The initial management of patients with small bowel obstruction should focus on aggressive fluid resuscitation and nasogastric decompression of the stomach to prevent further accumulation of intestinal fluid and air; in addition, nasogastric decompression decreases the potential for aspiration and relieves vomiting. These therapies should be instituted in all patients, whether they are treated operatively or undergo a trial of nonoperative management. Blood should be analyzed for serum electrolyte concentrations, typed and screened for potential transfusion, and, when necessary, arterial blood gases should be analyzed as well.
The most important initial step in management is vigorous crystalloid fluid resuscitation. Patients with small bowel obstruction often present with profound volume losses and may require large amounts of isotonic crystalloid solutions, such as normal saline (0.9% NaCl) or lactated Ringer's solution with additional potassium when necessary. Resuscitation should be guided by urine output, provided the patient is hemodynamically stable and has normal renal function. Patients who are hemodynamically unstable or have impaired cardiac, pulmonary, or renal function may require monitoring of central venous or pulmonary arterial pressure to better evaluate their volume status. Colloid solutions, such as 5% albumin or hetastarch, have little or no role in the resuscitation of patients with a small bowel obstruction. Steps should also be taken to correct metabolic or electrolyte imbalances, which may be severe. Specifically, in patients who have experienced prolonged vomiting, potassium and chloride should be measured to diagnose hypokalemic, hypochloremic alkalosis and replaced appropriately. Though potassium replacement is a critical component of therapy, replenishment of this electrolyte should begin only after renal function has been established by good urine output. Volume resuscitation, electrolyte replacement, and establishment of adequate urine output are critical before operative therapy is undertaken. Broad-spectrum antibiotics should be given to patients within an hour of the incision to prophylaxis against surgical site infection, but, otherwise, antibiotics have no defined utility in the later postoperative period or in those patients initially managed nonoperatively.
Most surgeons believe that nasogastric decompression is important to prevent further intestinal distention from swallowed air and to limit aborad transit of gastric contents. In addition, nasogastric decompression also helps to prevent aspiration during vomiting and on induction of general anesthesia. Symptomatically, gastric decompression helps relieve abdominal distension and can improve ventilation in patients with respiratory compromise.
Historically, long intestinal tubes placed distal to the pylorus were used to relieve small intestinal distention under the assumption that intestinal decompression may be therapeutic if related to adhesions, because the decompressed bowel may detort and thereby relieve the mechanical obstruction (Fig. 29-13). Success rates of up to 90% have been reported in some series of patients treated with a long nasointestinal tube.64 In contrast, however, most prospective and retrospective studies have failed to demonstrate the superiority of nasointestinal versus nasogastric intubation,64,65 making the added expense of fluoroscopic or endoscopic placement of a nasointestinal tube unwarranted. Use of these long intestinal tubes has fallen out of favor, and they are of historic interest in the preoperative treatment of small bowel obstruction.
Abdominal radiograph showing distal passage of a long nasointestinal decompression tube into the small bowel distal to the ligament of Treitz.
Nonoperative management of intestinal obstruction should be considered only in patients with uncomplicated intestinal obstruction in the absence of peritonitis, a progressive leukocytosis, or impaired bowel wall perfusion on imaging. When indicated, this approach is reported to be successful in 62–85% of patients.43,66–69 The rate of success is influenced likely by patient selection, type of bowel obstruction (complete versus partial), etiology (eg, adhesions, hernia, or neoplasm), and the surgeon's threshold for conversion to operative management. Patients successfully managed nonoperatively require lesser hospital stays66,67 and avoid the morbidity or convalescence necessitated by an operation. Few studies have compared the long-term outcomes of patients with a small bowel obstruction treated nonoperatively versus operatively. One such study with over 4 years of follow-up reported by Landercasper and colleagues70 found a recurrence rate of 29% in patients managed operatively versus a recurrence rate of 53% for patients managed nonoperatively. Even though the recurrence rates may be greater with nonoperative management, the authors point out that about half of the patients managed nonoperatively never developed a recurrent small bowel obstruction.
A recent study by Rocha et al71 used the radiologist definition of “high-grade” obstruction and reported that in these patients, comparing those treated conservatively versus those treated by operation, the conservatively treated patients had a significantly greater readmission rate at 5 years (24 vs 9%) than those treated operatively. Use of this radiologic finding may potentially extend the “indication” when criteria are met for high grade but not complete obstruction.
