Small Bowel Obstruction




Extent of the Problem


Small bowel obstruction is a common problem that is responsible for more than 1 million inpatient hospital days and more than $1 billion in health care costs per year in the United States. In some European countries, medical expenses for small bowel obstruction exceed those for gastric cancer and almost parallel those for colon cancer.


The most common cause of small bowel obstruction is intestinal adhesions from previous surgery, particularly colorectal surgery. Hernias, malignancy, volvulus, Crohn disease, chronic radiation enteritis, inflammation involving other abdominal viscera, intussusception, volvulus, ischemia, and gallstone ileus are other less common causes. In a study using Medicare administrative data, Beck et al reported that 14% of patients undergoing abdominal surgery will require hospitalization for small bowel obstruction within 2 years of their operation and 2.6% of these patients will require adhesiolysis. Based on the Scottish Surgical and Clinical Adhesions Research database, an estimated 35% of patients with a previous laparotomy will need to be readmitted for problems related to adhesive small bowel obstruction more than once within 10 years. Approximately 2% to 5% of these patients will have to undergo adhesiolysis after failed nonoperative management.




Clinical Presentation


Abdominal pain, nausea and vomiting, abdominal distension, and obstipation are the cardinal signs of small bowel obstruction. The presence of these signs, their order of appearance, and their intensity depend upon the location, degree, and duration of the obstruction. Other important factors to consider include the patient’s age and general condition, associated intra-abdominal disease, and the masking effect of medications such as steroids. History should be directed at factors known to be associated with the development of obstruction such as previous laparotomies, hernias, or a history of malignancy, especially if its treatment included abdominal or pelvic radiotherapy.


Physical examination should include an assessment of the general condition of the patient with an emphasis on hydration and end organ perfusion, and then a complete examination of the abdomen that encompasses the flanks, groins, and a rectal examination. In addition to surgical scars, hernias, or masses, abdominal examination detects tenderness or peritoneal signs that may indicate an urgent need for exploration. Percussion typically reveals a tympanitic abdomen, whereas upon auscultation, obstruction is associated with characteristic high-pitched, tinkling bowel sounds. The conversion of an abdomen with exaggerated bowel sounds to a quiet abdomen without any bowel sounds has been described to be an ominous sign that indicates the development of ileus, perhaps as a result of peritonitis or ischemia. A digital rectal examination may detect fecal impaction or an obstructing rectal cancer, whereas emptiness of the rectal vault suggests a more proximal obstruction.


Uncomplicated small bowel obstruction may progress to strangulation, greatly increasing mortality. A high index of suspicion is needed to identify and prevent this complication. Strangulation typically occurs in the setting of twisting or incarceration in an internal hernia, causing disruption of the arterial supply or venous drainage of a segment of small bowel. Simple mechanical obstruction due to adhesions rarely results in infarction unless there is a tight adhesive band or a longstanding obstruction, where the intraluminal pressure may exceed the venous hydrostatic pressure, resulting in bowel wall ischemia. Strangulation may be associated with fever, tachycardia, leukocytosis, and peritonism. These signs, however, are not specific to bowel ischemia and may even be absent.


Investigations that help in the decision-making process include laboratory tests such as a complete blood cell count, serum electrolytes, blood urea nitrogen and creatinine, serum amylase, and lipase. These tests may reveal the severity of the obstruction and its sequelae and rule out conditions that mimic obstruction. At the same time, these tests may be misleading because the results can be normal even in cases of acute small bowel obstruction, and when the results are abnormal, they cannot be relied upon as a sole determinant of the need for a laparotomy. Similarly, serum lactate levels, pH, base deficit, and anion gap measurements allow an assessment of acidosis but again cannot be relied upon as sole indicators of intestinal ischemia. Instead, they should be evaluated in the context of the overall clinical presentation, because other causes of metabolic acidosis such as renal failure, ketoacidosis, or medication-related effects may influence their levels.




