Evaluation and Management of Intestinal Obstruction PATRICK G. JACKSON, MD, and MANISH RAIJI, MD Georgetown University Hospital, Washington, District of Columbia Acute intestinal obstruction occurs when there is an interruption in the forward flow of intes- tinal contents. This interruption can occur at any point along the length of the gastrointestinal tract, and clinical symptoms often vary based on the level of obstruction. Intestinal obstruc- tion is most commonly caused by intra-abdominal adhesions, malignancy, or intestinal hernia- tion. The clinical presentation generally includes nausea and emesis, colicky abdominal pain, and a failure to pass flatus or bowel movements. The classic physical examination findings of abdominal distension, tympany to percussion, and high-pitched bowel sounds suggest the diagnosis. Radiologic imaging can confirm the diagnosis, and can also serve as useful adjunc- tive investigations when the diagnosis is less certain. Although radiography is often the initial study, non-contrast computed tomography is recommended if the index of suspicion is high or if suspicion persists despite negative radiography. Management of uncomplicated obstructions includes fluid resuscitation with correction of metabolic derangements, intestinal decompres- sion, and bowel rest. Evidence of vascular compromise or perforation, or failure to resolve with adequate bowel decompression is an indication for surgical intervention. (Am Fam Physician. 2011;83(2):159-165. Copyright © 2011 American Academy of Family Physicians.) ▲ Patient information: ntestinal obstruction accounts for pass through the intestinal tract leads to a A handout on intestinal approximately 15 percent of all emer- cessation of flatus and bowel movements. obstruction, written by the gency department visits for acute Intestinal obstruction can be broadly dif- authors of this article, is 1 provided on page 166. abdominal pain. Complications of ferentiated into small bowel and large bowel I intestinal obstruction include bowel isch- obstruction. emia and perforation. Morbidity and mor- Fluid loss from emesis, bowel edema, and tality associated with intestinal obstruction loss of absorptive capacity leads to dehydra- have declined since the advent of more tion. Emesis leads to loss of gastric potassium, sophisticated diagnostic tests, but the condi- hydrogen, and chloride ions, and signifi- tion remains a challenging surgical diagno- cant dehydration stimulates renal proximal sis. Physicians who are treating patients with tubule reabsorption of bicarbonate and loss intestinal obstruction must weigh the risks of of chloride, perpetuating the metabolic alka- surgery with the consequences of inappropri- losis.3 In addition to derangements in fluid ate conservative management. A suggested and electrolyte balance, intestinal stasis leads approach to the patient with suspected small to overgrowth of intestinal flora, which may bowel obstruction is shown in Figure 1. lead to the development of feculent emesis. Additionally, overgrowth of intestinal flora Pathophysiology in the small bowel leads to bacterial translo- The fundamental concerns about intesti- cation across the bowel wall.4 nal obstruction are its effect on whole body Ongoing dilation of the intestine increases fluid/electrolyte balances and the mechani- luminal pressures. When luminal pressures cal effect that increased pressure has on exceed venous pressures, loss of venous intestinal perfusion. Proximal to the point drainage causes increasing edema and of obstruction, the intestinal tract dilates as hyperemia of the bowel. This may eventu- it fills with intestinal secretions and swal- ally lead to compromised arterial flow to lowed air.2 Failure of intestinal contents to the bowel, causing ischemia, necrosis, and Downloaded from the American Family Physician Web site at www.aafp.org/afp. Copyright © 2011 American Academy of Family Physicians. For the private, noncommercial January 15,use 2011 of one ◆ individual Volume user83, ofNumber the Web 2site. All other rights reserved.www.aafp.org/afp Contact [email protected] for copyright questionsAmerican and/or permission Family requests. Physician 159 Intestinal Obstruction perforation. A closed-loop obstruction, in and herniation (Table 1). Adhesions resulting which a section of bowel is obstructed proxi- from prior abdominal surgery are the pre- mally and distally, may undergo this pro- dominant cause of small bowel obstruction, cess rapidly, with few presenting symptoms. accounting for approximately 60 percent Intestinal volvulus, the prototypical closed- of cases.5 Lower abdominal surgeries, includ- loop obstruction, causes torsion of arterial ing appendectomies, colorectal surgery, inflow and venous drainage, and is a surgical