What are the signs, symptoms, and management of bowel obstruction in a patient with a history of abdominal surgery, cancer, or inflammatory bowel disease?

Signs and Symptoms of Bowel Obstruction

Bowel obstruction presents with colicky abdominal pain, absence of flatus (90% of cases), absence of bowel movements (80.6%), nausea/vomiting, and abdominal distension (65.3%), with critical warning signs including fever, tachycardia, intense unresponsive pain, peritoneal signs, and absent bowel sounds indicating life-threatening strangulation or ischemia. 1

Cardinal Symptoms

Gastrointestinal Symptoms:

• Colicky abdominal pain that worsens as the bowel attempts to overcome the obstruction 1
• Absence of flatus occurs in 90% of cases and is highly specific for mechanical obstruction 1
• Absence of bowel movements occurs in 80.6% of cases 1
• Nausea and vomiting are more prominent and occur earlier in small bowel obstruction compared to large bowel obstruction 1, 2
• Abdominal bloating is a common presenting complaint 1

Physical Examination Findings:

• Abdominal distension occurs in 65.3% of cases and has a positive likelihood ratio of 16.8, making it a strong predictive sign 1
• Abdominal tenderness on palpation 1
• Hyperactive bowel sounds early in the course, representing the intestine's increased motor activity attempting to push contents through the blockage 1
• Visible peristalsis may be seen in thin patients with mechanical obstruction 1, 2
• Digital rectal examination may reveal blood or a rectal mass in colorectal cancer cases 1

Critical Warning Signs Requiring Emergency Intervention

Signs of Strangulation/Ischemia (mortality up to 25% if not promptly treated):

• Fever, tachypnea, tachycardia, and confusion 1, 2
• Intense pain unresponsive to analgesics 1, 2
• Diffuse abdominal tenderness, guarding, or rebound tenderness indicating peritonitis 1, 2
• Absent bowel sounds (transition from hyperactive to absent sounds indicates progression to ischemia) 1

Signs of Shock:

• Hypotension, cool extremities, mottled skin, and oliguria 1

Laboratory Findings Suggesting Complications:

• Leukocytosis and neutrophilia 1
• Elevated lactic acid levels 1
• Low serum bicarbonate and arterial blood pH indicating metabolic acidosis 1
• Elevated amylase levels 1
• Abnormal renal function tests indicating dehydration 1

Distinguishing Small vs. Large Bowel Obstruction

Small Bowel Obstruction:

• More frequent vomiting that occurs earlier in the course 1, 2
• Green/yellow vomit in proximal obstruction 1, 2
• Most commonly caused by adhesions (55-75% of cases), particularly in patients with prior abdominal surgery 1, 3
• History of prior abdominal surgery has 85% sensitivity for adhesive small bowel obstruction 1, 3

Large Bowel Obstruction:

• Less frequent vomiting 1
• Feculent vomiting can occur in distal obstruction 1, 2
• More gradual development of symptoms 1
• Recurrent left lower quadrant abdominal pain 1
• Most commonly caused by cancer (60% of cases) 1
• Previous complaint of bloody stools may be present 1

Diagnostic Approach

History and Physical Examination:

• Focus on previous abdominal surgeries (85% sensitivity for adhesive small bowel obstruction) 1, 3
• Inquire about previous diverticulitis episodes, chronic constipation, rectal bleeding, or unexplained weight loss 1
• Examine all hernia orifices and previous surgical incision sites 1, 3

Laboratory Studies:

• Complete blood count to assess for leukocytosis 1, 3
• Electrolyte panel to identify imbalances 1, 3
• Renal function tests to evaluate dehydration 1, 3
• Lactate levels to assess for intestinal ischemia 1, 3

Imaging Studies:

• CT scan with IV contrast is the diagnostic standard with approximately 90% accuracy and can identify signs of ischemia (abnormal bowel wall enhancement, mesenteric edema, pneumatosis) that mandate immediate surgery 1, 3
• No oral contrast is needed in suspected high-grade obstruction 1, 3
• Abdominal ultrasound can be used as an alternative with 90% sensitivity and 96% specificity, particularly useful in pregnancy and for bedside evaluation 1
• Plain abdominal X-rays have limited diagnostic value (sensitivity 50-60%) and are non-diagnostic in 36% of cases 1

Common Pitfalls to Avoid

• Mistaking incomplete obstruction with watery diarrhea for gastroenteritis can lead to dangerous delays in diagnosis 1
• Overlooking bowel obstruction in elderly patients where pain may be less prominent 1
• Relying solely on plain radiographs when clinical suspicion is high 1
• Delaying CT scan when warning signs of ischemia are present 1, 3

Special Considerations in Cancer Patients

Malignant Bowel Obstruction:

• Occurs in 5.5-42% of ovarian cancer patients and 10-28.4% of colorectal cancer patients 4, 5
• Intestinal colic reported in 72-76% of patients 5
• Abdominal pain due to distension, hepatomegaly, or tumor masses in 92% of patients 5
• Vomiting in 68-100% of cases 5
• Emergency surgical intervention is not generally necessary but is appropriate in patients with reversible cause, good performance status, and lack of complicating factors 2
• Patients should be offered at least one of the following treatments: surgery, stenting, decompression percutaneous gastrostomy tube, nasogastric tube, or octreotide 2

Management Options for Inoperable Malignant Obstruction:

• Octreotide should be considered early (150-300 mcg SC bid or continuous subcutaneous infusion) due to high efficacy and tolerability 2
• Corticosteroids (up to 60 mg/d dexamethasone, discontinue if no improvement in 3-5 days) 2
• Antiemetics (avoid prokinetic agents like metoclopramide in complete obstruction, but may be beneficial in incomplete obstruction) 2
• Anticholinergics (scopolamine, hyoscyamine, glycopyrrolate) 2

Inflammatory Bowel Disease Considerations

Free Perforation:

• Occurs in 1-3% of Crohn's disease patients and is more frequent in severe acute ulcerative colitis 2
• Surgical exploration is mandatory in the presence of radiological signs of pneumoperitoneum and free fluid 2
• Delayed surgery correlates with high mortality and morbidity 2

Strictures:

• Small bowel obstruction affects up to 54% of Crohn's disease patients 2
• Surgery is warranted for symptomatic strictures not responding to medical therapy and not amenable to endoscopic dilatation 2
• Any colorectal stricture should be assessed with endoscopic biopsies to exclude malignancy 2