Imaging


A radiologic diagnosis of small bowel obstruction can be made using several different imaging modalities, including plain radiographs, contrast studies, computed tomography (CT), magnetic resonance imaging (MRI), and even ultrasound. The presence of a segment of dilated small bowel (usually defined as having a diameter >2.5 to 3 cm) proximal to a collapsed segment of bowel suggests obstruction. The degree of dilatation has been shown to correlate both with the duration and severity of obstruction, in particular the risk of segmental ischemia and subsequent transmural necrosis. Although plain radiographs and contrast studies have some value as the initial imaging, many authors now recommend early contrast CT scanning.


In acute small bowel obstruction, plain radiographs of the abdomen usually reveal dilated, air-filled loops of small bowel, air-fluid levels with a “step-ladder pattern,” and a paucity or absence of air in the colon. Pneumoperitoneum may be revealed on a radiograph taken in the upright position when perforation has occurred and is a late sign, as are pneumatosis intestinalis and portal vein gas, which are worrisome for advanced bowel ischemia. Plain radiographs are also helpful in the determination of the level of obstruction and the identification of sigmoid and cecal volvulus. However, abdominal radiographs are diagnostic in only 50% to 60% of cases. An analysis of the value of plain films for obstruction revealed a sensitivity of only 66% in proven cases of small bowel obstruction, with a false-negative rate of 21%. Considering these limitations of plain films, careful correlation of clinical and radiologic findings is crucial.


CT scanning is the most important imaging modality for the evaluation of small bowel obstruction. The latest scanners provide thin-slice imaging, faster scanning times, and less radiation exposure compared with previous generations. Initial studies using conventional CT in small bowel obstruction reported a sensitivity of 96%, a specificity of 96%, and an accuracy of 95%. Most of these studies, however, included patients with high-grade obstruction, and thus in a mixed population of patients with both high- and low-grade obstruction, these percentages could be lower. In addition to establishing a diagnosis of small bowel obstruction, CT scanning may also precisely define a transition point and reveal the cause of obstruction such as a tumor, hernia, intussusception, volvulus, or inflammatory condition such as Crohn disease and radiation enteritis. A CT scan may also reveal closed loop obstruction and signs of progressive ischemia, such as bowel wall thickening, pneumatosis, or portal vein gas, thereby greatly facilitating the identification of patients in need of urgent laparotomy rather than nonoperative management.


Contrast studies with water-soluble agents are useful in several circumstances. A Gastrografin follow-through helps differentiate partial from complete obstruction and hence facilitates the decision for surgery. In fact, some authors have used small bowel contrast studies as a “screening test” for patients presenting with adhesive obstruction. Failure of contrast material administered orally or by nasogastric tube to reach the colon by 24 hours is used as an indication for surgical exploration. At least two recent randomized studies have reported improved outcomes with the use of oral water-soluble contrast agents for patients presenting with adhesive small bowel obstruction. Use of contrast studies either reduced the length of time until spontaneous clinical resolution of the obstruction occurred or reduced the proportion of patients requiring surgery. Even so, it remains unclear whether antegrade contrast material may help resolve small bowel obstruction in patients who are considered surgical candidates at initial presentation. In particular, early laparotomy should not be withheld from patients who show clear signs of peritonitis or bowel ischemia. When a distal small bowel obstruction is suspected, a contrast enema helps exclude colonic obstruction as the predisposing cause. Although barium studies are not used in patients with acute obstruction because of their risk of converting a partial to a complete obstruction, they can be valuable for the evaluation of chronic or vague symptoms, particularly when other investigations have not been fruitful. In such cases, enteroclysis, in which barium is administered beyond the pylorus via a nasoenteric catheter, is worth consideration. Because this method minimizes the dilution of the barium during its distal passage, it can reveal mucosal lesions. CT (and MR) enterography is particularly useful in providing similar information. Intestinal malrotation presenting in adult life with vague symptoms is also sometimes diagnosed with this modality.


