Best Practice & Research Clinical Gastroenterology 27 (2013) 691–707

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Best Practice & Research ClinicalGastroenterology

6

Acute GI obstruction

Tomas Hucl, MD, PhD, Consultant Gastroenterologist *

Department of Gastroenterology and Hepatology, Institute for Clinical and Experimental Medicine, Videnska9, 140 21 Prague 4, Czech Republic

Keywords:Gastrointestinal obstructionMechanical ileusEndoscopic therapyDilationSelf-expandable metal stent

* Corresponding author. Tel.: þ420 261362600;E-mail address: tomas.hucl@ikem.cz.

1521-6918/$ – see front matter � 2013 Publishedhttp://dx.doi.org/10.1016/j.bpg.2013.09.001

a b s t r a c t

Acute gastrointestinal obstruction occurs when the normal flow ofintestinal contents is interrupted. The blockage can occur at anylevel throughout the gastrointestinal tract. The clinical symptomsdepend on the level and extent of obstruction. Various benign andmalignant processes can produce acute gastrointestinal obstruc-tion, which often represents a medical emergency because of thepotential for bowel ischemia leading to perforation and peritonitis.Early recognition and appropriate treatment are thus essential. Thetypical clinical symptoms associated with obstruction includenausea, vomiting, dysphagia, abdominal pain and failure to passbowel movements. Abdominal distention, tympany due to an air-filled stomach and high-pitched bowel sounds suggest the diag-nosis. The diagnostic process involves imaging including radiog-raphy, ultrasonography, contrast fluoroscopy and computertomography in less certain cases. In patients with uncomplicatedobstruction, management is conservative, including fluid resusci-tation, electrolyte replacement, intestinal decompression andbowel rest. In many cases, endoscopy may aid in both the diag-nostic process and in therapy. Endoscopy can be used for boweldecompression, dilation of strictures or placement of self-expandable metal stents to restore the luminal flow either as afinal treatment or to allow for a delay until elective surgical ther-apy. When gastrointestinal obstruction results in ischemia, perfo-ration or peritonitis, emergency surgery is required.

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fax: þ420 261362615.

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Introduction

Gastrointestinal obstruction occurs whenever the normal flow of swallowed content is interrupted.This interruption can occur at any place along the gastrointestinal tract. When occurring in the uppergastrointestinal tract such as in the esophagus, stomach or duodenum, it tends to have a less urgentpresentation, whereas in the small bowel and colon it often presents as amedical emergency. Intestinalobstruction accounts for approximately 15 percent of all emergency department visits for acuteabdominal pain [1]. It is a severe conditionwith a highmorbidity rate andmay result in patients’ death.It thus requires a rapid, correct diagnosis followed by prompt, effective therapy.

Mechanical blockage in the gastrointestinal tract is caused by intrinsic or extrinsic processes thatcan be benign ormalignant. In the upper gastrointestinal tract, malignant disease is nowadays themostcommonly encountered obstruction. Small bowel obstruction accounts for about 80% of all intestinalobstructions [2]. The most common causes are adhesions, hernias and malignant tumors, togetheraccounting for almost 90% of all intestinal obstructions [2]. Inflammatory strictures, such as peptic orthose caused by inflammatory bowel disease, volvulus, intussusceptions or diverticulitis are encoun-tered less frequently. Blockage from foreign bodies is dealt with elsewhere in the same issue of thejournal.

The blockage of the gastrointestinal tract results in local and systemic toxicity. First, the part of thetract proximal to the site of obstruction dilates and gets filled with secretions and air [3]. As a result, thebowel cease to produce faeces and flatus and the luminal content is vomited. Emesis leads to dehy-dration, loss of gastric potassium, hydrogen and chloride, which in turn stimulates bicarbonate reab-sorption by the kidneys, accompanied by further loss of chloride. As a result, metabolic alkalosisdevelops [4]. As the luminal content is trapped in a dilated intestine, the absorptive function is lostleading to even more fluid sequestration. The luminal pressure rises, exceeding first the venous andlater the arterial flow, resulting in strangulation, ischemia, necrosis, perforation, peritonitis and sepsis.Bacterial overgrowth may occur and result in feculent emesis and bacterial translocation [5]. A closed-loop obstruction develops when a part of the intestine is obstructed at two different locations.

Gastrointestinal obstruction needs to be differentiated form non-mechanical obstruction such asparalytic ileus occurring for example after abdominal operations, in a vascular compromise, acutepancreatitis or hypokalemia. In colonic pseudoobstruction, the colon is massively dilated withoutmechanical obstruction.

Diagnosis

Making the diagnosis of gastrointestinal obstruction is based upon evaluation of a combination ofthe patient’s history and symptoms, physical examination, laboratory examination and imaging. Ahistory of previous abdominal surgery should be sought. The vast majority (65–100%) of patients withadhesive obstruction have undergone previous surgery [2,6]. The presence of hernia, intra-abdominalmalignancy or inflammatory bowel disease can predispose to obstruction development [7]. Patientsshould also be asked about symptoms suggestive of these diseases.

