Bowel Obstruction

Small Bowel Obstruciton

Small bowel obstruction (SBO) is obstruction of the gastrointestinal tract at the level of the small intestine. It is a common surgical condition. It is mostly caused by mechanical obstruction of the bowel (intraluminal or extraluminal). Aetiology varies from region to region. The most common being adhesions from prior abdominal surgery (accounts for 75% in the west and 25% in sub-Saharan Africa). Other common causes include small bowel volvulus, ileal knotting (compound volvulus) and intestinal parasites e.g. Ascariasis. Small bowel volvulus, though uncommon, can obstruct the bowel, block mesenteric vessels and result in bowel ischemia. Symptoms that are progressive and chronic may point to a neoplasm. Obstruction due to adhesions and volvulus tends to be more acute. It is important to find out whether the patient has intestinal ischemia due to bowel strangulation (persistent tachycardia, writhing pain and focal tenderness).

Classification of Small Bowel Obstruction

Classification	Description
Complete bowel obstruction	Obstruction with vomiting or distension, but with no passage of any flatus or stool (obstipation). More surgically urgent
Partial bowel obstruction	Obstruction with vomiting or distention, but continues to pass flatus and liquid stool

Causes of Small Bowel Obstruction

Classification	Examples of causes
Intrinsic	Neoplasm (benign or malignant, primary or metastatic), hematoma, inflammatory disease (Crohn’s), infectious disease (tuberculosis), intussusception, ischemia (stricture), congenital (webs, malrotation, Meckel’s diverticulum)
Extrinsic	Adhesions, hernias, small bowel volvulus, ileal knotting, ileosigmoid knotting, endometrioma, hematoma, abdominal or pelvic tumor
Intraluminal	Parasites (ascariasis), foreign bodies, bezoars, gallstone (gallstone ileus)

Forms of Small Bowel Volvulus

Forms of volvulus	Description
Malrotation	The small intestine twists about its mesentery
Knotting	One portion of the intestine wraps around the others as ileo-ileal knots (ileal knotting) or ileo-sigmoid knots (compound volvulus)

Clinical features of SBO

Clinical feature	Signs and symptoms
Cardinal signs and symptoms	Crampy abdominal pain, distention, vomiting, diarrhoea followed by obstipation
Signs of proximal obstruction	More acute and severe pain, bilious vomiting
Signs of distal obstruciton	Longer lasting subacute pain, severe abdominal distention

