Intestinal Obstruction Clinical Overview
I. The "On-Call" Snapshot
Clinical Significance in Malaysia: This is one of the most common reasons for an acute surgical admission. Your ability to recognise the red flags for strangulation can be the difference between a patient going home in a week or ending up in ICU.
High-Yield Definition: Intestinal obstruction is the mechanical impairment or complete arrest of the passage of intestinal contents. It can be a small bowel (SBO) or large bowel (LBO) obstruction.
Clinical One-Liner: Basically, there's a blockage in the gut. Your job is to find out where, why, and how urgently we need to fix it before the bowel dies.
II. Etiology & Risk Factors
The causes for SBO and LBO are different. Don't mix them up.
Small Bowel Obstruction (SBO)
Etiology:
Adhesions (Most common, >75%): Scar tissue from previous surgeries (e.g., appendicectomy, C-section, laparotomy) is the number one cause. Always ask about past surgical history.
Hernias: Incarcerated or strangulated hernias (inguinal, femoral, umbilical, incisional). This is the second most common cause. You must examine the hernial orifices.
Malignancy: Less common for SBO, usually from extrinsic compression or metastasis.
Large Bowel Obstruction (LBO)
Etiology:
Malignancy (Most common, >60%): Colorectal carcinoma is the primary culprit in our population.
Volvulus: Twisting of the bowel, most commonly sigmoid volvulus in the elderly, followed by caecal volvulus.
Strictures: From diverticulitis, inflammatory bowel disease (IBD), or radiation.
Risk Factors:
Modifiable: None, really. It's about the underlying cause.
Non-Modifiable: Previous abdominal/pelvic surgery, history of malignancy, advanced age, history of hernias.
III. Quick Pathophysiology
It's simple cause and effect.
Blockage: Intestinal contents (fluid, food, gas) can't pass.
Accumulation: The bowel proximal to the blockage dilates as gas and fluid build up. The patient gets distended and starts vomiting.
Third Spacing: Huge amounts of fluid are secreted into the bowel lumen and also leak into the peritoneal cavity. This leads to profound dehydration and electrolyte imbalance (hypovolemia, hyponatremia, hypokalemia).
Ischemia & Perforation: As the bowel distends, the pressure inside increases, compromising blood flow to the bowel wall (strangulation). Bacteria translocate, and eventually, the bowel becomes ischemic, necrotic, and perforates. This is a surgical catastrophe.
IV. Clinical Assessment
This is where you earn your keep.
Red Flags & Immediate Actions:
Peritonism (Guarding, rebound tenderness): → Indicates ischemia or perforation. Alert senior immediately.
Fever, persistent tachycardia, hypotension: → Signs of sepsis or strangulation. Alert senior, secure two large bore IV lines, start fluid bolus, take blood cultures.
Worsening, localised pain (changes from colicky to constant): → Suggests strangulation. Keep NBM, alert senior.
History (The 4 Cardinal Symptoms):
Abdominal Pain: Classically colicky (comes in waves). Central for SBO, more in the flanks for LBO. Constant pain is a red flag.
Vomiting: Early and profuse in proximal SBO. Can become faeculent (looks and smells like stool) late in distal obstruction. Less prominent in LBO if the ileocaecal valve is competent.
Abdominal Distension: More pronounced in distal SBO and LBO.
Absolute Constipation (Obstipation): Inability to pass flatus or faeces. This is a late sign in complete obstruction. If the patient is still passing flatus, it might be a partial obstruction.
Physical Examination:
General: Look for signs of dehydration (dry mucous membranes, reduced skin turgor), cachexia (malignancy). Check vitals for tachycardia, hypotension, fever.
Abdomen:
Inspect: Look for distension, visible peristalsis (in thin patients), and most importantly, surgical scars.
Auscultate: Early on, bowel sounds are high-pitched and "tinkling." Late-stage, they become silent.