gynecologic procedures, and hernia repairs, emergency. confer a greater risk of adhesive small bowel obstruction. Less common causes of Causes and Risk Factors obstruction include intestinal intussuscep- The most common causes of intestinal tion, volvulus, intra-abdominal abscesses, obstruction include adhesions, neoplasms, gallstones, and foreign bodies. Management of Small Bowel Obstruction Patient presents with signs and symptoms of small bowel obstruction Clinically stable? No Yes Exploratory Radiography or laparotomy computed tomography Vascular compromise Complete Partial or perforation? obstruction obstruction Yes No Exploratory No oral intake, No oral intake, laparotomy nasogastric intubation, nasogastric intubation, intravenous rehydration intravenous rehydration Resolution within 24 to 48 hours? Resolution within 24 to 48 hours? No Yes Yes No Exploratory Upper gastrointestinal/ laparotomy small bowel follow- through/enteroclysis? Yes Advance diet Resolution? No Exploratory laparotomy Figure 1. Algorithm for evaluation and treatment of patients with suspected small bowel obstruction. 160 American Family Physician www.aafp.org/afp Volume 83, Number 2 ◆ January 15, 2011 Intestinal Obstruction Table 1. Causes of Intestinal Obstruction Adhesive disease (60 percent) Neoplasm (20 percent) The development of metabolic acidosis, espe- Herniation (10 percent) cially in a patient with an increasing serum Inflammatory bowel disease (5 percent) lactate level, may signal bowel ischemia. Intussusception (< 5 percent) RADIOGRAPHY Volvulus (< 5 percent) Other (< 5 percent) The initial evaluation of patients with clinical signs and symptoms of intestinal obstruction should include plain upright History and Physical Examination abdominal radiography. Radiography can Patients should be asked about their history quickly determine if intestinal perforation of abdominal neoplasia, hernia or hernia has occurred; free air can be seen above the repair, and inflammatory bowel disease, liver in upright films or left lateral decubi- because these conditions increase the risk tus films. Radiography accurately diagno- of obstruction. The hallmarks of intesti- ses intestinal obstruction in approximately nal obstruction include colicky abdominal 60 percent of cases,6 and its positive predic- pain, nausea and vomiting, abdominal dis- tive value approaches 80 percent in patients tension, and a cessation of flatus and bowel with high-grade intestinal obstruction.7 movements. It is important to differentiate However, plain abdominal films can appear between true mechanical obstruction and normal in early obstruction and in high other causes of these symptoms (Table 2). jejunal or duodenal obstruction. Therefore, Distal obstructions allow for a greater intes- when clinical suspicion for obstruction is tinal reservoir, with pain and distension high or persists despite negative initial radi- more marked than emesis, whereas patients ography, non-contrast computed tomogra- with proximal obstructions may have mini- phy (CT) should be ordered.8 mal abdominal distension but marked In patients with small bowel obstruc- emesis. The presence of hypotension and tion, supine views show dilation of multiple tachycardia is an indication of severe dehy- loops of small bowel, with a paucity of air in dration. Abdominal palpation may reveal a the large bowel (Figure 2). Those with large distended, tympanitic abdomen; however, bowel obstruction may have dilation of the this finding may not be present in patients with early or proximal obstruction. Aus- cultation in patients with early obstruction Table 2. Differential Diagnosis of Abdominal Pain, reveals high-pitched bowel sounds, whereas Distension, Nausea, and Cessation of Flatus and those with late obstruction may present with Bowel Movements minimal bowel sounds as the intestinal tract becomes hypotonic. Alternate diagnosis Clues Diagnostic Testing and Imaging Ascites Acute liver failure, history of hepatitis or alcoholism LABORATORY TESTS Medications (e.g., tricyclic Review of medications; diagnosis of Laboratory evaluation of patients with sus- antidepressants, narcotics) exclusion pected obstruction should include a com- Mesenteric ischemia History of peripheral vascular disease, plete blood count and metabolic panel. hypercoagulable state, or postprandial Hypokalemic, hypochloremic metabolic abdominal angina; recent use of alkalosis may be noted in patients with vasopressors severe emesis. Elevated blood urea nitrogen Perforated viscus/intra- Fever, leukocytosis, acute abdomen, free abdominal sepsis air on imaging levels are consistent with dehydration, and Postoperative paralytic ileus Recent abdominal surgery with no hemoglobin and hematocrit levels may be postoperative flatus or bowel movement increased.