Clinical presentation

Clinical symptoms vary based on the level of obstruction of the gastrointestinal tract. The mostcommon symptoms are colicky abdominal pain, nausea and vomiting, abdominal distention andinability to pass flatus/absence of bowel movements [3]. In proximal obstruction, there may be morenausea and less distention compared to distal obstruction. In esophageal obstruction, dysphagia,odynophagia and vomiting will dominate. Obstruction above the intestine (esophagus, stomach) willoften have a more chronic course of disease, whereas intestinal obstruction will present more acutely.

Physical examination

A detailed physical examination is required. General inspection may reveal signs of cachexia sug-gesting a malignant obstruction. Signs of systemic alteration such as fever, tachycardia, hypotension or

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dry mucous membranes are suggestive of a severe form of obstruction with strangulation, ischemia,necrosis or perforation. Inspection of the abdomen may reveal the presence of scars from previousoperations or obvious hernias in the umbilical, inguinal, femoral or incisional sites. Percussiontenderness, rebound phenomenon or guarding are indicators of peritonitis. On palpation, a distendedabdomen with tympany due to air-filled stomach or loops of small intestine is often observed.Auscultationwill reveal frequent high-pitched bowel sounds. The presence of resistancemay indicate atumor or an abscess.

Laboratory investigation

There is no specific laboratory test to diagnose gastrointestinal obstruction or its location. Leuko-cytosis, elevation of C-reactive protein (CRP) and lactate suggest the presence of ischemia or sepsis [8].Vomiting may lead to hypokalemia, hypochloremia and metabolic alkalosis. Increased hemotocrit andblood urea nitrogen suggest severe dehydration.

Imaging

Plain radiography

The examination of choice in a patient with suspected acute gastrointestinal obstruction is plainupright abdominal radiography. The presence of free air indicates perforation. In small bowelobstruction, dilation of multiple bowel loops will be seen accompanied by a lack of air in the largebowel (Fig. 1). In contrast, distal obstruction will show dilation of the colon with decompressed smallbowel. Laddering air-fluid levels may be seen on upright or lateral films. The accuracy of radiography indiagnosing obstruction is around 60% [9].

Ultrasonography

Ultrasonography can also be used for diagnosis of gastrointestinal obstruction. In some cases, it ismore sensitive and specific than plain radiography, however it has been largely replaced by comput-erized tomography (CT). It may be valuable in patients where CT is not appropriate such as in severelyill and unstable patients or those who should avoid radiation exposure [10].

Computerized tomography

The CT scan (Fig. 1) is a very sensitive test (sensitivity over 90%) for high-grade gastrointestinalobstruction, but its sensitivity for partial obstruction is lower [3]. CT should be the next step in thediagnostic process in those patients, where history, clinical examination and plain films have not ruledout obstruction. It provides information about the presence or absence of obstruction, its level, severityand cause. The CT picture may be suggestive of ischemia in case of a thickened intestinal wall and poorinflow of contrast. It can also suggest necrosis and perforationwhen hemorrhagic mesenteric changes,pneumatosis intestinalis, and free intraperitoneal air are present [2,3,11].

Contrast fluoroscopy

In clinically stable patients with suspected partial obstruction, contrast fluoroscopy can aid thediagnosis of obstruction. It may also define the anatomy of the stricture, providing information aboutthe length, tightness and character of the stenosis [3]. Furthermore, in some patients with partialobstruction of the small bowel, the use of water-soluble contrast may even be therapeutic. Interest-ingly, in a randomized trial, patients receiving gastrografin follow-through had a 74% reduction in theneed for surgery within 24 hours of presentation [12]. In colonic obstruction patients, rectal fluoros-copy can aid in the diagnosis process.

Fig. 1. Imaging in diagnosis of acute GI obstruction in a patient with small bowel obstruction. (A.) Plain abdominal radiograph (B.)computer tomography.

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Endoscopy

Endoscopy is often useful to establish the diagnosis of esophageal obstruction, gastric outletobstruction or colonic obstruction and to identify a specific cause. Nasogastric tube suction prior togastroscopy is recommended to decrease the retained stomach content. Cautious administration of astandard bowel prep or an enema is used prior to colonoscopy. Passage of a standard endoscopethrough a tight stenosis is often not possible and forceful attempts at passage should not be performed.Instead, pediatric or nasal endoscopes can be used to pass a stricture or to place a wire prior toendoscopic intervention. Endoscopic biopsies may be needed for tissue diagnosis of an obstruction.

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Differential diagnosis

In differential diagnosis of acute GI obstruction, mainly non-obstructive motility disorders need tobe excluded. Paralytic ileus may occur following abdominal operations or be a consequence of acutepancreatitis, peritonitis, ischemia, trauma or electrolyte disorders, particularly hypokalemia. Toxicmegacolon or intestinal pseudoobstruction are characterized by dilation of the colon without me-chanical obstruction.

Management

Management of patients with gastrointestinal obstruction is directed at removing the source ofobstruction and dealing with the local and systemic consequences. A large proportion of patients withintestinal obstruction may be successfully treated conservatively without the need of surgical inter-vention [2], with gastroenterologists playing an important role in their management. Non-operativelytreated patients are more likely to include those with obstruction of the proximal gastrointestinaltract, whereas patients with distal obstruction are more likely to be treated surgically. In a study of 150patients with intestinal obstruction, almost 70% of small bowel obstruction patients were treatedconservatively, whereas only 25% of patientswith large intestinal obstruction did not require surgery [2].