MRI and Ultrasound


Several studies have evaluated the sensitivity and specificity of either MRI or transabdominal ultrasound in the diagnosis of small bowel obstruction, because these modalities do not expose the patient to (sometimes repetitive) radiation. MRI has traditionally had limited applicability in the radiologic evaluation of intestinal obstruction. Reasons include its limited availability, long acquisition times, and high cost. With progressively shorter acquisition times, it is now possible to provide MR imaging of the entire abdomen and pelvis within 10 minutes, and newer studies have shown sensitivity and specificity similar to that of CT scanning in the diagnosis of small bowel obstruction. MR enteroclysis is another newly developed technique with great potential because it allows direct multiplanar imaging with functional information and soft-tissue contrast obtained without exposure to ionizing radiation. In contrast to most imaging modalities, abdominal ultrasound provides real-time information of small bowel motility and peristalsis. Although both sensitivity and specificity have been shown to be high for both ultrasound and MRI, such drawbacks as interobserver variability for abdominal ultrasound and cost/availability for MRI outweigh any benefits in most instances of acute small bowel obstruction. Both modalities, however, have a role in pregnant patients with suspected small bowel obstruction when radiation exposure needs to be kept to a minimum.




Management of Small Bowel Obstruction


When suspicion for strangulation is low, and particularly when postoperative adhesions are the most likely cause of obstruction, management is initially nonoperative. The strategy includes bowel rest with nasogastric decompression, intravenous fluids, and close monitoring of the intravascular volume status using clinical and laboratory parameters combined with sequential abdominal examinations. Partial small bowel obstruction resulting from adhesions will resolve spontaneously in 80% of cases. The success rate for patients initially presenting with complete obstruction is much lower. When any change occurs in the patient’s condition that suggests the development of strangulation, or if no resolution occurs within 24 to 48 hours, laparotomy is required. Under certain circumstances, some surgeons will wait for up to 5 days before proceeding to surgery.


The distinctions between obstruction with and without intestinal ischemia and partial and complete small bowel obstruction is important because the need and threshold for operating are different. Although the need for surgery is obvious in some cases, neither clinical nor laboratory parameters consistently identify patients at risk for or with (imminent) ischemia and hence provide an indication for surgery. Serial abdominal examinations aided by a careful interpretation of laboratory parameters and imaging studies in the context of the patient’s clinical picture is the best approach. Early CT imaging may identify strangulation or closed loop obstruction. In the absence of CT findings that are suspicious for ischemia, patients should be aggressively rehydrated with isotonic intravenous fluids. Persistence of tachycardia, hypotension, or acidosis, particularly in the setting of a change in the patient’s general condition or worsening abdominal pain, should prompt an immediate laparotomy. Adherence to this simple algorithm should minimize the risk of progression of obstruction to strangulation and limit the number of unnecessary laparotomies.


In some cases, the need for an urgent laparotomy is apparent at initial presentation. Patients without a previous history of abdominal surgery or other predisposing factors who present with the classical picture of obstruction, which is then corroborated on imaging studies, and those who have symptoms and signs that raise a concern for strangulation, should proceed to a laparotomy. Thus the presence of obvious peritonitis or findings suggesting that resolution of an obstruction is unlikely, such as an incarcerated or strangulated hernia, an abdominal mass, unresolving intussusception (particularly associated with a lead-point), or volvulus, should prompt immediate surgery. While waiting for surgery, nasogastric decompression, active fluid resuscitation, and broad-spectrum antibiotic coverage allows optimization of the patient.


Recent studies have shown that postoperative morbidity, return of bowel function, and length of stay are all adversely affected in patients in whom surgery was delayed for more than 48 hours. The differentiation of partial obstruction, which is more likely to respond to conservative management, from complete obstruction is important but can be challenging. Although stool or flatus can continue to occur in patients with complete obstruction until the bowel distal to the site of obstruction is evacuated, it usually signals resolution of the obstruction. The continued passing of gas or stool together with an improvement of symptoms such as a diminution of abdominal distension, crampy pain, and vomiting indicate resolution of the obstruction. With partial small bowel obstruction, large volumes of watery stool can occur in the context of vomiting and distention. A Richter hernia whereby only a part of the circumference of the small bowel may be entrapped is a special situation in which the risk of strangulation persists despite the presence of ongoing bowel function. As discussed earlier in this chapter, radiographic studies may be able to differentiate complete and partial obstruction. In situations where CT scans are noncontributory, a Gastrografin follow-through can be both therapeutic and diagnostic, in that failure of contrast material administered orally or by the nasogastric tube to reach the colon by 24 hours may serve as an indication for surgical exploration.


