Definition
Bowel obstruction occurs when the flow of intestinal contents is disrupted along the course of the large or small bowel. Although a more common occurrence in the small bowel, 25% of obstructions occur in the large bowel. The obstructions can occur in two ways:
A.Mechanical—can be partial or complete; occurring insidiously or acutely:
1.Mass/stricture.
2.Adhesions.
3.Volvulus.
4.Intussusception.
5.Congenital anomalies.
6.Fecal impaction.
7.Diverticular disease.
B.Functional—due to altered physiology of the intestines.
C.Intestinal pseudo-obstruction related to nerve and muscle disorders:
1.Parkinson’s disease.
2.Multiple sclerosis.
3.Hirshsprung’s disease.
4.Diabetes.
5.Medications.
D.Small bowel obstruction can be characterized as follows:
1.Partial or complete:
a.Simple.
b.Strangulated.
The absence of bowel activity, stool and flatus, is a predictor for complications, such as ischemia, necrosis, or perforation.
Metabolic disturbances may mimic intra-abdominal etiologies.
Porphyria and lead poisoning sometimes simulate bowel obstruction because they can cause cramping, abdominal pain, and hyperperistalsis.
Incidence
A.In patients with a history of abdominal surgery, the postsurgical incidence is around 9%.
B.In patients without a history of abdominal surgery, the incidence is 3% to 9%.
C.The small bowel is implicated in 75% to 80% of all intestinal obstructions.
D.Average age 65 to 70 in both males and females. Volvulus occurs in the sigmoid colon or cecum in greater than 95% of cases. Typically presents during ages 60 to 80 with other chronic medical and neuropsychological conditions.
Pathogenesis
A.Obstruction can be caused by extrinsic (outside the bowel wall), intrinsic (in the bowel wall), or intraluminal factors. Blockages can be complete or incomplete.
B.With obstruction, dilation of the bowel wall occurs proximally, leading to edema, fluid accumulation, and loss of absorptive function. Emesis can create metabolic alkalosis due to loss of electrolytes. With intensifying distention, the vessels within the wall of the intestines become compromised leading to reduced perfusion, resulting in ischemia or the tissue and possible necrosis and perforation. Peritoneal irritation: Severe pain due to the rich innervation of the parietal peritoneum. Focal injury results in well-localized discomfort that is described as a sharp aching or burning.
Predisposing Factors
A.Cancer:
1.Colorectal cancer (CRC; 30%).
2.Pancreatic.
3.Ovarian.
4.Prostatic neoplasm.
B.Previous radiation therapy.
C.Prior abdominal surgery.
D.Prior colorectal resection.
E.Inflammatory bowel disease (IBD; Crohn’s or ulcerative colitis).
F.Abdominal wall hernias.
G.Structural abnormality:
1.Volvulus.
2.Fecal impaction.
H.Rectal stenosis.
I.Endometriosis.
J.Tuberculosis.
K.Lymphogranuloma venereum.
L.Medications:
1.Opioids.
2.Tricyclic antidepressants.
Common Complaints
Acute obstruction presents with severe paroxysmal colicky
pain or pain that is wavelike in nature; it makes the pain relentless. Systemic signs—fever, tachycardia, hypotension, altered mental state—may be associated with strangulation.
Cardinal symptoms.
A.Abdominal pain.
B.Distention.
C.Severe and obstinate constipation.
Other Signs and Symptoms
A.Nausea and vomiting (may be bile-colored emesis in small bowel obstruction).
B.Focal abdominal pain can indicate peritoneal irritation caused by ischemia or necrosis.
C.Pain occurring in the lower pelvis can be due to rectal tenesmus, indicating rectal obstruction.
D.Pencil thin bowel movements (BMs).
E.Obstructions may develop slowly over weeks to months may be relatively subtle in presentation.
Subjective Data
A.The history should focus on the identification of risk factors:
1.Review the location, onset, location, onset, character, associated factors, timing, exacerbating factors, and severity of symptoms.
2.Is the patient able to pass stool and flatus?
3.Is the patient able to keep liquids down?
a.When was the last fluid intake?
b.Is the patient urinating?
4.Does the patient have any of the following as noted in Predisposing factors
?
a.Cancer(s), previous radiation therapy.
b.Does the patient have a diagnosis of IBD?
c.Has the patient had recent surgeries or a colon resection?
d.Has the patient had gastroenteritis? Is any other family member ill?
e.Has the patient ever had a colonoscopy and been diagnosed by diverticular disease?
5.Review all medications, over-the-counter (OTC), and herbal products. Does the patient have a history of chronic opioid use?
