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What is colitis?
In medicine, colitis is the inflammation of the colon, the second major segment of the large intestine.
The colon is a section of the digestive tract located between the cecum and the rectum, and is anatomically divided into three main portions:
- The ascending colon
- The transverse colon
- The descending colon
The colon’s primary function is to move digested food content along its length through segmental and propulsive contractions of the muscles within its wall. As food moves through the colon, it processes the waste products remaining after digestion in the small intestine, primarily by reabsorbing water and residual electrolytes. What remains after this process forms the food residue known as stool, which is then transported to the rectum, where it is eventually expelled through the anus.
There are numerous possible causes of colitis, including:
- Infections
- Inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis
- Ischemic colitis
- Allergic reactions
The term “colitis” should therefore always be paired, whenever possible, with a more specific term clearly identifying the underlying condition, or otherwise used only to describe inflammation whose exact cause has not yet been determined. Despite this, the word “colitis” is still frequently misunderstood today, as it is commonly used, particularly outside of medical settings, to refer to one specific condition of the colon known as irritable bowel syndrome, also called spastic colitis or nervous colitis. For more information on this specific condition, please refer to our dedicated article and the article on the necessary dietary approach.
The causes of colitis can broadly be divided into acute and chronic forms.
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Acute colitis refers to inflammation of the colon that develops rapidly, within hours or a few days. A classic example of acute colitis is that caused by an infection.
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Chronic colitis, on the other hand, refers to inflammation that develops more slowly, insidiously and gradually over the course of weeks or even months, and that persists with an intermittent pattern over long periods of time. Among the chronic forms of colitis, the most significant are irritable bowel syndrome and inflammatory bowel disease.
Colitis can be further classified based on whether it affects the entire colon or is limited to only certain segments. For example, Crohn’s disease typically affects only specific portions of the colon, while infectious colitis usually involves the colon in its entirety.
Colitis typically presents with classic gastrointestinal symptoms, including:
- Constipation and/or diarrhea
- Abdominal pain and cramping, sometimes relieved by having a bowel movement or passing gas
- Bloating and flatulence
- Mucus in the stool, and sometimes blood in the stool as well
Diagnosing the specific underlying cause of colitis is often a lengthy, complex, and multi-step process. It is typically first suspected based on the patient’s clinical history, and confirming the diagnosis usually requires numerous blood tests, stool tests, and, in many cases, instrumental investigations such as colonoscopy.
Treatment approaches for colitis vary considerably depending on the specific underlying cause. These are often long-term therapies, sometimes needing to be continued for life. In certain cases, particularly with inflammatory bowel disease, surgical treatment may also become necessary.
Causes
The causes of colitis are numerous, complex, and highly specific depending on the particular type of inflammation involved.
The most important causes of colitis include:
Infectious Colitis
Infectious colitis is, in most cases, caused by bacterial infections, although cases caused by viruses, fungi, or parasites also occur. Among the bacteria most frequently responsible for colitis are:
- Campylobacter
- Clostridium difficile
- Shigella
- Escherichia coli
- Yersinia
- Salmonella
These infections typically occur as a result of ingesting contaminated food. Symptoms usually develop acutely and can, in some cases, involve other organs as well, since the bacteria themselves, or the toxins they produce, can be absorbed through the colon’s mucosal lining and enter the bloodstream.
Inflammatory Bowel Disease (IBD)
This category includes Crohn’s disease and ulcerative colitis. Crohn’s disease can affect any part of the gastrointestinal tract, including the colon, while ulcerative colitis, as its name suggests, involves only the mucosal lining of the rectum and colon, most often affecting its final (distal) portion.
Inflammatory bowel diseases are considered idiopathic, meaning their exact underlying cause remains unknown. They show a degree of familial clustering, meaning the risk of developing these conditions is somewhat increased if close relatives are also affected, although they are not considered truly hereditary diseases in the strict genetic sense. They affect men and women in roughly equal numbers, and most commonly develop in young adults between the ages of 15 and 45.