Nonadhesive Obstruction


Hernias


Hernias are the second most common cause of intestinal obstruction after adhesions. A careful examination of the inguinal and femoral canals, as well as any abdominal or flank incisions and stoma sites, is mandatory in any patient presenting with abdominal pain or obstruction and may reveal a tender or nonreducible swelling. Obese patients may have no bulge, but palpation should reveal a tender lump. Parastomal hernias also can be subtle, although pain and a cough impulse are usually present if the impacted bowel is obstructed. An obturator hernia is a rare entity, and when incarcerated, it presents with intestinal obstruction associated with pain along the inner aspect of the thigh (the Howship-Romberg sign). When small bowel obstruction develops as a result of a hernia, urgent exploration is often required to avoid the risk of strangulation. Findings of erythema and edema of the skin overlying the incarcerated hernia, along with tenderness, are signs of strangulation and an indication for immediate surgery. If such warning signs are not present and tenderness is not present over the hernia, gentle manual pressure over the hernia together with the administration of an anxiolytic agent and elevation of the foot end of the bed for inguinal and femoral hernias has been described as being effective in reducing an incarceration. If this approach is successful, elective repair may be performed in the near future. “Reduction en masse” in which a strangulated segment may be reduced into the peritoneal cavity together with the hernial ring is a rare complication that produces the paradox of continued obstruction after apparent reduction of the hernia.


Crohn Disease


Stricture of the small bowel as a result of inflammation or fibrosis from Crohn disease may precipitate small bowel obstruction. In some instances an inflammatory phlegmon or internal or enterocutaneous fistula also may accompany the obstruction. Small bowel may also be drawn into areas of intra-abdominal inflammation as a result of abscesses from any cause, such as diverticulitis or tumor (desmoplastic reaction) and become obstructed. In these circumstances, the management of obstruction is usually dictated by the primary condition. Surgery occasionally may be indicated for the obstruction itself, in which case the primary disease needs to be addressed as discussed in the relevant chapters relating to these conditions.


Malignancy


Small bowel obstruction as a result of malignant disease usually results from metastases or involvement of the small intestine by advanced cancer in a nearby organ. Primary small bowel cancers, usually adenocarcinomas or gastrointestinal stromal cell tumors, are less common causes of obstruction. Diagnosis is often made by imaging, although sometimes the cancer is apparent only at laparotomy.


Intussusception


Intussusception is a rare cause of small bowel obstruction in adults. In most cases the lead point for the intussusception is an intraluminal neoplasm that is passed distally in the bowel by peristalsis. As the proximal segment (the intussusceptum) is drawn further into the distal bowel (the intussuscipiens), the mesentery is compressed and ischemia of the intussusceptum may result. Intermittent episodes of obstruction accompanied by the passage of bloody stool mixed with mucus (“red currant jelly”) is pathognomonic. The diagnosis may be made by imaging or colonoscopy, but in many cases it presents as an unexpected finding at laparotomy. Because of the difference in cause of the intussusception in adults when compared with the pediatric population, attempts at reduction of the intussusception, either by hydrostatic techniques or at surgery, are not advised.


Gallstone Ileus


Gallstone ileus is another very rare cause of small bowel obstruction. Patients are usually elderly women. The condition is caused by a large gallstone eroding from the gallbladder directly into an adjacent segment of the small or large intestine (the duodenum, jejunum, or hepatic flexure of the colon) that has become adherent to the gallbladder as a result of inflammation. The stone then passes distally into the intestinal tract until it becomes impacted. The site of impaction is usually in the narrowest portion of the small intestine, typically in the terminal ileum. A plain radiograph of the abdomen may reveal the classic findings of small bowel obstruction, a radiopaque gallstone outside the right upper quadrant, and pneumobilia. This combination, Rigler’s triad , is present in fewer than 10% of cases, because most gallstones are radiolucent.


