What is the most likely diagnosis for a bedridden patient with a history of immobilization and occasional use of tranquilizers, presenting with intestinal obstruction after a fall?

Most Likely Diagnosis: Fecal Impaction

In a bedridden patient taking tranquilizers who presents with intestinal obstruction, fecal impaction (Option D) is the most likely diagnosis. This clinical scenario represents a classic constellation of risk factors for severe constipation leading to complete colonic obstruction.

Key Clinical Reasoning

Risk Factor Profile Strongly Favors Fecal Impaction

• Immobilization is the dominant risk factor: Bedridden patients have dramatically reduced gastrointestinal motility, making fecal impaction extremely common in this population 1
• Tranquilizers compound the problem: Medications with anticholinergic effects (common in many tranquilizers) directly decrease colonic motility and worsen constipation 2
• Elderly institutionalized patients are the classic demographic: This population has the highest incidence of fecal impaction, particularly when receiving psychotropic medications 2
• Fecal impaction is the third most common cause of lower GI obstruction after diverticular stricture and colon cancer 1

Why Other Diagnoses Are Less Likely

Sigmoid volvulus (Option A) typically presents in:

• Patients from endemic "volvulus belt" countries with chronic constipation and high-fiber diets 2
• Those with previous episodes of abdominal distension (30-41% report this) 2
• Classic "coffee bean sign" on plain radiographs projecting toward upper abdomen 2
• The fall from bed is a red herring—volvulus doesn't result from trauma

Rectal cancer (Option B) would present with:

• History of rectal bleeding or unexplained weight loss 3
• More gradual symptom development over weeks to months 3
• Digital rectal exam revealing a mass 3
• Cancer causes 60% of large bowel obstructions but requires chronic symptoms 3

Pseudo-obstruction (Option C) is:

• A rare syndrome requiring chronic symptoms (>6 months by definition) 2
• Associated with severe malnutrition (BMI <18.5 or >10% weight loss) 2
• Typically diagnosed after extensive workup excluding mechanical causes 2
• The acute presentation after a fall doesn't fit this chronic condition 4

Diagnostic Approach

Physical Examination Findings to Confirm

• Pathognomonic "gush sign": Digital rectal examination revealing hard stool in the rectal vault, followed by explosive release of liquid stool when the impaction is passed 5
• Abdominal distension with palpable stool masses in the left lower quadrant 1
• Paradoxical diarrhea or fecal incontinence (liquid stool bypassing the impaction) 6, 1

Imaging Confirmation

• Plain abdominal radiographs typically show large amounts of stool throughout the colon with dilated proximal bowel 1
• CT scan can confirm the diagnosis and rule out complications like perforation or stercoral ulceration 1

Critical Pitfalls to Avoid

Do not mistake overflow diarrhea for gastroenteritis: Patients with severe fecal impaction often present with liquid stool leaking around the impaction, which can be misdiagnosed as infectious diarrhea 2, 6

Recognize serious complications: Fecal impaction can progress to stercoral ulceration, perforation, peritonitis, and systemic inflammatory response syndrome (SIRS), particularly in neurologically impaired patients 6, 1

The fall is likely incidental: While the question mentions a fall from bed, this is probably unrelated to the obstruction etiology—the chronic immobilization and medication use are the true culprits 2