Conservative management

Multiple randomized controlled trials have indicated that clinically stable patients can be treatedconservatively [6,13,14]. A careful selection of patients for conservative treatment is essential. Rigorousserial examination and clinical-status monitoring are required in these patients to discover early signsof deterioration and incipient ischemia and then proceed with surgery.

Correction of the physiological consequences of obstruction is performed by bowel rest (nothing peros, NPO), volume resuscitation and correction of electrolyte imbalances. Indirect decompression of thedistended GI tract is performed using nasogastric tubes, intestinal tubes or colonoscopy. Interestingly,the use of small bowel follow-through may be therapeutic in some patients with incompleteobstruction [12].

Apart from nonspecific, supportive medical therapy, there are some drugs acting specifically on thegastrointestinal tract that may be of benefit in patients with obstruction. Parenteral proton pump in-hibitors are commonly used in any patient with bowel obstruction, but are mainly recommended inesophageal and gastric outlet obstruction to decrease gastric secretion and treat inflammation in caseof peptic origin of stricture [15]. In patients with signs suggestive of bowel ischemia, antibiotics againstGram-negative organisms and anaerobes should be administered. Prophylactic antibiotics should beconsidered in patients with complete obstruction and markedly dilated colon undergoing a colonicstent placement because of the high risk of complications [16].

A number of drugs have been used to relieve symptoms of obstruction. Opioids are administered totreat colicky or continuous pain associated with obstruction, often together with centrally acting drugssuch as haloperidol, cyclizine or methotrimeprazine. Hyoscin butylbromide, an anticholinergic anti-spasmodic, decreases secretion and eventually reduces vomiting and pain in terminal cancer patientswith inoperable tumor obstruction [17]. The somatostatin analog octreotide acts as an inhibitor ofgastrointestinal secretions, thus reducing nausea, vomiting and pain in patients with untreatablemalignant obstruction [18]. Corticosteroids, such as dexamethasone administered subcutaneously orintravenously are helpful in treating bowel obstruction because of their antiemetic and analgesic action[19]. In contrast, prokinetics such as metoclopramide, neostigmine or erythromycin may be used inpatients with partial obstruction or functional disorders, such as pseudoobstruction syndrome [20].Conservative management also includes avoidance of any offending medications.

Surgery

A preoperative diagnosis of strangulation and imminent perforation cannot be definitely made orexcluded by any of the available parameters or their combination. However, surgical therapy is

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warranted in patients with intestinal obstruction accompanied with presumed or confirmed ischemia,necrosis, perforation and peritonitis or in those in whom the obstruction did not resolve within 48hours of conservative therapy [2,3,21]. Some studies indicate that conservative management beyond48 hours does not diminish the need for surgery, but may even increase surgical morbidity [3,14]. Thedetails of surgical therapy of bowel obstruction are beyond the scope of this paper.

In cases where there is no imminent risk of ischemia or perforation, management requires carefulassessment and the appropriate treatment needs to be tailored to the individual situation, disease andpatient. In many patients, we are confronted with a situation that may be solved either by an endo-scopic or a surgical approach. When evaluating such a patient, the following factors need to beconsidered. Firstly, the decision is influenced by the level of obstruction. There is no easy surgicalalternative to endoscopic dilation or stent placement for esophageal obstruction, but there are alter-natives once the obstruction is localized distally. Secondly, the consequences of surgery need to beconsidered. A gastrojejunostomy (GJJ) will leave the patient with a different quality of life than a co-lostomy. Thirdly, the character of the disease is important. For example, a patient with a gastric outletobstruction due to a peptic stricture will be treated by endoscopic therapy, whereas a patient withgastric obstruction from chronic pancreatitis will be sent for surgery. Fourthly, the condition of thepatient needs to be considered. Endoscopic treatment is generally less invasive. Fifthly, we havesearched the literature for data comparing both treatments. As seen later in the manuscript, these dataare often controversial, and a clear recommendation cannot always be made.

Endoscopy

Endoscopy has gained an important role in the management of patients with acute gastrointestinalobstruction from benign and malignant conditions. It can be used to determine the cause ofobstruction, obtain tissue for diagnosis and provide treatment. The benign causes of obstruction willusually be treated with dilations or plastic/biodegradable stent placement; the malignant causes willbe treated by self-expandable metal stents (SEMS). Nonspecific procedures such as endoscopicdecompression will be used irrespective of the cause.

Since the approach to intestinal obstruction is specific to the level and cause of obstruction, theendoscopic management of different causes throughout the gastrointestinal tract will now bedescribed separately. Esophageal and gastric outlet obstruction are conditions that are less likely topresent as an emergency but often have a rather indolent course, however they will be presented forcompleteness of the review.