Bariatric Patient


Small bowel obstruction occurs in approximately 3.5% of patients with a history of laparoscopic Roux-en-Y gastric bypass. These patients appear to be at a higher risk of developing an internal hernia compared with patients after open bypass surgery because iatrogenic mesenteric defects remain patent as a result of less intensive adhesion formation after laparoscopy. A frequent site of herniation is the “Petersen space” between the Roux limb mesentery and the transverse mesocolon in patients who have undergone an antecolic Roux-en-Y bypass. Although immediate closure of mesenteric defects is advocated by bariatric surgeons to decrease the risk of internal herniation, such closure can be difficult to achieve in morbidly obese patients. Even so, any patient who has had a gastric bypass should be considered at risk. Herniation with strangulation may occur late after the bypass once the patients have lost weight and are predisposed to herniation by the thinner mesentery surrounding the (sometimes partly closed) defects. Patients who have undergone gastric bypass may present with vague complaints, an unremarkable physical examination, and laboratory values. A low index of suspicion for this potentially life-threatening complication is essential, and an early CT scan is recommended. In patients with a strong suspicion for internal hernia and volvulus, surgery may be recommended even in cases with negative imaging studies because false negative reports may be misleading.


Surgical Technique


Adhesive Obstruction


Whereas most patients can be placed supine, the Lloyd-Davies position allows ease of access to the pelvis and the performance of colonoscopy. When patients have previously undergone pelvic surgery or radiation, or when the level of obstruction is not clear, the latter position is preferable. After adequate resuscitation, a midline incision that encompasses any previous scar (if also midline) is used for laparotomy. The risk for inadvertent enterotomy is high during abdominal entry because the bowel loops are distended and likely to be adherent to the abdominal wall. Patients with a thinned-out abdominal wall or a frank incisional hernia pose a special problem because there is a particular risk of damage to the distended intestine. We use a scalpel for entry into the peritoneal cavity. Lifting up on the abdominal wall on either side allows controlled division of the skin and subcutaneous tissues, the fascia, and the peritoneum and entry into any windows of peritoneal cavity that are relatively free of adhesions. When no such windows exist, our preference is to precisely incise the peritoneum. Once the surface of the intestine is encountered, dissection is then developed in a lateral direction to “clear the lateral space” because this then permits the identification of the fused peritoneum to intra-abdominal contents, upon which further peritoneal entry is facilitated. An alternative strategy is to enter the peritoneal cavity above or below the previous incisional scar prior to the dissection being developed along the entire length of the incision.


In some cases, a single constricting band may be encountered, which is divided to relieve the obstruction. In other cases, many adhesions are encountered, with the peritoneal cavity sometimes totally obliterated by scar tissue. Great care is necessary during lysis to minimize inadvertent damage to the small bowel or other structures and allow identification of the site of obstruction. The incision is gradually extended by continually separating underlying small bowel from the undersurface of the midline scar so that the entire length of incision is ultimately opened. The incision is extended when indicated. Adhesiolysis then extends outward on either side of the midline to develop the lateral space. If bowel distention is severe, needle decompression occasionally may be used to gain additional working space. Typically, this involves the placement of a purse-string suture on the antimesenteric portion of a distended segment of small bowel for control through which a wide-bore needle is introduced tangentially into the lumen. Suction tubing attached to the end of the needle facilitates decompression of air, as well as liquid stool. In some instances, interrupted seromuscular sutures may be placed or the previously placed purse-string suture may be tied to facilitate closure of the needle puncture site. Attention is then turned to the remainder of the abdomen. Often the most difficult adhesions may be encountered in the pelvis or pelvic side walls. Gentle traction is applied to small bowel while the dissection is pursued along the lateral aspects of the pelvis, with the dissection then directed distally to deliver the bowel from the pelvis. The posterior aspect of the small bowel and the attached mesentery is then dissected away from the retroperitoneum from down to up. Once mobilization has been completed, interloop adhesions are lysed. Injection of saline solution in the planes between adjacent segments of small bowel and between the small bowel and the abdominal wall, other structures, and retroperitoneum may facilitate dissection of dense adhesions. The need for complete adhesiolysis after the point of obstruction is freed depends upon the cause of the obstruction, the likelihood of associated disease, and the intensity of the adhesions and the presence of a proximal enterotomy. When adhesions are particularly dense, adhesiolysis can be limited as long as the point of transition is demonstrated, the cause of the transition is obvious, and the obstructing element can be addressed or resection can be completed relatively easily.