Absolute contraindications to nonoperative management include suspected ischemia, large bowel obstruction, closed-loop obstruction, acutely incarcerated or strangulated hernia, and perforation. In an attempt to define which patients with an uncomplicated small bowel obstruction can be successfully treated nonoperatively, Chen and colleagues43 used an orally administered, water-soluble contrast agent (Urografin) to study 116 patients with small bowel obstruction. The presence of contrast material within the colonic lumen within 8 hours of oral administration had an accuracy of 93% for predicting which patients would benefit from nonoperative therapy. In their study, only 19% of patients with a small bowel transit time of more than 8 hours had resolution of their obstruction with nonoperative treatment. One of the criteria for conversion to operative treatment was the failure of contrast to reach the colon within 8 hours. Therefore, the 81% failure rate in patients in whom contrast never reached the colon within 8 hours after administration may be artificially high based on study design.
A relative contraindication to nonoperative management is complete small bowel obstruction, that is, dilated small intestine with no air in the bowel distally. In a prospective study by Fleshner and associates,67 all patients with an uncomplicated small bowel obstruction underwent an initial trial of nonoperative management. They were able to manage 45% of patients successfully with a complete obstruction (by their definition), while 66% of patients with a partial obstruction were successfully managed nonoperatively, all with no mortality. These investigators, however, did not describe the incidence of intestinal ischemia at operation based on the presence or absence of complete versus partial obstruction. Another study by Fevang and colleagues66 reported a 42% success rate in managing patients with a complete small bowel obstruction nonoperatively. When they compared complete and partial obstructions managed nonoperatively, there was a greater rate of bowel strangulation (10 vs 4%) and need for resection (14 vs 8%) in the group with complete obstruction at the time of operation for treatment failure. This group noted a mortality of 6% in patients with a complete obstruction initially managed nonoperatively versus 0% mortality for patients with a partial obstruction initially managed nonoperatively. Other groups have also noted a greater rate of ischemic bowel coupled with a lesser success rate in those patients with a complete obstruction managed nonoperatively.65,72 These studies and the unreliability of clinical acumen to recognize strangulation obstruction accurately have led many surgeons to favor early operation for all patients with a complete small bowel obstruction,69 leading to the often-quoted phrase “The sun should never rise or set on a (complete) small bowel obstruction.” If nonoperative management is attempted in a patient with complete obstruction, the decision should be made with the understanding that there is a definite risk of overlooking an underlying strangulation obstruction,72 and thus there should be a low threshold for operative intervention in patients with complete obstruction.
When patients with a small bowel obstruction are initially managed nonoperatively, vigilant attention must be paid to volume resuscitation, electrolyte homeostasis, and nasogastric decompression. Patients managed nonoperatively require the same aggressive resuscitation and realistic replacement of daily losses with an appropriate crystalloid solution and electrolyte replacement as patients who are managed operatively. Fluid replacement should take into consideration the volume and electrolyte loss in the output of the nasogastric tube, urinary output, and insensible losses. Electrolytes should be monitored frequently and corrected as necessary. Delayed correction of potassium and magnesium concentrations may lead to delayed return of bowel function and misdiagnosis of obstruction versus ileus.
Adequate proximal decompression is important to allow the bowel an opportunity to become unobstructed. This concept is accomplished by maintaining a functioning nasogastric tube. If the patient becomes progressively more distended or develops vomiting, tube placement should be evaluated and tube function confirmed by bedside evaluation. Standard nasogastric tubes should be inserted, such that the second of four marks is evident at the tip of the nares. The first mark is 40 cm from the tip of the tube, that is, the normal distance from the nares to the esophagogastric junction. Thus, if all four marks are outside the nares, the tube most likely is not in the stomach. Likewise, if no marks are visible, the tube is coiled within the stomach or is in the duodenum. On occasion, an abdominal radiograph is necessary to confirm placement. If the tube is noted on radiograph to be out of position, it should be repositioned and imaged again for proper placement. On evaluation, the tube should be connected to the suction apparatus, sumping properly (if the tube has a sump port), and should be checked for patency by flushing and aspirating water through the suction lumen. Oral intake should be minimized in the presence of a nasogastric tube, and, when allowed for patient comfort, the volume of ingested fluid should be recorded carefully to allow quantitation of gastric aspiration. In addition, the tube should never be “clamped” for prolonged periods of time, because by traversing the esophagogastric junction, the tube will lead to an incompetent lower esophagogastric sphincter and potential aspiration. Connection of the tube to a drainage bag for a brief trial is an appropriate alternative to clamping and may be used as a test to determine patient readiness for nasogastric tube removal.
