Bowel, Obstruction Small


Article Author:
Michael Schick


Article Editor:
Marcelle Meseeha


Editors In Chief:
Jesse Cole


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Avais Raja
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Phillip Hynes
Komal Shaheen
Sandeep Sekhon


Updated:
11/14/2018 7:24:23 AM

Introduction

Small bowel obstruction is a common surgical emergency due to a mechanical blockage of the bowel. Small bowel obstruction can be caused by many pathologic processes, but the leading cause in the developed world is intra-abdominal adhesions. Small bowel obstructions can be partial or complete and can be non-strangulated or strangulated.[1][2][3]

Etiology

Post-surgical adhesions most commonly cause small bowel obstruction.  Incarcerated hernias are the second most common etiology. Other common etiologies include malignancy, inflammatory bowel disease (Crohn), stool impaction, foreign bodies, and volvulus. In the pediatric population, common causes include congenital atresia, pyloric stenosis, other congenital anomalies, and intussusception.[4]

Epidemiology

It is estimated that more than 300,000 laparotomies are performed each year in the United States for small bowel obstruction. The small bowel comprises 80% of bowel obstructions. There is a similar incidence of males and females. There is higher incidence with age and number of intra-abdominal procedures.

Pathophysiology

Twisting of the bowel leads to proximal bowel distention and distal bowel decompression. Initially, peristalsis may increase, leading to frequency bowel movements. Distention of the proximal bowel may lead to vomiting. The twisted bowel will first cut off venous blood flow and lead to bowel wall edema and inflammation. The third spacing of fluid often occurs as well. The thickened and inflamed bowel wall is at risk for ischemia and bacterial translocation. Bacterial translocation can cause peritonitis and bacteremia, most commonly from Escherichia coli. As the bowel further twists, the arterial flow will be cut off, leading to bowel ischemia and eventually perforation, peritonitis, and death if untreated.[5]

History and Physical

History of previous abdominal surgeries, inflammatory bowel disease, malignancy, or a hernia is a critical point to ascertain. Patients often present with complaints of abdominal pain, distention, nausea, and vomiting. Abdominal pain may be progressive or intermittent.  Patients may have constipation or obstipation but could also have flatus and even loose bowel movements.

Bowel sounds may be reduced and high pitched. Abdominal tenderness on exam may be diffuse or focal. Distention may be present. Signs of peritonitis such as rebound, guarding, and rigidity are late findings which may be present depending on the time of presentation.  Evaluation for hernias, surgical scars, masses including in the rectum and fecal impactions may demonstrate the possible etiology. Additionally, patients can present with symptoms and signs of dehydration and sepsis. 

Evaluation

Small bowel obstruction may be diagnosed with physical exam alone, but often further diagnostics are required for surgical evaluation and management. While traditionally a physical exam was used to diagnose small bowel obstruction, the invention of computed tomography has greatly improved the accuracy and characterization of this disease. X-ray is often used as a supplementary imaging modality; however, ultrasound is more sensitive and specific than an x-ray. Additionally, ultrasound does not result in radiation exposure and has the benefit of rapid and serial examinations.[1][6]

Plain radiography has poor sensitivity, ranging from 50% to 80%, and may be an initial screening test for obvious air-fluid levels and free intra-abdominal air but cannot be relied upon to rule out small bowel obstruction. Small bowel diameter of greater than 6 centimeters, large bowel greater than 12 centimeters, and cecum greater than 15 centimeters is worrisome for obstruction. 

CT is the gold standard imaging modality in many centers of care. Intravenous contrast should be used if the patient has normal renal function and does not have a contraindication. If the patient has subnormal renal function, a non-contrast study may be obtained, but consultation with the radiologist to determine the optimal study is best. Oral contrast is most often unnecessary in the evaluation of small bowel obstruction as it can lead to delayed diagnosis and complications.  Magnetic resonance imaging may be appropriate in specific circumstances such as young patients who have had multiple computed tomography evaluations previously.   

