Solitary Rectal Ulcer Syndrome

A 31-year-old woman presents with an 8-month history of rectal bleeding, mucus passage, and tenesmus. She has chronic constipation with excessive straining and admits to digital disimpaction. Sigmoidoscopy reveals a solitary, shallow, well-circumscribed ulcer with fibrinous slough on the anterior rectal wall 7 cm above the dentate line, surrounded by hyperemic, polypoid, thickened mucosa. Biopsy demonstrates fibromuscular obliteration of the lamina propria with splayed muscularis mucosa and regenerative crypt distortion, without granulomas or crypt abscesses. The condition marked **B** in the diagram is characterized by which of the following pathophysiologic mechanisms?

A 35-year-old woman presents with a 2-year history of chronic rectal bleeding and incomplete evacuation. Sigmoidoscopy reveals a well-demarcated ulcer with heaped erythematous edges on the anterior rectal wall, 8 cm from the anal verge. Multiple biopsies show fibromuscular obliteration of the lamina propria with thickening of the muscularis mucosae. The structure marked **A** in the diagram represents this anterior rectal wall lesion. Which of the following is the PRIMARY PATHOPHYSIOLOGIC MECHANISM underlying the formation of this lesion?

A 38-year-old woman presents with 18 months of intermittent rectal bleeding, incomplete evacuation, and tenesmus. She has a lifelong history of chronic constipation with prolonged straining and habitual digital evacuation. Flexible sigmoidoscopy reveals the lesion marked **A** in the diagram—a shallow, well-demarcated ulcer on the anterior rectal wall 6–8 cm from the anal verge with surrounding hyperemic edematous mucosa and a whitish fibrinous base. Biopsies show fibromuscular obliteration of the lamina propria and muscularis mucosa hypertrophy with splaying of muscle fibers. Defecography demonstrates paradoxical puborectalis contraction with internal rectal intussusception. Which of the following best explains the pathophysiology underlying the lesion marked **A**?