INTESTINAL OBSTRUCTION

MSU Medical Students. Batch 2.Group 2.

CONTENTS• Definition• Introduction• Etiologies• Categories• Pathophysiologiy• Clinical Manifestation• Investigations• Treatment• Complication

Definition

• Intestinal obstruction is a partial or complete blockage of the bowel caused by whether mechanical or functional obstruction of the intestines that results in the failure of the intestinal contents to pass through.

Introduction• Mechanical obstruction is divided into: a)Obstruction of the small bowel (including the

duodenum) and b)Obstruction of the large bowel. • Obstruction may be partial or complete. a)About 85% of partial small-bowel obstructions

resolve with non-operative treatment, whereas

b)About 85% of complete small-bowel obstructions require operation.

Etiologies• Overall, the most common causes of

mechanical obstruction are adhesions, hernias, and tumors.

• Other general causes are diverticulitis, foreign bodies (including gallstones), volvulus (twisting of bowel on its mesentery), intussusception (telescoping of one segment of bowel into another and fecal impaction.

• Specific segments of the intestine are affected differently.

AetiologiesLOCATION CAUSES

Colon •Tumors (usually in left colon)•Diverticulitis (usually sigmoid)•Volvulus (sigmoid or cecum)•Fecal impaction •Hirschprung's disease

Duodenum Adult •Cancer of duodenum•Cancer of head of pancreas•Ulcer disease

Neonates •Atresia•Volvulus•Bands•Annular pancreas

LOCATION CAUSES

Jejunum and Ileum Adult •Hernias•Adhesions (common)•Tumors•Foreign body•Meckel's diverticulum•Crohn's disease (uncommon)•Ascaris infestation•Midgut volvulus•Intussusception by tumor (rare)

Neonates •Meconium ileus•Volvulus of malrotated gut•Atresia•Intussusceptiom

Categories

• Complete or Partial• Mechanical versus Functional• Small versus Large intestine• Acute, Sub-Acute, Chronic

Mechanical vs. FunctionalA. Mechanical1.Extraluminal: adhesions (bands of scar tissue),

hernias, volvulus (twisted bowel), tumours.2.Intramural: tumors, IBD (e.g Crohn’s),

strictures, paralytic, intussusception (telescoping bowel)

3.Intraluminal (partial or complete): foreign bodies, fecal impaction, gallstones, bezoars, worms

Mechanical vs. FunctionalB. Functional – Paralytic Ileus• Failure of peristalsis to move intestinal contents:

adynamic ileus (paralytic ileus, ileus) due to neurologic or muscular impairment

• Accounts for most bowel obstructions• Causes includea. Post gastrointestinal surgeryb. Tissue anoxia or peritoneal irritation from hemorrhage,

peritonitis, or perforationc. Hypokalemiad. Medications: narcotics, anticholinergic drugs,

antidiarrheal medicationse. Spinal cord injuries, uremia, alterations in electrolytes

Pathophysiology1) In simple MECHANICAL obstruction, blockage occurs

without vascular compromise. 2) Ingested fluid and food, digestive secretions, and gas

accumulate above the obstruction. 3) The proximal bowel distends, and the distal segment

collapses. 4) The normal secretory and absorptive functions of the

mucosa are depressed, and the bowel wall becomes edematous and congested.

5) Severe intestinal distention is self-perpetuating and progressive, intensifying the peristaltic and secretory derangements and increasing the risks of dehydration and progression to strangulating obstruction.

6) Strangulating obstruction is obstruction with compromised blood flow; it occurs in nearly 25% of patients with small-bowel obstruction.

7) It is usually associated with hernia, volvulus, and intussusception.

8) Strangulating obstruction can progress to infarction and gangrene in as little as 6 h.

9) Venous obstruction occurs first, followed by arterial occlusion, resulting in rapid ischemia of the bowel wall.

10) The ischemic bowel becomes edematous and infarcts, leading to gangrene and perforation.

11) In large-bowel obstruction, strangulation is rare (except with volvulus).