Point-of-Care Ultrasound

  1. With the patient in the supine position, select the transducer of the highest frequency possible that will provide adequate depth for the patient. In pediatric patients, this will often be a linear high-frequency transducer (5 to 10MHz) and for adult patients it may be a curvilinear transducer (3 to 5MHz).
  2. Begin in the right lower quadrant of the abdomen in the transverse plane. Apply serial compressions every three centimeters along all four quadrants of the abdomen, ending in the left lower quadrant.
  3. Then place the transducer in the longitudinal or sagittal orientation and compress the bowel in all four quadrants ending in the right lower quadrant. A dilated small bowel that measures more than three centimeters is suggestive of an obstruction or ileus. Additionally, an edematous bowel wall that measures more than three millimeters is suggestive of an obstruction or other intestinal inflammatory process. The noncompressibility of bowel and free fluid further suggests obstruction. Anterograde-retrograde or back and forth peristalsis is specific for obstruction. Lastly, visualization of a transition point is specific for obstruction. A transition point on ultrasound demonstrates a dilated, thick, noncompressible bowel adjacent to small, decompressed bowel.

Ultrasound is not a replacement for CT and should not delay surgical consultation. However, it is useful in the instances when it can facilitate diagnosis, surgical consultation, and rule out other diagnoses. 

Typical laboratory studies also need to be sent to evaluate for bowel ischemia, inflammation, extent of dehydration, pre-operative care, and to rule out possible confounding diagnoses. These may include a complete blood count, lactic acid, complete metabolic profile, urine studies, and coagulation studies.

Treatment / Management

Surgery consultation should be utilized without delay as many small bowel obstruction patients require surgical management. Initial treatment of small bowel obstruction involves fluid resuscitation, pain control, antibiotics, and, often, nasogastric decompression.  Antibiotics of choice for small bowel obstruction should target gut flora and cover both gram-negative and anaerobic bacteria. [7][8][4]

Ileus and partial small bowel obstructions often can be treated conservatively with nasogastric decompression. Surgical consultation should still be sought, but surgical intervention may not be required. 

Differential Diagnosis

  • Viral or bacterial gastroenteritis
  • Ileus
  • Mesenteric ischemia
  • Acute pancreatitis
  • Intussusception
  • Constipation

Complications

  • Bowel necrosis and perforation
  • Wound dehiscence
  • Intra-abdominal abscess
  • Aspiration
  • Short bowel syndrome

Pearls and Other Issues

A dilated, non-compressible bowel is the hallmark of small bowel obstruction on ultrasound. A small bowel more than three centimeters is dilated. The small bowel wall is thick when it is more than three millimeters. Back and forth peristalsis and visualizing a transition point are specific findings for obstruction on ultrasound. CT scan remains an accurate method to diagnose and characterize a small bowel obstruction.

Enhancing Healthcare Team Outcomes

A multidisciplinary approach to small bowel obstruction

Small bowel obstruction is a common presentation to the emergency department. Because of the high morbidity and mortality associated with this disorder, it is imperative that a multidisciplinary team evaluate and manage the patient. The triage nurse must be aware of the signs and symptoms of SBO; any delay in diagnosis can quickly turn fatal. With prompt diagnosis and management, the prognosis for most patients with small bowel obstruction is good. However, complete obstructions even though treated can have a high recurrence rate. When surgery is performed within 24-36 hours, the mortality rates are low but if surgery is delayed, the mortality rates can exceed 10%. All patients at discharge should be educated about the signs and symptoms of a recurrent bowel obstruction and when to present to the emergency department.[9][10]


Attributed To: Contributed by Michael Schick DO, MA

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Bowel, Obstruction Small - Questions

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A 45-year-old with severe asthma undergoes a laparotomy for a bowel obstruction. Postoperatively he has minimal nausea or vomiting. Which of the following could be the reason for the antiemetic effect?



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Which of the following should cause one to suspect a complete small bowel obstruction?



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A patient has a suspected small bowel obstruction. Which is not involved in the initial management?



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A 35-year-old woman presents with bowel obstruction three years after a total abdominal hysterectomy with bilateral salpingo-oophorectomy. What is the likely cause?



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A 17-year-old young male presents with bowel obstruction. What should be the main focus of the physical exam?



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In a patient with a history of appendectomy 20 years ago, what is the most likely cause of bowel obstruction?



