Differentials
Acute colonic pseudo-obstruction (Ogilvie syndrome)
SIGNS / SYMPTOMS
Impressive abdominal distension yet little or no abdominal tenderness.
Around 49% of patients have underlying surgical disorder, 45% have precipitating medical disorder, 6% are idiopathic.[46]
Typically seen in older patients who are admitted to the hospital with a severe illness, for example, chest infection, myocardial infarction, stroke, renal failure, retroperitoneal malignancy, orthopedic trauma, or electrolyte disturbances.[3][36]
Drug history may include neuroleptics, opioids, and laxatives.[1]
Concomitant conditions may include diabetes, myxoedema, scleroderma, Parkinson disease, lupus, hyperparathyroidism, and recent metabolic illness.
Recent trauma or orthopedic surgery.
INVESTIGATIONS
Gas in the rectum in the absence of a rectal exam is often present, and this has been demonstrated radiographically in right lateral decubitus and prone lateral views.[47] Computed tomography or water-soluble contrast enema distinguishes acute colonic pseudo-obstruction from a mechanical large bowel obstruction.[3][36]
Chronic/idiopathic megacolon
SIGNS / SYMPTOMS
Longstanding history of constipation, diarrhea, or incontinence.
Visceral neuropathy. May also be part of an acquired visceral neuropathy (e.g., Chagas disease).
Drug history may include risperidone.
Preceding viral infection.
Recurrence after resection implies a misdiagnosed megacolon.
INVESTIGATIONS
Difficult to differentiate; can be radiologically similar to sigmoid volvulus and respond rapidly to rectal tube decompression.
Colonic transit studies and anorectal manometry assist in this difficult diagnosis. A slow colonic transit may be identified. Anorectal physiology excludes Hirschsprung disease where a normal recto-anal inhibitory reflex is identified.
Toxic megacolon
SIGNS / SYMPTOMS
Presence of an initial colitis of any cause.
Signs of sepsis (e.g., fever, tachycardia, hypotension, poor capillary refill) in early stages.
INVESTIGATIONS
Diagnosis may be apparent from clinical picture.
Plain abdominal x-ray may show "thumb printing" or intraluminal soft tissue mass (pseudopolyps).
Cautious colonoscopy confirms the diagnosis not only by the typical mucosal appearance, but also by biopsy.
Colonoscopy should be with minimal insufflation and rarely proceeds beyond the rectum and sigmoid once colitis is confirmed endoscopically, owing to the risk of perforation.
Endometriosis
SIGNS / SYMPTOMS
Previous history of endometriosis. History of pelvic pain and dysmenorrhea. May present with genitourinary or gastrointestinal symptoms or unexplained subfertility. Colonic endometriosis causing obstruction is rare.
INVESTIGATIONS
Ultrasonography (transabdominal and transvaginal) shows endometriotic cysts, but has a limited role in detecting endometrial implants. MRI can detect extra-pelvic and rectovaginal implants. MRI may be used to assess the extent of deep endometriosis involving the bowel, bladder, or ureter.
Pseudomembranous colitis
SIGNS / SYMPTOMS
Recent history of antibiotic or immunosuppressant use.
Profuse, foul-smelling diarrhea.
INVESTIGATIONS
Elevated WBC count.
Colonoscopy may identify pseudomembranes and exclude mechanical obstruction.
Stool culture isolates Clostridium difficile.
Small bowel obstruction
SIGNS / SYMPTOMS
Signs and symptoms are often abrupt while those of large bowel obstruction may be insidious.[34] Vomiting occurs late in the course of large bowel obstruction, but is more commonly seen in small bowel obstruction.[48] The vomitus may be bilious in high small bowel obstruction, and feculent in low small bowel obstruction.[48] The abdomen may be more markedly distended in large bowel obstruction, but may vary depending on the point of obstruction.
INVESTIGATIONS
X-ray shows small bowel dilation and lack of colonic dilation with relative paucity or absence of colonic gas. CT scans are highly accurate in diagnosing intestinal obstruction.
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