Irritable Bowel Syndrome (IBS)
Also commonly referred to simply as “colitis”, or as nervous colitis or spastic colitis, IBS is a functional gastrointestinal disorder, meaning it involves an alteration in the normal functioning of an organ or system (in this case, the colon) without any identifiable structural or anatomical abnormality.
According to the Rome III diagnostic criteria, irritable bowel syndrome is defined as recurrent abdominal pain or discomfort occurring for at least 3 days per month over the previous 3 months, associated with two or more of the following characteristics:
- Improvement in symptoms following a bowel movement
- Onset associated with a change in the frequency of bowel movements
- Onset associated with a change in the consistency (form) of the stool
Ischemic Colitis
Ischemic colitis occurs when there is a reduction, or complete loss, of blood flow to the colon. Ischemia refers to this reduced or absent blood supply to an organ, in this case, the colon. When the colon loses its normal blood supply, it can become inflamed and develop the classic symptoms of colitis, which typically appear acutely (suddenly).
Ischemic colitis can result from a variety of underlying causes, the most important of which include:
- Thrombosis occurring on top of an atherosclerotic plaque
- Thromboembolism, often originating from the heart, particularly in patients with atrial fibrillation, which can also lead to pulmonary embolism in other contexts
- Hemodynamic shock (a severe drop in blood pressure and blood flow throughout the body)
- Intestinal volvulus (twisting of the intestine)
- Strangulated intestinal hernia
Allergic Colitis
Characteristic of infants under 1 year of age, allergic colitis is often caused by an allergy to cow’s milk protein. It often resolves spontaneously as the child grows, in correlation with the natural maturation of the immune system and the local defense mechanisms of the intestine.
Symptoms
The most common signs and symptoms of colitis affect the gastrointestinal system. Among the most significant, found in nearly all forms of colitis, are:
- Diarrhea, or conversely, constipation
- Abdominal pain and cramping, sometimes relieved by having a bowel movement or passing gas
- Abdominal bloating
- Flatulence
- The presence of mucus and/or blood in the stool
In addition, depending on the specific underlying condition causing the colitis, one or more of the following symptoms may also be present:
- Fever, sometimes accompanied by chills
- A general feeling of being unwell
- Persistent fatigue
- Weakness
- Dizziness
- Decreased urine output (oliguria)
- Bad breath
- A burning sensation in the mouth or throat
- Nausea and vomiting
- Early feelings of fullness and loss of appetite
- Intestinal rumbling or gurgling sounds (borborygmi)
- Anal pain or discomfort
- Headache
- Muscle and tendon pain
- Unexplained weight loss
Diagnosis
The diagnosis of colitis begins with a detailed medical history and the collection of the patient’s signs and symptoms. Patients typically report poorly defined, diffuse abdominal pain or cramping, often accompanied by bloating and flatulence. Patients may also report having noticed the presence of mucus or blood in their stool.
While the presence of these signs and symptoms makes it relatively straightforward to suspect colitis as a general diagnosis, identifying the specific underlying cause is often a lengthy, complex process requiring numerous laboratory and instrumental investigations. The most commonly used diagnostic tools include:
Blood Tests
Blood tests typically begin by evaluating hemoglobin levels and red blood cell count, since chronic intestinal inflammation can, in some cases, lead to anemia. Markers of inflammation are also assessed, including elevated white blood cell counts, an increased erythrocyte sedimentation rate (ESR), and elevated C-reactive protein (CRP) levels.
It is also important to analyze various blood electrolytes, since colitis can interfere with the colon’s normal physiological function of reabsorbing sodium, potassium, bicarbonate, magnesium, and chloride.
When infectious colitis is suspected, blood tests may also directly search for the causative microorganisms, which may have entered the bloodstream, or alternatively, for the antibodies the body has produced in response to their presence.
