Large bowel obstruction may be caused by neoplasms or anatomic abnormalities, such as volvulus, incarcerated hernia, stricture, or obstipation. The challenges in managing this condition are distinguishing colonic obstruction from ileus, ruling out nonsurgical causes, and determining the best surgical management.
Large bowel obstruction from an anatomic abnormality leads to colonic distention, abdominal pain, anorexia, and, late in the course, feculent vomiting. Persistent vomiting may result in dehydration and electrolyte disturbances.
The morbidity and mortality often are related to the surgical procedure used to relieve the colonic obstruction and, in the long term, to the underlying disease that caused the obstruction.
Age
Colonic obstruction is most common in elderly individuals because the incidence of neoplasms and other causative diseases is higher in this population.
In neonates, colonic obstruction may be caused by an imperforate anus or other anatomic abnormalities. Obstruction also may be secondary to meconium ileus.
Hirschsprung disease resembles colonic obstruction in the pediatric population.
History focuses initially on the failure to pass stools or gas. One should attempt to distinguish complete bowel obstruction from partial obstruction, which is associated with passage of some gas or stools, and from ileus.
Further historical questioning may be directed at the patient's current and past history in an attempt to determine the most likely cause.
Complete obstruction is characterized by the failure to pass either stools or flatus and the presence of an empty rectal vault upon rectal examination, unless the obstruction is in the rectum.
Partial obstruction, in which the patient appears obstipated but continues to pass some gas or stools, is a less urgent condition.
Distinguishing colonic ileus from organic obstruction is important.
Ileus may be suggested by abdominal pain as a dominant feature of the clinical presentation, by peritoneal signs, or by the presence of pronounced fever and leukocytosis.
Large bowel obstruction, or even constipation, may be accompanied by some degree of fever or leukocytosis. Similarly, based on peritoneal signs, distinguishing the tender gas-filled and stool-filled colon observed in organic obstruction from a tender abdomen due to peritonitis is difficult.
Obtaining a thorough history of previous bowel function, abdominal pain, and general systemic issues is important.
History of chronic weight loss and passage of melanotic bloody stools suggest neoplastic obstruction.
Conversely, a history of recurrent left lower quadrant abdominal pain over several years is more consistent with diverticulitis, a diverticular stricture, or similar problems.
A history of aortic surgery suggests the possibility of an ischemic stricture.
Although a complete physical examination is necessary, key elements of the physical examination should focus on thorough examination of the abdomen, groin, and rectum.
Abdominal examination
Perform the examination in standard fashion, that is, inspection, auscultation, percussion, and palpation.
Large bowel obstruction may be characterized by diminished or, in later stages, absent bowel sounds.
The abdomen is distended and may be tender.
The presence of true involuntary guarding or peritoneal signs should raise the specter of another intra-abdominal process, such as an abscess.
The practice of seeking rebound tenderness is misleading and potentially cruel. Many patients without peritoneal signs complain vigorously after an aggressive rebound maneuver. Seeking tenderness and pain by having the patient cough or by shaking the bed probably is more useful.
Examination of inguinal and femoral regions
This should be an integral part of the examination.
Incarcerated hernias represent a frequently missed cause of bowel obstruction.
In particular, colonic obstruction often is caused by a left-sided inguinal hernia with the sigmoid colon incarcerated in the hernia.
Digital rectal examination
Perform this to verify the patency of the anus in a neonate.
The examination focuses on identifying rectal pathology that may be causing the obstruction and determining the contents of the rectal vault.
Hard stools suggest impaction.
Soft stools suggest obstipation.
An empty vault suggests obstruction proximal to the level that the examining finger can reach.
Fecal occult blood testing should be performed, and a positive result may suggest the possibility of a more proximal neoplasm.
Studies are directed at evaluating the dehydration and electrolyte imbalance that may occur as a consequence of large bowel obstruction and at ruling out ileus as a diagnosis.
Routine serum chemistries and urine specific gravity should be evaluated.
Suggestion of an abnormal anion gap also should prompt an arterial blood gas measurement and/or a serum lactate level measurement.
A decreased hematocrit level, particularly with evidence of chronic iron-deficiency anemia, may suggest chronic lower gastrointestinal bleeding, particularly due to colon cancer.
A stool guaiac test also should be performed, for similar reasons.
Although bowel obstruction, or even constipation, may mildly elevate the WBC count, substantial leukocytosis should prompt reconsideration of the diagnosis. Ileus, secondary to an intra-abdominal or extra-abdominal infection or another process, is a possibility.
Flat and upright abdominal roentgenography demonstrates dilation of the small and/or large bowel and air fluid levels.
An upright chest x-ray generally is ordered simultaneously to determine whether free air is present, which would suggest perforation of a hollow viscus and ileus rather than organic obstruction.
Tracing colonic air around the colon, into the left gutter, and down into the rectum or demonstrating an abrupt cut-off in colonic air suggests the anatomic location of the obstruction.
A dilated colon without air in the rectum is more consistent with obstruction. The presence of air in the rectum is consistent with obstipation, ileus, or partial obstruction.
This finding can be misleading, particularly if the patient has undergone rectal examinations or enemas.
The characteristic bird's beak of volvulus may be seen.
Radiopaque contrast material may be administered and imaging of the colon may be performed under the following circumstances. Perform it if the diagnosis of large bowel obstruction is suspected but not proven. If differentiation between obstipation and obstruction is required, imaging with contrast is indicated. If localization is required for surgical intervention, imaging with contrast is indicated.
Water-soluble Gastrografin has important advantages over barium as a contrast agent and generally should be used first. It usually does not cause chemical peritonitis if the patient has colonic perforation. It has an osmotic laxative effect that may actually wash out an obstipated colon.