Once the decision has been made to pursue operative management, steps should be taken to prevent peri- and postoperative complications. Preoperative preparation includes assessing the medical fitness of the patient and, as time allows, taking steps to optimize the patient's medical status. Special consideration should be given to ensure that the patient has been resuscitated adequately, appropriate antibiotics have been given, and any electrolyte abnormalities have been addressed. Consideration should be given to the administration of beta-blockers to patients with cardiovascular comorbidities and especially to those who were on beta-blockers prior to admission.73 A nasogastric tube should already be in place to decrease the risk of aspiration during the induction of anesthesia; nevertheless, a “crash,” rapid-sequence induction will still be necessary to protect the airway during intubation, despite the presence of a nasogastric tube.
Several decisions must be made with regard to operative planning to provide the safest approach that will afford the best outcome for each individual patient. The choice of operative approach and incision is important to allow the surgeon adequate exposure and visibility. A laparoscopic approach should at least be considered in some patients.74 When an obstruction develops in the early postoperative period, the original incision should be reopened provided extensive adhesions were not present originally. Safe entrance into the peritoneal cavity may be best achieved by approaching this from the extremes of the previous incision rather than going directly through the midportion of the incision. In patients without a history of prior abdominal operation or those who are remote from their original operation, a midline celiotomy affords the best exposure to all four quadrants of the abdomen. For example, patients with upper oblique, transverse, or subcostal type incisions may have pelvic adhesions that are difficult to address from the upper abdomen, especially through a high transverse incision.
Once within the abdominal cavity, the first step is to identify the site and cause of obstruction. If the point of obstruction is not obvious, decompressed bowel distal to the obstruction can be identified and followed proximally to the point of obstruction. Care should be taken when handling the obstructed bowel at or near the point of obstruction when acutely obstructed, especially if it is fixed at an apparent site of obstruction or if it is ischemic. This region is at high risk for strangulation and infarction, making it more likely to rupture with spillage of bacteria-laden enteric contents into the abdomen. The dilated bowel proximal to the offending obstruction is often thin-walled and at increased risk for perforation if the obstruction is acute. After the offending obstruction has been corrected, a thorough exploration of all four quadrants should always be undertaken to ensure that all intestinal injuries are repaired, nonviable segments are resected, and a second site of obstruction or fixation is not overlooked; this concept is especially true for volvulated segments of small bowel where two points of fixation are often present. Sometimes obstructing bands traversing a sizeable part of the peritoneum can affect more than one loop of bowel. When a small bowel resection is necessary, intestinal continuity of the small bowel can be accomplished generally with a primary anastomosis unless there is generalized peritonitis and the edges of the remnant bowel are of questionable viability. When an intestinal anastomosis is performed, the discrepancy in bowel diameter and wall thickness between the obstructed proximal bowel and decompressed distal bowel are important factors in choosing anastomotic techniques. The surgeon may consider a side-to-side or end-to-side anastomosis in situations where massive dilation of the proximal bowel makes an end-to-end anastomosis difficult technically. In addition, a stapled anastomosis may be less safe in cases where a large discrepancy in bowel wall thickness exists or when there is bowel wall edema, because uniform approximation of the tissue for a given staple height may not be possible.
Abdominal closure may be difficult to achieve when the small bowel is massively dilated. In these cases, intraoperative intestinal decompression will facilitate closure. Techniques described for intraoperative decompression include manual retrograde decompression into the stomach (with careful handling of the obstructed bowel), intraoperative passage of a long nasointestinal tube, and, rarely, performance of a controlled enterotomy with passage of a decompressing tube; the latter technique is strongly discouraged except under very select circumstances, such as tremendous intestinal distention preventing abdominal closure or distention threatening bowel viability. Manual retrograde decompression of luminal contents around the ligament of Treitz, through the pylorus, and into the stomach allows for aspiration through the nasogastric tube by the anesthetist.75 This maneuver is the safest and quickest technique, because it allows closure of the abdominal wall while avoiding an enterotomy and excessive manipulation of the bowel. When decompressing the bowel, care must be taken to handle the inflamed and distended bowel gently, because experimental studies have demonstrated an increased rate of bacteremia after extensive manipulation of obstructed bowel.76 In addition, the anesthesia team should be alerted to the maneuver to be certain that their nasogastric tube is functioning well. Although intraoperative decompression has not been shown to decrease the rate of postoperative complications or the speed of return of bowel function, it certainly does make the closure easier, faster, and safer.
