Adhesion colic pathophysiology

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Adhesion Colic — Pathophysiology

"Adhesion colic" refers to the colicky abdominal pain produced when intra-abdominal adhesions cause partial or complete small bowel obstruction (SBO). Understanding it requires two interrelated concepts: how adhesions form, and how they cause obstruction and pain.

1. Formation of Intra-Abdominal Adhesions

Adhesions are abnormal fibrous bands between peritoneal surfaces that are normally separate. The vast majority are acquired; congenital adhesions (Ladd or Meckel bands) are a minority.

Triggering insult → fibrin deposition cascade:

"Tissue damage, hemorrhage, and inflammation in the peritoneal cavity lead to fibrin deposition on the peritoneal surfaces, allowing adjacent surfaces to adhere in this sticky matrix." — Sleisenger and Fordtran's Gastrointestinal and Liver Disease

Causes include:

Prior abdominal/pelvic surgery (most common — postoperative adhesions)
Secondary peritonitis (infection, perforation, appendicitis)
Intraperitoneal foreign bodies: suture material, clips, mesh, glove powder/cornstarch
Pelvic inflammatory disease (PID)
Inflammatory bowel disease, radiation enteritis

Mechanism of fibrous band maturation:

Peritoneal mesothelial injury → local inflammatory response
Fibrinous exudate forms between apposed serosal surfaces
Normally, fibrinolysis (via plasminogen activators) dissolves this fibrin within 3–5 days
When fibrinolysis is impaired (ischemia, infection, foreign bodies suppress tPA activity), fibroblasts invade the fibrin matrix
Collagen deposition and neovascularization convert the fibrinous band into a permanent fibrovascular adhesion

Adhesions are the most common cause of SBO, accounting for approximately 60–70% of cases.

2. How Adhesions Cause Obstruction

Adhesive bands cause obstruction by two main mechanisms:

A. Extrinsic compression / kinking A fibrous band crosses over a loop of bowel, compressing and angulating it from the outside — this is an open-loop obstruction (proximal and distal ends remain patent).

B. Closed-loop obstruction (more dangerous) The bowel twists around the axis of the adhesive band or the mesentery, trapping a segment with both an afferent and efferent limb occluded. The trapped loop rapidly accumulates gas and fluid with no exit, producing rapidly escalating intraluminal pressure.

"The onset of obstruction is often caused by twisting of the bowel around the axis of its mesentery induced by an adhesive band... Reflex hyperperistalsis and twisting of the mesentery occur early and are associated with intense pain and reflex nausea and vomiting." — Mulholland and Greenfield's Surgery, Scientific Principles and Practice

3. Pathophysiology of the Colic and Downstream Events

Once obstruction is established, a cascade of events unfolds:

A. Gas and Fluid Accumulation

Swallowed air (nitrogen) is the principal component of early luminal distension
Intestinal secretions continue proximal to the block, but absorption ceases → fluid sequestration ("third spacing") into the bowel lumen and wall

B. Motor Response → Colicky Pain

The bowel initially relaxes to keep intraluminal pressure low
Followed by hyperperistalsis — forceful peristaltic contractions attempting to clear the blockage
These high-amplitude contractions against a fixed obstruction generate the classic colicky pain: cramping waves that wax and wane, typically periumbilical or in the distribution of the obstructed segment
Pain is intermittent and cramping in open-loop obstruction (proximal SBO: intense and frequent; distal SBO: less intense, more distension-dominant)
In closed-loop obstruction, pain rapidly becomes constant as ischemia supervenes

C. Bacterial Overgrowth and Mucosal Disruption

Luminal stasis → rapid bacterial proliferation in the obstructed segment
Microbial toxins impair mucosal secretion and absorption
Bacterial translocation occurs through the damaged epithelium to the bowel wall, mesenteric lymphatics, and systemic circulation — a key driver of septic complications

D. Vascular Compromise → Strangulation

The most feared complication:

"When luminal pressure exceeds mural venous pressure and then capillary perfusion pressures, inflammatory cells are recruited from surrounding peritoneal structures... Peritoneal findings (localized tenderness, involuntary guarding, rebound or referred tenderness) and fevers appear." — Mulholland and Greenfield's Surgery

Sequence:

Venous outflow obstructed first (mesenteric veins compressed by elevated intraluminal/twist pressure) → venous congestion, edema, hemorrhagic infarction
Arterial inflow subsequently compromised → ischemia → gangrene
Full-thickness necrosis → perforation → fecal peritonitis, septic shock

E. Systemic Effects

Level of Obstruction	Dominant Effect
Proximal jejunum (open loop)	Bilious vomiting → loss of H⁺, Cl⁻, K⁺ → metabolic alkalosis, hyponatremia
Distal ileum (open loop)	Progressive distension, feculent vomiting, electrolyte derangements
Closed loop (any level)	Rapid ischemia, toxin release, circulatory collapse

Summary Diagram of Pathophysiology

Peritoneal injury (surgery / infection / foreign body)
        ↓
Fibrin deposition (impaired fibrinolysis)
        ↓
Fibroblast invasion → permanent fibrovascular adhesion
        ↓
Extrinsic kinking OR closed-loop twist of bowel
        ↓
Luminal gas/fluid accumulation → distension
        ↓
Hyperperistalsis → COLICKY PAIN
        ↓
Mucosal disruption → bacterial translocation
        ↓
Venous congestion → arterial ischemia → STRANGULATION
        ↓
Gangrene / perforation / peritonitis / shock

Key clinical implication: The shift from intermittent colicky pain (simple obstruction, hyperperistalsis) to constant pain with peritoneal signs signals progression to strangulation — a surgical emergency. Fever, tachycardia, leukocytosis, and localized tenderness are the hallmarks of this transition.

Sources: Mulholland and Greenfield's Surgery, 7e | Sleisenger and Fordtran's Gastrointestinal and Liver Disease

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