Physical Examination
A.Check temperature, blood pressure (BP) sitting and standing, pulse, respirations, height, and weight to calculate a body mass index (BMI). (Dehydration is manifested by tachycardia and orthostatic hypotension.)
B.Inspect:
1.Patients with complications from obstruction appear acutely ill.
2.Check mucous membranes for signs of severe dehydration.
3.Evaluate presence of abdominal distention.
4.Surgical scars indicating past abdominal surgeries.
5.Hernias—incisional or groin.
C.Auscultate:
1.Abdomen all four quadrants: High-pitched bowel sounds indicate acute obstruction followed by muffling of the bowel sounds as distention progresses; finally, the bowel sounds become hypoactive. Evaluate for ascites.
2.Heart.
3.Lungs.
D.Palpate:
1.Abdomen: Identify mass (abscess, volvulus, tumor) or hernia.
2.Check for hepatosplenomegaly.
3.Evaluate rebound tenderness.
E.Percussion:
1.Abdomen:
a.Tympany of the abdomen due to distention; tympany over the liver suggests free intraabdominal air.
b.Dullness of the abdomen over fluid filled dilated loops.
c.Tenderness to percussion can indicated peritonitis.
F.Rectal examination—identifies rectal mass; check for occult blood.
G.Neurological exam.
Diagnostic Tests
A.Laboratory studies:
1.Complete blood count (CBC) with differential.
2.Metabolic profile.
3.Blood urea nitrogen (BUN)/creatinine levels (may be elevated in dehydration due to vomiting).
4.Urinalysis.
5.Guaiac any stool from the rectal examination.
B.Imaging:
1.Abdominal x-ray. (Relevant findings include dilated loops of bowel or a size difference between the proximal and distal bowel with the proximal being dilated and the distal appearing collapsed.)
2.Chest radiograph—used to assess for aspiration in patients who have been vomiting.
3.Ultrasound.
4.Endoscopy.
5.CT:
a.Significant findings include increased thickening of bowel wall greater than 3 mm, mesenteric edema, abdominal ascites, and submucosal edema or hemorrhage.
b.Target sign, whirl sign, and venous cut-off sign are all radiological findings suggestive of specific etiology.
6.Magnetic resonance (MR) enterography is useful with low-grade bowel obstruction is suspected.
Differential Diagnoses
A.Bowel obstruction:
1.Small bowel obstruction—most common etiologies is adhesions, hernias, and malignancy.
2.Large bowel obstruction—most common etiologies are tumor, adhesions, and volvulus.
B.Nonobstructive motility disorder:
1.Paralytic ileus.
2.Pseudo-obstruction.
C.Constipation.
D.Fecal impaction.
E.Porphyria.
F.Lead poisoning.
Plan
Treatment depends on the location and severity of the obstruction.
A.Patients with suspected bowel obstruction should be kept NPO to avoid gastric distention.
B.The crampy abdominal pain of bowel obstruction does not generally respond to pharmacologic therapy. Use of opioids is discouraged except among cancer patients.
C.There is a subset of patients with partial bowel obstruction who may be managed with medical observation for 12 to 24 hours by a specialist or surgeon. Pharmaceutical therapy: Treatment depends on the findings from the history, physical, and testing, as well as the clinical diagnosis.
Follow-Up
A.Variable, depending on diagnosis.
Emergent Issues/Instructions
A.All patients identified as having a complete bowel obstruction should be admitted to the hospital for consideration of surgical exploration.
B.Without treatment, abdominal pain can increase as a result of bowel perforation and ischemia.
Consultations
A.Surgical consult.
B.Depending on the urgency, consult with a gastroenterologist.
Individual Considerations
A.Geriatrics:
1.Signs of dehydration include confusion, muscle weakness, fever, dizziness, poor skin turgor, hypotension, and tachycardia.
2.Delirium is a common early sign of acute illness or infection in the elderly. It is more common in patients with existing cognitive impairment. At a minimum, patients and family should be asked if the patient has experienced episodes of altered mental status:
a.The Brief Confusion Assessment Method (bCAM) is a well-documented assessment for delirium. It is available at www.mnhospitals.org/Portals/0/Documents/ptsafety/LEAPT%20Delirium/HELP%20Program%20CAM%20Flowsheet.pdf.
3.Elderly patients have a diminished sensorium, allowing pathology to advance to a dangerous point prior to symptom development:
a.The level of pain is much less severe at presentation and continues to be at a lower level of pain.
b.The elderly may present with altered mental status. Cognitive impairment can make assessment and diagnosis of pain more difficult. For dementia or non-communicative patients the American Medical Directors Association has endorsed the Pain Assessment in Advanced Dementia (PAINAD) Scale, which scores the following items:
i.Breathing: Examples include normal, labored, hyperventilation.