A 29-year-old man with a 6-year history of ulcerative colitis presents to the emergency department with worsening abdominal pain and bloody diarrhea. During the past week, he has experienced more than 10 bloody bowel movements daily despite adherence to mesalamine therapy. He also reports fever, nausea, and progressive abdominal distention. His temperature is 39.1°C (102.4°F), blood pressure is 94/58 mm Hg, pulse is 126/min, and respiratory rate is 22/min. On physical examination, he appears ill. His abdomen is markedly distended and diffusely tender. Bowel sounds are decreased.
Laboratory studies reveal the following:
Abdominal radiography demonstrates colonic dilation measuring 7.5 cm in diameter.
Which of the following is the most likely diagnosis?
The correct answer is:
D) Toxic megacolon
This patient has toxic megacolon, a life-threatening complication of severe ulcerative colitis. The diagnosis is suggested by severe colitis accompanied by systemic toxicity and radiographic evidence of marked colonic dilation.
Toxic megacolon occurs when severe inflammation extends through the colonic wall, leading to loss of smooth muscle tone and progressive colonic dilation. Patients typically present with severe abdominal pain, abdominal distention, fever, tachycardia, leukocytosis, and ongoing bloody diarrhea. Imaging demonstrates significant colonic dilation, usually greater than 6 cm.
The major danger is colonic perforation, which can rapidly lead to peritonitis, sepsis, and death. Importantly, perforation is a feared complication but is not required for the diagnosis. Recognition before perforation occurs is critical because timely treatment can be lifesaving.
Management includes bowel rest, intravenous fluids, correction of electrolyte abnormalities, broad-spectrum antibiotics when indicated, and high-dose intravenous corticosteroids. Patients require close monitoring, and emergent colectomy is indicated for perforation, uncontrolled hemorrhage, clinical deterioration, or failure of medical therapy.
A classic Step 2 clue is a patient with known ulcerative colitis who develops systemic toxicity and colonic dilation greater than 6 cm.
Answer choice A: Acute appendicitis, is incorrect.
Appendicitis typically causes localized right lower quadrant pain, fever, and leukocytosis. It does not cause diffuse colonic dilation or severe bloody diarrhea in a patient with ulcerative colitis.
Answer choice B: Colonic perforation, is incorrect.
Colonic perforation is a complication of toxic megacolon. He does not have evidence of colonic perforation, such as free air on abdominal imaging.
Answer choice C: Mechanical large bowel obstruction, is incorrect.
Mechanical obstruction may cause abdominal distention and pain, but it would not explain the severe inflammatory symptoms, bloody diarrhea, and systemic toxicity characteristic of toxic megacolon.
Answer choice E: Volvulus, is incorrect.
Volvulus causes acute bowel obstruction and colonic dilation but is usually associated with obstipation and obstructive symptoms rather than severe inflammatory diarrhea and systemic manifestations of ulcerative colitis.
Key Learning Point
Toxic megacolon is a life-threatening complication of severe ulcerative colitis characterized by systemic toxicity and colonic dilation greater than 6 cm. Prompt recognition and aggressive management are essential to prevent perforation and death.
