Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
OBSTRUCTION The description of patients presenting with small bowel obstruction dates back to the third or fourth century, when Praxagoras created an enterocutaneous fistula to relieve a bowel obstruction. Despite this success with operative therapy, the nonoperative management of these patients with attempted reduction of hernias, laxatives, ingestion of heavy metals (e.g., lead or mercury), and leeches to remove toxic agents from the blood was the rule until the late 1800s, when antisepsis and aseptic surgical techniques made operative intervention safer and more acceptable. A better understanding of the pathophysiology of bowel obstruction and the use of isotonic fluid resuscitation, intestinal tube decompression, and antibiotics have greatly reduced the mortality rate for patients with mechanical bowel obstruction.[30] [31] However, patients with a bowel obstruction still represent Figure 46-11 The mucosal barrier of the gut. Antigens contact specialized microfold (M) cells overlying Peyer’s patches, which then process and present the antigen to the immune system. When B lymphocytes are stimulated by antigenic material, the cells develop into antibody-forming cells that secrete various types of immunoglobulins (Igs), the most important of which is IgA. (Adapted from Duerr RH, Shanahan F: Food allergy. In Targan SR, Shanahan F [eds]: Immunology and Immunopathology of the Liver and Gastrointestinal Tract. New York, Igaku-Shoin, 1990, p 510.) 1335 Figure 46-12 Common causes of small bowel obstruction in industrialized countries. some of the most difficult and vexing problems that surgeons face with regard to the correct diagnosis, the optimal timing of therapy, and the appropriate treatment. Ultimate clinical decisions regarding the management of these patients dictates a thorough history and work-up and a heightened awareness of potential complications. Etiology The causes of a small bowel obstruction can be divided into three categories: (1) obstruction arising from extraluminal causes such as adhesions, hernias, carcinomas, and abscesses; (2) obstruction intrinsic to the bowel wall (e.g., primary tumors); and (3) intraluminal obturator obstruction (e.g., gallstones, enteroliths, foreign bodies, and bezoars) ( Box 46–1 ). The cause of small bowel obstruction has changed dramatically during the past century.[32] At the turn of the 20th century, hernias accounted for more than half of mechanical intestinal obstructions. With the routine elective repair of hernias, this cause has dropped to the third most common cause of small bowel obstruction in industrialized countries. Adhesions secondary to previous surgery are by far the most common cause of small bowel obstruction ( Fig. 46–12 ). Adhesions, particularly after pelvic operations (e.g., gynecologic procedures, appendectomy, and colorectal resection), are responsible for more than 60% of all causes of bowel obstruction in the United States.[33] [34] This preponderance of lower abdominal procedures to produce adhesions that result in obstruction is thought to be due to the fact that the bowel is more mobile in the pelvis and more tethered in the upper abdomen. Malignant tumors account for approximately 20% of the cases of small bowel obstruction. The majority of these tumors are metastatic lesions that obstruct the intestine secondary to peritoneal implants that have spread from an intra-abdominal primary tumor such as ovarian, pancreatic, gastric, or colonic. Less often, malignant cells from distant sites, such as breast, lung, and melanoma, may metastasize hematogenously and account for peritoneal implants and result in an obstruction. Large intra-abdominal tumors may also cause small bowel obstruction through extrinsic compression of the bowel lumen. Primary colonic cancers (particularly those arising from Box 46-1. Causes of Mechanical Small Intestinal Obstruction in Adults * Lesions Extrinsic to the Intestinal Wall Adhesions (usually postoperative) Hernia External (e.g., inguinal, femoral, umbilical, or ventral hernias) Internal (e.g., congenital defects such as paraduodenal, foramen of Winslow, and diaphragmatic hernias or postoperative secondary to mesenteric defects) Neoplastic Carcinomatosis Extraintestinal neoplasms Intra-abdominal abscess Lesions Intrinsic to the Intestinal Wall Congenital Malrotation Duplications/cysts Inflammatory Crohn’s disease Infections Tuberculosis Actinomycosis Diverticulitis Neoplastic Primary neoplasms Metastatic neoplasms Traumatic Hematoma Ischemic stricture Miscellaneous Intussusception Endometriosis Radiation enteropathy/stricture Intraluminal/Obturator Obstruction Gallstone the cecum and ascending colon) may present as a small bowel obstruction. Primary small bowel tumors can cause obstruction but are exceedingly rare. Hernias are the third leading cause of intestinal obstruction and account for approximately 10% of all cases. Most commonly, these represent ventral or inguinal hernias. Internal hernias, usually related to prior abdominal surgery, can also result in small bowel obstruction. Less common hernias can also produce obstruction, such as femoral, obturator, lumbar, and sciatic hernias. 