Benign esophageal obstruction

A vast majority of benign esophageal strictures is caused by long standing gastroesophageal reflux[22]. The remaining cases may be caused by caustic ingestion, surgical anastomosis, esophagealsclerotherapy or external radiation. Patients with benign esophageal obstruction typically present withamore indolent course of disease, with dysphagia and vomiting being the leading symptoms. The goalsof treatment are obstruction relief and prevention of its recurrence. Endoscopy is the main diagnosticand important therapeutic modality in esophageal obstruction. Barium studies may help in diagnosisand guidance of therapy. Endoscopic treatment options consist of mechanical dilators and through-the-scope (TTS) balloon dilators. There are also Maloney dilators available for self-dilation at home.Savary–Gilliard mechanical dilators are made out of plastic, have a tapered tip, come in different sizesand are introduced over a wire [23]. Similarly, dilation balloons come in different sizes, and each onewill expand to three different diameters [24]. Dilations are performed on an outpatient basis usingconscious sedation. Antibiotic prophylaxis is not required. The initial dilator should be approximatelythe same width as the stricture [24]. Fluoroscopy is convenient to increase safety; however, it is notrequired for esophageal dilations. Generally, no more than three mechanical dilators of increasing sizeshould be used in a single session [25]. Similarly, one balloon with three incremental inflations is usedin one session. However, this rule has never been proven in a randomized study. There is no standard asto the number and duration of inflations with a TTS balloon. The use of diluted contrast to fill the

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balloon enables visualization of a waist that effaces. A prospective comparison did not show any dif-ference in safety of the two methods [26].

The effects of dilation are judged by patients’ symptom relief and the need for repeated dilation,however a general rule indicates that a lumen of 15mmdiameter will allowawell-chewed, regular dietto pass. To achieve sustained obstruction relief, many patients will require repeated dilation sessions.These are usually scheduled in an interval of 5–30 days. The use of proton pump inhibitors is indicatedin peptic strictures to reduce the risk of recurrence [27]. Steroid injection may reduce the need forrepeated dilations, probably by reducing scar formation [28].

In recent years, the temporary placement of self-expandable stents has been shown to be successfulin managing refractory strictures. Plastic stents (e.g., Polyflex, Boston Scientific Corporation, Natick,MA), fully-covered, self-expandable metal stents (e.g., Wallflex esophageal stent, Boston Scientific;Evolution esophageal stent, Cook Medical Inc, Winstron-Salem, NC) or biodegradable stents (e.g., SX-Ella Esophageal Degradable BD Stent, Hradec Kralove, Czech Republic) have been successfully used. Thereported rate of stent migration has been rather high [29].

Malignant esophageal obstruction

Patients with malignant esophageal obstruction typically present with a more indolent course ofdisease. The most commonly observed symptoms are dysphagia, vomiting and weight loss. Endoscopyallows for therapy by means of self-expandable metal stents. Metal stents should be used for patientswho have locally advanced disease, metastatic disease or poor functional status not allowing for sur-gery. They can be used for intraluminal as well as extraluminal malignancies obstructing theesophagus.

Self-expandable metal stents are made out of a variety of metal alloys and may be uncovered, fullycovered or partially covered. Covered stents were developed to overcome the problem of tumoringrowth, however at a cost of increased migration risk. Covered stents can also be removed. Partiallycovered stents try to combine benefits of both types of stents while eliminating their side effects.Covered esophageal stents are preferred over uncovered stents mainly because of lower rates of tumoringrowth [30]. Esophageal stents are too large to pass through an endoscope. They may be deliveredunder fluoroscopic or endoscopic guidance. Some esophageal stents have an anti-reflux valve.Numerous esophageal stents produced by different companies are available on themarket. The efficacyof SEMS for malignant esophageal obstruction is high and stent patency at onemonth is usually around90%, however reinterventions for migration or ingrowth are required in up to half of the patients[31,32]. The most commonly encountered adverse events are pain, bleeding, perforation, migration,occlusion, gastroesophageal reflux and fistula formation. Chemoradiotherapy after stent placement ispossible and improves prognosis [33].

Plastic or biodegradable stents primarily intended for benign strictures may be used to relievemalignant esophageal obstruction in the setting of neoadjuvant therapy or as a bridge to surgery[34,35].

Gastric outlet obstruction

Gastric outlet obstruction (GOO) is a syndrome occurring when the stomach content cannot beemptied distally into the small bowel due to a mechanical obstruction. Distal gastric, duodenal andextraluminal diseases are responsible for GOO. The spectrum of causes has changed over years.Complicated peptic ulcer disease has been replaced as the leading cause by pancreatic malignanciesand distal gastric cancer [36]. Other causes include gastric lymphomas, polyps, carcinoids or metas-tasis, duodenal cancers, Crohn’s disease, acute and chronic pancreatitis, pancreatic pseudocysts, causticinjury, biliary ileus, amyloidosis, tuberculosis, eosinophilic esophagitis or gastric volvulus. Patientswith GOO typically present with abdominal pain, vomiting and abdominal distention. Weight loss maybe apparent in a more indolent course of disease. In differential diagnosis, gastric dysmotility pre-senting in a similar way has to be considered.