After adhesiolysis, the bowel is inspected for any coexisting disease and for enterotomies or serosal tears created during the course of mobilization. The classic technique of “milking” the intestinal contents back into the stomach to be aspirated by a nasogastric tube has recently been evaluated in a randomized controlled trial but was not found to affect outcome in any meaningful way and therefore should be abandoned. When the intestine is grossly distended and edematous, there is a risk of extensive serosal denudation as a result of stripping of the serosa. When the small bowel needs to be emptied to facilitate abdominal closure or anastomosis, we prefer using a “hand-over-hand” emptying technique. In this technique, the small bowel is compressed in the palm of one hand between the flat of the fingers and the thenar eminence followed sequentially by the other hand. We have found that this technique is associated with a much lower risk for inadvertent small bowel injury.


Bowel viability usually can be assessed using the triad of color, peristalsis, and mesenteric pulsations. If viability is questionable, the ischemic segment should be wrapped in warm, wet packs, 100% oxygen should be administered, and viability should be reassessed after 10 to 15 minutes. If some doubt still exists, use of the Doppler flow probe or systemic injection of fluorescein dye followed by inspection of the bowel under a Wood’s lamp may aid decision making. If viability is doubtful for a short segment of small bowel, resection of the segment is the best strategy. However, if an extensive segment is of questionable viability, then a second-look operation may be required the following day, which will allow resuscitation of the patient and an opportunity for borderline viable small bowel to demarcate and thus potentially limit the extent of small bowel resection.


Hernias


Incarcerated inguinal hernias are explored through an oblique inguinal incision, although, on occasion, a midline laparotomy or vertical incision overlying the hernia and extending upwards toward the abdomen or downward toward the thigh may be a better option, particularly for strangulated femoral hernias. With a local incision, the constricting ring should be released after the hernia sac is opened, and the bowel can be inspected for viability. If the hernia contents reduce spontaneously before an adequate assessment of their viability could be performed, a laparotomy may be required. If the contents of the hernia are viable, the bowel is returned to the peritoneal cavity, the sac is excised, and standard hernia repair is performed. Necrotic bowel can usually be resected through an inguinal approach, and after healthy small bowel is delivered through the defect, an anastomosis is performed. Repair of an inguinal hernia that contains strangulated bowel is best performed using a layered repair with permanent monofilament suture. Mesh repair of an incarcerated inguinal (or other) hernia was long believed to be hazardous because of the risk of infection with subsequent need for mesh removal. Recent reports, however, have challenged this dogma, and polypropylene mesh repair has been advocated as being effective and safe even for patients requiring resection of strangulated bowel. Although consensus has not been reached on the issue, some authors support prolonged postoperative antibiotic prophylaxis when mesh repair of an incarcerated hernia is performed. Incarcerated femoral hernias can be approached using a low inguinal incision, a preperitoneal approach, or a low midline incision. Conversion to a lower midline incision may be necessary if necrotic bowel is present.


Crohn Disease and Other Inflammatory Conditions


When obstruction is a result of inflammatory conditions such as Crohn disease, diverticulitis, desmoid disease, and other intra-abdominal disease, management of the obstruction is part of management of the disease and is discussed in the corresponding chapters.


Malignancy


In cases of obstruction resulting from an advanced systemic malignancy, palliation of obstruction can be achieved and is expected to improve quality of life. In general, resection may offer better palliation than bypass, but the findings at the time of surgery determine the best approach. In cases that include a localized obstruction that cannot be easily resected, bypass is the best strategy. When extensive carcinomatosis is present, including cases with a frozen abdomen, creation of a loop stoma in the bowel proximal to the obstruction may be the only meaningful option and provides palliation of obstructive symptoms. In some cases, a combination of resection, bypass, or ostomy may allow relief of obstruction and restitution of oral intake so that patients can be discharged home. If no small bowel can be mobilized, then a gastrostomy tube is placed for decompression. If this situation is recognized preoperatively, placement of a percutaneous gastrostomy tube together with hyperalimentation is a reasonable alternative that allows discharge of the patient from the hospital to home surroundings. Involvement of a palliative care specialist in these cases is important because narcotic pain medication, antiemetic agents, anticholinergic drugs, and somatostatin analogs will be the mainstays of treatment.


