🔵Small Bowel Obstruction (SBO) — Overview
DefinitionMechanical impediment to the normal flow of intestinal contents within the small bowel (jejunum/ileum), constituting ~80% of all intestinal obstructions.
Causes by Frequency
- Adhesions — 60% (post-surgical scar tissue; most common cause)
- Hernia — 20% (incarcerated/strangulated inguinal, femoral, incisional)
- Malignancy — intrinsic tumour or extrinsic compression
- Volvulus — twisting of small bowel loop on mesenteric axis
- Intussusception — telescoping of bowel; adults often have lead point (tumour)
- Crohn's stricture — inflammatory/fibrotic narrowing
- Gallstone ileus — large gallstone erodes into bowel via cholecystoenteric fistula
Classic Presentation
- Colicky central abdominal pain — cramping, comes in waves
- Vomiting — early & profuse in SBO; becomes faeculent if prolonged
- Abdominal distension — more pronounced in distal SBO
- Absolute constipation — LATE sign; patient may pass residual stool initially
- Tinkling bowel sounds — active peristalsis against obstruction
- Silent bowel — strangulation or paralytic ileus; DANGER sign
- Dehydration signs — dry mucous membranes, reduced skin turgor, tachycardia
Classification of SBO
Partial vs Complete
| Feature | Partial | Complete |
|---|---|---|
| Gas beyond obstruction | Present | Absent |
| Flatus | May pass | None |
| Severity | Milder | Severe |
| Management | Often conservative | May need surgery |
Simple vs Strangulated
| Feature | Simple | Strangulated |
|---|---|---|
| Blood supply | Intact | Compromised |
| Pain character | Colicky | Constant + colicky |
| Peritonism | Absent | Present |
| Fever | Low-grade | High |
| Lactate | Normal | Raised (>2 mmol/L) |
| Management | Conservative trial | Emergency surgery |
Investigations
Abdominal X-Ray (AXR)
- Dilated small bowel loops >3 cm
- Multiple horizontal fluid levels (step-ladder pattern)
- Absent gas in colon — differentiates from LBO
- Valvulae conniventes cross entire bowel width (vs haustra)
- Central distribution
Erect CXR
- Identifies free air under diaphragm — perforation
- Mandatory in all acute abdominal presentations
- Air under right hemidiaphragm more common
Bloods
- U&E — dehydration, hypokalaemia
- FBC — raised WBC = infection/ischaemia
- CRP — inflammatory marker
- Lactate — raised >2 mmol/L = gut ischaemia/strangulation
- LFT, coagulation, G&S
CT Abdomen (Gold Standard)
- Identifies transition point — site of obstruction
- Closed-loop obstruction — C-shaped loop, mesenteric swirl
- Signs of ischaemia: bowel wall thickening, pneumatosis intestinalis, portal venous gas
- Identifies cause: adhesion band, hernia, tumour
- CT with IV contrast preferred
- Confirms free air if CXR equivocal
🟡Large Bowel Obstruction (LBO) — Overview
Key DistinctionLBO is typically more insidious onset than SBO. Vomiting is LATE and less prominent. Distension is more marked and peripheral. Gas pattern on AXR shows dilated colon with haustra.
Causes by Frequency
- Colorectal cancer — 60% (most common cause in adults; left colon more common)
- Sigmoid volvulus — twisted loop; GCC-relevant
- Diverticular stricture — fibrotic narrowing from recurrent diverticulitis
- Faecal impaction — common in elderly, opioid-induced constipation
- Anastomotic stricture, hernia, extrinsic compression (rare)
Presentation vs SBO
| Feature | SBO | LBO |
|---|---|---|
| Pain | Central, colicky | Lower abdominal/colicky |
| Vomiting | Early, profuse | Late, faeculent |
| Distension | Moderate, central | Marked, peripheral |
| Constipation | Late | Early/prominent |
| AXR gas | Central, no colon gas | Peripheral colonic gas |
Sigmoid Volvulus
MechanismRedundant sigmoid colon twists on its mesentery — leads to closed-loop obstruction. Common in chronic constipation, high-fibre diet populations, elderly institutionalised patients.
