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Colitis is a medical condition characterized by inflammation in the colon caused by infection, autoimmune disease, reduced blood flow (ischemia), drugs, or toxins.
Colitis can be acute or chronic with symptoms ranging from mild to severe. Acute diarrhea typically lasts no longer than 7–10 days, whereas chronic diarrhea persists or is recurring beyond 2–4 weeks. (1)
Symptoms of colitis include the following:
Types of Colitis and Their Causes
Colitis has four types:
1. Infectious colitis
Infectious colitis is transmitted by contaminated food or from person to person. The infection is caused by bacterial food poisoning, a parasite, or a virus:
- Bacterial colitis is caused by, in order of most common to least, Campylobacter jejuni, Salmonella, Escherichia coli, Yersinia enterocolitica, Clostridium difficile, and Mycobacterium tuberculosis. These pathogens account for almost half of the cases of acute diarrhea.
- Entamoeba histolytica is the most common parasitic infection of the colon.
- A common cause of viral colitis is Cytomegalovirus (CMV). This virus is transmitted via exposure to infected body fluids such as saliva, urine, blood, tears, semen, and breast milk. In some cases, colitis occurs in someone who has been previously exposed and the virus is reactivated after remaining dormant in the body following initial exposure.
2. Inflammatory bowel disease
Inflammatory bowel disease includes Crohn’s disease and ulcerative colitis. These conditions are autoimmune diseases of the gastrointestinal tract leading to chronic inflammation.
Crohn’s disease differs from ulcerative colitis in that the inflammation involves all four layers of the intestine and can affect any part of the gastrointestinal tract from the mouth to the anus. Inflammation is typically limited to a certain portion of the gastrointestinal tract with areas that are normal. Vitamin D intake reduces the risk of Crohn’s disease.
Ulcerative colitis, as the name infers, involves only the colon. The inflammation is limited to the mucosal layer (surface layer) of the colon and is contiguous from the rectum. (2) Varying lengths of the colon can be involved in the inflammatory process.
In the early stages, the symptoms of colitis stemming from inflammatory bowel disease are indistinguishable from those of infectious colitis. If the symptoms are recurrent or persist beyond 4 weeks, another process should be considered.
Some common symptoms are:
Complications of inflammatory bowel disease include arthritis, arthropathy, skin rash, eye disease, liver disease, hematologic disorders, and lung disease.
The risk of colon cancer is higher in patients with ulcerative colitis and Crohn’s colitis at 7–10 years of disease. At this point, patients should undergo screening colonoscopy every 1–2 years. (2) This complication of inflammatory bowel disease occurs in a minority of patients.
3. Ischemic colitis
Ischemic colitis refers to inflammation in the colon resulting from a transient reduction in blood flow.
It tends to occur in the “watershed” areas of the colon where there is limited collateral blood flow such as in the splenic flexure and rectosigmoid junction. In many instances, a cause cannot be identified. This type of colitis tends to occur in middle-aged to elderly individuals. (3)
4. Microscopic colitis
Microscopic colitis is a chronic inflammatory disease of the colon characterized by watery, non-bloody diarrhea that can be intermittent. This type of colitis commonly occurs in middle-aged women. The median age of incidence in North America is 65 years.
Microscopic colitis has two subtypes: lymphocytic colitis and collagenous colitis. Both are treated similarly. (4)
5. Eosinophilic colitis
Eosinophilic colitis is a rare form of colitis characterized by an eosinophilic inflammatory infiltrate in the colonic mucosa. Patients experience abdominal pain, diarrhea that can be bloody, and weight loss.
This type of colitis may be related to food allergies as patients with eosinophilic colitis can have other allergic diseases such as eczema, allergic rhinitis, or asthma. It affects any age from infancy to adulthood.
Eosinophilic infiltration of the colon can occur secondarily with other conditions such as parasitic infections, drug reactions (clozapine, carbamazepine, rifampicin, gold, naproxen), and vasculitis. Thus, primary eosinophilic colitis is a diagnosis of exclusion. (5)
Colitis management involves the following treatment options:
Infectious colitis is typically self-limiting (resolve spontaneously) except for those caused by Mycobacterium tuberculosis and Entamoeba histolytica, which require treatment. Treatment of Cytomegalovirus colitis may be necessary in some cases. Antiviral medications can be administered in these instances.
Inflammatory bowel disease
Treatments for inflammatory bowel disease include:
- Anti-tumor necrosis factor drugs
- Anti-integrin drugs
- Anti-Janus kinase enzyme drugs
- Anti-metabolites and anti-interleukin 12 and 23 antagonists (2)
All of the treatments except for the anti-inflammatory drugs are immune suppressing, targeting different parts of the intestinal inflammatory cascade. If a patient is on an immunomodulator or anti-tumor necrosis factor drug, they should be monitored for skin cancer with yearly dermatologic examinations.
Inflammatory bowel disease can go into remission, but the more common scenario is lifelong treatment with one or more of these drugs.
