Colitis is an inflammation of the colon. Colitis may be acute and self-limited or long-term. It broadly fits into the category of digestive diseases. In a medical context, the label colitis (without qualification) is used if:

The cause of the inflammation in the colon is undetermined; for example, colitis may be applied to Crohns disease at a time when the diagnosis is unknown, or
The context is clear; for example, an individual with ulcerative colitis is talking about their disease with a physician who knows the diagnosis. Signs and symptoms
The signs and symptoms of colitis are quite variable and dependent on the cause of the given colitis and factors that modify its course and severity.Common symptoms of colitis may include: mild to severe abdominal pains and tenderness (depending on the stage of the disease), persistent hemorrhagic diarrhea with pus either present or absent in the stools, fecal incontinence, flatulence, fatigue, loss of appetite and unexplained weight loss.More severe symptoms may include: shortness of breath, a fast or irregular heartbeat and fever.Other less common or rare non-specific symptoms that may accompany colitis include: arthritis, mouth ulcers, painful, red and swollen skin and irritated, bloodshot eyes.Signs seen on colonoscopy include: colonic mucosal erythema (redness of the colons inner surface), ulcerations and hemorrhage. Diagnosis
Symptoms suggestive of colitis are worked-up by obtaining the medical history, a physical examination and laboratory tests (CBC, electrolytes, stool culture and sensitivity, stool ova and parasites et cetera). Additional tests may include medical imaging (e.g.
abdominal computed tomography, abdominal X-rays) and an examination with a camera inserted into the rectum (sigmoidoscopy, colonoscopy).An important investigation in the assessment of colitis is biopsy. A very small piece of tissue (usually about 2mm) is removed from the bowel mucosa during endoscopy and examined under the microscope by a histopathologist. It can provide important information regarding the cause of the disease and the extent of bowel damage. Types
There are many types of colitis. They are usually classified by the cause. Types of colitis include:

Autoimmune
Inflammatory bowel disease (IBD) – a group of chronic colitides. Ulcerative colitis (UC) – a chronic colitis that affects the large intestine. Crohns disease (CD) – another type of IBD that often leads to colitis. Unknown
Microscopic colitis – a colitis diagnosed by microscopic examination of colonic tissue; macroscopically ("to the eye") it appears normal. Lymphocytic colitis
Collagenous colitis

Treatment-caused
Diversion colitis
Chemical colitis
Chemotherapy-induced colitis
Radiation colitis
Checkpoint inhibitor induced colitis

Vascular disease
Ischemic colitis

Infectious
Infectious colitisA subtype of infectious colitis is Clostridioides difficile colitis, which is informally abbreviated as "C-diff colitis". It classically forms pseudomembranes and is often referred to as pseudomembranous colitis, which is its (nonspecific) histomorphologic description. Enterohemorrhagic colitis may be caused by Shiga toxin in Shigella dysenteriae or Shigatoxigenic group of Escherichia coli (STEC), which includes serotype O157:H7 and other enterohemorrhagic E. coli.Parasitic infections, like those caused by Entamoeba histolytica, can also cause colitis. Unclassifiable colitides
Indeterminate colitis is the classification for colitis that has features of both Crohns disease and ulcerative colitis.