1336 Crohn’s disease is the fourth leading cause of small bowel obstruction and accounts for approximately 5% of all cases. Obstruction can result from acute inflammation and edema, which may resolve with conservative management. In patients with long-standing Crohn’s disease, strictures can develop that may require resection and reanastomosis or strictureplasty. An important cause of small bowel obstruction that is not routinely considered is obstruction associated with an intra-abdominal abscess, commonly from a ruptured appendix, diverticulum, or dehiscence of an intestinal anastomosis. The obstruction may occur as a result of a local ileus in the small bowel adjacent to the abscess. In addition, the small bowel can form a portion of the wall of the abscess cavity and become obstructed by kinking of the bowel at this point. Miscellaneous causes of bowel obstruction account for 2% to 3% of all cases but should be considered in the differential diagnosis. These include intussusception of the bowel, which in the adult is usually secondary to a pathologic lead point such as a polyp or tumor; gallstones, which can enter the intestinal lumen by a cholecystenteric fistula and cause obstruction; enteroliths originating from jejunal diverticula; foreign bodies; and phytobezoars. Pathophysiology Early in the course of an obstruction, intestinal motility and contractile activity increase in an effort to propel luminal contents past the obstructing point. The increase in peristalsis that occurs early in the course of bowel obstruction is present both above and below the point of obstruction, thus accounting for the finding of diarrhea that may accompany partial or even complete small bowel obstruction in the early period. Later in the course of obstruction, the intestine becomes fatigued and dilates, with contractions becoming less frequent and less intense. As the bowel dilates, water and electrolytes accumulate both intraluminally and in the bowel wall itself. This massive third-space fluid loss accounts for the dehydration and hypovolemia. The metabolic effects of fluid loss depend on the site and duration of the obstruction. With a proximal obstruction, dehydration may be accompanied by hypochloremia, hypokalemia, and metabolic alkalosis associated with increased vomiting. Distal obstruction of the small bowel may result in large quantities of intestinal fluid into the bowel; however, abnormalities in serum electrolytes are usually less dramatic. Oliguria, azotemia, and hemoconcentration can accompany the dehydration. Hypotension and shock can ensue. Other consequences of bowel obstruction include increased intra-abdominal pressure, decreased venous return, and elevation of the diaphragm, compromising ventilation. These factors can serve to further potentiate the effects of hypovolemia. As the intraluminal pressure increases in the bowel, a decrease in mucosal blood flow can occur. These alterations are particularly noted in patients with a closed-loop obstruction in which greater intraluminal pressures are attained. A closed-loop obstruction, produced commonly by a twist of the bowel, can progress to arterial occlusion and ischemia if left untreated and may potentially lead to bowel perforation and peritonitis. In the absence of intestinal obstruction, the jejunum and proximal ileum of the human are virtually sterile. With obstruction, however, the flora of the small intestine changes dramatically, in both the type of organism (most commonly Escherichia coli, Streptococcus faecalis, and Klebsiella) and the quantity, with organisms reaching concentrations of 109 to 1010 /mL. Studies have shown an increase in the number of indigenous bacteria translocating to mesenteric lymph nodes and even systemic organs.[35] However, the overall importance of this bacterial translocation on the clinical course has not been entirely defined. Clinical Manifestations and Diagnosis A thorough history and physical examination are critical to establishing the diagnosis and treatment of the patient with an intestinal obstruction. In the majority of patients, a meticulous history and physical examination complemented by plain abdominal radiographs are all required to establish the diagnosis and to devise a treatment plan. More sophisticated radiographic studies may be necessary in certain patients in whom the diagnosis and cause are uncertain. However, a computed tomographic (CT) scan of the abdomen should not be the starting point in the work-up of a patient with intestinal obstruction. History The cardinal symptoms of intestinal obstruction include colicky abdominal pain, nausea, vomiting, abdominal distention, and a failure to pass flatus and feces (i.e., obstipation). These symptoms may vary with the site and duration of obstruction. The typical crampy abdominal pain associated with intestinal obstruction occurs in paroxysms at 4- to 5-minute intervals and occurs less frequently with distal obstruction. Nausea and vomiting are more common with a higher obstruction and may be the only symptoms in