscopic extent of ulcerative colitis and associated factors in Pakistani population. Pak J Med Sci. 2022;38:276-280. doi:10.12669/pjms.38.1.4648

  2. Waugh N, Cummins E, Royle P, et al. Faecal calprotectin testing for differentiating amongst inflammatory and non-inflammatory bowel diseases: systematic review and economic evaluation. Southampton (UK): NIHR Journals Library; 2013 Nov. (Health Technology Assessment, No. 17.55.)

  3. Zhang YZ, Li YY. Inflammatory bowel disease: pathogenesis. World J Gastroenterol. 2014;20:91–99. doi:10.3748/wjg.v20.i1.91

  4. Rogler G, Zeitz J, Biedermann L. The search for causative environmental factors in inflammatory bowel disease. Dig Dis. 2016;34 Suppl 1:48-55. doi:10.1159/000447283

  5. University Hospitals. Inflammatory bowel disease diet.

  6. Park J, Yoon H, Shin CM, et al. Clinical factors to predict flare-up in patients with inflammatory bowel disease during international air travel: a prospective study. PLoS One. 2022;17(1):e0262571.  doi:10.1371/journal.pone.0262571

  7. Feagins LA, Iqbal R, Spechler SJ. Case-control study of factors that trigger inflammatory bowel disease flares. World J Gastroenterol. 2014;20:4329-4334. doi:10.3748/wjg.v20.i15.4329

  8. Lamb CA, Kennedy NA, Raine T, et al. British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults. Gut. 2019;68(Suppl 3):s1-s106. doi:10.1136/gutjnl-2019-318484

  9. Rubin DT, Ananthakrishnan AN, Siegel CA, et al. ACG Clinical Guideline: ulcerative colitis in adults. Am J Gastroenterol. 2019;114:384-413. doi:10.14309/ajg.0000000000000152

  10. Kayal M, Rubin P, Bauer J, Waye JD. The Kock pouch in the 21st century (with videos). Gastrointest Endosc. 2020;92:184-189. doi:10.1016/j.gie.2020.02.031. 

  11. Olendzki B, Bucci V, Cawley C, et al. Dietary manipulation of the gut microbiome in inflammatory bowel disease patients: pilot study. Gut Microbes. 2022;14:2046244. doi:10.1080/19490976.2022.2046244

  12. Cox SR, Lindsay JO, Fromentin S, et al. Effects of low FODMAP diet on symptoms, fecal microbiome, and markers of inflammation in patients with quiescent inflammatory bowel disease in a randomized trial. Gastroenterology. 2020;158:176-188.e7. doi:10.1053/j.gastro.2019.09.024. 

  13. Mount Sinai. Ulcerative colitis.

  14. Oliveira SB, Monteiro IM. Diagnosis and management of inflammatory bowel disease in childrenBMJ. 2017;357:j2083. doi:10.1136/bmj.j2083

  15. Cabrera JM, Sato TT. Medical and surgical management of pediatric ulcerative colitis. Clin Colon Rectal Surg. 2018;31:71-79. doi:10.1055/s-0037-1609021

  16. Fumery M, Singh S, Dulai PS, et al. Natural history of adult ulcerative colitis in population-based cohorts: a systematic review. Clin Gastroenterol H. 2018;16:343-356.e3. doi:10.1016/j.cgh.2017.06.016

  17. Ungaro R, Mehandru S, Allen PB, et al. Ulcerative colitis. Lancet. 2017;389:1756-1770. doi:10.1016/s0140-6736(16)32126-2. 

  18. Taft TH, Ballou S, Bedell A, Lincenberg D. Psychological considerations and interventions in inflammatory bowel disease patient care. Gastroenterol Clin North Am. 2017;46:847-858. doi:10.1016/j.gtc.2017.08.007

Additional Reading

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.