S5126 From Dysentery to Disaster: Shigella-Induced Toxic Megacolon

Introduction: Toxic megacolon is a life-threatening non-obstructive colonic dilation in the setting of systemic toxicity commonly associated with IBD or C. difficile. Shigellosis has been linked to toxic megacolon but is rare in immunocompetent adults. Identifying infection and differentiating from inflammatory causes is critical, as management strategies differ. Surgical intervention, although rare, is necessary for refractory disease. Case Description/Methods: Sixty-six-year-old Indian man with a 2-week history of profuse diarrhea, initially bloody, presented with fever, tachycardia, leukocytosis (12.7 × 109/L), anemia (10.7 g/dL), and electrolyte imbalances (potassium 2.7 mmol/L) after recent travel to Virginia. Stool polymerase chain reaction (PCR) was positive for Enteroinvasive E. coli/Shigella species. Initial in-hospital stool culture was negative for Shigella but Shigella flexneri 2 was identified on a sample sent to state health lab. He was treated with ceftriaxone, later escalated to cefepime and azithromycin due to persistent symptoms. X-ray abdomen showed progressive colonic dilatation to 12.5 cm. Colonic decompression by flexible sigmoidoscopy was attempted which revealed ulcerated, inflamed mucosa. Biopsies were negative for IBD. C. difficile PCR and toxin were negative. Ongoing fever, tachycardia, electrolyte abnormalities, anemia and radiographic findings confirmed toxic megacolon. As he failed to respond to more than 10 days of antibiotics, he underwent total colectomy with end ileostomy due to impending risk of perforation. Pathology confirmed ischemic hemorrhagic colitis with ulcerations consistent with Shigella colitis. He recovered well and later underwent ileostomy reversal. Discussion: Toxic megacolon due to Shigella is rare but can be fatal. Early identification of etiology is essential, as corticosteroids used in IBD can be harmful in infections. Stool cultures may be delayed or even negative, requiring high clinical suspicion. In our case, culture-guided antibiotics and serial imaging supported medical management initially, but worsening colonic dilation warranted surgery. It is important to consider differentials like C. difficile colitis and IBD in cases of shigellosis, as these conditions may coexist or occur in close succession. Antibiotic management of shigellosis is also complicated by resistance, and the association with hemolytic uremic syndrome. This case underscores the importance of recognizing rare infectious causes of toxic megacolon, and close coordination between medical and surgical teams.