patients with gastric outlet or high intestinal obstruction. An obstruction located distally is associated with less emesis, and the initial and most prominent symptom is the cramping abdominal pain. Abdominal distention occurs as the obstruction progresses, and the proximal intestine becomes increasingly dilated. Obstipation is a later development, and it must be reiterated that patients, particularly in the early stages of bowel obstruction, may relate a history of diarrhea that is secondary to increased peristalsis. Therefore, the important point to remember is that a complete bowel obstruction cannot be ruled out based on a history of loose bowel movements. The character of the vomitus is also important to obtain in the history. As the obstruction becomes more complete with bacterial overgrowth, the vomitus becomes more feculent, indicating a late and established intestinal obstruction. Enterolith Bezoar * Foreign bodyAdapted from Tito WA, Sarr MG: Intestinal obstruction. In Zuidema GD (ed): Surgery of the Alimentary Tract. Philadelphia, WB Saunders, 1996, pp 375–416. 1337 Physical Examination The patient with intestinal obstruction may present with tachycardia and hypotension, demonstrating the severe dehydration that is present. Fever suggests the possibility of strangulation. Abdominal examination demonstrates a distended abdomen, with the amount of distention somewhat dependent on the level of obstruction. Previous surgical scars should be noted. Early in the course of bowel obstruction, peristaltic waves can be observed, particularly in thin patients, and auscultation of the abdomen may demonstrate hyperactive bowel sounds with audible rushes associated with vigorous peristalsis (i.e., borborygmi). Late in the obstructive course, minimal or no bowel sounds are noted. Mild abdominal tenderness may be present with or without a palpable mass; however, localized tenderness, rebound, and guarding suggest peritonitis and the likelihood of strangulation. A careful examination must be performed to rule out incarcerated hernias in the groin, the femoral triangle, and the obturator foramen. A rectal examination should be performed to assess for intraluminal masses and to examine the stool for occult blood, which may be an indication of malignancy, intussusception, or infarction. Radiologic and Laboratory Examinations The diagnosis of intestinal obstruction is often immediately evident after a thorough history and physical examination. Therefore, plain radiographs usually confirm the clinical suspicion and define more accurately the site of obstruction. The accuracy of diagnosis of the small intestinal obstruction on plain abdominal radiographs is estimated to be approximately 60%, with an equivocal or a nonspecific diagnosis obtained in the remainder of cases. Characteristic findings on supine radiographs are dilated loops of small intestine without evidence of colonic distention. Upright radiographs demonstrate multiple air-fluid levels, which often layer in a stepwise pattern ( Fig. 46–13 ). Plain abdominal films may also demonstrate the cause of the obstruction (e.g., foreign bodies or gallstones) ( Fig. 46–14 ). In uncertain cases or when one is unable to differentiate partial from complete obstruction, further diagnostic evaluations may be required. In the more complex patient in whom the diagnosis is not readily apparent, CT has proved to be beneficial ( Fig. 46–15 ). [36] A CT is particularly sensitive for diagnosing complete or high-grade obstruction of the small bowel and for determining the location and cause of obstruction. The CT examination is less sensitive, however, in patients with partial small bowel obstruction.[37] [38] In addition, CT is helpful if an extrinsic cause of bowel obstruction (e.g., abdominal tumors, inflammatory disease, or abscess) is suggested ( Fig. 46–16 ). CT has also been described as useful in determining bowel strangulation. Unfortunately, CT findings associated with strangulation are those of irreversible ischemia and necrosis. Figure 46-13 Plain abdominal radiographs of a patient with a complete small bowel obstruction. A, Supine film shows dilated loops of small bowel in an orderly arrangement, without evidence of colonic gas. B, Upright film shows multiple, short, air-fluid levels arranged in a stepwise pattern. (Courtesy of Melvyn H. Schreiber, M.D., The University of Texas Medical Branch.) 1338 Figure 46-14 Plain abdominal film shows complete bowel obstruction caused by a large radiopaque gallstone (arrow) obstructing the distal ileum. Figure 46-15 CT scan through the mid abdomen shows dilated small bowel loops filled with fluid and decompressed ascending and descending colon. These are typical CT findings in small bowel obstruction. (Courtesy of Eric Walser, M.D., The University of Texas Medical Branch.) Barium studies have been a useful adjunct in certain patients with a presumed obstruction. In particular, enteroclysis, which involves the oral insertion of a tube into the duodenum to instill air and barium directly into the small intestine and to follow the movement fluoroscopically, Figure 46-16 CT scan of the abdomen of a patient with a mechanical bowel obstruction secondary to an abscess in the right lower quadrant (arrow). Multiple dilated and fluid-filled loops of small bowel are noted. (Courtesy of Melvyn H. Schreiber, M.D., The University of Texas Medical Branch.) has been helpful in the assessment of obstruction.