Stool Testing
Stool samples can be examined for the presence of blood and mucus, which are sometimes visible even to the naked eye. At the laboratory level, stool samples can also be tested for the presence of white blood cells, which indicate ongoing intestinal inflammation. When an infectious cause is suspected, stool cultures can be performed, or specific bacterial toxins can be directly tested for.
Colonoscopy
Colonoscopy is an instrumental diagnostic examination that, while unfortunately somewhat invasive, allows direct visualization of the inner walls of the rectum, sigmoid colon, and colon, in order to identify any lesions present. During the procedure, a biopsy can also be performed, in which the physician removes a small sample of tissue from the colon lining for subsequent laboratory examination.
CT Scan
For a CT scan of the colon, the patient is typically asked to drink a liquid containing barium sulfate (a contrast agent) beforehand. This examination allows detailed images to be obtained through the use of X-rays, meaning the risk-benefit ratio of this test should always be carefully considered before proceeding, given the radiation exposure involved.
Treatment
Before establishing an appropriate treatment plan for colitis, it is essential to determine with certainty the specific underlying cause responsible for the inflammation, since specific treatments exist for each individual cause of colitis.
Treatment approaches for colitis can generally be divided into pharmacological (medication-based) and surgical categories.
Medications
Several different classes of medication can be used to treat colitis, depending on the underlying cause. The most common include:
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Antibiotics and antifungal medications, used when colitis is caused by a bacterial or fungal infection, respectively.
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Anti-inflammatory medications, such as corticosteroids and mesalazine, which reduce inflammation and provide relief from pain.
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Immunosuppressants and biologic medications, used in the treatment of chronic inflammatory bowel disease, including azathioprine, cyclosporine A, methotrexate, infliximab, and adalimumab.
Your doctor will prescribe the appropriate medications based on the specific underlying cause identified.
Surgery
Surgical treatment is generally reserved for specific cases of chronic inflammatory bowel disease. For example, in ulcerative colitis, total proctocolectomy (surgical removal of the entire colon and rectum) is curative for the majority of patients. In contrast, for patients with Crohn’s disease, surgery is never truly curative and is generally reserved for severe cases involving complications such as abscesses, fistulas, obstructions due to strictures, perforations, or significant bleeding.
Diet
The dietary approach to managing colitis varies considerably depending on the specific type of colitis diagnosed, so we recommend consulting the dedicated articles for each specific condition for detailed guidance. For example, in cases of irritable bowel syndrome, many patients find significant relief by following the low-FODMAP diet, which involves temporarily reducing intake of certain fermentable carbohydrates known to trigger symptoms.
More broadly, patients with any form of colitis may benefit from certain general dietary principles during symptomatic flares, including:
- Eating smaller, more frequent meals rather than large meals, which can be harder to digest
- Temporarily reducing intake of high-fiber foods during acute flares, as fiber can worsen cramping and diarrhea in some individuals, while reintroducing fiber gradually during periods of remission
- Avoiding known trigger foods, such as spicy foods, excessive caffeine, alcohol, and artificial sweeteners, which can worsen symptoms in sensitive individuals
- Staying well hydrated, particularly important during episodes of diarrhea, to prevent dehydration and electrolyte imbalances
- Working with a registered dietitian, particularly for patients with inflammatory bowel disease, who may require specialized nutritional support to prevent deficiencies and manage symptoms during both flares and remission
When to See a Doctor
While mild, occasional digestive discomfort is common and often not a cause for concern, certain symptoms associated with colitis should prompt a prompt medical evaluation:
- Blood in the stool, whether bright red or dark and tarry in appearance
- Persistent diarrhea lasting more than a few days, particularly if accompanied by fever
- Severe abdominal pain, especially if sudden in onset or associated with a rigid, tender abdomen
- Signs of dehydration, including reduced urination, dizziness, or extreme thirst
- Unexplained weight loss alongside changes in bowel habits
- Persistent fever associated with gastrointestinal symptoms
- A family history of inflammatory bowel disease, combined with new, persistent digestive symptoms
- Symptoms that significantly interfere with daily life, work, or sleep
Prompt evaluation is particularly important for suspected inflammatory bowel disease and ischemic colitis, as early diagnosis and treatment can help prevent serious complications and improve long-term outcomes.
