Bowel Obstruction (Small and Large), Emergency Medicine

Basics

Description

Obstruction of normal intestinal flow from mechanical or nonmechanical causes
Small-bowel obstruction (SBO):
- 20% of acute surgical admissions
- Adhesions: Most common cause (60%)
- Neoplasms
- Hernias
- Strictures: Inflammatory bowel disease
- Trauma: Bowel wall hematoma
- Miscellaneous (e.g., ascaris infection)
Large-bowel obstruction (LBO):
- Disease primarily of the elderly
- Carcinoma (60%)
- Diverticular disease (20%)
- Volvulus (5%)
- Colitis (e.g., ischemic, radiation)
- Crohns disease
- Foreign bodies
Functional, nonmechanical:
- Paralytic ileus (e.g., electrolyte abnormalities, injury)
- Pseudo-obstruction (i.e., Ogilvie syndrome [e.g., operative and nonoperative trauma] 11%)

Etiology

Obstruction leads to proximal dilatation of intestines due to swallowed air and accumulated GI secretions, leading to increased intraluminal pressures.
Retrograde peristalsis causes vomiting.
Distended bowel becomes progressively edematous, and additional intestinal secretions cause further distention and 3rd spacing of fluid into the intestinal lumen.
Obstruction may lead to intestinal wall ischemia (strangulated obstruction), resulting in increased aerobic and anaerobic bacteria, and methane and hydrogen production. Peritonitis, sepsis, and death may follow.
Mortality is 100% in untreated strangulated obstruction, 8% if treated surgically within 36 hr, but 25% if surgery delayed after 36 hr.

Diagnosis

Signs and Symptoms

History

Previous surgery, malignancy, hernias, colonoscopy history, significant family history
Abdominal pain:
- Intermittent when early
- Symptoms may be vague in elderly or altered patients
- Constant with strangulated obstruction
Vomiting:
- Bile-stained emesis with proximal obstruction
- Feculent emesis with distal obstruction
Obstipation, constipation, diarrhea
Stool caliber changes, weight loss

Physical Exam

Vital signs:
- Tachycardia, hypotension with significant volume depletion
- Fever with strangulation or perforation
- Hypothermia with sepsis
Abdominal exam:
- Distention
- Variable tenderness, often diffuse
- Hyperactive and high-pitched bowel sounds when early; hypoactive when late
- Consider ischemic or gangrenous bowel if pain out of proportion to exam.
- Peritoneal signs indicate strangulation or perforation.
Hernia (ventral, inguinal, femoral)
Digital rectal exam:
- Rectal mass
- Blood in stool, gross or occult

Abdominal pain variable in elderly, may be vague
Nausea/vomiting and abdominal pain are common symptoms in elderly patients with acute myocardial infarctions:
- Abdominal distention, obstipation, and colicky pain suggest GI cause.

Intussusception:
- Leading cause of intestinal obstruction in infants
- Most common between 3 and 12 mo of age
Incarcerated inguinal/umbilical hernia
Malrotation with volvulus:
- Can occur as early as 3-7 days of age
- "Double bubble" sign seen on plain radiograph owing to partial obstruction of duodenum, resulting in air in stomach and in 1st part of duodenum
Pyloric stenosis:
- Progressive, projectile, nonbilious postprandial vomiting
- Male/female ratio: 5:1 incidence
- Onset usually 2-5 wk of age
Other causes include duodenal atresia, Hirschsprung, and imperforate anus.

Essential Workup

Careful history and physical exam

Diagnosis Tests & Interpretation

Lab

CBC:
- Leukocytosis common
Electrolytes, BUN/creatinine, glucose:
- Hypokalemia
- Hypochloremic metabolic alkalosis
- Prerenal azotemia
Lactate
Amylase/lipase
Liver enzymes/function to exclude hepatic/biliary pathology
Stool heme test
Urinalysis
Type and crossmatch
PT/PTT
ECG in patients at risk of coronary artery disease

Imaging

Upright CXR:
- Evaluate for pulmonary pathology.
- Check for free air beneath diaphragm.
Plain abdominal radiographs, supine and upright (75% sensitivity; 53% specificity):
- Distended loops of bowel (normal small bowel <3 cm in diameter)
- Distended cecum >13 cm indicates potential for perforation.
- Air-fluid levels
- "String of pearls" sign if small bowel loops nearly completely fluid filled
- Less helpful for distinguishing strangulation
Abdominal CT:
- Sensitivity:
  - 90% for SBO; 91% for LBO
- Detects neoplastic causes and stages malignancy
- Effective in defining location of obstruction
- More helpful than plain radiographs in identifying early strangulation (with IV contrast)
- Exclude other incidental findings/causes
- Has decreased use of contrast enemas due to ease of use
MRI:
- Sensitivity approached that of CT
- Availability variable
US:
- More sensitive and specific than plain films for SBO but not as accurate as CT

Diagnostic Procedures/Surgery
Upper GI/barium enemas/endoscopy:

If carcinoma or mass lesion suspected as cause
Use decreased with availability of CT scan
May be painful or difficult in sick patients

Differential Diagnosis

Paralytic ileus
Pseudo-obstruction (Ogilvie)
Perforated ulcer
Pancreatitis
Cholecystitis
Colitis
Mesenteric ischemia

Treatment

Pre-Hospital

Establish IV access for patients with dehydration, vomiting, or significant abdominal pain.