The importance of preventive health maintenance should be emphasized in patients with inflammatory bowel disease:
- Yearly vaccinations for influenza and pneumococcal pneumonia should be given along with yearly screening for tuberculosis, given the chronic immunosuppressed state.
- Herpes zoster vaccination should be given to patients aged 50 or older.
- All patients with inflammatory bowel disease should also receive the COVID-19 vaccine.
Medical treatment is dependent on the cause of the ischemia. If there is necrosis (death of the tissue) of the bowel wall, patients require surgery to remove the affected segment of intestine.
Patients with microscopic colitis may receive budesonide (locally active corticosteroid) or mesalamine (anti-inflammatory) drugs. Also, mild cases can be managed with antidiarrheal agents alone. When treated, 70% of patients achieve remission with 30% relapsing. Thus far, the risk of colon cancer is not increased. (4)
Elimination diets may be beneficial in identifying the food triggers. Corticosteroids and azathioprine (immunomodulator) have been shown to be of some benefit. Other drugs that have been shown to be beneficial include leukotriene receptor antagonists (montelukast), antihistamines, and mast cell stabilizers. (5)
When colitis is suspected, the doctor physically examines the patient’s abdominal area for any lumps or tenderness.
Acute onset of abdominal pain followed by bloody diarrhea in a middle-aged person is generally indicative of ischemic colitis, which tends to resolve completely without scarring of the colon in most cases.
But your doctor may order the following tests to accurately diagnose different types of colitis:
- Blood tests: Blood tests look for biomarkers such as the C-reactive protein (CRP), which indicates systemic inflammation. Levels of CRP correlate with Crohn’s disease activity. (6)
- Biopsy: Inflammatory bowel disease requires the attention of a specialist for diagnosis and treatment. First, infection should always be ruled out. Diagnosis is typically made when tissue biopsies of the affected area are obtained endoscopically (colonoscopy in the case of colitis). If infection is ruled out, colonoscopy with biopsies is indicated for diagnosis in microscopic colitis.
- Stool tests: Calprotectin and lactoferrin tests examine the patient’s fecal sample for the presence of certain substances released by white blood cells that are taken as a sign of inflammation. These tests are useful in determining if the illness is inflammatory or non-inflammatory in nature.
- Imaging studies and serologic testing: Tissue may be difficult to obtain in cases of Crohn’s disease, which is isolated to the small bowel, which is hard to reach. Therefore, imaging studies and serologic testing are used. Computed tomography scans and magnetic resonance imaging are generally used to get an inside picture of your abdomen, pelvis, and intestines without exposing the body to radiation. (7)
- Endoscopic biopsies: Diagnosis of eosinophilic colitis is made with endoscopic biopsies. Endoscopic biopsy may be instrumental in differentiating ischemic colitis from ulcerative or infectious colitis. (7)
Each type of colitis is linked to a different set of risk factors.
Risk factors associated with inflammatory bowel disease
- It is higher in individuals with affected family members and in patients of Jewish descent.
- Females are at a slightly higher risk of developing Crohn’s disease, whereas males are at a slightly higher risk of developing ulcerative colitis.
- Smoking is a risk factor for Crohn’s disease but may be beneficial for ulcerative colitis.
- Physical activity reduces the risk of Crohn’s disease but not ulcerative colitis.
- A high-fiber diet reduces the risk of Crohn’s disease but not ulcerative colitis.
- A high-fat diet (saturated and unsaturated) increases the risk for both.
- Sleep duration may affect the risk of ulcerative colitis with 7–8 hours being optimal.
- Infection is a probable risk factor for inflammatory bowel disease, as is antibiotic use. It is unclear whether or not it is the infection for which the antibiotics are being given or the antibiotic itself that increases the risk.
- Drugs including NSAIDs (nonsteroidal anti-inflammatory drugs), oral contraceptives and hormones, and isotretinoin may also increase the risk.
- Patients between the ages of 15 and 30 (most common) or 60 and 80, although inflammatory bowel disease does occur in children.
Risk factors associated with ischemic colitis
- Medical conditions characterized by reduced blood flow to the colon such as heart failure
- Blood clots forming in the colonic circulation or migrating to the colon from other areas
- Heart disease
- Hypercoagulable states (enhanced clot formation)
- Vascular disease (disease of the blood vessels)
- Bowel blockage and E. coli O157:H7 infection (8)
Risk factors associated with microscopic colitis
- Autoimmune disease
- Certain medications including proton pump inhibitors (lansoprazole in particular), statins, selective serotonin reuptake inhibitors, pembrolizumab, aspirin, NSAIDs, and anti-Parkinsonian drugs
- Smoking (9)
Different types of colitis stem from different underlying causes and are treated accordingly. Most cases subside on their own, but proper self-care and medication can help reduce the severity and frequency of flare-ups. If the condition persists or worsens despite the recommended treatment, consult your doctor immediately.