• Common causes of SBO
  • Surgical adhesions (MCC)
  • Small bowel tumor
  • Hernia
  • IBD
  • Volvulus
• Causes of SBO in Paediatrics
  • Congenital atresia
  • Pyloric stenosis
  • Intussusception (can be deadly)
• Signs and symptoms
  • Abdominal pain
    • Periumbilical (Visceral small bowel is midgut in origin)
    • Diffuse pain
    • Localized pain (may point to ischemic bowel or a different cause)
    • Colicky in nature (early – reflects contractions and peristalsis against the obstruction)
    • Constant (may indicate bowel ischemia)
  • Vomiting
  • Abdominal distention (varies based on the level of obstruction – proximal obstruction may have little or no distention)
  • Obstipation or decreased passage of flatus or stool
• Physical examination
  • Abdominal wall for surgical scars or hernias
  • Signs of peritonitis (indicates immediate operation after fluid resuscitations)
  • Hemodynamic instability (hypotension and tachycardia may be due to hypovolemia, poor oral intake or fluid sequestration in the bowel wall. If hemodynamic instability does not improve with fluid resuscitation the patient may have septic shock from ischemia or perforation)
  • Distension with tympanic percussion (uncomplicated obstruction)
  • Minimal tenderness (uncomplicated obstruction)
  • High-pitched (“squeaking”) bowel sounds
• Investigations
  • Abdominal X-ray (upright): 67% sensitivity and 83% specificity (proximal obstruction and fluid-filled bowel may mask the presence of small bowel obstruction
    • Distended loops of small bowel (> 3 cm)
    • Air-fluid levels
    • Lack of gas in the colon (if there is gas in the colon the cause could be large bowel obstruction or ileus)
  • CT scan abdomen: better sensitivity and specificity than X-ray. Can give better insight into the cause e.g. adhesion vs neoplasm. May help operative planning. Can detect ischemia.
  • Small bowel follow-through (SBFT) contrast study: Using Gastrograffin to evaluate the progression of contrast through the small bowel. Enables early identification of patients who need surgery and predicts those who will respond to non-operative treatment
    • Contrast within the colon by 24 hours: no obstruction or resolved obstruction (97% sensitivity and 96% specificity for adhesive small bowel obstruction)
  • CBC
  • U/E/Cs
  • Amylase
  • Urinalysis
  • B-hCG
  • Occult stool test: blood raises suspicion for strangulation
• Initial treatment
  • Admit for observation (mechanical obstruction usually resolves in 3 days)
  • Correct fluid and electrolyte losses (replace volume deficits): Normal saline is fluid of choice
  • Vasopressor support, antibiotics and plan for surgery in patients with septic shock
• Indication for non-operative management
  • Partial small bowel obstruction due to adhesions, or other aetiologies amenable to medical treatment e.g. Ascariasis, Crohns, with no evidence of bowel ischemia
• Indications for operative management
  • Obstructive process that will not resolve spontaneously: obstructing masses, volvulus, hernia
• Non-operative treatment
  • Nil per oral
  • Nasogastric tube (decompress proximal GI tract and relive vomiting)
  • IV fluids to replace losses and maintenance
  • Monitor electrolytes (if there are specific derangements or their is high NGT output)
  • Serial abdominal examination (ideally by the same clinician to detect evolving bowel ischemia)
  • Serial CBC for WBC count
  • SBFT may be used
  • Should resolve within 3 days (complications rates rise when non-operative therapy is extended beyond 72 hours)
• Signs of resolution in non-operative treatment
  • Improvement in symptoms with passage of gas and decreasing abdominal distention
  • Reduced NGT output and transition from bilious to non-bilious
• Operative treatment
  • Fluid resuscitation and correct electrolyte abnormalities
  • NGT to decompress stomach (reduces risk of aspiration at induction. RSI is used)
  • Pre-operative antibiotics (broad-spectrum and cover GP, GN and anaerobes)
  • Laparoscopic approach
  • Open approach (laparotomy): midline incision provides good access to the length of the small intestine
    • Adhesiolysis
    • Resection and anastomosis of non-viable bowl
    • Ileostomy can be performed if there is instability or gross intraperitoneal contamination
    • Inspect the bowel from ligament of treitz to the cecum for points of obstruction and iatrogenic injury
• Post-operative (admission) notes
  • Nasogastric tube
  • Bowel rest (prolonged bowel rest is rarely needed unless the patient develops ileus)
  • Remove NGT if output is minimal
  • Advance diet as tolerated
• Complications
  • Intestinal ischemia: suggested by elevated WBC, lactic acidosis (anion gap on ABG), and CRP > 75 mg/dL
  • Hypovolemic shock
  • Hypokalemic, hypochloremic, metabolic alkalosis due to persistent vomiting
• CT-scan findings indicative of intestinal ischemia
  • 500ml of free fluid or dense fluid (> 10 HU)
  • Oedema in the mesentery
  • Decreased contrast enhancement of the bowel wall
  • Thickened loops of small bowel
  • Pneumatosis intestinalis (air within the bowel wall)
  • Free air
  • Portal venous gas

Visible peristalsis

**https://youtu.be/M8v9ZLnNHnU**

Adynamic Ileus

Adynamic ileus is a temporary loss of intestinal motility without mechanical obstruction, caused by disruption of normal peristalsis due to neural, inflammatory, or metabolic factors. Ileus causes symptoms that are similar to bowel obstruction (abdominal distension, vomiting). Patients with ileus do not have mechanical obstruction of the bowel and therefore will not benefit from surgery. Treatment of ileus is supportive and focuses on treating the primary process contributing to the development of the ileus.