Intussusception


When intussusception is identified preoperatively or during surgery as a cause of obstruction, resection of the lead point and any associated strangulated tissue is the best approach.


Gallstone Ileus


The obstructing gallstone usually can be milked proximally into healthy bowel, where an enterotomy is made for stone extraction. If the stone is tightly impacted, then resection of the segment is indicated. Because multiple stones may occur in 5% of cases, the entire small bowel should be carefully palpated to identify the presence of other stones. In most cases, the gallbladder and the bilioenteric fistula is left alone at the primary surgery, with a cholecystectomy performed electively at a later date, if required.


The Bariatric Patient


Gastric bypass patients with an internal hernia or volvulus may present with vague symptoms and an unremarkable physical examination and laboratory values. A low index of suspicion is required for this potentially life-threatening complication, with early CT scanning and surgery even with negative imaging studies. In such instances, laparoscopy to rule out or diagnose internal hernia, reduce the herniated segment, and close any mesenteric defects is preferred. If strangulation has occurred or anatomy predisposes to further recurrence, resection of the involved segment or revision of the anastomosis may be required.


Laparoscopic versus Open Lysis of Adhesions


Laparoscopic lysis of adhesions for small bowel obstruction was first described in 1991 by Batsug and colleagues. Studies have shown that in select cases, laparoscopic adhesiolysis is safe and may offer better outcomes in terms of earlier return of bowel function, shorter length of hospital stay, and improved cosmetic results compared with the open technique. Despite these benefits compared with laparotomy, Mancini et al, using National Inpatient Sample data, found that in 2002 only 11.4% of all patients with adhesive small bowel obstruction in the United States were treated laparoscopically. Some persons have raised concerns about the safety of laparoscopy in the setting of dilated small bowel because of a perceived higher risk of inadvertent and missed enterotomies. An important factor in patient selection relates to the ability to gain safe access into the peritoneal cavity rather than the absolute number of previous operations. Factors that were associated with successful laparoscopic lysis of adhesions included operations limited to one or two areas of the abdomen (i.e., the pelvis), proximal obstruction, length of time since last laparotomy greater than 1 year, ability to insufflate more than 1 L of CO 2 , and absence of overt peritonitis or gross abdominal distension. Although studies have shown that laparoscopy is safe under such circumstances when performed by surgeons experienced in minimally invasive techniques, a low threshold to convert to an open technique is warranted.


Early Postoperative Bowel Obstruction


Early postoperative small bowel obstruction poses a unique challenge and requires specific attention. The major difficulty with this condition lies in its overlap with ileus. Even when a mechanical obstruction has been shown, management usually differs from that of obstruction remote from surgery because most postoperative obstructions resolve spontaneously. In addition, attempts at repeat laparotomy in the early postoperative period may be hazardous and can result in disastrous complications. Typically, an intense inflammatory response usually begins within the abdomen 7 to 10 days postoperatively and persists for at least 6 weeks. Surgery during this period is dangerous when dense hypervascular adhesions obliterate the peritoneal cavity. The risk of enterotomy and subsequent fistulization is high. In addition, injury to the small bowel mesentery, as well as extensive deserosalization of the bowel, may lead to extensive resections. Because of these risks, as well as the low risk for the development of strangulation, patients with postoperative obstruction should be managed conservatively with nasogastric suction and intravenous fluids. If resolution does not occur within 5 to 7 days, the patient is started on hyperalimentation and a percutaneous gastrostomy tube is placed for longer term decompression. Patients who have persistent obstruction are discharged from the hospital with parenteral nutrition, with the gastrotomy tube used as a vent to relieve obstruction. In most such patients the condition spontaneously resolves, although this process may be gradual. Such patients initially tolerate oral liquids, with the gastrostomy tube left clamped until such time as nausea or fullness dictates release of the clamp so as to vent the gastrointestinal tract. Progressively reduced frequency of the need for venting of the gastrostomy tube is noted as the gastrointestinal tract resumes function. Such patients are then transitioned to solid foods, and once reliable oral intake can be ensured, the gastrostomy tube is removed and parenteral nutrition is discontinued. In cases where obstruction is persistent, laparotomy may be performed in 3 to 6 months. Immediate surgery is indicated for peritonitis or signs of sepsis. There is a place for very early exploration within the first 7 to 10 days postoperatively if obstruction is recognized promptly, because adhesions encountered during this period are not usually severe.


