Clues Pointing TO This Diagnosis

67-year-old with prior appendectomy 40 years earlier — postoperative adhesions cause ~65% of small bowel obstructions and any prior abdominal/pelvic surgery is the leading risk factor
Crampy, colicky abdominal pain coming in waves every few minutes — peristalsis against a mechanical block produces intermittent cramping, the classic SBO pain pattern
Obstipation — no stool or flatus for two days — cessation of passage of flatus and stool is part of the classic clinical tetrad
Progressive abdominal distension/bloating — proximal bowel dilates from swallowed air and intraluminal fluid above the block
Nausea with emesis between the cramps — vomiting is a core feature, and its character reflects the level of obstruction
Adhesive band kinking the bowel identified as the mechanism — an adhesive band is the single most common cause of mechanical SBO
Plain film showing multiple dilated small bowel loops with air-fluid levels ("laddering") — the classic radiographic appearance of SBO
CT confirming a discrete transition point caused by adhesion with proximal dilation — small bowel >3 cm with a transition point and no colonic dilation is diagnostic
Absence of fever, peritonitis, marked leukocytosis, or CT ischemia signs — supports uncomplicated (non-strangulated) obstruction amenable to a nonoperative trial
Resolution with NG decompression and IV fluids, with return of flatus — ~75–85% of adhesive SBOs resolve nonoperatively, confirming a partial/uncomplicated obstruction

Why It's NOT the Similar Diseases

NOT paralytic ileus — ileus is a functional failure of peristalsis without a mechanical block, typically with diffuse gas including the colon and no discrete transition point; Clarence has a defined adhesive transition point with a decompressed distal bowel
NOT large bowel obstruction — LBO shows colonic dilation and is usually caused by malignancy, volvulus, or stricture; Clarence's imaging shows dilated small bowel with a decompressed colon
NOT mesenteric ischemia — that causes pain out of proportion to exam, often with lactic acidosis and cardiovascular disease, rather than crampy obstructive pain resolving with decompression
NOT incarcerated hernia — hernia is the second most common SBO cause but is found as a tender groin/abdominal wall bulge; Clarence's transition point is an intra-abdominal adhesion, not a hernia
NOT gastroenteritis — that produces diarrhea and diffuse crampy pain with continued passage of stool, whereas Clarence has obstipation with no flatus and dilated loops on imaging

Differential Diagnosis List

Paralytic ileus — ruled out by a discrete CT transition point with a decompressed distal bowel rather than diffuse dilation
Large bowel obstruction — ruled out by dilated small bowel with a decompressed colon on imaging
Mesenteric ischemia — ruled out by crampy obstructive pain that resolves with decompression and absence of acidosis/ischemia findings
Incarcerated/strangulated hernia — ruled out by an intra-abdominal adhesive transition point rather than a hernia sac
Gastroenteritis — ruled out by obstipation and radiographic dilated loops rather than diarrhea

Key Distinguishing Test

CT of the abdomen and pelvis with IV contrast is the confirmatory test: small bowel dilation >3 cm with a transition point, proximal dilation, and a decompressed distal bowel/colon establishes mechanical SBO (sensitivity ~94%, specificity ~96%), and it also identifies the cause and any signs of ischemia.
Upright/supine plain radiographs showing dilated loops with air-fluid levels and paucity of colonic gas support the diagnosis but are less sensitive, especially for partial obstruction.

Board Note

Classic associations: adhesions (from prior abdominal/pelvic surgery) are the most common cause, followed by hernias and malignancy; the clinical tetrad is crampy pain, vomiting, distension, and obstipation
Initial management of uncomplicated SBO is nonoperative: bowel rest (NPO), NG tube decompression, IV crystalloid resuscitation, and electrolyte correction, with serial abdominal exams and labs
Roughly 75–85% of adhesive SBOs resolve nonoperatively; a trial is generally limited to ~3 days (guidelines cite 3–5 days) because delaying needed surgery raises resection/ischemia risk
Escalate to urgent surgery for signs of strangulation/ischemia, closed-loop obstruction, perforation, peritonitis, complete obstruction, or failure of nonoperative management; red flags include fever, rising WBC, lactic acidosis, peritonism, and CT signs (reduced bowel-wall enhancement, wall thickening, mesenteric edema/fluid, pneumatosis, portal venous gas)
Water-soluble contrast (e.g., Gastrografin) can be both prognostic and therapeutic in adhesive SBO—contrast reaching the colon predicts nonoperative resolution
Refer/consult surgery for all SBO; a hernia or suspected neoplasm/closed loop is unlikely to resolve without operation

“Clarence’s Story”