Causes of ileus and their mechanism

Cause	Mechanism	Key Features
Post—operative ileus	Neural inhibition, inflammation, direct handling	Common in colon, resolves in 3–5 days
Opiates	μ-receptor activation → ↓ peristalsis	Constipation, bloating, opioid-induced bowel dysfunction
Hypokalemia	Smooth muscle hyperpolarization → ↓ contractions	Associated with vomiting, diuretics, NG suction
Sepsis	Inflammation, ischemia, cytokine-mediated suppression	Common in peritonitis, septic shock

Bowel recovery in post-operative ileus following abdominal surgery

Bowel	Time to recover
Small intestine	24 hours
Stomach	48 hours
Colon	3 – 5 days (most affected)

• Treatment
  • Correct electrolyte abnormalities
  • NGT decompression (in patients who are severely distended or vomiting)
• Measures to prevent post-operative ileus
  • Careful attention to fluids and electroltes
  • Minimize using opioids (narcotics)
  • Early ambulation
  • Chewing gum

Volvulus

A volvulus is a twist in any part of the hollow viscus of the alimentary tract. This twist may cause obstruction and compromise the mesentery leading to bowel ischemia. ****

Volvulus occurs most commonly in the sigmoid colon (80%),. 15% occur in the cecum and 3% involve the transverse colon. It is the most common cause of large bowel obstruction in sub-Saharan Africa. Approximately 50% of intestinal obstruction are due to volvulus. It commonly occurs in young males.

Sigmoid Volvulus

Sigmoid volvulus occurs in patients with a redundant sigmoid and lengthened mesentery. The most common cause of sigmoid volvulus is a high-fiber diet.

• Risk factors for sigmoid volvulus
  • High-fiber diet: Increases fecal load in the sigmoid. Chronic excess weight lengthens the sigmoid and its mesentery. The combination of weight in the bowel, redundancy of the bowel and lengthened mesentery cause it to twist around it’s mesenteric axis
  • Neurologic disorders
  • Chronic constipation
  • Pregnant patient
  • Pelvic mass
• Signs and symptoms
  • Obstipation
  • Crampy abdominal pain
  • Vomiting
• Signs and symptoms of ischemia
  • Increasing abdominal tenderness
  • Fever
  • Leukocytosis
• Investigations
  • Abdominal X-ray:
    • Distended colon with convexity in the right upper quadrant (bent inner tube or coffee-bean sign)
  • Gastrografin (water-soluble contrst) or barium enema: bird’s beak sign (do not use barium if peritonitis is suspected)
• Treatment
  • Sigmoidoscopy (flexible or rigid sigmoidoscope) to reduce the volvulus. Place a rectal tube to maintain reduction.
  • Semi-elective sigmoid resection with primary anastomosis (if not performed volvulus has a recurrence rat of 40-50%, causing increased morbidity and mortality) – done 48 – 72 hours after endoscopic reduction which allows bowl to return to normal caliber and for bowel prep to be performed
• Whirl sign
  • location of the obstruction and wist of the sigmoid
  • Visualized on endoscopy (colonoscopy)
• Contraindications to endoscopic reduction
  • Peritonitis on exam
  • Suspected gangrene or necrosis
  • Scope reveals dark blood, dark mucosa or mucosal ulceration
  • Free air on imaging

**https://youtu.be/3yo1yshKhug**

Cecal Volvulus

Cecal volvulus occurs in patients with inadequate mesenteric fixation of the cecum. The cecum can twist clockwise and counter-clockwise. It can also rarelely fold upwards on itself (cecal basule). Emergency surgery is indicated since a cecal volvulus cannot be reduced endoscopically.

• Investigations
  • Abdominal X-ray: less reliable than sigmoid volvulus
    • Distended colon with convexity on the left upper quadrant
    • Single-distended loop of bowel in the right mid-abdomen (for a cecal bascule)
  • Contrast enema
  • CT-scan
• Treatment
  • Right hemicolectomy with primary anastomosis (recommended even if the colon is gangrenous)
  • Cecopexy (fixing the cecum to the abdominal wall) or cecostomy tube are recommended when the patient cannot tolerate a right hemicolectomy

Compound volvulus

A volvulus involving both the large and small intestines synchronously.