Makindo Medical Notes

Intestinal obstruction refers to mechanical blockage of bowel contents, whereas ileus is a functional paralysis of peristalsis without a physical blockage. Both can cause abdominal pain, distension, vomiting, and failure to pass stool/flatus, and require careful differentiation for appropriate management.

📖 Introduction & Pathophysiology

• Mechanical obstruction: Physical blockage → ↑ intraluminal pressure → venous congestion, bowel wall oedema, reduced arterial flow → ischaemia, necrosis, perforation.
• Ileus (paralytic ileus): Impaired peristalsis due to neural/hormonal disturbance post-surgery, infection, metabolic derangements. No true blockage, but bowel dilatation and fluid stasis occur.
• Small vs large bowel: SBO is more common, often due to adhesions or hernia. LBO more often due to malignancy or volvulus.

⚠️ Causes

Type	Common Causes
Small Bowel Obstruction (SBO)	Adhesions (post-surgery), hernias, Crohn’s strictures, intussusception, gallstone ileus
Large Bowel Obstruction (LBO)	Colorectal cancer, diverticulitis stricture, volvulus (sigmoid, caecal), faecal impaction
Functional (Ileus)	Post-op (esp. abdominal surgery), peritonitis, sepsis, opioids, electrolyte imbalance (low K⁺, Mg²⁺, Na⁺), spinal/retroperitoneal pathology

🩺 Clinical Features

• Colicky abdominal pain (mechanical) vs constant dull pain (ileus/strangulation).
• Abdominal distension (earlier in LBO, less in SBO).
• Vomiting (early in SBO; late in LBO).
• Absolute constipation ± failure to pass flatus (esp. complete obstruction).
• Exam: High-pitched “tinkling” bowel sounds in obstruction; absent sounds in ileus. Tenderness, guarding, peritonism if ischaemia/perforation.

🔎 Investigations

• Bloods: FBC (↑ WCC if ischaemia), U&E (derangements from vomiting/third spacing), CRP, lactate (ischaemia).
• Plain AXR: SBO = central dilated loops, valvulae conniventes “stack of coins”. LBO = peripheral, haustra. No gas in rectum if complete obstruction. Ileus = diffuse dilatation without transition point.
• CT Abdomen/Pelvis: Gold standard – identifies level, cause, complications (closed-loop obstruction, strangulation).
• Other: CXR to detect free air (perforation).

💊 Management

Initial resuscitation: ABC, O₂, IV access, fluids, catheter for UO, NG tube for decompression, analgesia, antibiotics if infection/sepsis suspected.

• Small Bowel Obstruction: – Conservative (“drip & suck”) if no signs of strangulation: NBM, IV fluids, NG tube, monitor. – Surgery if strangulated/closed-loop obstruction or no improvement in 48–72 hrs.
• Large Bowel Obstruction: – Malignancy: resection/stent. – Sigmoid volvulus: endoscopic decompression ± sigmoidectomy. – Caecal volvulus: surgical resection.
• Ileus: – Treat underlying cause (stop opioids, correct electrolytes, treat sepsis). – Conservative: NBM, NG decompression, fluids, mobilise, supportive care.

⚠️ Complications

• Bowel ischaemia → necrosis → perforation → peritonitis.
• Sepsis, shock, multi-organ failure.
• Electrolyte imbalances, dehydration, AKI.
• Recurrent obstruction (esp. from adhesions).

📚 Summary Table

Feature	Mechanical Obstruction	Ileus
Pain	Colicky	Dull, constant
Bowel Sounds	High-pitched, “tinkling”	Absent / reduced
AXR	Dilated loops ± transition point	Generalised dilatation, no transition
Management	IV fluids, NG tube, possible surgery	Conservative, treat underlying cause

📌 Teaching Pearls

• SBO is most often adhesions; LBO most often cancer.
• Ileus is functional – think post-op, opioids, electrolytes.
• Always resuscitate early; strangulation and ischaemia carry high mortality.
• AXR is useful but CT is more definitive.
• Look out for “red flags”: peritonitis, fever, tachycardia, metabolic acidosis → urgent surgery.

🚫 Case 1 — Small Bowel Obstruction (Adhesions)

A 54-year-old woman presents with colicky central abdominal pain, bilious vomiting, and abdominal distension. She has a history of hysterectomy 10 years ago. Examination shows high-pitched "tinkling" bowel sounds. 💡 Adhesions from prior surgery are the most common cause of small bowel obstruction in the UK. They cause mechanical blockage leading to proximal dilatation and fluid sequestration. Initial management includes NG decompression, IV fluids, and monitoring, with surgery if conservative measures fail or if strangulation is suspected.

🚫 Case 2 — Large Bowel Obstruction (Colorectal Cancer)

A 72-year-old man presents with progressive abdominal distension, absolute constipation, and colicky left-sided abdominal pain. He has unintentional weight loss and iron deficiency anaemia. Examination reveals a distended, tympanic abdomen with empty rectum on PR. 💡 Large bowel obstruction is commonly due to colorectal carcinoma, particularly in the sigmoid colon. Diagnosis is confirmed with CT abdomen/pelvis. Management often requires urgent surgical intervention (e.g. resection or stenting), with attention to fluid/electrolyte balance pre-operatively.

🚫 Case 3 — Paralytic Ileus

A 65-year-old man is recovering from emergency laparotomy for perforated diverticulitis. On day 3 post-op, he develops abdominal distension, nausea, and absent bowel sounds. He has not passed flatus or stool. 💡 Ileus is a functional obstruction due to reduced gut motility, often secondary to recent surgery, electrolyte imbalance, or sepsis. Unlike mechanical obstruction, bowel sounds are absent. Management is conservative: NBM, NG tube, IV fluids, correcting underlying causes, and mobilising the patient until bowel function recovers.