[36] [39] Enteroclysis has been advocated as the definitive study in patients in whom the diagnosis of lowgrade, intermittent small bowel obstruction is clinically uncertain. In addition, barium studies can precisely demonstrate the level of the obstruction as well as the cause of the obstruction in certain instances ( Fig. 46–17 ). The main disadvantages of enteroclysis are the need for nasoenteric intubation, the slow transit of contrast material in patients with a fluid-filled hypotonic small bowel, and the enhanced expertise required by the radiologist to perform this procedure. Ultrasound has been reported to be useful in pregnant patients where radiation exposure is a concern. Magnetic resonance imaging (MRI) has been described in patients with obstruction; however, it appears to be no better diagnostically than CT. To summarize, plain abdominal radiographs are usually diagnostic of bowel obstruction in more than 60% of the cases, but further evaluation (possibly by CT or barium radiography) may be necessary in 20% to 30% of cases. CT examination is particularly useful in patients with a history of abdominal malignancy, in postsurgical patients, and in patients who have no history of abdominal surgery and present with symptoms of bowel obstruction. Barium studies are recommended in patients with a history of recurring obstruction or low-grade mechanical obstruction to precisely define the obstructed segment and degree of obstruction. Laboratory examinations are not helpful in the actual diagnosis of patients with small bowel obstruction but are extremely important in assessing the degree of dehydration. Patients with a bowel obstruction should routinely have laboratory measurements of serum sodium, chloride, potassium, bicarbonate, and creatinine. The serial determination of serum electrolytes should be performed to assess the adequacy of fluid resuscitation. Dehydration may result in hemoconcentration, as noted by an elevated 1339 Figure 46-17 Barium study demonstrates jejunojejunal intussusception. (Courtesy of Melvyn H. Schreiber, M.D., The University of Texas Medical Branch.) hematocrit. This value should be monitored because fluid resuscitation results in a decrease in the hematocrit and some patients (e.g., those with intestinal malignancies) may require blood transfusions before surgery. In addition, the white blood cell count should be assessed. Leukocytosis may be found in patients with strangulation; however, an elevated white blood cell count does not necessarily denote strangulation. Conversely, the absence of leukocytosis does not eliminate strangulation as a possibility. Simple Versus Strangulating Obstruction The majority of patients with small bowel obstruction are classified as having simple obstructions that involve mechanical blockage of the flow of luminal contents without compromised viability of the intestinal wall. In contrast, strangulation obstruction, which usually involves a closed-loop obstruction in which the vascular supply to a segment of intestine is compromised, can lead to intestinal infarction. Strangulation obstruction is associated with an increased morbidity and mortality risk, and therefore recognition of early strangulation is important in differentiating from simple intestinal obstruction. “Classic” signs of strangulation have been described and include tachycardia, fever, leukocytosis, and a constant, noncramping abdominal pain. However, a number of studies have convincingly shown that no clinical parameters or laboratory measurements can accurately detect or exclude the presence of strangulation in all cases.[40] CT examination is useful only in detecting the late stages of irreversible ischemia. Various serum determinations, including lactate dehydrogenase, amylase, alkaline phosphatase, and ammonia levels, have been assessed with no real benefit. Initial reports have described some limited success in discriminating strangulation by measuring serum D-lactate, creatine phosphokinase isoenzyme (particularly the BB isoenzyme), or intestinal fatty acid binding protein; however, these are only investigational and cannot be widely applied to patients with obstruction. Finally, noninvasive determinations of mesenteric ischemia were described by Richards and associates[41] using a superconducting quantum interference device (SQUID) magnetometer to noninvasively detect mesenteric ischemia. Intestinal ischemia is associated with changes in the basic electric rhythm of the small intestine. Clinical assessment of this technique is under way. To reiterate, it is important to remember that bowel ischemia and strangulation cannot be reliably diagnosed or excluded preoperatively in all cases by any known clinical parameter, combination of parameters, or current laboratory and radiographic examinations. Treatment