Acute and chronic peptic ulcer disease rarely cause GOO nowadays due to the widespread use ofproton pump inhibitors and Helicobacter pylori eradication [36]. Initially, an attempt for conservative

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treatment using supportive therapy and proton pump inhibitors should be done [15,37]. After a fewdays of medical therapy, reevaluation or a challenge with a liquid diet should be tried. Patients who donot respond to conservative therapy are indicated for endoscopic or surgical treatment [37]. Exclusionof malignancy should always be done prior to further treatment.

TTS balloon dilators are used in the treatment of benign strictures. Unless the stricture can bepassed with an endoscope, a wire and fluoroscopy should be used. The choice of a balloon is deter-mined by the initial diameter of the stricture. Rules similar to those applied in esophageal dilationsapply. Long strictures are generally more difficult to dilate than short ones. Many patients requiremultiple dilation sessions. Perforation is the most feared complication of dilation, and usually requiressurgical treatment.

Acute pancreatitis-associated strictures will resolve with resolution of the disease. Endoscopy hasbecome a standard and preferred approach to patients with symptomatic pancreatic pseudocysts.Endoscopic drainage is usually performed under endoscopic ultrasound guidance. Trangastric ortransduodenal cystostomy is carried out and plastic stents are introduced into the cyst through thegastrointestinal wall opening. They are left in place to allow drainage. Pseudocysts that contain infectednecrotic material may require endoscopic necrosectomy, performed through the initial cystostomy.

Gastric or duodenal polyps are usually resected with a polypectomy snare. Endoscopic derotationfollowed by percutaneous endoscopic gastrostomy (PEG) tube placement may be used to treat patientswith gastric volvulus. An attempt to derotate the stomach is made with careful manipulation of anendoscope through the stomach into the duodeneum. If successful, a PEG tube is placed to fix thestomach in the corrected position [38].

Currently, malignancies account for 50–80 % of cases of GOO [36]. SEMS should be considered inpatients with a symptomatic malignancy that is unresectable. Furthermore, SEMS should be consid-ered for patients with poor prognosis (life expectancy of less than half a year), whereas patients with abetter prognosis should be offered surgical bypass [39]. Relieving obstruction should allow the patientsto resume a normal diet and improve their quality of life.

Effective stenting cannot be expected if a downstream obstruction is present. Malignancies causingGOO, especially those located in the duodenum, are likely to cause a coexistent biliary obstruction [40].Once a duodenal stent is in place, it is difficult or impossible to reach the papilla and patients have toundergo percutaneous or endoscopic ultrasound guided drainage. Consequently, a downstream bowelobstruction as well as biliary obstruction should be excluded prior to stent placement. Patients withsigns of biliary obstruction should first have a metal biliary stent placed. Unfortunately, patients with abiliary SEMS who also undergo duodenal stenting are at increased risk of biliary stent dysfunction.

Nitinol uncovered stents, such theWallFlex (Boston Scientific) or Evolution (CookMedical) stents ofvarious lengths are commonly used. They have a width of 22 mm and a proximal and distal flare to awider diameter to prevent migration. The stent delivery systems enable their introduction through theendoscope channel of 3.8 mm or greater. A one-day liquid diet or placement of a nasogastric tube priorto procedure is recommended [41]. The stricture is approached with an endoscope, and a wire isintroduced through a biliary cannula and advanced through the lesion under fluoroscopy. Once thewire is safely beyond the lesion, contrast is injected through the cannula to evaluate the length of thestricture. A proper size of stent is chosen to allow sufficient extra length at both sides of the lesion.During deployment, a point is reached at which there is no possibility of stent recapture. At this time,the endoscopist makes sure that the stent is properly positioned and finishes the deployment (Fig. 2). Ittakes an additional day, or two days, for the stent to fully expand.

Technical success of stent placement for GOO can be achieved in about 90% of cases. The mostcommon reason for failure is inability to pass a wire through the stricture. Clinical success can beexpected in about 80% of patients [42]. In some patients, no effect is seen even when the stent iscorrectly placed. In some series, reintervention rates have been high [43]. Stent obstruction was themost common complication (18%) in a review of over 600 patients. Severe complications, such asbleeding and perforations were reported in only 1.2%. Migration occurred in 5% of patients [44].

In contrast to esophageal stenting, SEMS placement for GOO has a surgical alternative. In the SUS-TENT study, a prospective randomized study of 18 patients with GJJ and 21 patients with SEMS. Foodintake improved more rapidly after stent placement (5 vs. 8 days), but long term relief of obstructivesymptomswas better afterGJJ (duration of 50 vs. 72days).Moremajor complications occurred andmore

Fig. 2. Self-expandable metal stent for gastric outlet obstruction. Fluoroscopic image of: (A.) stricture (due to pancreatic cancer)distal to papilla with a wire passed through; (B.) uncovered SEMS in place with a typical post-deployment waist. Note the biliarySEMS in place.

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reinterventions were performed after stent placement than after GJJ. Initial costs, as well as total costs,were higher for GJJ [39]. Another study prospectively compared 9 patients in both groups. Efficientgastric emptying resumed more quickly in patients with SEMS, the operative time and hospital stayswere shorter in the stent group. However, there were no differences in clinical outcomes between thegroups at 3 months. Two cases of stent migration and 2 cases of food impaction occurred [45].