Nonviable bowel needs to be identified and resected. Resection should be undertaken with caution, especially in patients with a limited length of bowel from a previous resection or those with large sections of ischemia. Adjuncts for determining bowel viability include the use of Doppler US and intravenous fluorescein. These tests are relatively subjective, should be used with caution, and are only adjuncts to sound clinical judgment. In patients who would otherwise be left with less than two-thirds of their original bowel length after resection of all bowel of questionable ischemia, consideration may be given to resecting all the grossly necrotic or obviously nonviable bowel, but preserving bowel of questionable viability and performing an end ostomy or a second-look procedure 12–24 hours later, particularly if the viability of the ends to be anastomosed is in question.
In patients with an incurable malignant small bowel obstruction, if the offending obstruction is unable to be released or it is deemed unsafe to attempt to dissect out the point of obstruction, intestinal bypass can be performed. Bypass relieves the obstruction while reestablishing intestinal continuity and preventing a closed-loop obstruction; however, the advisability of a bypass procedure should be considered. For instance, in the presence of carcinomatosis, a bypass may prove fastest and safest, because patient survival will be short. In contrast, patients with certain chronic inflammatory diseases will remain at risk for ongoing problems (eg, Crohn's disease or tuberculosis) related to the inflammation in any “bypassed” segment and therefore such patients may be served better by resection than simple bypass.
The surgeon should at least consider an initial laparoscopic, minimal access approach in patients with uncomplicated small bowel obstruction. Laparoscopy is known to cause fewer adhesions than open laparotomy77 and in that regard may be superior to laparotomy for the treatment of adhesive small bowel obstruction. Several studies have shown laparoscopy to be a safe and effective means of access for the operative treatment of small bowel obstruction.74,78–80 When successful, a laparoscopic approach decreases both the duration of hospital stay74,78,80 and the complication rate.78,80 Patients successfully treated laparoscopically appear to have more rapid return of bowel function.78,80 These reports showing a large benefit to laparoscopic treatment for small bowel obstruction, however, need to be interpreted carefully. Many series compare patients treated laparoscopically to those who failed initial laparoscopic treatment. Those patients unable to be treated laparoscopically likely had more extensive adhesions or complicated pathology possibly requiring resection. Operative intervention in these patients would be more involved and complex whether done open or laparoscopically. One would expect these patients to have greater hospital stays, greater complication rates, and slower return of bowel function independent of the method of abdominal access. In addition, the skill and confidence level of the surgeon should weigh in the decision to approach the obstruction laparoscopically. First, if the surgeon lacks skill in using moderately advanced laparoscopic techniques, an open operation may be a better choice. Similarly, if the patient is known to have a frozen abdomen or has either a severely distended, tense abdomen with markedly distended bowel or multiple dense adhesions at the time of insertion of the laparoscope, conversion to an open procedure is wise. Initial access for creating the pneumoperitoneum in a patient with a small bowel obstruction is achieved best by a fully open approach under total visual control, but limited data support this concept.
Recurrent Small Bowel Obstruction
Although the results of individual studies vary, between 4 and 34% of patients will experience recurrent small bowel obstruction regardless of management modality.5,66,68–70,81,82 This wide range of recurrence rates likely results from variations both in the duration and quality of follow-up between studies as well as the etiology of the original bowel obstruction. Recurrent obstruction is more common in patients with multiple adhesions, matted adhesions, previous admissions for small bowel obstruction, and previous pelvic, colonic, and rectal surgery.5,70
In the past, numerous attempts have been made by surgeons to control the formation of adhesions in an effort to prevent future mechanical obstruction. A simple technique to prevent adherence of the bowel to the undersurface of the fascial incision is to interpose the omentum between the bowel and the incision. Theoretically, when adhesions from the posterior surface of the anterior abdominal wall form after omental interposition, they will involve the omentum and not the underlying bowel. Other more intricate techniques, such as the Noble plication and the Childs-Phillips transmesenteric placation, have been described in the more distant past. These procedures involve the suturing adjacent loops of small bowel into an orderly pattern in an attempt to plicate the bowel permanently in a position that will not allow mechanical obstruction.82 Although initial reports were encouraging, the Noble and Childs-Phillips procedures have multiple complications and are of historic interest only. The problems associated with plication procedures have included prolonged operative times and high rates of enterocutaneous and enteroenteric fistula, abdominal abscess, and wound infection; moreover, the rate of recurrent obstruction is as great as 19%, questioning seriously their efficacy. Attempts to “plicate” the bowel with a long intestinal tube, so-called intraluminal plication, are also of questionable efficacy.
