Anatomy Thorax Abdomen · Year 1 · from Anatomy Thorax Abdomen
Case 1: Small Bowel Obstruction
Patient Demographics
- Age: 68 years old
- Sex: Female
- Occupation: Retired nurse
Chief Complaint
Progressive abdominal pain, distension, and vomiting for 48 hours.
History of Present Illness
The patient presents with crampy, periumbilical abdominal pain that started gradually two days ago. She reports progressive abdominal distension and has vomited multiple times with bilious content. She has not passed flatus or had a bowel movement for 36 hours. Past surgical history is significant for an open appendectomy 25 years ago and a cesarean section 40 years ago. She denies fever, bloody vomiting, or bloody stools.
Physical Examination
- Vitals: HR 98 bpm, BP 128/76 mmHg, RR 18, Temp 37.2C, SpO2 98% on room air
- General: Moderate distress, uncomfortable
- Abdomen: Distended, tympanic to percussion, high-pitched bowel sounds with occasional rushes, mild diffuse tenderness without peritoneal signs
- Rectal examination: Empty rectal vault, no masses, guaiac negative
Imaging Workup
- Supine abdominal radiograph: Multiple dilated loops of small bowel centrally located with valvulae conniventes visible traversing the entire bowel width. No gas visible in the colon or rectum.
- Upright abdominal radiograph: Multiple air-fluid levels at different heights within the same loop of bowel (differential air-fluid levels), consistent with mechanical small bowel obstruction.
- CT abdomen/pelvis with IV contrast: Dilated small bowel loops up to 4.5 cm proximal to a discrete transition point in the right lower quadrant. The transition zone shows a band-like structure consistent with adhesion. The decompressed distal small bowel confirms mechanical obstruction. No evidence of bowel wall thickening, pneumatosis, or portal venous gas to suggest ischemia.
Clinical Image
Upright abdominal radiograph demonstrating dilated small bowel loops with multiple air-fluid levels characteristic of mechanical small bowel obstruction.
Image Source: Wikimedia Commons - File:Upright X-ray demonstrating small bowel obstruction.jpg by James Heilman, MD, licensed under CC BY-SA 3.0
Diagnosis
Adhesive small bowel obstruction secondary to postoperative adhesions.
Anatomical Correlation
The imaging findings demonstrate key anatomical features distinguishing small bowel from large bowel. The valvulae conniventes (plicae circulares) are mucosal folds that traverse the entire width of the small bowel lumen and are characteristic of jejunum in particular. In contrast, the haustra of the large bowel are incomplete folds that do not cross the entire lumen. Small bowel is considered dilated when measuring greater than 3 cm on plain radiograph or 2.5 cm on CT. The central location of dilated loops suggests small bowel, as the colon frames the periphery of the abdomen. The "small bowel feces sign" may be seen on CT at the transition point, representing particulate matter mixed with fluid in obstructed small bowel. Adhesions are the most common cause of small bowel obstruction in developed countries, accounting for 65-75% of cases.
Treatment
- Conservative management: NPO, nasogastric tube decompression, IV fluid resuscitation, electrolyte correction
- Serial examinations: Monitoring for signs of strangulation (fever, tachycardia, localized tenderness, leukocytosis)
- Water-soluble contrast challenge: Gastrografin administration to predict resolution and potentially therapeutic
- Surgical intervention: Laparoscopic adhesiolysis if no resolution within 48-72 hours or if signs of strangulation develop