Diagnosis
- AXR: Coffee bean sign — massively dilated sigmoid loop pointing to RUQ
- Inverted U shape, apex in RUQ
- CT confirms: whirl sign of mesentery, transition points at both limbs
- No rectal gas on AXR
Management
- First-line: Sigmoidoscopic decompression — rigid/flexible sigmoidoscope; flatus tube left in situ 24–48h
- Flatus tube per rectum if sigmoidoscopy not immediately available
- Surgery if: fails endoscopic, peritonism, recurrence, gangrenous bowel
- Elective sigmoid colectomy recommended after first episode to prevent recurrence
- Hartmann's procedure if gangrenous — end colostomy
Caecal Volvulus & Pseudo-Obstruction
Caecal Volvulus
- Mobile caecum twists on its mesentery — less common than sigmoid
- AXR: distended caecum in LUQ or central abdomen (axial twist) or kidney-bean shape
- Requires surgical management — cannot decompress endoscopically
- Options: caecostomy (decompression + fixation), right hemicolectomy if gangrenous
- Higher mortality than sigmoid volvulus
Ogilvie Syndrome (Pseudo-Obstruction)
- Massive colonic dilatation WITHOUT mechanical cause
- In critically ill: post-op, sepsis, cardiac events, electrolyte imbalance, opioids
- Caecal diameter >12 cm — risk of perforation
- First-line: Neostigmine IV 2mg slow IV (monitor for bradycardia, have atropine ready)
- Colonoscopic decompression if neostigmine fails
- Treat underlying cause, stop constipating drugs, electrolyte correction
Closed-Loop Obstruction
Emergency — Perforation RiskWhen the ileo-caecal valve is competent (present in ~70%), obstruction of the colon creates a closed loop — proximal decompression impossible. Caecal diameter >9 cm signals imminent perforation. Caecal perforation carries 40–50% mortality. CT urgently to assess caecal size. Proceed to emergency surgery.
- Caecum at highest risk — thinnest wall, greatest diameter (law of Laplace)
- Urgent large bowel decompression: loop colostomy, Hartmann's, or right hemicolectomy
🟢"Drip and Suck" — Conservative Management of SBO
IndicationTrial of conservative management is appropriate for adhesional SBO without signs of strangulation or peritonitis. Success rate ~80% for adhesional SBO. Must be reviewed every 4–6 hours.
Core Interventions
- IV Fluids — isotonic crystalloid (0.9% NaCl or Hartmann's); correct dehydration and electrolytes
- NG Tube on Free Drainage — decompress stomach, reduce vomiting, relieve pain
- NBM — nothing by mouth; sips of water only when tolerating
- Urinary catheter — strict hourly fluid balance
- DVT prophylaxis — TED stockings, LMWH when appropriate
- Regular analgesia — opioids acceptable; do NOT withhold as they do not mask peritonism signs on exam
Fluid Balance Monitoring
- Hourly urine output — target >0.5 ml/kg/hr
- NG drainage — record and replace with 0.9% NaCl mL-for-mL
- Daily weight when possible
- Hypokalaemia very common — K+ depleted via vomiting & NG drainage
- IV potassium replacement (max 10 mmol/hr peripherally, 40 mmol/hr centrally with monitoring)
- Repeat U&E 4–6 hourly initially
- Oliguria (<0.5 ml/kg/hr for 2hrs) → IV fluid bolus + escalate
Water-Soluble Contrast (Gastrografin)
Dual Role — Therapeutic & DiagnosticGastrografin (diatrizoate meglumine) — hyperosmolar water-soluble contrast. Draws fluid into bowel lumen, reduces oedema at obstruction site, and has osmotic laxative effect.
Protocol
- 100 ml Gastrografin via NG tube after clamped for 1 hour
- AXR at 4 and 24 hours
- Contrast in colon at 24h = likely to resolve conservatively (sensitivity 96%)
- No contrast progress at 24h = high likelihood surgery required
- Reduces need for surgery by ~20% and reduces hospital stay
Nursing Role
- Ensure NG tube position confirmed pre-administration
- Document exact time of administration
- Perform and document AXR at prescribed timepoints
- Monitor for aspiration risk
- Contraindicated if suspected perforation
Serial Abdominal Examinations — Signs of Strangulation
Critical Nursing SkillEvery 4–6 hours minimum. Deterioration = strangulation until proven otherwise. Do not delay escalation.
