What Causes Pain on the Left Side of the Abdomen?

In middle-aged patients, ulcerative colitis may cause symptoms including diarrhea, abdominal distension, and even nausea, vomiting, bloody stools, or mucopurulent bloody stools. The exact etiology remains unclear but is thought to involve impaired immune function (e.g., autoimmune dysregulation). Oral immunomodulatory agents, in combination with sulfasalazine, are recommended. During treatment, regular colonoscopic surveillance is essential.

Alternatively, left-sided abdominal pain may stem from intestinal tumors—such as sigmoid colon or rectal malignancies—often accompanied by altered bowel habits, including loose stools, alternating diarrhea and constipation. Surgical intervention may be necessary in such cases. Additionally, abdominal pain may result from gastroenteritis, frequently associated with diarrhea and sometimes fever. Acute-phase management requires intravenous antimicrobial therapy and a predominantly liquid diet.