In some patients, it will become evident during the course of the operation that complete or adequate adhesiolysis is not possible or may risk vascular injury to a substantial segment of bowel because of the acute inflammatory nature or tenacity of the adhesions. This situation is especially common when celiotomy is deemed necessary or performed too soon after a previous intra-abdominal procedure (see the following section on early postoperative small bowel obstruction). This situation is especially common when the previous operation involved an extensive adhesiolysis. In such situations, it may be important to control any bowel injuries present, end any further dissection, and conclude the operation to prevent further bowel injury and its potential sequelae. This approach has been used by the senior author five times in 25 years of practice. This “conservative” approach may allow the acute inflammatory process to resolve or regress (often 3–6 months); should the obstruction not resolve by 6 months, the plan should be to reoperate at a time when the adhesions have matured, allowing a more controllable and much safer adhesiolysis. In some situations, the mature decision might be to provide proximal diversion with a proximal enterostomy if the obstruction has no chance for resolution (eg, due to malignancy or radiation) or if a more distal bowel repair is tenuous, or to place a tube gastrostomy for diversion and patient comfort. Pursuing a futile attempt to complete the adhesiolysis puts the patient at risk for serious bowel injury or devascularization injury necessitating resection of otherwise normal bowel with the risk of enterocutaneous fistulation or subsequent short bowel syndrome.
Over the last 100 years, multiple approaches have been employed in an attempt to prevent the formation of unwanted postoperative adhesions. These attempts include, among others, the use of cow cecum, shark peritoneum, sea snake venom, and fish bladder, as well as multiple fluids, mechanical barriers, and gels.81 The concept of separating injured surfaces mechanically to prevent adhesions is a very attractive one. The formation of fibrin bridges (and thus adhesions) may be preventable by separating injured surfaces in the postoperative interval during the critical period of healing and mesothelialization by application of an absorbable “biofilm.” Estimates of the minimum amount of time necessary for an impermeable or semipermeable barrier to prevent adhesion formation appear to be about 36 hours. Some authors have placed a Silastic sheet between two injured peritoneal surfaces; when left in place for 36 hours, no adhesions formed between these surfaces thereafter.17 Others have postulated that separating the surfaces at risk for the first 5–7 days until full mesothelialization occurs would seem to be most effective; however, the barrier should not incite its own inflammatory response and should not decrease fibrinolytic activity or suppress access to oxygen. The ideal product, therefore, should be bioabsorbable (preferably via a process such as hydrolysis), last only about 5–7 days, be easy to apply, be interposed between all injured surfaces, and not itself incite an inflammatory reaction.
The most effective method to date has been the application of a sheet of bioresorbable, hyaluronate membrane; this approach has been shown to decrease the formation of adhesions at the site of application.81,83 In addition, two recent systematic reviews have demonstrated that use of this product, indeed, decreases adhesion formation at the site of application.84,85 These reviews, however, both support the observation that use of a hyaluronate membrane application did not decrease the incidence of postoperative bowel obstruction nor did it decrease the need for operative intervention for intestinal obstruction. Furthermore, if the membrane is wrapped around an intestinal anastomosis, the leak rate is increased.
Initial concerns that were raised over the safety of hyaluronate barriers appear unfounded, with the exception of iron cross-lined hyaluronate that was withdrawn from the market. A prospective, randomized, controlled trial showed that hyaluronate barriers did not increase the risk of intra-abdominal abscess or pulmonary embolism83; however, in a post-hoc subgroup analysis of 289 patients in whom the hyaluronate membrane was wrapped around a fresh anastomosis, the rates of leak, fistula formation, peritonitis, abscess, and sepsis were increased. Based on these studies and assumptions, the use of hyaluronate membranes in elective abdominal surgery does decrease the amount of postoperative adhesions at the site of application but does not decrease the incidence of intestinal obstruction or the need for future reoperation for obstruction. Use of these products requires careful consideration, because they are expensive and their clinical benefit appears to be relatively low.
Other materials or substances are being developed that someday may move to the forefront of adhesion prevention. These include gel and liquid preparations such as hyaluronic acid and carboxymethylcellulose, hydrogel, fibrin sealant, and protein polymers. Other adhesion barriers include oxidized regenerated cellulose (ORC). ORC has been well studied and does help prevent adhesion formation, but its use requires a blood-free field that at times is not practical to achieve. The use of ORC, like hyaluronate membranes, has not been shown to decrease the incidence of subsequent adhesive small bowel obstruction.86
Early Postoperative Small Bowel Obstruction
Early postoperative small bowel obstruction is a relatively uncommon problem but remains a very real dilemma encountered in every practice performing abdominal operations. Although the surgery literature defines early obstruction from 30 days to 6 weeks after the original operation, for the purposes of this chapter, we will consider early intestinal obstructions as those occurring within 6 weeks of operation. Obstructions occurring after 6 weeks are managed similarly to other bowel obstructions.