Pain Character Change
- Continuous severe pain (was colicky) = ischaemia
- Patient becoming very still — peritonism
- Movement worsens pain
Examination Findings
- Peritonism — guarding, rigidity, rebound tenderness
- Localised tenderness at hernia site
- Silent abdomen
- Fever >38°C
Biochemical Markers
- Raised WBC — >15 × 10⁹/L
- Lactate >2 mmol/L — gut ischaemia
- Rising CRP trend
- Tachycardia, hypotension
Surgical Indications
Emergency Surgery
- Signs of strangulation at any point
- Perforation (free air on CXR/CT)
- Peritonitis
- Closed-loop obstruction
- Gangrenous bowel on CT
- Complete LBO (especially competent ICV)
Semi-Urgent / Elective Surgery
- Failure to resolve at 48–72 hours despite conservative management
- No contrast passage on Gastrografin at 24h
- Recurrent adhesional SBO
- Underlying malignancy requiring resection
- Elective: recurrent hernia, elective repair
🟣Hernia Types & Anatomy
| Type | Location / Anatomy | Key Features | Strangulation Risk |
|---|---|---|---|
| Indirect Inguinal | Through deep inguinal ring → inguinal canal | Most common; follows path of testicular descent; young males | Moderate |
| Direct Inguinal | Through Hesselbach's triangle (weakness in posterior wall) | Older males; acquired muscular weakness; medial to epigastric vessels | Lower |
| Femoral | Below inguinal ligament through femoral canal | More common in females; narrow neck → HIGH strangulation risk; never watch and wait | HIGH |
| Umbilical | Through umbilical ring | Adults: acquired (obesity, ascites, pregnancy); children: congenital | Moderate |
| Incisional | Through previous surgical scar | 10–20% after laparotomy; risk factors: obesity, infection, poor nutrition | Moderate |
| Hiatus | Stomach through diaphragmatic hiatus | Sliding (90%) vs para-oesophageal (10% — higher strangulation risk) | Low–Mod |
| Spigelian | Through linea semilunaris (lateral edge of rectus) | Rare; often interparietal — hard to detect; CT needed | HIGH |
| Parastomal | Through stoma aperture in abdominal wall | Common after colostomy/ileostomy; can impair stoma function | Moderate |
Hernia Assessment — Clinical Classification
Reducible
- Contents return to abdominal cavity spontaneously or with pressure
- Non-tender, soft lump
- No immediate danger
- Elective repair can be planned
Irreducible / Incarcerated
- Cannot be reduced; contents stuck in sac
- May be tender
- No immediate ischaemia
- Urgent surgical review — risk of progressing to strangulation
Strangulated — SURGICAL EMERGENCY
- Non-reducible + tender + signs of ischaemia
- Severe localised pain, erythema over hernia, patient systemically unwell
- Bowel ischaemia/gangrene if not treated within hours
- Immediate surgical referral — no attempt at manual reduction if strangulated
- Prepare for emergency theatre
Conservative & Surgical Management
Conservative (Elective / Mild)
- Weight loss — reduces intra-abdominal pressure
- Avoid heavy lifting and straining
- Treat chronic cough (e.g., smoking cessation, COPD management)
- Treat constipation — avoid straining at stool
- Hernia truss (temporary) — not recommended long-term due to risks
- Conservative NOT appropriate for femoral hernias — repair all
Surgical Repair Options
- Open Lichtenstein mesh repair — gold standard for inguinal; tension-free; low recurrence
- Laparoscopic TAPP (Trans-Abdominal Pre-Peritoneal) — laparoscopic approach; good for bilateral/recurrent
- Laparoscopic TEP (Totally Extra-Peritoneal) — avoids peritoneal cavity; preferred by many centres
- Emergency repair — strangulated/incarcerated: open preferred; mesh-free if contaminated field
Acute Hernia Presentation — Nursing Actions
Priority Actions on Admission
Immediate
- IV access × 2 large bore
- IV fluid resuscitation if systemically unwell
- Analgesia — IV opioids (morphine/fentanyl)
- NBM immediately (potential emergency theatre)
- NEWS2 observations
Investigations
- Bloods: FBC, U&E, LFT, CRP, lactate, coagulation, G&S
- ECG (if >40 yrs/cardiac history)
- CT abdomen/pelvis — confirm diagnosis & viability
- AXR if obstruction suspected
Escalation Criteria
- Peritonism — immediate surgical review
- Lactate >2, WBC >15
- Fever, tachycardia, hypotension
- Erythema/oedema over hernia sac
- Failure to reduce with gentle manipulation
🔴Strangulated Hernia — Emergency Management
Time-CriticalBowel ischaemia begins within hours of strangulation. Mortality rises sharply with bowel gangrene. Must reach theatre within 2–4 hours of diagnosis ideally.
