Diverticulitis: The most common cause of lateral colitis, diverticulitis is an inflammation of the diverticula in the colon wall, often presenting with left lower quadrant pain, fever, and changes in bowel habits.

Ischemic Colitis: Reduced blood flow to the colon can cause ischemic colitis, presenting with sudden onset of abdominal pain, bloody diarrhea, and potentially fever.
Infectious Colitis: Bacterial, viral, or parasitic infections can cause colitis, with symptoms including diarrhea, abdominal pain, fever, and sometimes blood in the stool.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic inflammation of the colon, leading to symptoms such as diarrhea, abdominal pain, weight loss, and fatigue.

Colon Cancer: Although less likely, colon cancer can present with similar symptoms to colitis, including changes in bowel habits, blood in the stool, and abdominal pain. Missing this diagnosis could be fatal.
Mesenteric Ischemia: A serious condition where the blood flow to the intestine is blocked, leading to severe abdominal pain, which might not always be accompanied by other symptoms initially.
Appendicitis: If the appendix is located near the lateral aspect of the colon, appendicitis could mimic lateral colitis, with symptoms including severe abdominal pain, fever, and vomiting.

Eosinophilic Colitis: A rare condition characterized by an increased number of eosinophils in the colon, often associated with allergic reactions or parasitic infections.
Microscopic Colitis: Includes conditions like lymphocytic colitis and collagenous colitis, which are characterized by microscopic inflammation of the colon and can cause chronic diarrhea.
Radiation Colitis: Inflammation of the colon due to radiation therapy, which can occur months to years after the treatment, leading to symptoms such as diarrhea, rectal bleeding, and abdominal pain.