It is often difficult, if not impossible, to distinguish early obstruction from postoperative ileus, but fortunately the management is usually quite similar. Patients with suspected early mechanical small bowel obstruction should be managed initially by nasogastric decompression, fluid resuscitation, and correction of any electrolyte abnormalities. After a thorough physical examination and the decision that emergent intervention is not indicated, a search for the cause of obstruction should be undertaken. CT can be helpful in determining the etiology of an obstruction but is notoriously unreliable at differentiating ileus versus partial obstruction. Obstructions caused by extrinsic bowel compression amenable to percutaneous correction, including fluid collections, abscesses, and hematomas, may be diagnosed and treated by CT-guided drainage. CT may be able to detect those causes of obstruction that will likely require operative intervention, such as internal hernia, fascial dehiscence, and uncontrolled anastomotic leak. Early CT may be warranted in patients who had a laparoscopic operation and have signs of early obstruction, because a port site hernia may be evident and would require prompt operation.
Generally, two categories of patients with early postoperative small bowel obstruction have been recognized.69 The first category includes those in whom the obstruction becomes evident within 10 days of an abdominal operation. Conservative management is advised usually as long as signs and symptoms of ischemia and strangulation obstruction are not present and other remediable causes have been excluded. Patients within this time frame are not at a substantially increased risk of bowel-related complications after celiotomy, provided there are no internal hernias and, if the original operation was done laparoscopically, that port site hernias can be excluded. It is important to rule out correctable causes of extrinsic compression and reverse any electrolyte abnormalities, especially if ileus is also suspected. Strangulation obstruction, albeit rare, can occur in this group of patients, and thus a high index of suspicion must always be maintained; the etiology of a strangulation obstruction in this group is almost never related to adhesions but rather to some surgical misadventure, such as internal hernia, an overlooked segment of ischemia at the original celiotomy, bowel entrapped in the fascial closure, or an overlooked abdominal wall hernia.
The second category of patients is those presenting between 10 days and 6 weeks after operation.69 Conservative management is also advised strongly whenever possible for patients in this category as well. The risk of iatrogenic bowel complications during and after reoperation so early after celiotomy increases dramatically in this group secondary to the dense adhesions often present during this period after abdominal operation. The time period from 7–10 days up until 6–12 weeks postoperatively represents the window when the greatest inflammatory reaction is present intraperitoneally. The developing adhesions are highly vascular and friable. If the patient had no or very minimal adhesions at the time of celiotomy, reoperation is warranted; however, in a small, unpredictable group of patients without any previous adhesions and reliably so in those with dense adhesions that had required substantial adhesiolysis at the time of original celiotomy, an acute inflammatory reaction involving the peritoneal surfaces may agglutinate adjacent loops of bowel, often involving the omentum and mesenteric surfaces.
Operations performed during this period have a much greater rate of iatrogenic injury and subsequent fistula formation. Those patients not responding to conservative management during this period are best placed on parenteral nutrition until the obstruction resolves or they are more than 6–12 weeks out from their last celiotomy. At this time, the decision to reoperate is made based on several considerations. First, if the patient had relatively few adhesions at the time of celiotomy, reexploration at 6 weeks to 3 months postoperatively may be warranted. In contrast, in those patients who required an extensive adhesiolysis at the time of original celiotomy, many experienced surgeons wait for a full 6 months prior to reoperation for several reasons: (1) by 6 months, the adhesions are reliably less vascular and more mature; (2) reoperation prior to 3 months may reveal a frozen abdomen in which the obstruction may be unable to be dissected free safely; and (3) about half the time, the obstruction will resolve as the adhesions mature (see the earlier section on recurrent small bowel obstruction).
Bowel Obstruction after Roux-En Y Gastric Bypass Surgery
As with all other operations and maybe more so in the current era of laparoscopic Roux-en-Y gastric bypass (RYGB), bowel obstruction is a worrisome complication after bariatric surgery for morbid obesity. Estimates of the rate of bowel obstruction after RYGB vary within a reported range of 0.3% to greater than 9% depending on the technique used to perform the operation. The rate of bowel obstruction appears to be less after open RYGB, but there are no large prospective studies comparing laparoscopic to open procedures at this time. In a large, collected review of more than 9500 patients undergoing laparoscopic RYGB, the rate of bowel obstruction was 3.6%.87 Although some controversy exists, most authors suggest that the rate of bowel obstruction is less with use of an antecolic versus a retrocolic orientation of the Roux limb for the gastric bypass.87–90 Bowel obstruction after RYGB can occur secondary to a variety of etiologies; however, the four most common etiologies in decreasing order of frequency are internal hernia, adhesive obstruction, stenosis at the jejunojejunostomy, and incisional hernia.
