Bowel Obstruction Overview

Bowel Obstruction

• Bowel obstruction (intestinal obstruction) is a condition where intestinal contents cannot pass through the gastrointestinal tract. It can be partial or complete, and affect the small intestine (SBO) or large intestine (LBO).
• Partial obstructions allow some fluid and gas to pass, usually resolving with non-surgical treatment.
• Complete obstructions totally block the lumen, generally requiring surgery.
• Simple obstructions have an intact blood supply, whereas strangulated obstructions do not.

Types of Bowel Obstruction

• Mechanical obstruction results from a physical blockage in the intestinal lumen.
  • Surgical adhesions are the most common cause of small bowel obstruction (SBO).
  • Other causes of SBO include hernias, cancers, strictures (e.g., Crohn's disease), and intussusception (following bariatric surgery).
  • Colorectal cancer (CRC) is the most common cause of Large Bowel Obstructions (LBO), followed by diverticular disease.
  • Other causes include adhesions, ischemia, volvulus, and Crohn's disease.
• Nonmechanical obstruction results from decreased or absent peristalsis due to altered neuromuscular transmission.
  • Paralytic ileus (lack of intestinal peristalsis and bowel sounds) is the most common type, often occurring after abdominal surgery.
  • Other causes include peritonitis, inflammatory responses (e.g., pancreatitis, appendicitis), electrolyte imbalances (e.g., hypokalemia), and spinal fractures.
  • Pseudo-obstruction mimics a mechanical obstruction, but no cause is identified through imaging. It can be associated with various conditions (neurologic, medication related, endocrine/metabolic, lung, trauma or burn).
• Vascular obstruction is rare, caused by impaired blood flow to the intestines, most often from emboli or atherosclerosis of the mesenteric arteries.

Etiology and Pathophysiology

• Fluid (about 6-8 liters daily) and gas (mostly swallowed air) accumulate proximal to the obstruction.
• This distention reduces fluid absorption and stimulates secretions, leading to fluid and electrolyte imbalances (extravasation into peritoneal cavity).
• Bowel muscle fatigue and cessation of peristalsis happen.
• Reduced circulating blood volume leads to hypotension and hypovolemic shock; ischia, necrosis, perforation, edema, cyanosis, and gangrene can occur if blood flow is insufficient.

Clinical Manifestations

• Four hallmark manifestations: abdominal pain, nausea and vomiting, distension, and constipation. Symptoms vary by cause, location, and type.
• Small bowel obstruction (SBO) pain is often sudden, colicky (4-5 minutes apart for proximal, less frequent for distal), and accompanied by rapid/projectile bile-containing vomiting which can provide temporary relief from pain, progressing to increasingly fecal and foul-smelling.
• Bowel sounds above the obstruction may be high-pitched.
• Large bowel obstruction (LBO) pain is persistent and cramping, with abdominal distension, obstipation (or significant change in bowel habits), and lack of flatus; bowel sounds are usually present and progressively decrease.
• Strangulation causes severe, constant, rapidly onset pain. Signs of both include abdominal tenderness, rigidity and the patient may appear acutely ill, with signs of dehydration, tachycardia, dry mucous membranes, and hypotension; fever may occur.

Diagnostic Studies

• Thorough history & physical examination.
• Imaging (abdominal x-rays, CT scan, contrast enema, sigmoidoscopy/colonoscopy) to identify and guide surgical decisions.
• Blood tests (CBC, blood chemistries) to assess for dehydration, strangulation, perforation (high WBC), bleeding, hemoconcentration (increased hematocrit), serum electrolyte levels (BUN, creatinine) and acid-base imbalances.

Interprofessional Care

• Treatment aims to restore intestinal patency.
• Emergency surgery may be needed for strangulation or perforation.
• Possible conservative approaches depending on the cause, such as NG tube for decompression, nutritional support if needed (parenteral nutrition – PN)
• Stents (via endoscopic/fluoroscopic procedures) can be used for palliative treatment or a "bridge to surgery".
• Corticosteroids may be used for decreasing edema and inflammation.
• Surgery options include resection and anastomosis, or colectomy/colostomy/ileostomy for extensive obstruction or necrosis.

Nursing Management: Bowel Obstruction

• Assessment:

  • Detailed history and physical exam focusing on pain (location, duration, intensity, frequency, restlessness, position changes), vomiting (onset, frequency, color, odor), bowel sounds, abdominal distension/tenderness/rigidity, and patient's vital signs.

• Monitoring: strict intake and output, hourly urine output (less than 0.5 mL/kg/hour is significant), laboratory and arterial blood gas values (metabolic acidosis/alkalosis, electrolytes as relevant), signs of deterioration (hypovolemic shock, sepsis).

• Planning: Patient goals include relief of obstruction, minimal pain, and normalized fluid/electrolyte/acid-base balance.

• Implementation: comfort measures and fluid/electrolyte balance management postoperatively (per general laparotomy care principles).