Small Bowel Obstruction for the NP Exam

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Small Bowel Obstruction (SBO) for Nurse Practitioner Licensing Exam

Definition

Small Bowel Obstruction (SBO): A mechanical or functional blockage of the small intestine that prevents the normal passage of intestinal contents, leading to bowel distention, ischemia, and potential necrosis or perforation.

Etiology

Adhesions: The most common cause of SBO, particularly in patients with a history of abdominal surgery.
Hernias: A major cause worldwide, especially when bowel loops become trapped in abdominal wall defects.
Malignancy: Tumors can cause obstruction by invading or compressing the small bowel.
Inflammatory Bowel Disease (Crohn’s disease): Leads to SBO via strictures caused by chronic inflammation.
Volvulus: Twisting of the bowel, leading to obstruction and possible vascular compromise.

Pathophysiology

Bowel Distention: Accumulation of gas and fluid proximal to the obstruction increases pressure and distends the bowel.
Ischemia: Increased pressure on the bowel wall reduces blood flow, leading to ischemia, necrosis, and possible perforation.
Fluid Shifts: Fluid loss into the bowel lumen and vomiting lead to dehydration and electrolyte imbalances, including hypokalemia.

Clinical Features

Abdominal Pain: Colicky and intermittent, becoming constant with ischemia.
Nausea and Vomiting: Bilious vomiting in proximal SBO, feculent vomiting in distal obstruction.
Abdominal Distention: More pronounced in distal obstructions.
Obstipation: Complete obstruction results in an inability to pass gas or stool.
Bowel Sounds: Initially hyperactive and high-pitched, later hypoactive or absent with bowel ischemia.

Diagnosis

Abdominal X-ray: First-line imaging showing dilated loops of small bowel with air-fluid levels.
CT Abdomen with Contrast: Gold standard for diagnosing the cause and location of obstruction and identifying complications like ischemia or perforation.

Management

Non-Surgical: NPO status, nasogastric tube decompression, IV fluids, and electrolyte replacement are used for partial obstructions.
Surgical: Indicated for complete obstruction, bowel ischemia, or failure of conservative management. Procedures may include lysis of adhesions or resection of necrotic bowel.

Complications

Bowel Ischemia, Necrosis, or Perforation: Untreated SBO can lead to these life-threatening complications.
Sepsis: Secondary to bowel perforation and peritonitis.

Key Points

Small bowel obstruction (SBO) is commonly caused by adhesions, hernias, and malignancy.
Diagnosis is typically made with an abdominal x-ray or CT scan, which identifies the site and severity of the obstruction.
Non-surgical management includes bowel rest, NG tube decompression, and IV fluids, but surgery is needed for complete obstruction or ischemia.
Prompt recognition and treatment are essential to avoid complications such as bowel necrosis, perforation, and sepsis.