| Feature | SBO | LBO |
|---|---|---|
| #1 Cause | Adhesions | Colorectal cancer |
| Other | Hernias, malignancy, Crohn | Volvulus (sigmoid > cecal) |
| Conservative | NGT, NPO, IVF ×48–72h | Depends on cause |
| Surgery | Complete, strangulation, failure to resolve | Cancer → resection. Cecal volvulus → surgery |
| Type | First-Line | Definitive |
|---|---|---|
| Sigmoid | Endoscopic decompression | Interval resection |
| Cecal | Surgery (scope does NOT work) | Right hemicolectomy |
| Finding | Significance |
|---|---|
| Transition point | Dilated proximal bowel → decompressed distal bowel. Identifies the site of obstruction. Distinguishes SBO from ileus (no transition point in ileus). |
| Air-fluid levels | Multiple, differential levels on upright film. Stepladder pattern classic for SBO. |
| Small bowel feces sign | Particulate matter in dilated SB near transition point. Suggests prolonged obstruction with bacterial overgrowth. |
| Closed-loop obstruction | U-shaped or C-shaped dilated loop with 2 transition points converging. HIGH risk of strangulation → surgical emergency. |
| Pneumatosis intestinalis | Air within bowel wall = ischemia/necrosis. Requires urgent surgery. |
| Portal venous gas | Air in portal system = bowel necrosis. Extremely ominous sign. Emergency laparotomy. |
| Mesenteric haziness / stranding | Suggests venous congestion or early ischemia. Correlate with lactate. |
| Whirl sign | Swirling of mesentery and bowel around a point = volvulus or internal hernia. |
| Criteria | Conservative (Trial of Non-Op) | Operative (Go to OR) |
|---|---|---|
| Obstruction type | Partial SBO (contrast passes on CT) | Complete SBO, any LBO with obstruction |
| Etiology | Adhesive SBO (no virgin abdomen) | Hernia, closed-loop, volvulus, tumor |
| Clinical status | Stable, no peritonitis, tolerating NGT | Peritonitis, sepsis, hemodynamic instability |
| Labs | Normal lactate, normal WBC | Elevated lactate, leukocytosis, acidosis |
| Imaging | No closed-loop, no pneumatosis, no portal gas | Any sign of strangulation or ischemia |
| Time frame | Resolution expected within 48–72h | Failure to improve after 48–72h of conservative Rx |
| Step | Action | Details |
|---|---|---|
| 1 | Confirm appropriateness | Partial adhesive SBO, no signs of strangulation, no complete obstruction, no peritonitis |
| 2 | Administer Gastrografin | 100 mL water-soluble contrast via NGT (or PO if no NGT). Clamp NGT ×2h after administration |
| 3 | Abdominal X-ray at 8–24h | Check if contrast has reached the colon/cecum |
| 4a | Contrast in colon = RESOLVING | Advance diet. High negative predictive value for need of surgery (~98%). Defined by Defined, Abbas et al. meta-analysis, 2014 |
| 4b | Contrast NOT in colon by 24–48h | Likely requires operative intervention. Surgical consult if not already involved |
| Etiology | Acute Management | Definitive Treatment |
|---|---|---|
| Colorectal cancer | Colonic stent (bridge to surgery) or diverting colostomy | Oncologic resection with primary anastomosis or Hartmann procedure |
| Sigmoid volvulus | Endoscopic decompression + rectal tube | Interval sigmoid resection (recurrence rate >50% without surgery) |
| Cecal volvulus | Surgery (endoscopy does NOT work) | Right hemicolectomy (cecopexy has high recurrence) |
| Pseudo-obstruction (Ogilvie) | Neostigmine 2 mg IV (monitor for bradycardia). Colonoscopic decompression if fails | Correct underlying cause (post-op, electrolytes, medications) |
| Drug | Role |
|---|---|
| NS / LR | Aggressive volume resuscitation |
| Gastrografin | 100mL via NGT (diagnostic + therapeutic) |
| Ondansetron | Antiemetic 4mg IV q6h |
| Pip-tazo / Cefepime + Metro | If strangulation/perforation suspected |
Patient: 54F with history of open appendectomy (20 years ago) and prior cesarean section. Presents with 24 hours of crampy abdominal pain, nausea, bilious vomiting ×4, and obstipation. No prior SBO episodes.
Exam: Abdomen distended, tympanitic, diffusely tender without rebound or guarding. High-pitched bowel sounds. No hernias on exam. Temp 37.1, HR 98, BP 110/70.
Labs: WBC 9.2, lactate 1.1, BMP notable for K+ 3.2, Cr 1.3 (baseline 0.8, dehydration).
CT abdomen/pelvis: Dilated small bowel loops up to 4.5 cm with a transition point in the RLQ at a band adhesion. Decompressed distal ileum and colon. No closed-loop, no pneumatosis, no portal venous gas. Small amount of contrast passes the transition point (partial SBO).
Management:
Key lesson: Partial adhesive SBO without strangulation signs is the ideal candidate for conservative management. Gastrografin reaching the colon by 8–24h has a 98% negative predictive value for need of surgery.
Patient: 68M with history of multiple prior abdominal surgeries (cholecystectomy, ventral hernia repair with mesh). Presents with acute-onset severe periumbilical pain ×8 hours, now constant and worsening. Multiple episodes of non-bilious emesis.
Exam: Distended, rigid abdomen with involuntary guarding and rebound tenderness. Absent bowel sounds. Temp 38.9, HR 122, BP 88/54, lactate 6.8.
Labs: WBC 22,000, lactate 6.8, BMP with K+ 5.1, Cr 2.1, metabolic acidosis (pH 7.28, bicarb 16).
CT abdomen/pelvis: Closed-loop obstruction in mid-abdomen with C-shaped dilated loop, two adjacent transition points, pneumatosis intestinalis in the affected segment, mesenteric haziness, and small-volume free fluid. No portal venous gas.
Management:
Key lesson: Peritonitis + hemodynamic instability + closed-loop + pneumatosis = NO role for conservative management. These patients need immediate operative intervention. Elevated lactate >4 with leukocytosis strongly suggests bowel ischemia.
Patient: 73M with 3-week history of progressive constipation, abdominal distension, and colicky pain. No BM ×5 days. No prior abdominal surgery. 15 lb weight loss over 2 months.
Exam: Markedly distended abdomen, tympanitic. Mild diffuse tenderness, no peritonitis. Empty rectal vault on DRE. Temp 37.2, HR 90, BP 135/80.
Labs: WBC 11, lactate 1.4, Hgb 9.2 (microcytic, iron deficiency), CEA 28 (elevated).
CT abdomen/pelvis: Dilated colon (cecum 10 cm) with transition point at splenic flexure, circumferential mass causing near-complete LBO. No perforation. Multiple hepatic lesions concerning for metastatic disease. Ileocecal valve competent (no decompression into small bowel).
Management:
Key lesson: Colonic stenting as a bridge to surgery in malignant LBO allows decompression, staging, and optimization before definitive surgery. Emergent surgery for obstructing CRC has significantly higher morbidity and mortality than elective resection. CReST Collaborative, Lancet Oncol, 2022
| Parameter | Frequency |
|---|---|
| Abdominal exam | q4–8h |
| NGT output | q shift |
| CBC, lactate | q8–12h |