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In a patient who had surgery for a Meckel diverticulum at age 12, what is the most likely cause of small bowel obstruction at age 55?



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What is the most common cause of mechanical bowel obstruction in adults?



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Which is false about bowel obstruction?



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Which of the following is false regarding small bowel obstruction?



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A patient has vomiting and colicky abdominal pain for 2 days. She has had no flatus or bowel movements for a day. Obstructive series shows multiple distended loops of small bowel, air-fluid levels, and no gas in the colon. What is the most likely diagnosis?



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An adult male has "bloating" abdominal pain, anorexia, and nausea. On examination he is afebrile with a distended tympanitic abdomen, no bowel sounds, and a mass in his right groin that cannot be reduced. What will abdominal radiographs most likely show?



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A patient presents with nausea, vomiting, and an old lower abdominal midline scar. X-ray reveals dilated loops of bowel and air in the rectum. What is the next step?



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Which of the following is not a common cause of small bowel obstruction in the pediatric population?



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What is the most common cause of small bowel obstruction?



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Which of the following is not a complication of small bowel obstruction?



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A 2 week old male infant presents with increased fussiness and bilious emesis. What is the initial management of this patient?



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What is an abnormal small bowel diameter when using ultrasound to diagnose small bowel obstruction?



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At what thickness is small bowel wall considered thick or edematous by ultrasound?



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When using ultrasound to diagnose small bowel obstruction, what transducer should be used?



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A 65-year-old male with a history of a total proctocolectomy with ileoanal pouch anastomosis for ulcerative colitis presents to the emergency department with several hours of nausea, vomiting, and abdominal pain. He says he has not had a bowel movement since his symptoms started despite having 6 to 8 bowel movements/day since surgery. A nasogastric tube is inserted, and patient reports improvement in nausea and vomiting symptoms. What is the most likely etiology of his presentation?



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Bowel, Obstruction Small - References

References

Linden AF,Raiji MT,Kohler JE,Carlisle EM,Pelayo JC,Feinstein K,Kandel JJ,Mak GZ, Evaluation of a water-soluble contrast protocol for nonoperative management of pediatric adhesive small bowel obstruction. Journal of pediatric surgery. 2018 Oct 5     [PubMed]
Grigsby CK,Falkenstrom KL,Merchen TD, Small Bowel Obstruction from a 3-cm Gallstone in the Setting of Child-Pugh C Liver Cirrhosis. The American surgeon. 2017 Dec 1     [PubMed]
Gilbert JD,Byard RW, Obturator hernia and the elderly. Forensic science, medicine, and pathology. 2018 Nov 5     [PubMed]
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Edwards MK,Kuppler CS,Croft CA,Eason-Bates HM, Adhesive Closed-loop Small Bowel Obstruction. Clinical practice and cases in emergency medicine. 2018 Feb     [PubMed]
Behman R,Nathens AB,Look Hong N,Pechlivanoglou P,Karanicolas PJ, Evolving Management Strategies in Patients with Adhesive Small Bowel Obstruction: a Population-Based Analysis. Journal of gastrointestinal surgery : official journal of the Society for Surgery of the Alimentary Tract. 2018 Dec     [PubMed]
Ozturk E,van Iersel M,Stommel MM,Schoon Y,Ten Broek RR,van Goor H, Small bowel obstruction in the elderly: a plea for comprehensive acute geriatric care. World journal of emergency surgery : WJES. 2018     [PubMed]
Tang L,Zhao P,Kong D, The risk factors for benign small bowel obstruction following curative resection in patients with rectal cancer. World journal of surgical oncology. 2018 Oct 22     [PubMed]
Dong XW,Huang SL,Jiang ZH,Song YF,Zhang XS, Nasointestinal tubes versus nasogastric tubes in the management of small-bowel obstruction: A meta-analysis. Medicine. 2018 Sep     [PubMed]
Trevino CM,VandeWater T,Webb TP, Implementation of an adhesive small bowel obstruction protocol using low-osmolar water soluble contrast and the impact on patient outcomes. American journal of surgery. 2018 Aug 29     [PubMed]

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