What are the causes of closed loop obstruction?

Causes of Closed Loop Obstruction

Closed loop obstruction is primarily caused by adhesions, volvulus, hernias, and tumors that obstruct the bowel at two adjacent points, creating a segment with no outlet that rapidly progresses to ischemia and potential necrosis if not promptly treated. 1, 2

Definition and Mechanism

• Closed loop obstruction occurs when a segment of bowel is obstructed at two points, creating a section with no outlet for decompression 3
• This condition rapidly leads to increased intraluminal pressure, impaired capillary perfusion, and potential strangulation if not promptly addressed 4
• The trapped fluid and gas cause progressive distension, vascular compromise, and eventual ischemia of the affected bowel segment 2, 5

Common Causes

Adhesions

• Post-surgical adhesions are the most common cause of closed loop obstruction, particularly in patients with previous abdominal surgeries 4, 2
• Even patients without prior surgery can develop adhesions from previous intra-abdominal infections 6

Volvulus

• Sigmoid volvulus is a frequent cause of closed loop obstruction, accounting for approximately one-third of colonic emergencies in elderly patients 4
• Types of volvulus causing closed loop obstruction include:
  • Type I: sigmoid wraps around its own mesentery (90% of cases) 4
  • Type II: sigmoid wraps around ileum (5% of cases) 4
  • Type III: ileocecal region wraps around sigmoid (less than 5% of cases) 4

Hernias

• External hernias (inguinal, femoral, incisional) can create closed loop obstructions when bowel becomes incarcerated 3, 5
• Internal hernias can cause closed loop obstruction through focal intraperitoneal segregation of bowel loops 3

Colorectal Cancer

• Obstructing colorectal tumors can create closed loop scenarios, especially when combined with a competent ileocecal valve 4, 7
• Right-sided colonic tumors typically present with less acute obstruction than left-sided tumors 4

Other Causes

• Laparoscopic adjustable gastric bands can create closed loop obstructions in bariatric surgery patients 8
• Diverticular disease can lead to adhesion formation and subsequent closed loop obstruction 6
• Double closed loop obstruction can occur with sigmoid volvulus combined with a competent ileocecal valve 7

Diagnostic Features

• CT scan with IV contrast is the preferred imaging modality for diagnosing closed loop obstruction, with approximately 90% accuracy 1, 2
• Key radiologic features suggesting closed loop obstruction include:
  • Crossing defects obstructing two segments of bowel due to adhesive bands 3
  • Focal fixation or twisting of bowel folds suggesting volvulus 3
  • C-shaped incarcerated loop or radial distribution of dilated bowel loops 5
  • Triangular/fusiform tapering or "whirl sign" at the obstruction site 5

Clinical Significance and Management

• Closed loop obstructions rapidly progress to strangulation and ischemia, with mortality rates reaching 70% if not promptly treated 4
• Signs suggesting need for urgent surgery include abnormal bowel wall enhancement, wall thickening, mesenteric edema, and pneumatosis 2
• Damage control surgery should be initiated promptly in unstable patients with signs of sepsis, acidosis (pH <7.2), hypothermia (<35°C), or coagulopathy 4
• For right-sided obstructions, right colectomy with terminal ileostomy is often the procedure of choice in unstable patients 4
• For left-sided obstructions, Hartmann's procedure is typically recommended 4

Pitfalls to Avoid

• Delayed diagnosis significantly increases morbidity and mortality, with intestinal necrosis observed in up to 70% of cases 4
• CT findings may underestimate the extent of bowel ischemia, as demonstrated in cases where imaging showed localized ischemia but surgery revealed more extensive involvement 7
• Relying solely on plain radiographs is inadequate due to their limited sensitivity (50-60%) for bowel obstruction 2