Which is the most likely anatomical location for this condition? A 78-year-old man has a 3-day history of diarrhea, left lower quadrant abdominal pain, and fever. His leukocyte count is slightly elevated, his hematocrit level reveals slight anemia, and his platelets are normal. A biopsy is obtained and shown in the image.

Sigmoid colon

The correct answer is D. Diverticulitis is inflammation of diverticula, often in the sigmoid colon. It is related to retention of material within a diverticulum and fecalith formation. Diverticulitis typically manifests as left lower quadrant pain with fever, anorexia, and diarrhea and presents most commonly in older people. Diverticulitis should be distinguished from diverticulosis, which simply refers to the presence of diverticula. Diverticula occur when pressure causes herniation of the colonic wall through its own muscularis propria. A lowfiber diet is a known risk factor for diverticulosis. The sigmoid colon is the most common location affected by diverticulosis, likely due to the high pressure in this region. Occasionally, a diverticulum may cause rupture of a nutrient artery where it penetrates the muscularis propria; this results in bright red, painless bleeding from the rectum. However, only 20% of patients with diverticula experience hemorrhage. Thus, hemorrhage from diverticula is not always associated with diverticulitis, and diverticulitis may occur in the absence of bleeding Answer A is incorrect. The appendix contains similar layers to the colon with additional lymphoid tissue in the mucosa and submucosa. Acute appendicitis occurs more often in adolescents and young adults, and typically presents with right lower quadrant or periumbilical pain, nausea, and vomiting Answer B is incorrect. The ileum is not affected in diverticulosis Answer C is incorrect. Hemorrhoidal disease affects the rectum. The vasculature in this region normally protects the sphincter muscle, but prolonged straining and engorgement results in prolapse into the anal canal. Symptoms include pain, bleeding, and protrusion of hemorrhoidal vessels Answer E is incorrect. The transverse colon is rarely affected in diverticulitis, and only 5% of patients have pancolonic diverticula.