Prevention of Adhesions


Adhesions can occur after any laparotomy and are likely a result of injury to the serosal surfaces that lead to an inflammatory response and scarring. In general, reduction of iatrogenic peritoneal damage, inhibition of the inflammatory response, prevention of fibrin formation and promotion of fibrinolysis, prevention of collagen formation and deposition, and finally, the use of mechanical barriers are mechanisms that have been used to prevent the development of adhesions. Potentially, any of these aims may be achieved by use of clean surgical technique, systemic medications, or topical agents applied directly to the site of the operation. Although various investigators have evaluated these agents, few clinical trials have been performed, and even fewer of these strategies have found their way into clinical practice. Regardless, careful, clean operative technique with gentle handling of tissues and avoidance of leaving devascularized tissue, use of powder-free gloves to avoid the deposition of talc, and copious lavage of the peritoneal cavity at the conclusion of the operation are simple measures that should be universal. Local chemoprophylactic agents to reduce or eliminate adhesions through a barrier mechanism have been developed. Although a large multicenter study by Fazio and associates that evaluated the role of a bioresorbable membrane of modified sodium hyaluronate and carboxymethylcellulose (Seprafilm, Sanofi, Paris, France) demonstrated that the overall bowel obstruction rate was unchanged, the incidence of adhesive small-bowel obstruction requiring reoperation was significantly reduced (relative risk of 47%). However, other reports have raised concerns about an increased rate of intra-abdominal abscess formation and anastomotic leakage when Seprafilm was wrapped around a fresh anastomosis. A recent Cochrane review concluded that although the incidence of intestinal obstruction or the need for surgery is in fact not improved by Seprafilm, its use is safe and Seprafilm may be applied at the surgeon’s discretion.


Systemic agents such as heparin, corticosteroids, and nonsteroidal antiinflammatory drugs (NSAIDs) have all been shown to decrease fibrin deposition and thus reduce adhesion formation in experimental models . NSAIDs work by inhibiting the early inflammatory response. Heparin inhibits the coagulation cascade through factor Xa and antithrombin formation. Corticosteroids exert a multitude of antiinflammatory and immune-modulating effects, but their effectiveness in preventing adhesion formation has not been proven in experimental models. Similarly, the prevention of fibrin formation with therapeutic anticoagulation has not been shown to exert a significant effect on adhesion formation in animal models, and concerns regarding its clinical value given an increased risk of postoperative hemorrhage remain justified. Novel medications that succeed in reducing the early inflammatory response and counteract the formation and deposition of fibrin products without affecting wound healing and causing postoperative bleeding are needed.


Finally, a number of studies have reported a lower incidence of adhesion-related small bowel obstruction after laparoscopic compared with open colorectal resection. A 25% reduction in postoperative adhesions in patients undergoing laparoscopic as opposed to open gastrointestinal surgery, as well as a significant attenuation of the severity of the adhesions encountered, has been shown. In fact, a recent large British study on 187,000 patients admitted to National Health Services hospitals could demonstrate significantly lower rates of readmission and reintervention rates for adhesion-related small bowel obstruction after laparoscopic compared with open colorectal surgery. Although the use of a pneumoperitoneum itself has been shown to exert some proadhesive effects by inducing peritoneal hypoxia, leading to an increased release of vascular endothelial growth factor, it appears as if the beneficial aspects of laparoscopy in reducing adhesion formation outweigh these opposing mechanisms in the clinical setting. Smaller incisions, less tissue trauma and bleeding, a reduced inflammatory response, and an earlier recovery of bowel function with the minimally invasive approach are likely responsible for this advantage.

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Jul 15, 2019 | Posted by in GENERAL | Comments Off on Small Bowel Obstruction
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