Gastroenterology · Colorectal Surgery
The facts most likely to be tested
Colorectal malignancy is the most common cause of large bowel obstruction (LBO) in adults.
Volvulus is the most common cause of LBO in patients with a history of chronic constipation or institutionalization, with sigmoid volvulus presenting as a coffee bean sign on abdominal imaging.
Abdominal CT with IV contrast is the gold standard diagnostic modality to determine the transition point and etiology of the obstruction.
Cecal volvulus is associated with a whirl sign on CT and typically requires surgical resection rather than endoscopic decompression.
Contrast enema (water-soluble) is the diagnostic test of choice for suspected sigmoid volvulus if the patient is hemodynamically stable and lacks signs of peritonitis.
Peritoneal signs, fever, leukocytosis, or tachycardia are clinical indicators of bowel ischemia or perforation, necessitating emergent surgical exploration.
Ogilvie syndrome (acute colonic pseudo-obstruction) presents with massive colonic dilation without a mechanical obstruction and is managed with neostigmine if conservative measures fail.
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A 72-year-old male with a history of chronic constipation presents to the emergency department with 3 days of progressive abdominal distension, nausea, and obstipation. Physical examination reveals a tympanitic abdomen and high-pitched bowel sounds. An abdominal radiograph shows a dilated loop of colon arising from the left lower quadrant and extending toward the right upper quadrant, resembling a coffee bean. The patient is hemodynamically stable with no signs of peritonitis.
What is the most appropriate next step in management?
Flexible sigmoidoscopy
The clinical presentation and 'coffee bean' sign are classic for sigmoid volvulus; in a stable patient without peritonitis, endoscopic decompression is the initial treatment of choice.
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Etiology / Epidemiology
Primary causes are malignancy (60%) and volvulus. Most common in the elderly population.
Clinical Manifestations
Presents with obstipation, abdominal distension, and tinkling bowel sounds. Peritonitis indicates perforation.
Diagnosis
CT scan with contrast is the gold standard. Cecal diameter >10-12 cm indicates high risk of rupture.
Treatment
Fluid resuscitation and nasogastric decompression. Avoid colonoscopy if perforation is suspected.
Prognosis
Mortality increases significantly with ischemia or perforation. Early surgical intervention is critical.
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Epidemiology & Etiology
Colorectal cancer is the leading cause of LBO in adults. Other common etiologies include volvulus (sigmoid or cecal), diverticulitis, and fecal impaction. It is predominantly a disease of the elderly.
Pertinent Anatomy
The colon's diameter is the primary determinant of rupture risk. The cecum is the most dilated portion and follows Laplace's Law, making it the most prone to perforation.
Pathophysiology
Obstruction leads to proximal bowel distension and fluid sequestration. Increased intraluminal pressure compromises mucosal blood flow, leading to ischemia. If the ileocecal valve is incompetent, the small bowel may also distend, potentially masking the primary colonic obstruction.
Clinical Manifestations
Patients present with progressive abdominal pain, distension, and obstipation (absence of flatus/stool). Physical exam reveals tympany and high-pitched bowel sounds. Fever, tachycardia, and localized tenderness are red flags for perforation or ischemia.
Diagnosis
CT scan of the abdomen/pelvis with IV contrast is the diagnostic study of choice. A cecal diameter >12 cm is a critical threshold for urgent surgical consultation. A plain abdominal radiograph may show a coffee bean sign in sigmoid volvulus.
Treatment
Initial management requires IV fluid resuscitation and nasogastric tube placement. If the obstruction is mechanical and non-strangulated, surgical consultation is mandatory. Colonoscopy is contraindicated in cases of suspected perforation or acute peritonitis.
Prognosis
Prognosis is dictated by the presence of bowel necrosis or perforation. Patients require close monitoring for sepsis and electrolyte imbalances. Mortality rates rise sharply if surgery is delayed beyond 24 hours.
Differential Diagnosis
Small Bowel Obstruction: central abdominal pain and more frequent vomiting
Paralytic Ileus: absent bowel sounds and diffuse gaseous distension
Pseudo-obstruction: Ogilvie syndrome, typically in hospitalized/critically ill patients
Fecal Impaction: palpable stool in the rectal vault
Diverticulitis: localized LLQ pain and inflammatory markers