12) Perforation may occur in an ischemic segment (typically small bowel) or when marked dilation occurs.

13) The risk is high if the cecum is dilated to a diameter ≥ 13 cm.

14) Perforation of a tumor or a diverticulum may also occur at the obstruction site.

Pathophysiology• COLICKY PAIN due to excessive contraction • PROXIMAL DISTENSION due to accumulation

of fluid, gas • Impaired absorption of fluid and electrolyte -

DEHYDRATION• SEPSIS - bacterial overgrowth due to stasis• Impairment of venous & arterial flow -

STRANGULATION, INFARCTION, PERFORATION

Clinical Features• Colicky low abdominal

pain• Vomiting• Abdominal distension• Absolute constipation• Others - dehydration,

fever, tachycardia, oliguria, hypotension, peritonism

Manifestations Small Bowel Obstructiona. Vary depend on level of obstruction and speed of

developmentb. Cramping or colicky abdominal pain, intermittent,

intensifyingc. Vomiting1. Proximal intestinal distention stimulates vomiting center2. Distal obstruction vomiting may become feculentd. Bowel sounds1. Early in course of mechanical obstruction: borborygmi

and high-pitched tinkling, may have visible peristaltic waves

2. Later silent; with paralytic ileus, diminished or absent bowel sounds throughout

e. Signs of dehydration

Manifestation Large Bowel Obstructiona. Only accounts for 15% of obstructionsb.Causes include cancer of bowel, volvulus,

diverticular disease, inflammatory disorders, fecal impaction

c. Manifestations: deep, cramping pain; severe, continuous pain signals bowel ischemia and possible perforation; localized tenderness or palpable mass may be noted

Investigation

• FBC• Electrolytes and Urea• Plain supine AXR - dilated SB, central, valvulae

coniventes, air fluid level• Contrast X-rays – barium/gastrograffin follow-

through/enema• CT scan with oral contrast

Treatment 1 - Resuscitation

• NBM • Fluid replacement - IV fluid• IV antibiotic• Correction of electrolyte imbalance• Nasogastric suction• Monitoring - vital signs, fluid balance• Adequate analgesia

Treatment 2 - Surgery

Indications • Non-resolving or failure of conservative treatment • Perforation / peritonitis • Underlying disease e.g hernia, crohns, tumour

Avoid in obstruction due to adhesions High mortality in poorly resuscitated patients

Treatment 3• Resuscitation• Surgerya. Laparotomy b. Hemicolectomy- Right / extended right / left c. Sigmoid colectomyd. Anterior resectione. Abdominoperineal resection f. Hartmann’s procedureg. Colostomy

• Staged laparotomy 1, 2 or 3-stage procedures

Complicationsa. Hypovolemia and hypovolemic shock can

result in multiple organ dysfunction (acute renal failure, impaired ventilation, death)

b.Strangulated bowel can result in gangrene, perforation, peritonitis, possible septic shock

c. Delay in surgical intervention leads to higher mortality rate

SBO

SBO

SBO

Intussusception Volvulus

Large-bowel obstruction. This chest radiograph demonstrates free air under the diaphragm, indicating bowel perforation.

Abdominal (KUB) film of a patient with obstipation. Dilation of the

colon is associated with large-bowel obstruction.

Large-bowel obstruction. Gastrografin study in a patient

with obstipation reveals colonic obstruction at the

rectosigmoid level.

Large-bowel obstruction. Contrast study demonstrates colonic

obstruction at the level of the splenic flexure, in this case due to carcinoma.

Large-bowel obstruction. Abdominal (KUB) radiograph depicting massive dilation of

the colon due to a cecal volvulus.

Large-bowel obstruction. Contrast study of patient with cecal volvulus. The column of

contrast ends in a "bird's beak" at the level of the volvulus.

Large-bowel obstruction. Massive dilation of the colon due to a sigmoid

volvulus.

References1. Merck Manual Professional2. eMedicine (http://emedicine.medscape.com)3. MedlinePlus (http://medlineplus.gov)