Palpate: Assess for tenderness. Is it generalised or localised? Is there guarding or rebound tenderness?
Must-Do Procedures:
Examine Hernial Orifices: Inguinal, femoral, umbilical. Don't forget this. A missed incarcerated hernia is a lawsuit.
Digital Rectal Exam (DRE): Check for rectal masses and the nature of stool in the vault (e.g., empty vault supports obstruction).
Clinical Pearl: The site of the obstruction determines the symptoms. Proximal SBO = lots of vomiting, less distension. LBO = lots of distension, vomiting is a late feature.
V. Diagnostic Workflow
Differential Diagnosis:
Paralytic Ileus: Bowel is adynamic (not moving) but not mechanically blocked. Often post-operative or due to electrolyte imbalance. Bowel sounds are absent, and pain is less of a feature. AXR shows generalised dilation of both small and large bowel.
Ogilvie's Syndrome (Pseudo-obstruction): Massive colonic dilation without a mechanical blockage. Seen in elderly, sick, bed-bound patients.
Mesenteric Ischemia: Severe, constant abdominal pain that is "out of proportion" to clinical findings. A very important differential to consider.
Investigations Plan:
Bedside / Initial (First 15 Mins):
ECG: Especially in elderly patients to rule out cardiac causes of abdominal pain.
Urinalysis: Rule out urological causes.
Pregnancy Test: In all women of childbearing age.
First-Line Labs & Imaging:
Bloods:
FBC: Look for leukocytosis (strangulation, inflammation). High hematocrit suggests dehydration.
Renal Profile: Essential. Check for electrolyte imbalance (Na, K) and acute kidney injury from dehydration.
Serum Lactate: A rising lactate is a very specific sign of bowel ischemia. If it's high, get worried.
Group & Cross Match (GXM): The patient may need surgery.
Imaging:
Supine & Erect Abdominal X-ray (AXR):
SBO Findings: Dilated small bowel loops (>3 cm), central location, valvulae conniventes visible. Multiple air-fluid levels on the erect film.
LBO Findings: Dilated large bowel loops (>6 cm, >9 cm for caecum), peripheral location, haustra visible.
Confirmatory / Gold Standard:
CT Scan of Abdomen & Pelvis with IV Contrast: This is the investigation of choice. It will confirm the diagnosis, identify the level and cause of obstruction (the "transition point"), and detect complications like ischemia, perforation, or volvulus.
VI. Staging & Severity Assessment
We classify obstruction based on a few key features that dictate management.
Simple vs. Complicated:
Simple: Blood supply is intact. No peritonism.
Complicated (Strangulated): Blood supply is compromised. Patient has signs of peritonism, sepsis, and a high lactate. This is a surgical emergency.
Complete vs. Partial (Incomplete):
Complete: Total blockage. Patient has obstipation.
Partial: Lumen is narrowed but not fully blocked. Patient may still be passing some flatus or liquid stool.
Closed-Loop vs. Open-Loop:
Closed-Loop: A segment of bowel is obstructed at two points (e.g., volvulus, hernia). This is dangerous as pressure builds up rapidly, leading to a high risk of strangulation and perforation.
Impact on Management: Uncomplicated, partial, adhesive SBO can often be managed conservatively. Complicated obstructions, closed-loop obstructions, and most cases of complete LBO require surgery.
VII. Management Plan
Your immediate plan for every patient is "Drip and Suck."
Immediate Stabilisation (The ABCDE Plan):
A/B: Ensure airway is patent. Give high-flow oxygen via face mask (10-15L/min) if hypoxic or in shock.
C:
IV Access: Secure two large-bore (16G or 18G) IV cannulas.
Fluid Resuscitation: These patients are incredibly dry. Start aggressive IV fluid resuscitation with crystalloids (e.g., Normal Saline or Hartmann's). A typical adult might need 3-4 litres over the first 24 hours, guided by urine output and hemodynamics.
D: Monitor consciousness level.