SEMS are effective in palliation of GOO, offering a rapid relief of obstruction, lower morbidity andlower costs compared with surgery. However, there is a considerable risk of complications and aworselong-term relief. Thus, they should be considered inpatientswith poor prognosis (life expectancy of lessthan half a year), whereas patients with a better prognosis should be offered a surgical bypass [39,43].

Small bowel obstruction

Small bowel obstruction accounts for about 80% of total acute bowel obstruction cases. In a study ofMarkogiannakis et al, the following were causes of small bowel obstruction: adhesions (73.8%), hernia(18.5%), large bowel cancer (2.6%), small bowel tumor (2.6%), Crohn’s disease (1.7%) and small bowelvolvulus (0.8%). Since adhesions and hernias comprised together a vast majority of cases (92.3%), mostpatients were treated in surgical wards by either conservative or surgical management [2].

Crohn’s disease can present with obstructive symptoms. Strictures can develop in any part of thesmall bowel, colon and typically at the ileocolonic anastomosis. In Crohn’s disease, active inflammationresults in edema, cytokine release, inflammatory cell infiltration and damage to the bowel wall. Thisprocess activates fibroblasts and smoothmuscle cells to a fibrogenic response. Consequently, stricturesin Crohn’s disease have an inflammatory and fibrotic component, even though the fibrotic part usuallydominates [46,47]. Patients presenting with obstruction and some inflammatory activity are thusinitially treated by anti-inflammatory drugs including corticosteroids.

Experience to support the use of endoscopic balloon dilation in obstructive Crohn’s disease islimited. Many published studies are heterogeneous and small in size. In a systematic review of 347patients from 13 studies, endoscopic dilation was mainly applied to postsurgical strictures, beingtechnically successful in almost 90% of cases. The long-term efficacy was 58% with up to 33 monthsfollow-up. A stricture length of less than 4 cm was associated with a surgery free outcome. Thecomplication rate was between 2 and 10% [47]. Balloon dilation is thus an effective technique, espe-cially for disease recurrence after ileocolonic resection, however complications may occur. Anotherproblemwith small bowel strictures may be their accessibility with an endoscope. Steroid injection forreducing the risk of recurrence has been shown to work in children, but not in adults [48,49].Biodegradable as well as fully covered metal stents have been tried in a small number of patients withvariable results [50,51].

Fig. 3. Balloon dilations for colonic postsurgical stricture. Endoscopic image of: (A.) rectal stricture prior to dilation; (B.) through-the-scope balloon dilation; C. post-dilation appearance of stricture.

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Fig. 4. Self-expandable metal stent for colonic obstruction. Fluoroscopic image of: (A.) colonic stricture; (B.) a wire passed throughthe stricture; (C.) deployment mechanism through across the stricture; (D.) uncovered SEMS with a typical post-deployment waist.

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Colonic obstruction

Acute colonic obstruction is less frequent than acute small bowel obstruction. In a study of Mar-kogiannakis et al, it was caused by large bowel cancer (47.4%), adhesions (36.3%), retroperitoneal tu-mors (5.5%), hernia (2.7%), ovarian cancer (2.7%), diverticulitis (2.7%) and sigmoid volvulus (2.7%) [2].Crohn’s disease strictures or postsurgical anastomotic strictures in the colon may be dilated with a TTSballoon (Fig. 3) as described earlier in this article. Small reports have shown successful use of SEMS fordiverticular strictures, enabling delayed, one-step surgery, however the experience is very limited [52].Biodegradable stents have been used in a few patients in the treatment of postsurgical strictures andfistulas with promising short-medium term results [53]. Volvulus can occur at all levels of the colonexcept the rectum. Endoscopy can be attempted to derotate and decompress the colon. It may be a finalprocedure, however, since the chance of recurrence is high, an elective one-step colon resection isusually performed. In case of failure, surgery is performed urgently [21].

Malignancies constitute the most frequent cause of large bowel obstruction with a prevalence of40–90% [2]. Up to 30% of patients with colorectal cancer will present with signs of obstruction [54].Endoscopy plays an important role in the management of these patients, especially by means of SEMSplacement. The purpose of SEMS insertion is to perform decompression of the obstructed bowel. It maybe later followed by one-step surgery (primary resection and anastomosis), thus saving the patientfrom a standard two-step procedure. In those patients who are not surgical candidates, either becausesignificant comorbidities or because of locally advanced or metastatic disease, the SEMS placementmay be a final palliation [21]. SEMS are also useful in patients with obstructing rectal cancer who are toundergo neoadjuvant chemoradiation [55]. Colonic stenting should not be attempted in patients wheresigns of systemic toxicity resulting from bowel ischemia, necrosis or perforation are present [21].

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There is a variety of colonic stents available on the market. For malignant colonic obstruction,uncovered or covered stents are used. The absence of covering increases the chance of tumor ingrowth,on the other hand it decrease the chances of migration. Studies that compared uncover and cover stentsdid not show any significant difference in technical or clinical success rates [56,57], however a highermigration rate was seen with the covered stents and a loss of stent function occurred at a lower ratewith the uncovered stents. Apart from stents from several South Korean manufactures, the mostcommonly used stents are the Wallstent (6 cm and 9 cm long; 20 and 22 mm internal diameter), thenitinol WallFlex stent (6, 9 and 12 cm long; 22 and 25 mm internal diameter) and the nitinol Evolutionstent (6, 9 and 12 cm long; 22 and 25 mm internal diameter). All of the above stents are made forthrough-the-scope delivery with the scope having an accessory channel of at least 3.8 mm. There arealso larger stents available that require along-the-scope delivery [21,58].