Initial Stabilization/Therapy

ABCs
0.9% normal saline (NS) or lactated ringers (LR) IV fluid resuscitation for significant volume depletion and strangulated or perforated bowel:
- Adults: 1 L bolus
- Peds: 20 mL/kg bolus
Correct electrolyte abnormalities, especially hypokalemia.

Ed Treatment/Procedures

IV fluids (isotonic saline or lactated Ringer's)
Nasogastric tube (NGT)
Foley catheter to monitor urine output
Surgical consultation
Antibiotics for suspected strangulated/perforated bowel:
- Antibiotic choices should cover gram-negative aerobic and anaerobic organisms:
Analgesics
Antiemetics
Treat underlying etiology, appropriate steroids for inflammatory bowel disease, radiation enteritis

Medication

Antibiotic choices (broad spectrum, for suspected ischemia):
- Combination therapy:
  - Metronidazole (Flagyl): 1 g IV, then 500 mg IV q6h (peds: 7.5-30 mg/kg/24h IV div. q6-8h)
  - Ciprofloxacin (Cipro): 400 mg IV q12h
  - Ceftriaxone (Rocephin): 1-2 g (peds: 25-75 mg/kg/d IV up to 2 g div. q12-24h) IV q24h
- Single therapy:
  - Piperacillin-tazobactam (Zosyn): 3.375 g (peds: 150-400 mg/kg/24h IV div. q6-8h) IV q4-6h
  - Ampicillin-sulbactam (Unasyn): 1.5-3 g (peds: 100-400 mg/kg/24h IV div. q6h) IV q6h
  - Meropenem (Merrem): Adult: 1 g (peds: 60-120 mg/kg/24h IV q8h) IV q8h
  - Imipenem-cilastatin (Primaxin): 250-1,000 mg (peds: 50-100 mg/kg/24h IV q6-12h) IV q6-8h
Analgesics:
- Morphine: 2-10 mg/dose (peds: 0.1-0.2 mg/kg IV/IM/SC q2-4h) IV/IM/SC q2-6h PRN
Antiemetics:
- Ondansetron (Zofran): 4 mg (peds: 0.1 mg/kg IV div. q8h) IV q4-8h PRN
- Promethazine (Phenergan): 12.5-25 mg (peds: >2 yr: 0.25-1 mg/kg/d IV/IM/PR div. q4-6h PRN) IV/IM/SC q4h

Follow-Up

Disposition

Admission Criteria
All patients with suspected/confirmed intestinal obstruction should be admitted with early surgical consultation.
Discharge Criteria
Normal lab/radiology results with resolution of symptoms and no further suspicion for intestinal obstruction.
Issues for Referral
Surgery consult for patients with suspected bowel obstruction

Followup Recommendations

Discharged patients:

Normal lab and radiologic studies
Timely appointment for re-evaluation
Explicit instructions detailing signs/symptoms to return to emergency department

Pearls and Pitfalls

Carefully examine patient with history of vomiting for incarcerated hernias.
Failure to diagnose strangulated bowel obstruction:
- Symptoms potentially vague in very old and very young and in altered patients
Failure to adequately replete fluid losses and electrolyte imbalances

Additional Reading

Batke M. Cappell MS. Adynamic ileus and acute colonic pseudo-obstruction. Med Clin North Am. 2008;92(3):649-670.
Diaz JJ Jr, Bokhari F, Mowery NT, et al. Guidelines for management of small bowel obstruction. J Trauma. 2008;64(6):1651-1654.
Hopkins C. Large-bowel obstruction workup. Available at http://emedicine.medscape.com/article/774045-workup#aw2aab6b5b5aa. Updated Nov 11, 2011. Accessed February 2013.
Noble BA. Small-bowel obstruction. Available at http://emedicine.medscape.com/article/774140-overview. Updated Oct 5, 2011. Accessed February 2013.
Walker GM, Raine PA. Bilious vomiting in the newborn: How often is further investigation undertaken? J Pediatr Surg. 2007;42(4):714-716.

Codes

ICD9

560.9 Unspecified intestinal obstruction
560.81 Intestinal or peritoneal adhesions with obstruction (postoperative) (postinfection)
560.89 Other specified intestinal obstruction
560.1 Paralytic ileus
560.2 Volvulus
560.8 Other specified intestinal obstruction

ICD10

K56.5 Intestinal adhesions w obst (postprocedural) (postinfection)
K56.60 Unspecified intestinal obstruction
K56.69 Other intestinal obstruction
K56.0 Paralytic ileus
K56.2 Volvulus
K56.6 Other and unspecified intestinal obstruction

SNOMED

81060008 Intestinal obstruction (disorder)
281255004 small bowel obstruction (disorder)
281254000 large bowel obstruction (disorder)
67766009 Intestinal adhesions with obstruction (disorder)
23065003 Stenosis of intestine (disorder)
55525008 Paralytic ileus (disorder)

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