Fluid Resuscitation and Antibiotics Patients with intestinal obstruction are usually dehydrated and depleted of sodium, chloride, and potassium, requiring aggressive intravenous replacement with an isotonic saline solution such as lactated Ringer’s. Urine output should be monitored by the placement of a Foley catheter. After the patient has formed adequate urine, potassium chloride should be added to the infusion if needed. Serial electrolyte measurements, as well as hematocrit and white blood cell count, are performed to assess the adequacy of fluid repletion. Because of large fluid requirements, patients, particularly the elderly, may require central venous assessment and, in some cases, the placement of a Swan-Ganz catheter. Broad-spectrum antibiotics are given prophylactically by some surgeons based on the reported findings of bacterial translocation occurring even in simple mechanical obstructions. In addition, antibiotics are administered as a prophylaxis for possible resection or inadvertent enterotomy at surgery. Tube Decompression In addition to intravenous fluid resuscitation, another important adjunct to the supportive care of patients with intestinal obstruction is nasogastric suction. Nasogastric suction with a Levin tube empties the stomach, reducing the hazard of pulmonary aspiration of vomitus and minimizing further intestinal distention from preoperatively swallowed air. The use of long intestinal tubes (e.g., Cantor or Baker tubes) has been advocated by some groups. However, prospective randomized trials demonstrated 1340 no significant differences with regard to the decompression achieved, the success of nonoperative treatment, or the morbidity rate after surgical intervention compared with the use of nasogastric tubes.[42] Furthermore, the use of these long tubes has been associated with a significantly longer hospital stay, duration of postoperative ileus, and postoperative complications in some series. Therefore, it appears that long intestinal tubes offer no benefit in the preoperative setting over nasogastric tubes. Patients with a partial intestinal obstruction may be treated conservatively with resuscitation and tube decompression alone. Resolution of symptoms and discharge without the need for surgery have been reported in 60% to 85% of patients with a partial obstruction.[32] Enteroclysis can assist in determining the degree of obstruction, with higher-grade partial obstructions requiring earlier operative intervention. Although an initial trial of nonoperative management of most patients with partial small bowel obstruction is warranted, it should be emphasized that clinical deterioration of the patient or increasing small bowel distention on abdominal radiographs during tube decompression warrants prompt operative intervention. The decision to continue to treat a patient nonoperatively with a presumed bowel obstruction is based on clinical judgment and requires constant vigilance to ensure that the clinical course has not changed. Operative Management In general, the patient with a complete small bowel obstruction requires operative intervention. A nonoperative approach to selected patients with complete small intestinal obstruction has been proposed by some, who argue that prolonged intubation is safe in these patients provided that no fever, tachycardia, tenderness, or leukocytosis is noted. Nevertheless, one must realize that nonoperative management of these patients is undertaken at a calculated risk of overlooking an underlying strangulation obstruction and delaying the treatment of intestinal strangulation until after the injury becomes irreversible. Retrospective studies report that a 12- to 24-hour delay of surgery in these patients is safe but that the incidence of strangulation and other complications increases significantly after this time period.[43] The nature of the problem dictates the approach to management of the obstructed patient. Patients with intestinal obstruction secondary to an adhesive band may be treated with lysis of adhesions. Great care should be used in the gentle handling of the bowel to reduce serosal trauma and avoid unnecessary dissection and inadvertent enterotomies. Incarcerated hernias can be managed by manual reduction of the herniated segment of bowel and closure of the defect. The treatment of patients with an obstruction and a history of malignant tumors can be particularly challenging. In the terminal patient with widespread metastasis, nonoperative management, if successful, is usually the best course; however, only a small percentage of cases of complete obstruction can be successfully managed nonoperatively. In this case, a simple bypass of the obstructing lesion, by whatever means, may offer the best option rather than a long and complicated operation that may entail bowel resection. Patients with an obstruction secondary to Crohn’s disease will often resolve with conservative management if the obstruction is acute. If a chronic fibrotic stricture is the cause of the obstruction, then a bowel resection or strictureplasty may be required. Patients with an intra-abdominal abscess can