Obtaining a water-soluble/barium enema study or a CT scan prior to the procedure is helpful toguide the endoscopic procedure. Information about location, tightness, shape and length of thestricture is valuable. These studies will also rule out a perforation or any other obstruction proximal tothe stricture. In case of complete obstruction, the stools below the lesion have usually already evac-uated, decreasing the need for bowel preparation and a couple of rectal enemas should be sufficient toprepare the colon [21]. In subtotal obstruction, a carefully administered standard colonoscopy prepmay be used. The procedure usually starts with the patient in the left decubitus position and may bechanged to enable smooth access to the stricture. The supine position allows for better fluoroscopycontrol. Standard intravenous conscious sedation is adequate.

Colonic SEMS are usually placed through the scope under endoscopic and fluoroscopic guidance. Inthe clinical scenario of acute bowel obstruction, the stenosis is usually so tight that an endoscopecannot pass through. A standard biliary catheter loaded with awire is used to pass the stricture. If a softhydrophilic guidewire is used for initial cannulation, it is convenient to exchange it for a flexible tip stiff0.035 wire for stent deployment [21]. Balloon dilations should be avoided unless the delivery mech-anism cannot pass through the stricture [54]. Next, contrast is usually administered by the biliarycatheter to define the anatomy. Finally, the stent is passed over the guidewire and is deployed underendoscopic and fluoroscopic guidance. The stent should be at least 4 cm longer than the stricture toallow for a proper placement that can be assumed from a visiblewaist and flares shape of the stent afterdeployment (Fig. 4). In case this typical picture is not seen, another stent may need to be used tocompletely traverse the lesion [59]. Following the procedure, the patients should be instructed tomaintain a low fiber diet that will result in soft consistency stool. Stool softener, laxatives or mineral oilcan be used in addition [16].

Most studies report on stents placed for left sided colonic obstruction except for the distal 5 cm fromthe anal verge [60]. Stent placement in the proximal colon may be more challenging but comparable inefficiency to distal stenting [61] whereas stent placement in the terminal rectum may be associatedwith rectal symptoms such as tenesmus, pain or fecal incontinence [21]. In a study that evaluated 168patients who underwent SEMS placement for palliation and 65 patients who underwent SEMSplacement as a bridge to surgery, technical and immediate clinical success rates were 96% and 99% inthe first group and 95% and 98% in the second group. However, almost a quarter of the patients in eachgroup had complications including perforation (9%), occlusion (9%), migration (5%) and erosion/ulcer(2%). The mean stent patency was 145 days in the palliative group and almost 90% of patients were freeof obstruction at the time of death. Risk factors for complication were male sex, complete obstruction,stent diameter �22 mm, stricture dilation during SEMS insertion and operator experience. In thepalliative group, higher complication rates were seen in intraluminal lesions, bevacizumab treatmentand distal colon stent placement. Bevacizumab therapy nearly tripled the risk of perforation [62]. In arecent large European study, the technical success rate of colonic stenting was 94.8% and clinicalsuccess rate was 90.5%. Perforations occurred in 3.9% of patients, migrations in 1.8% of patients. Theauthors concluded that colonic SEMS were safe and highly effective with a low risk of perforation [63].

Complications of colonic stenting include perforation, stent migration, bleeding, tumor ingrowth orabdominal pain [21]. Perforation is the most common complication, with a reported median rate of4.5% in a systematic review [64]. However, the reported range of incidence was 0–83%, suggesting thatrisk factors such as patients’ characteristics and technical variables widely influence the outcome [64].There is an increasing amount of evidence that treatment with the antiangiogenic agent bevacizumab

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may increase the risk of perforation [62]. In a recent study that retrospectively evaluated 201 patientswith palliative SEMS placement, 12 patients had a perforation. Fifty percent of those receiving bev-acizumab experienced a perforation (OR 20, CI 5.9–65) [65]. Thus, this observation may need to beconsidered in patients evaluated for SEMS placement. Other risk factors such as prior dilation with aballoon and lack of endoscopist’s experiencemay be overcomemore easily. Migration occurred in 5% ofpatients in the study of Small et al [62] and in 11% in a systematic review byWatt et al [64]. Migration ismore likely to occur with covered stents, narrow and short stents, in the presence of non-obstructivestrictures or as a result of tumor shrinkage following oncologic therapy [54]. It occurs primarily within1 week and distally, proximal migration following successful placement generally does not occur [21].Bleeding is usually minor and self-limiting. Pain is typically mild, temporary and does not require anytreatment apart from use of analgesics.

