Differential Diagnosis for Colitis

When diagnosing colitis, it's crucial to consider a wide range of potential causes due to the varying presentations and severity of the condition. The differential diagnosis can be organized into the following categories:

• Single Most Likely Diagnosis

  • Ulcerative Colitis (UC): This is often considered the most likely diagnosis for colitis due to its prevalence and the fact that it is a common cause of chronic diarrhea and abdominal pain. UC is characterized by chronic inflammation and ulceration of the colon's inner lining, typically starting in the rectum and extending proximally in a continuous manner.

• Other Likely Diagnoses

  • Crohn's Disease: While it can affect any part of the gastrointestinal tract, Crohn's disease often presents with colitis and should be considered in the differential diagnosis due to its similarity in symptoms with ulcerative colitis, though it tends to cause skip lesions and can affect the entire thickness of the bowel wall.
  • Infectious Colitis: Caused by bacterial, viral, or parasitic infections, infectious colitis can present acutely and is a common cause of colitis, especially in individuals with recent travel history, antibiotic use, or exposure to contaminated food and water.
  • Ischemic Colitis: This condition occurs when there is an interruption or reduction of blood flow to the colon, leading to inflammation. It's more common in older adults and those with cardiovascular disease.

• Do Not Miss Diagnoses

  • Clostridioides difficile (C. diff) Infection: Although not the most common cause, C. diff infection is critical to identify due to its potential for severe complications, including toxic megacolon and death, especially in hospitalized or recently hospitalized patients.
  • Diverticulitis: While primarily an inflammatory condition of the diverticula, diverticulitis can lead to complications that might mimic colitis, such as abscess formation or perforation, which are medical emergencies.
  • Invasive Bacterial or Parasitic Infections: Certain infections, like those caused by Salmonella, Shigella, or amoebiasis, can lead to severe colitis and have significant morbidity and mortality if not promptly treated.

• Rare Diagnoses

  • Microscopic Colitis: Characterized by inflammation that is only visible under a microscope, microscopic colitis can cause chronic, watery diarrhea and is often diagnosed after other causes have been ruled out.
  • Eosinophilic Colitis: A rare condition associated with an increased number of eosinophils in the colon, often related to allergic reactions or parasitic infections.
  • Radiation Colitis: Occurs in individuals who have undergone radiation therapy to the abdominal or pelvic area, leading to chronic inflammation and damage to the colon.
  • Behçet's Disease: A form of vasculitis that can cause colitis among other systemic symptoms, including oral and genital ulcers and eye inflammation.

Each of these diagnoses has distinct clinical features, and a thorough history, physical examination, laboratory tests, and sometimes endoscopy are necessary to establish the correct diagnosis and guide appropriate treatment.