present in a manner indistinguishable from those with mechanical bowel obstruction. CT is particularly useful in diagnosing the cause of the obstruction in these patients; drainage of the abscess percutaneously may be sufficient to relieve the obstruction. Radiation enteropathy, as a complication of radiation therapy for pelvic malignancies, may cause bowel obstruction. Most cases can be treated nonoperatively with tube decompression and possibly corticosteroids, particularly during the acute setting. In the chronic setting, nonoperative management is rarely effective and will require laparotomy with possible resection of the irradiated bowel or bypass of the affected area. At the time of exploration, it can sometimes be difficult to evaluate bowel viability after the release of a strangulation. If intestinal viability is questionable, the bowel segment should be completely released and placed in a warm, saline-moistened sponge for 15 to 20 minutes and then reexamined. If normal color has returned and peristalsis is evident, it is safe to retain the bowel. A prospective controlled trial comparing clinical judgment with the use of a Doppler probe or the administration of fluorescein for the intraoperative discrimination of viability found that the Doppler flow probe added little to the conventional clinical judgment of the surgeon.[44] In difficult borderline cases, fluorescein fluorescence may supplement clinical judgment. Another approach to the assessment of bowel viability is the “second look” laparotomy 18 to 24 hours after the initial procedure. This decision should be made at the time of the initial operation. A second-look laparotomy is clearly indicated in a patient whose condition deteriorates after the initial operation. Some groups have evaluated the efficacy of laparoscopic management of acute small bowel obstruction.[45] [46] The laparoscopic treatment of small bowel obstruction appears to be effective and leads to a shorter hospital stay in a highly selected group of patients. Patients fitting the criteria for consideration of laparoscopic management include those with (1) mild abdominal distention allowing adequate visualization, (2) a proximal obstruction, (3) a partial obstruction, and (4) an anticipated single-band obstruction. Currently, patients who have advanced, complete, or distal small bowel obstructions are not candidates for laparoscopic treatment. Unfortunately, the majority of patients with obstruction are in this group. Similarly, patients with matted adhesions or carcinomatosis or those who remain distended after nasogastric intubation should be managed with conventional laparotomy. Therefore, the future role of laparoscopic procedures in the treatment of these patients remains to be defined. 1341 Management of Specific Problems Recurrent Intestinal Obstruction All surgeons can readily (and most often painfully) remember the complicated patient with multiple previous abdominal operations and a “frozen” abdomen who presents with yet another bowel obstruction. An initial nonoperative trial is usually desirable and often safe. In those patients who do not respond conservatively, reoperation is required. This can often be a long and arduous procedure with great care taken to prevent enterotomies. In these difficult patients, various surgical procedures and pharmacologic agents have been tried in an effort to prevent recurrent adhesions and obstruction. External plication procedures have been described in which the small intestine or its mesentery is sutured in large, gently curving loops.[47] [48] Common complications have included the development of fistulas, gross leakage, peritonitis, and death. For this reason, and because of the low overall success rate, these procedures have largely been abandoned. Several series have reported moderate success with internal fixation or stenting procedures using a long intestinal tube inserted via the nose, a gastrostomy, or even a jejunostomy and left in place for 2 weeks or longer.[49] [50] Complications associated with these tubes include prolonged drainage of bowel contents from the tube insertion site, intussusception, and difficult removal of the tube, which may require surgical reexploration. Pharmacologic agents, including corticosteroids and other anti-inflammatory agents, cytotoxic drugs, and antihistamines, have been used with limited success. The use of anticoagulants, such as heparin, dextran solutions, dicumarol, and sodium citrate, has modified the extent of adhesion formation, but their side effects far outweigh their efficacy. Intraperitoneal instillation of various proteinases (e.g., trypsin, papain, and pepsin), which cause enzymatic digestion of the extracellular protein matrix, has been unsuccessful. Hyaluronidase has been of questionable value, and conflicting results have been obtained with fibrinolytic agents such as streptokinase, urokinase, and fibrinolytic snake venoms. In a prospective, multicenter trial, Becker and colleagues[51] reported that the use of a hyaluronate-based, bioresorbable membrane reduced the incidence and severity of postoperative adhesion formation. Another study by Vrijland and associates found that placement of this membrane reduced the severity, but not the incidence, of postoperative adhesion in patients undergoing a Hartmann procedure.