Similar to GOO, colonic stenting has a surgical alternative that is a widely available, standardprocedure. However, in the setting of colorectal obstruction, it usually requires a two-step approach. Inthe first step, resection of the tumor and a temporary stoma are performed. Primary anastomosis isavoided because of concern that the uncleansed colon proximal to the obstruction will lead tobreakdown of the colonic anastomosis [21]. Furthermore, endoscopic decompression allows for clinicalstabilization of acutely ill patients as well as detailed evaluation of the extent of their disease.Morbidity and mortality of emergent surgery are significantly higher than morbidity and mortality ofelective surgery [66]. However, studies comparing SEMS versus surgery in acute colonic obstructionhave reported conflicting results. In a recentmeta-analysis of four randomized control studies with 234patients, the technical and clinical success rates for stenting were 70.7% and 69.0%, respectively. Theclinical perforation rate was 6.9% and the silent perforation rate was 14%. SEMS placement resulted in asignificantly higher rate of successful primary anastomosis (RR 1.58, CI 1.22–2.04) and lower overallstoma rate (RR 0.71, CI 0.56–0.89, p ¼ 0.004). No differences were observed in primary anastomosis,permanent stoma, anastomotic leak and 30 day reoperation rates and in-hospital mortality [67].Interestingly, three of the four evaluated studies from this metaanalysis were stopped prematurely.One trial found that overall morbidity was significantly greater in patients with emergency surgery[68]. In contrast, Pirlet et al stopped their trail after finding a high number of stent-related compli-cations [69]. Van Hooft et al stopped their trail because of an unexpectedly increased absolute risk of30-day morbidity in the SEMS group. However, 70% of their patients had complete obstruction [70].The degree of obstruction has been suggested as a risk factor for complications [62]. A cost-effectiveness analysis stated that colonic SEMS placement followed by surgery was more effectiveand less costly than emergency surgery [71].

The stent can serve as a long-term palliation in case patients will not be eligible for surgery. Surgicalpalliation with a stoma is also possible. The results of comparisons between palliative stenting andsurgery are also not fully clear. In a retrospective study that compared palliative stenting with surgeryin 114 patients, the early success rates were comparable. The median patency of the first SEMSwas lessthan surgery, however this improved following placement of a second stent. There were fewer earlycomplications but more late complications in the SEMS group, most commonly obstruction from stentocclusion, however these differences were not statistically significant [72]. A study that randomizedpatients to palliative SEMS placement or surgery had to be stopped due to a high rate of perforations inthe stenting group [70].

Acute colonic pseudoobstruction

Acute colonic pseudoobstruction (ACPO), first described by Ogilvie in 1948, is characterized bymassive colonic dilation with symptoms and signs of colonic obstruction but without mechanicalblockage. It is associated with high morbidity and mortality. Spontaneous perforation occurs in up to15% of cases, with at least 50% mortality when it occurs. ACPO results from an alteration of the auto-nomic regulation of the digestive tract. However, the exact pathogenesis remains unclear. The majorityof patients have the syndrome in association with a predisposing factor such as trauma, infection,cardiac disease, abdominal, obstetric or orthopedic surgery. The colon is grossly dilated on examina-tion. Neostygmin and erythromycin have been used to treat ACPO. Colonoscopic decompression maybe helpful in ACPO, but it is associated with a greater risk of complications. Enemas may be used to

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prepare the colon. Once the right colon is reached, a tube for decompression should be placed over aguidewire with fluoroscopic guidance. The wire is left in position, the endoscope is removed, and thetube is inserted over the wire with the aid of fluoroscopy. Percutaneous cecostomy is another way todecompress the colon. Those who fail medical or endoscopic therapy, and those with signs of ischemiaor perforation are candidates for surgery [20].

Summary

Even though acute gastrointestinal obstruction if often an emergency that requires surgical therapy,many patients will be treated conservatively in medical wards. Medical treatment plays an importantpart of their management. Patients present with signs of dehydration and metabolic disturbance thatneed to be corrected. Endoscopy has become an important part of the diagnostic and therapeuticprocess of gastrointestinal obstruction management. Endoscopic relief of obstruction using self-expandable metal stents has been shown to be feasible and efficient for patients with malignantobstruction of the gastrointestinal tract. It has become an accepted palliative treatment of obstructionof the esophagus, stomach, duodenum and colon, even though its complications need to be considered.In the esophagus and colon, in may also serve as a bridge to surgery or to allow for neoadjuvanttreatment. Endoscopy can also be useful in treatment of benign strictures or volvulus. Emergencysurgery remains the only possibility for patients with suspected vascular compromise or perforation orwhen conservative management including endoscopy fails.

Practice points

� Acute gastrointestinal obstruction can be a life threatening situation that requires promptdiagnosis and effective therapy

� Endoscopy plays an important role in the diagnosis and therapy of acute gastrointestinalobstruction

� The use of self-expandable metal stent has proven efficient and safe in treating gastroin-testinal obstruction either as a bridge to surgery or palliation

Research agenda

� The benefits of stenting over surgery in the treatment of gastric outlet and colonic obstructionare inconsistent across studies with some reports suggesting lower long-term relief and highmorbidity

� Detailed analysis of available data and prospective randomized trials comparing endoscopicand surgical therapy including a larger number of patients are needed to define advantages ofthe two modalities and possibly allow for a better selection of patients benefiting from eithertherapy

Conflict of interest

The author declares no conflict of interest.

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