The diagnosis of bowel obstruction after laparoscopic RYGB is more difficult than after other surgical procedures secondary to the altered GI anatomy produced by the procedure and the often less typical response of the patient with morbid obesity. After RYGB, the symptoms of bowel obstruction can be vague, and, because the most common etiology is internal hernia, the symptoms are often intermittent. Abdominal pain is the most common symptom present in 82% of patients in one large series and, importantly, nausea and vomiting were seen in fewer than 50% of patients in this series. All three symptoms were present in only 28% of patients.89 Unfortunately, imaging studies also have a lesser sensitivity for bowel obstruction in patients after RYGB, with reported sensitivities of 51, 57, and 33% for CT, UGI contrast study, and plain abdominal radiography, respectively.89 When patients with unexpected GI symptoms after RYGB are assessed, a very high index of suspicion for bowel obstruction is warranted. Given the frequency of internal hernia as a cause of postoperative bowel obstruction and the low sensitivity of radiologic evaluation for bowel obstruction in patients after RYGB, a low threshold for laparoscopic exploration is warranted in patients with suspected bowel obstruction.
Internal hernia is the most common cause of bowel obstruction after RYGB. Anatomically, there are three different types of internal hernias seen after RYGB. All three types of internal hernias are transmesenteric defects created during the formation of the Roux limb and are illustrated in Fig. 29-3. The so-called Peterson hernia occurs in the infracolic compartment through the potential space between the mesentery of the Roux limb, the transverse mesocolon, and the retroperitoneum and can be seen with either an antecolic or retrocolic Roux limb. Herniation through the mesenteric defect created by the jejunojejunostomy is the second site of internal hernia observed after RYGB and can occur with both antecolic and retrocolic gastric bypass. Herniation through the mesenteric defect in the transverse mesocolon created by passage of the retrocolic Roux limb is the third type of internal hernia observed in RYGB and is only seen in retrocolic gastric bypass; this type of internal hernia was the most common type before the importance of meticulous closure of this defect was appreciated. Most authors believe that bowel obstruction after RYGB is substantially more common after laparoscopic retrocolic bypass, with reported rates of 3.2–5.1 % after retrocolic and 0.3–1.7% after antecolic bypass reported in the largest series.87,90 Meticulous closure of all potential hernia spaces with nonabsorbable suture at the time of RYGB is the best way to prevent internal hernia; however, care must be taken when closing the mesocolic defect, because obstruction at the mesocolic window from tight scar formation has also been reported as a cause of bowel obstruction after RYGB.91 When operating on a patient with internal hernia after RYGB, careful closure of the hernia defect with nonabsorbable suture after reduction in the hernia is the treatment of choice.
The management of radiation enteropathy is often difficult and frustrating. The clinical presentation can be quite diverse with recurrent intermittent small bowel obstruction, a true, chronic, persistent partial small bowel obstruction, or chronic diarrhea/malabsorption. Operative management is often extremely challenging secondary to the dense adhesions and chronic inflammatory reaction present after radiation. These patients also tend to develop recurrent areas of enteropathy (progression of disease) in bowel that appeared normal previously, because this ischemic disease is an ongoing and progressive chronic process. The need for operative correction with a resection and anastomosis has been reported to have a mortality rate as high as 21% in some series.82 Patients with radiation enteropathy also have a high rate of anastomotic leak and fistulation after operation because of the compromised vascular supply to the bowel. These effects are magnified in patients with atherosclerosis, hyperlipidemia, or type 2 diabetes. For these reasons, a cautious, conservative approach to the patient with radiation enteropathy is warranted whenever possible.
When operative management is necessary, the surgeon must decide between resection, bypass of the affected segment, or adhesiolysis. As mentioned previously, resection has been reported to have a high mortality rate with a 36% incidence of leak after primary anastomosis.82 In the same study, bypass of the affected segment had a 10% mortality and 6% leak rate. Surgeons advocating aggressive resection back to healthy bowel, however, have reported leak rates between 0 and 8% when confounding conditions (abscess, fistula, necrosis, or recurrent cancer) were absent; such an aggressive approach may require an extensive resection but often involves resection of nonfunctional bowel anyway. Worry of a short bowel syndrome is always a concern, especially because the involved bowel is usually the distal ileum.