[52] This could represent a significant advance if the long-term incidence of obstruction is likewise shown to be reduced. To date, the most effective means of limiting the number of adhesions is a good surgical technique, which includes the gentle handling of the bowel to reduce serosal trauma, avoidance of unnecessary dissection, exclusion of foreign material from the peritoneal cavity (the use of absorbable suture material when possible, the avoidance of excessive use of gauze sponges, and the removal of starch from gloves), adequate irrigation and removal of infectious and ischemic debris, and preservation and use of the omentum around the site of surgery or in the denuded pelvis.[53] Acute Postoperative Obstruction Small bowel obstruction that occurs in the immediate postoperative period presents a challenge in both the diagnosis and treatment. Diagnosis is often difficult because the primary symptoms of abdominal pain and nausea or emesis may be attributed to a postoperative ileus. Electrolyte deficiencies, particularly hypokalemia, can be a cause of ileus and should be corrected. Plain abdominal films are usually not helpful in distinguishing an ileus from obstruction. CT may be useful in this regard and, in particular, enteroclysis studies may be quite helpful in determining if an obstruction exists and, if so, then the level of the obstruction. Conservative management should be attempted for a partial obstruction. Complete obstruction requires reoperation and correction of the underlying problem. Ileus An ileus is defined as intestinal distention and the slowing or absence of passage of luminal contents without a demonstrable mechanical obstruction. An ileus can result from a number of causes, including drug induced, metabolic, neurogenic, and infectious ( Box 46–2 ). Pharmacologic agents that can produce an ileus include anticholinergic drugs, autonomic blockers, antihistamines, and various psychotropic agents, such as haloperidol and tricyclic antidepressants. One of the more common causes of drug-induced ileus in the operative patient is the use of opiates, such as morphine or meperidine. Metabolic causes of ileus are common and include hypokalemia, hyponatremia, and hypomagnesemia. Other metabolic causes include uremia, diabetic coma, and hypoparathyroidism. Neurogenic causes of an ileus include postoperative ileus, which occurs after abdominal operations. Spinal injury, retroperitoneal irritation, and 1342 orthopedic procedures on the spine or pelvis can result in an ileus. Finally, a number of infectious causes can result in an ileus; common infectious causes include pneumonia, peritonitis, and generalized sepsis from a nonabdominal source. Patients often present in a manner similar to those with a mechanical small bowel obstruction. Abdominal distention, usually without the colicky abdominal pain, is the typical and most notable finding. Nausea and vomiting may occur but may also be absent. Patients with an ileus may continue to pass flatus and diarrhea, and this may help distinguish these patients from those with a mechanical small bowel obstruction. Radiologic studies may help to distinguish ileus from small bowel obstruction. Plain abdominal radiographs may reveal distended small bowel as well as large bowel loops. In cases that are difficult to differentiate from obstruction, barium studies may be beneficial. The treatment of an ileus is entirely supportive with nasogastric decompression and intravenous fluids. The most effective treatment to correct the underlying condition may be aggressive treatment of the sepsis, correction of any metabolic or electrolyte abnormalities, and discontinuation of medications that may produce an ileus. Pharmacologic agents have been used but for the most part have been ineffective. Drugs that block sympathetic Box 46-2. Causes of Ileus † Post laparotomy Metabolic and electrolyte derangements (e.g., hypokalemia, hyponatremia, hypomagnesemia, uremia, diabetic coma) Drugs (e.g., opiates, psychotropic agents, anticholinergic agents) Intra-abdominal inflammation Retroperitoneal hemorrhage or inflammation Intestinal ischemia Systemic sepsis † Adapted from Turnage RH, Bergen PC: Intestinal obstruction and ileus. In Feldman M, Scharschmidt FG, Sleisenger MH (eds): Gastrointestinal and Liver Disease. Pathophysiology/Diagnosis/Management. Philadelphia, WB Saunders, 1998, pp 1799– 1810. input (e.g., guanethidine) or stimulate parasympathetic activity (e.g., bethanechol or neostigmine) have been tried. In addition, hormonal manipulation, using cholecystokinin or motilin, has been evaluated, but the results have been inconsistent. Intravenous erythromycin has been ineffective, and cisapride, although apparently beneficial in stimulating gastric motility, does not appear to alter intestinal ileus. Bookmark URL: /das/book/view/41787982-18/1235/467.html/top Copyright © 2004 Elsevier Inc. All rights reserved. www.mdconsult.com