Pre-operative Management
- Immediate surgical referral — do not delay
- IV antibiotics: broad spectrum (piperacillin-tazobactam or cefuroxime + metronidazole)
- IV fluid resuscitation — 500ml crystalloid bolus if haemodynamically compromised
- NG tube on free drainage if obstruction present
- Urinary catheter — hourly urine output monitoring
- NBM, consent for bowel resection and possible stoma
- Blood cultures if septic
- ICU/HDU bed booking if elderly/comorbid
Operative Considerations
- Open approach preferred for emergency
- Bowel viability assessment — warm packs, reperfusion 5 minutes
- Non-viable bowel → resection + primary anastomosis or stoma
- Mesh-free repair in contaminated field — use tissue repair (Shouldice/Bassini) to avoid mesh infection
- May require right hemicolectomy if caecal involvement
- Hartmann's procedure for perforated LBO
Post-operative Nursing — Return of Bowel Function
Wound Care
- Inspect wound daily — healing by primary intention
- Watch for: erythema, discharge, dehiscence, haematoma
- Drain output — volume, colour, consistency
- Dressing changes per protocol
- Contaminated wounds: may be left open / delayed closure
Bowel Function Monitoring
- Bowel sounds — auscultate 4-hourly; return in 24–48h
- Passage of flatus — first sign of bowel function return
- Bowel opening — confirms recovery
- Reintroduce diet: sips → clear fluids → light diet when tolerating
- NG tube removal when bowel sounds present and patient tolerating
Stoma Care (if formed)
- Stoma nurse specialist referral — day 1
- Observe stoma: pink/red = healthy; dark/black = ischaemia → urgent review
- Output recording — ileostomy: 500–1500 ml/day; colostomy: formed stool
- Patient education: bag changes, skin care, diet
- Discuss reversal timeline
Paralytic Ileus — Postoperative
DefinitionTemporary cessation of coordinated bowel motility following abdominal surgery — distinct from mechanical obstruction. Expected duration 2–3 days (small bowel recovers first, then stomach, then colon takes longest 3–5 days).
Recognition
- Absent bowel sounds on auscultation
- Abdominal distension
- No passage of flatus
- Nausea, vomiting if on oral intake
- Prolonged if >3–5 days post-op
- If prolonged → CT to exclude mechanical obstruction
Management
- Mobilisation — early walking is #1 intervention
- Chewing gum (sham feeding) — stimulates cephalic-vagal reflex, proven to shorten ileus
- Prokinetics — metoclopramide, erythromycin (low dose)
- NG on free drainage if distended/vomiting
- Correct electrolytes: K+, Mg²+ (low levels worsen ileus)
- Minimise opioids — use NSAIDs/paracetamol where safe
- Alvimopan (mu-opioid antagonist) — specialist centres
Nutritional Support
Enteral Nutrition (Preferred)
- Start early enteral feeding when bowel function returns
- NG or NJ feeding if unable to tolerate oral
- ERAS (Enhanced Recovery After Surgery) protocols — early oral intake within 24h
- Dietitian referral for all surgical patients
Parenteral Nutrition (PN)
- PN indicated if ileus >7 days with no prospect of early enteral feeding
- Central venous access required (PICC/central line)
- Monitor: blood glucose (4-hourly), LFTs, TGs, electrolytes daily
- Strict infection control — CVC care bundle
- Risks: CVC infection, hyperglycaemia, liver dysfunction, refeeding syndrome
🌍GCC-Specific Clinical Context
Adhesional SBO in GCC
- Very high prevalence of adhesional SBO in GCC due to high rates of previous abdominal surgery
- GCC has among the world's highest Caesarean section rates (40–50% in some centres)
- High rates of gynaecological surgery (fibroid resection, ovarian cystectomy)
- Prior appendicectomy and laparotomy also major contributors