E (Exposure & Environment):
Strict NBM (Nil By Mouth): Rest the bowel.
Nasogastric (NG) Tube Insertion: Decompress the stomach and proximal bowel ("Suck"). Set to free drainage and monitor the output.
Urinary Catheter: To accurately monitor urine output as a guide for fluid resuscitation.
Analgesia: Give IV opioids for pain (e.g., IV Morphine 2.5-5mg).
Antibiotics: If there are signs of sepsis or strangulation, start broad-spectrum IV antibiotics (e.g., as per local hospital guidelines, often IV Cefoperazone + Metronidazole).
Definitive Treatment (The Ward Round Plan):
Conservative Management (for Uncomplicated Adhesive SBO):
Continue "drip and suck."
Monitor vitals, abdominal exam, and NG tube output closely.
If the patient improves (pain resolves, distension reduces, starts passing flatus) within 48-72 hours, you can consider a trial of water.
Surgical Management:
Indications: Peritonism, signs of strangulation, closed-loop obstruction, failure of conservative trial after 48-72 hours, or most cases of malignant/volvular LBO.
Procedure: Usually an emergency laparotomy. The goal is to find the cause, relieve the obstruction (e.g., adhesiolysis for adhesions, reduction of hernia), and assess bowel viability. If a segment of bowel is necrotic, it will need to be resected. This may result in a stoma.
VIII. Complications
From the disease and the treatment.
Immediate (<24 hours):
Bowel Ischemia/Perforation: Management: Emergency laparotomy and resection.
Sepsis/Septic Shock: Management: Fluid resuscitation, antibiotics, vasopressor support in ICU.
Acute Kidney Injury: Management: Aggressive fluid resuscitation.
Short-Term (Days to Weeks):
Wound Infection/Dehiscence: Management: Wound care, antibiotics.
Anastomotic Leak: Management: This is a major complication requiring re-operation.
Prolonged Ileus: Management: Continued bowel rest and supportive care.
Long-Term (Months to Years):
Recurrent Obstruction from new adhesions: Management: May require further surgery.
Short Gut Syndrome (if extensive bowel resection): Management: Nutritional support, often TPN.
Incisional Hernia: Management: Elective surgical repair.
IX. Prognosis
Mortality:
Simple Obstruction: <5%
Strangulated Obstruction: Can be as high as 20-30%, especially with delayed presentation.
Prognostic Factors: The most important factors are the presence of bowel ischemia, the patient's age and comorbidities, and the timeliness of surgical intervention.
X. How to Present to Your Senior
Keep it short, structured, and safe.
"Dr., for review please. This is Mdm. Lim in Bed 10, a 75-year-old lady with a background of an open appendicectomy, who presented with 2 days of colicky central abdominal pain, vomiting, and has not opened her bowels. On examination, she is tachycardic at 110, her abdomen is distended with generalised tenderness, but no guarding. My main differential is an adhesive small bowel obstruction. I have kept her NBM, inserted an NG tube, sent off bloods including a lactate, and started IV fluids. The AXR shows dilated central bowel loops. I would like your opinion on whether we should proceed with a CT scan."
XI. Summary & Further Reading
Top 3 Takeaways:
"Drip and Suck": Every suspected obstruction gets IV fluids, NBM status, and an NG tube immediately.
Examine the Hernial Orifices: Do not miss an incarcerated hernia. It's a clinical diagnosis.
Constant Pain, Fever, Tachycardia, or a High Lactate = Strangulation. Escalate for urgent surgery.
Key Resources:
UpToDate: Search for "Small Bowel Obstruction" and "Large Bowel Obstruction." It has excellent, detailed management algorithms.
Amboss: A good, concise resource for quick review on the ward.
Review Article: Sabiston Textbook of Surgery is the standard surgical text. Look up the chapter on Intestinal Obstruction. For a journal article, this one is a good overview:
Now go and clerk the patient properly. Let me know if the lactate comes back high.