Frequently Asked Questions
Is “colitis” the same thing as irritable bowel syndrome?
Not exactly, although the term is often used this way in everyday language. Medically, “colitis” refers specifically to inflammation of the colon, which can be caused by infections, inflammatory bowel disease, or reduced blood flow. Irritable bowel syndrome (IBS), on the other hand, is a functional disorder involving altered bowel function without any visible inflammation or structural damage to the colon, even though it is commonly nicknamed “nervous colitis” or “spastic colitis”.
Can stress cause colitis?
Stress does not directly cause structural inflammation of the colon in conditions like infectious colitis or inflammatory bowel disease. However, stress is well known to worsen symptoms in irritable bowel syndrome and can also trigger flares in patients who already have inflammatory bowel disease, through complex interactions between the brain and the gut (the so called gut-brain axis).
How long does colitis typically last?
This depends entirely on the underlying cause. Infectious colitis usually resolves within a few days to two weeks with appropriate treatment. Inflammatory bowel disease, on the other hand, is a chronic, lifelong condition characterized by alternating periods of flares and remission, requiring ongoing management even during symptom-free periods.
Is colitis the same as colon cancer?
No, colitis and colon cancer are different conditions, although chronic, long-standing inflammatory bowel disease, particularly ulcerative colitis affecting the entire colon, is associated with an increased long-term risk of developing colorectal cancer. This is why patients with longstanding IBD typically require more frequent colonoscopy screening than the general population.
Can diet alone cure colitis?
Diet plays an important supportive role in managing symptoms of colitis, particularly in irritable bowel syndrome, where dietary changes such as the low-FODMAP diet can be highly effective. However, for infectious colitis, inflammatory bowel disease, and ischemic colitis, diet alone is not sufficient to treat the underlying cause, and appropriate medical or surgical treatment is necessary alongside any dietary modifications.
Is ulcerative colitis curable?
Ulcerative colitis can be effectively managed with medication in the vast majority of patients, achieving long periods of remission. In cases that do not respond to medical treatment, surgical removal of the colon and rectum (total proctocolectomy) is considered curative for ulcerative colitis, since the disease is confined to these organs, unlike Crohn’s disease.
Sources and Bibliography
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Ulcerative Colitis. niddk.nih.gov.
- Crohn’s & Colitis Foundation. What is Crohn’s Disease? crohnscolitisfoundation.org.
- Longstreth GF, et al. Functional bowel disorders. Gastroenterology. 2006;130(5):1480-1491.
- Brandt LJ, Feuerstadt P. Ischemic colitis. American Journal of Gastroenterology. 2015;110(1):18-44.
- DuPont HL. Acute infectious diarrhea in immunocompetent adults. New England Journal of Medicine. 2014;370(16):1532-1540.
- Ordás I, et al. Ulcerative colitis. Lancet. 2012;380(9853):1606-1619.
- Baumgart DC, Sandborn WJ. Crohn’s disease. Lancet. 2012;380(9853):1590-1605.
- World Gastroenterology Organisation (WGO). Global Guidelines: Irritable Bowel Syndrome. worldgastroenterology.org.
- Ford AC, et al. Irritable bowel syndrome. New England Journal of Medicine. 2017;376:2566-2578.
- Gearry RB, et al. Reduction of dietary poorly absorbed short-chain carbohydrates (FODMAPs) improves abdominal symptoms in patients with inflammatory bowel disease. Journal of Crohn’s and Colitis. 2009;3(1):8-14.