Most surgeons approach the treatment of radiation enteropathy cautiously. In those patients with recurrent cancer and radiation enteropathy, treatment should consist of palliative bypass of the diseased segment with creation of an anastomosis in visibly normal tissue. If the obstructive process is localized, wide resection back to healthy, nonirradiated tissue (if possible) with primary anastomosis is acceptable, provided adequate absorptive area is preserved. Usually this means anastomosis from small bowel to the ascending colon, because the terminal ileum has usually been involved in the radiation field. While ideally a complete resection of the entire involved small bowel is optimal, the surgeon must consider the extent of the resection necessary as well as the anatomic segment involved. Usually, the involved small intestine is the distal ileum; major resection back to reliably normal, nonirradiated small bowel may require a total or subtotal ileal resection that carries its own nutritional complications, and a decision will need to be made concerning preservation of mildly involved but functional ileum if the only alternative is complete resection. In contrast, if the bowel is severely involved and nonfunctional, resection (despite its side effects) may be the best option. When the affected area contains dense adhesions or is stuck deep within the pelvis, bypass may be a better choice to avoid the very real concern of potential iatrogenic injury to the bowel, bladder, pelvic organs, and ureters; however, if there is a localized abscess or associated septic process, bypass is not a good option, just as with Crohn's disease, because the ischemic inflammatory process will continue. Attempts at complete lysis of adhesions alone without resection are controversial due to the risk of traumatizing the intestine with potential fistula formation. For the patient with advanced disease who presents years after irradiation, adhesiolysis may not be a good option, especially if the bowel is matted and agglutinated. In contrast, in the case of isolated adhesive bands and the patient being early (<2 years) after irradiation, lysis alone may be warranted; much of the decision needs to be based on the quality of the involved bowel and the site of obstruction. If the bowel is thickened, woody, and strictured, resection or bypass is best.
Carcinomatosis and Malignant Obstruction
Bowel obstruction in the setting of carcinomatosis often represents the terminal phase of the malignant disease. Operative management is entirely palliative and needs to be applied selectively. In the case of limited life expectancy and malignant cachexia or ascites, nonoperative palliative measures are advised, because operative intervention would be unnecessary and associated with a lesser, end-of-life, quality of life due to the convalescence required after a noncurative celiotomy. In contrast, other patients with a good performance status may have a long life expectancy, and in this case, operative bypass with the idea of permitting renewed oral intake may be indicated. Patients and their families should be counseled that the relief of their obstruction will not affect disease progression but may improve quality of life. In addition, the surgeon should remember that up to one-third of bowel obstructions presenting in the setting of carcinomatosis are due to adhesions and not to malignant obstruction.68 Therefore, a short trial of conservative therapy with rehydration and nasogastric decompression is usually advisable, although many (possibly most) patients with carcinomatosis will fail this intervention. In addition, depending on the location and extent of the malignant disease involving the GI tract, a palliative endoscopic stent placement may relieve the obstruction (Fig. 29-14).
An initial minimal access, laparoscopic approach should at least be entertained in patients with a malignant obstruction provided the access to the peritoneal cavity is safe. The least invasive approach is best for these patients, and if palliation, such as a bypass or gastrostomy tube, can be achieved laparoscopically, the patient would benefit substantially with decreased pain, possibly a shorter convalescence, and decreased duration of hospital stay, all of which are important considerations in the palliative care of patients with a limited life expectancy.
A. Obstructing rectal cancer (arrows). B. Intraluminal self-expanding metal stent restores luminal patency. (Reproduced, with permission, from Hünerbein M, Krause M, Moesta KT, Rau B, Schlag PM. Palliation of malignant rectal obstruction with self-expanding metal stents. Surgery. 2005;137:42–47.)
At exploration, multiple scenarios may be encountered. Some patients will have an isolated area of adhesions and require only adhesiolysis. Others will have a solitary metastasis causing either an intra- or extraluminal obstruction that can be corrected with a limited resection or bypass. If multiple areas of adhesions are present or the affected area is adherent to the abdominal wall or intra-abdominal structures in the patients with incurable malignant obstruction, bypass of the involved segment will provide symptom relief and the fewest opportunities for complication. One should consider placement of a tube gastrostomy if there is any question of the success of the operation, if impending obstruction seems imminent, or if relief of the obstruction is not possible. In the event of reobstruction, a tube gastrostomy can be used to decompress the stomach and avoid the discomfort associated with a nasogastric tube. The decision to place a palliative, decompressive, tube gastrostomy is more difficult in the presence of ascites. In this situation, a better option would be a tube pharyngostomy.92 Additionally, if histologic diagnosis of the neoplasm had been obtained previously, a repeat biopsy should be entertained to ensure that the neoplasm has histologic characteristics consistent with the original biopsy.