Emergent Care / Stabilization:

• Wear appropriate personal protective equipment (PPE) and observe strict hand hygiene for those at risk for infectious colitis, particularly Clostridioides difficile colitis.
• Assess volume status and dehydration.
• Determine systemic effects from active colitis (eg, fever, tachycardia, leukocytosis, lactatemia).
• Establish adequate intravenous (IV) access.
• Consider early consultation with gastroenterology if diagnostic colonoscopy is required (eg, ongoing bleeding for inflammatory bowel disease [IBD] flares).
• Consider early consultation with general surgery or colorectal surgery for severe invasive / infectious colitis with signs of obstruction or peritoneal involvement (eg, toxic megacolon).

Diagnosis Overview:
Colitis is a broad term used to describe inflammation of the colon. Cases vary widely in terms of disease duration and severity. Colitis can occur as a primary condition (ie, acute infection) or secondary to a distinct condition or insult (ie, radiation colitis). Important etiologies are listed below.

While risk factors vary with etiology, some patient populations are uniquely susceptible to specific conditions, including necrotizing enterocolitis in neonates and neutropenic enterocolitis (or typhlitis) in immunocompromised patients.

Infectious colitis can be caused by:

• Shigellosis
• Campylobacter infection
• Diarrheagenic Escherichia coli infection
• Yersinia enterocolitica infection
• Enterotoxigenic E coli (ETEC)
• Parasitic colitis (giardiasis, microsporidiosis, amebic colitis, etc)
• Cytomegalovirus (CMV) infection
• Other viral etiologies (rotavirus, adenovirus, etc)
• Tuberculous enteritis
• Salmonellosis
• Pseudomembranous Clostridioides difficile infection

Drug-induced colitis can be caused by:

• NSAIDs
• Checkpoint inhibitors, eg, ipilimumab, nivolumab
• See Drug Reaction Data below for further information.

Additional forms of inflammatory, iatrogenic, and other colitis include:

• Ischemic colitis
• Ulcerative colitis
• Crohn disease colitis
• Microscopic colitis
• Radiation-induced colitis (see acute radiation enteritis)
• Immunotherapy-induced colitis
• Diversion colitis
• Stercoral colitis
• Neutropenic enterocolitis (including typhlitis)
• Necrotizing enterocolitis (neonatal)
• Food protein-induced enterocolitis syndrome

A detailed history and physical examination can often significantly narrow this broad differential. Obtain a thorough history, including the time course of illness, presence or absence of systemic symptoms, stooling habits (ie, number, consistency, presence of blood), upper gastrointestinal (GI) symptoms, recent travel, exposures to illness, recent dietary habits, past medical history, and an accurate medication list that includes over-the-counter medications and supplements.

Symptoms of colitis vary depending on etiology but can include diarrhea, abdominal pain, urgency, tenesmus, and hematochezia. Systemic symptoms such as fevers and chills may be present.

Signs on examination can include abdominal tenderness with or without rebound and guarding, abdominal distension, tachycardia, and fever, as well as rectal bleeding. In patients with significant diarrhea, make a particular note of assessment of hydration status, including mucous membrane moisture, skin turgor, and capillary refill.

Systemic symptoms and peritoneal signs on abdominal examination should raise concern for complications, including toxic megacolon, intestinal perforation, obstruction, and abscess formation.

Infectious colitis remains a leading cause of malnutrition and death worldwide, particularly in children younger than age 5 years.