- Multiple previous surgeries = complex adhesions = higher strangulation risk
Colorectal Cancer & Sigmoid Volvulus
- Colorectal cancer rising in GCC — dietary westernisation, low fibre, obesity
- Leading cause of LBO across GCC hospitals
- Sigmoid volvulus more common in African and South Asian expatriate workers — dietary fibre patterns, delayed presentation, constipation
- Coffee bean sign on AXR a key SCFHS/DHA exam question
Hernia in GCC Workforce
- Hernias highly prevalent in GCC construction sector — millions of heavy manual labour workers
- Incarcerated and strangulated hernia is a common surgical emergency in GCC Emergency Departments
- Delayed presentation by migrant workers: lack of health insurance, language barriers, fear of job loss
- Presents at strangulation stage — higher complication rates, bowel resection more frequent
Regulatory & Exam Context
- DHA (Dubai Health Authority) — surgical nursing competency includes bowel obstruction assessment, stoma care, perioperative management
- DOH (Abu Dhabi Department of Health) — HAAD exam covers SBO/LBO differential, strangulation signs, NG management
- SCFHS (Saudi Commission for Health Specialties) — surgical nursing exam: conservative vs surgical management decision-making, hernia classification, ileus management
- Prometric MCQ format common for all three bodies
DHA / DOH / SCFHS Exam Prep — High-Yield Topics
| Topic | Key Fact to Know | Exam Relevance |
|---|---|---|
| SBO vs LBO — AXR | SBO: central dilated loops, no colonic gas, valvulae conniventes. LBO: peripheral, haustra | Very High |
| Most common SBO cause | Adhesions (60%) | Very High |
| Most common LBO cause | Colorectal cancer (60%) | Very High |
| Sigmoid volvulus AXR sign | Coffee bean sign pointing to RUQ | Very High |
| First-line sigmoid volvulus Rx | Sigmoidoscopic decompression (NOT immediate surgery) | Very High |
| Strangulation indicator | Lactate >2 mmol/L + constant pain + peritonism | Very High |
| Gastrografin | Water-soluble contrast — therapeutic in adhesional SBO; 90% resolve without surgery if contrast passes to colon | High |
| Highest strangulation hernia | Femoral hernia — narrow neck, women more common | High |
| Paralytic ileus treatment #1 | Early mobilisation | High |
| NG tube drainage replacement | 0.9% NaCl mL-for-mL | High |
| Closed-loop obstruction risk | Caecal perforation when ICV competent; caecum >9cm = danger | High |
| Ogilvie syndrome treatment | Neostigmine IV (have atropine ready) + colonoscopic decompression if fails | Moderate |
| Mesh in contaminated field | Do NOT use mesh in strangulated/perforated/contaminated hernia repair | Moderate |
| PN indication in ileus | Ileus >7 days with no prospect of enteral feeding | Moderate |
| Chewing gum evidence | Proven to shorten post-op ileus — stimulates cephalic-vagal reflex (sham feeding) | Moderate |
Quick Differentials — Exam Summary Cards
SBO Triad
- Colicky central pain
- Early profuse vomiting
- Tinkling bowel sounds
- Constipation = late
- AXR: central, >3cm loops, no colon gas
LBO Triad
- Progressive distension
- Constipation = early
- Vomiting = late/faeculent
- AXR: peripheral colon gas, haustra
- Caecum at risk if ICV competent
Strangulation Signs
- Continuous (not colicky) pain
- Peritonism
- Fever + tachycardia
- WBC >15, Lactate >2
- Silent abdomen
- → Emergency surgery
Bowel Obstruction Assessment Tool
Enter clinical findings to generate probability assessment, strangulation risk, and nursing action plan.
Obstruction Type
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Strangulation Risk
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Management
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Immediate Nursing Actions: