Acute Intestinal Obstruction¶
Chapter 341 | Part 10: Disorders of the Gastrointestinal System
KEY CLINICAL POINTS¶
- Acute intestinal obstruction is a surgical emergency with mortality rates up to 8% for strangulated cases operated within 24–30 h of symptom onset.
- Mechanical obstruction (75–90% of cases) vs. nonmechanical (dysmotility, ischemia) causes; 80% of cases involve small bowel.
- Key diagnostic imaging: CT with oral/IV contrast (95% sensitivity for high-grade obstruction) and upright abdominal X-ray for 'staircasing' pattern.
- Management includes early resuscitation, nasogastric decompression, and surgical intervention for strangulation or irreversible ischemia.
- Postoperative adhesions account for >50% of recurrent obstructions; laparoscopic techniques reduce but do not eliminate adhesion risk.
1. DEFINITION & OVERVIEW¶
Acute intestinal obstruction refers to any condition that impedes the passage of intestinal contents, leading to bowel dilation, distension, and potential necrosis. It may be mechanical (blockage) or nonmechanical (dysmotility, ischemia).
Table 341-1: Most Common Causes of Acute Intestinal Obstruction¶
| Category | Causes |
|---|---|
| Extrinsic Disease | Adhesions, hernias, neoplasms, endometriosis, idiopathic sclerosis |
| Intrinsic Disease | Congenital anomalies, inflammatory bowel disease, neoplasms, radiation injury |
| Intraluminal Abnormalities | Bezoars, feces, foreign bodies, gallstones, enteroliths |
| Other | Intussusception, volvulus, duodenal obstruction, aganglionosis |
1.1 Classification¶
Mechanical obstruction: Adhesions (50%), tumors (20%), hernias (10%), volvulus/intussusception (<15%). Nonmechanical: Ischemia (vasospasm, thrombosis), ileus (postoperative, Ogilvie’s syndrome).
1.2 Pathophysiology¶
Closed-loop obstruction (volvulus, hernia) leads to ischemia, necrosis, and strangulation. Proximal dilation, distal collapse, and bacterial overgrowth cause systemic inflammation and metabolic derangements.
2. EPIDEMIOLOGY¶
Global incidence/prevalence increased over 20 years; mortality decreasing. 80% of cases involve small bowel. 25–30% of patients with strangulation require reoperation within 10 years. Postoperative adhesions cause 50–70% of recurrent obstructions.
Table 341-2: Acute Small-Intestinal and Colonic Obstruction Incidences¶
| Cause | Incidence |
|---|---|
| Postoperative adhesions | >50% overall |
| Neoplasms | ~20% |
| Hernias | ~10% |
| Inflammatory bowel disease | ~5% |
| Intussusception/volvulus | <15% |
2.1 Demographics¶
Colonic volvulus more common in Eastern Europe/Russia/Africa; sigmoid volvulus peaks in 70–80-year-olds. Ileus more common in postoperative patients and those with neuropsychiatric disorders.
2.2 Risk Factors¶
Previous abdominal surgery (adhesions), malignancy (carcinomatosis), hernias, inflammatory bowel disease, radiation, and iatrogenic causes (e.g., laparoscopic procedures).
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Mechanical obstruction: Adhesions (50%), tumors (20%), hernias (10%), volvulus/intussusception (<15%). Nonmechanical: Ischemia (vasospasm, thrombosis), ileus (postoperative, Ogilvie’s syndrome). Closed-loop obstruction leads to ischemia, necrosis, and strangulation.
Table 341-3: Most Common Causes of Ileus (Functional Obstruction)¶
| Cause | Description |
|---|---|
| Postoperative ileus | Most common form after abdominal surgery |
| Ogilvie’s syndrome | Colonic pseudo-obstruction with megacolon |
| Medications | Opiates, anticholinergics, tricyclic antidepressants |
| Electrolyte abnormalities | Hypokalemia, hypomagnesemia |
| Systemic sepsis | Inflammatory myopathies/neuropathies |
3.1 Pathophysiology¶
Proximal dilation, distal collapse, bacterial overgrowth, and systemic inflammation. Ischemia causes epithelial necrosis, edema, and transmural necrosis within 12–24 h. Metabolic acidosis and lactic acidosis develop with prolonged obstruction.
3.2 Vascular Compromise¶
Mesenteric venous thrombosis (acute/subacute) and arterial occlusion (embolism/thrombosis) lead to bowel necrosis. Anticoagulation is contraindicated in acute phases.
4. CLINICAL FEATURES¶
Cardinal signs: Colicky abdominal pain, distension, emesis, obstipation. Distal obstruction causes greater distension and delayed emesis; proximal obstruction presents with more vomiting. Signs of peritonitis or localized tenderness suggest strangulation.
4.1 Physical Findings¶
Abdominal distension, high-pitched bowel sounds (early), hypoactive sounds (later), guarding, rebound tenderness. Sigmoid volvulus presents with classic closed-loop findings: severe pain, vomiting, and obstipation.
4.2 Complications¶
Bowel necrosis, perforation, sepsis, metabolic acidosis, and systemic inflammatory response syndrome (SIRS).
5. DIFFERENTIAL DIAGNOSIS¶
Acute mesenteric ischemia, appendicitis, cholecystitis, bowel infarction, and ileus. Distinguish mechanical obstruction from functional (ileus) using imaging and clinical findings.
5.1 Functional vs. Mechanical¶
Ileus: No mechanical blockage, absent bowel sounds, no flatus/stool passage. Mechanical obstruction: Distended bowel, possible passage of flatus/stool, localized tenderness.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnostic imaging: CT (gold standard) with oral/IV contrast (95% sensitivity for high-grade obstruction). Abdominal X-ray for 'staircasing' pattern. Laboratory tests: CBC, electrolytes, creatinine, d-lactate, and lactate levels.
Table 341-1: Most Common Causes of Acute Intestinal Obstruction¶
| Category | Causes |
|---|---|
| Extrinsic Disease | Adhesions, hernias, neoplasms, endometriosis, idiopathic sclerosis |
| Intrinsic Disease | Congenital anomalies, inflammatory bowel disease, neoplasms, radiation injury |
| Intraluminal Abnormalities | Bezoars, feces, foreign bodies, gallstones, enteroliths |
| Other | Intussusception, volvual, duodenal obstruction, aganglionosis |
6.1 Imaging Criteria¶
CT findings: Dilated bowel loops (>2.5 cm), air-fluid levels, absence of colonic gas. Volvulus: 'Coffee bean' sign. Mesenteric venous gas indicates necrosis.
6.2 Laboratory Findings¶
Hypokalemia, metabolic alkalosis, elevated WBC with immature forms suggest severe ischemia. Serum d-lactate and intestinal fatty acid binding protein may indicate ischemia.
7. MANAGEMENT & TREATMENT¶
Immediate resuscitation with IV fluids, NG tube decompression, and broad-spectrum antibiotics. Surgical intervention for strangulation, necrosis, or irreversible ischemia. Endovascular stenting for chronic mesenteric ischemia.
Table 341-2: Acute Small-Intestinal and Colonic Obstruction Incidences¶
| Cause | Incidence |
|---|---|
| Postoperative adhesions | >50% overall |
| Neoplasms | ~20% |
| Hernias | ~10% |
| Inflammatory bowel disease | ~5% |
| Intussusception/volvulus | <15% |
7.1 Surgical Options¶
Laparotomy for resection of necrotic bowel, exploratory laparotomy for second-look (24–48 h post-revascularization). Laparoscopic approaches for early, non-adhesive obstructions.
7.2 Medical Management¶
Vasodilators (papaverine, prostaglandins) for spastic obstruction. Neostigmine for Ogilvie’s syndrome. Anticoagulation for thrombosis (avoid in acute phases).
8. PROGNOSIS & COMPLICATIONS¶
Mortality: 8% for strangulated obstruction within 24–30 h; triples after 30 h. Complications: Reoperation (12–47%), sepsis, bowel perforation, and long-term adhesion formation. Postoperative ileus occurs in 10–30% of patients.
8.1 Risk Factors¶
ASA class III–V, resection therapies, and preoperative comorbidities increase complication risk. Laparoscopic procedures reduce adhesion risk but do not eliminate it.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: Avoid barium studies; use CT with caution. Pediatrics: Malrotation, intussusception, and congenital anomalies are common. Elderly: Higher risk of ischemia and delayed presentation.
9.1 Obstetric Considerations¶
Avoid barium enemas in pregnant patients. Use CT with IV contrast for diagnosis. Laparoscopic approaches preferred to minimize radiation exposure.
10. KEY POINTS & CLINICAL PEARLS¶
- CT with oral/IV contrast is the gold standard for diagnosis. 2. Second-look laparotomy within 24–48 h is critical for viable bowel assessment. 3. Postoperative ileus is common but usually transient. 4. Barium studies are contraindicated in acute obstruction. 5. Early resuscitation and surgical intervention reduce mortality.