If large bowel perforation is ruled out using a Gastrografin study but a more detailed anatomic definition is required (particularly of the right colon), a barium enema may be performed.
Although CT scanning is useful to help rule out intra-abdominal abscess or other causes of ileus, it generally is not used initially in patients with large bowel obstruction unless a diagnosis has been made. CT scan, particularly with rectal contrast, may demonstrate a mass or evidence of metastatic disease. Generally, the findings do not alter management because these patients will be explored and operatively decompressed, regardless of the CT scan findings. CT colography may be useful in evaluating these patients, not only to delineate the source of the obstruction but also to rule out synchronous proximal lesions, which may occur in about 1% of patients and which might motivate a more extended resection if identified and if the patient's condition will tolerate the more extensive procedure.[1]
Flexible endoscopy preceded by rectal enema may be useful in evaluating left-sided colonic obstruction, including the anatomic location and pathology of the lesion.
Because the cecum is not reached in such cases, the endoscopist must be alert to the possibility of incorrectly identifying anatomic landmarks and the location of the obstruction.
An abdominal roentgenogram with the tip of the endoscope at the site of the obstruction may be extraordinarily helpful in identifying and documenting the location of the large bowel obstruction.
Although flexible endoscopy is relatively comfortable for the patient and provides a better view than rigid sigmoidoscopy, the latter also may be used, depending on the availability of resources and training of personnel.
Right-sided colonic obstruction is more difficult to evaluate without first administering an oral bowel preparation, which is contraindicated in the setting of bowel obstruction.
This procedure is indicated for sigmoid volvulus when peritoneal signs are absent, which would imply dead bowel or perforation. It also is indicated when evidence of mucosal ischemia is not present upon endoscopy.
This procedure is not indicated for the less common cecal or transverse colon volvulus.
An experienced person should perform the procedure.
A rigid sigmoidoscope may be used if a flexible instrument is not available. The endoscopist must have sufficient experience with this technique.
Reduction of a volvulus does not imply cure. The sigmoid usually revolvulizes if definitive treatment is not carried out.
These patients generally are admitted, subjected to mechanical bowel preparation, and managed surgically by sigmoid resection, unless contraindications are present.
Barium enema for reduction of intussusception
This is useful and often successful in children in whom a pathological leading point for the intussusception is unlikely.
It should be performed by an experienced radiologist because the risk of perforation is significant.
In adults, typically a pathologic leading point for the intussusception is present. Success is far less likely, and patients still require surgery to deal with their pathology.
Cleansing enemas
Perform these if obstipation is suspected rather than true large bowel obstruction.
Also perform them to prepare the distal colon for endoscopic evaluation.
Endoscopic dilation and stenting of colonic obstruction
This procedure is indicated for colonic near total obstruction through which some small amount of lumen remains.
The procedure may be palliative in a high-risk patient with an unresectable malignancy, accepting a risk of reobstruction of the stent, or preparatory to surgical resection.
In cases in which the stent is deployed prior to surgery, it permits relief of the acute obstruction, resuscitation of the patient, and mechanical bowel preparation prior to a one-stage colonic resection and reanastomosis, thus avoiding temporary or permanent colostomy.
The procedure should be performed only by an endoscopist experienced in such procedures.
Surgical consultation and backup should be available, as the risk of perforation is increased during attempts at such procedures, with a potentially catastrophic result.
Although some experience with stenting has been positive,[2] with some retrospective preference for the Ultraflex stent over the Wallstent because of ease of placement, a recent multicenter trial of endoscopic stenting using the Wallstent versus surgery for stage IV left-sided colorectal cancer was terminated early because of an unacceptably high incidence of perforation.[3] Whether this reflects the technical aspects of the procedure in that study, the particular stent used, or a truly unacceptable incidence of this dangerous complication awaits further study.
Histology is of minimal relevance to the acute management of a large bowel obstruction because the obstruction must be relieved regardless of the pathology. However, the histological distinction between malignant and benign causes of obstruction obviously is important for subsequent patient management.
Medical care of colonic obstruction involves resuscitation, correction of the fluid and electrolyte imbalance, and nasogastric decompression to temporarily treat the obstruction and to prevent vomiting and aspiration.
Medical care is directed primarily at supporting the patient and treating any comorbid illnesses.
For a small subset of patients, in whom the obstruction not only is malignant but also reflects substantially disseminated or even inoperable disease, consideration of completely nonoperative palliative therapy within the context of a palliative care or hospice approach may be appropriate. This might include somatostatin therapy and may or may not include nasogastric decompression.[4]
Surgical care is directed at relieving the obstruction.
In most patients, the obstructing lesion is resected. Because the colon has not been cleansed, anastomosis often is risky. After resection, most surgeons perform a proximal colostomy if the obstruction is on the left side or ileostomy if it is on the right side.
In patients with substantial comorbidity and surgical risk or in the presence of an unresectable tumor, a diverting proximal colostomy or ileostomy may be performed without resection.
A diverting transverse loop colostomy may be the least invasive procedure for a very ill patient with a left colonic obstruction. It permits relief of the obstruction and further resuscitation without compromising chances for a subsequent resection. A recent case report describes the use of hand-assisted laparoscopy via the loop colostomy site for subsequent resection of the obstructing lesion.[5]
A sigmoid colostomy without resection may be used in patients with a rectal obstruction that cannot be managed without a combined abdominoperineal approach.
Cecostomy should not be performed because the diversion is inadequate.
In younger patients without substantial comorbidity, some surgeons would consider primary anastomosis, rather than ileostomy, in the right colon, assuming no intraoperative hypotension, blood loss, or other complications are present.
If resection and proximal colostomy or ileostomy are performed, a mucous fistula generally is extracted from the distal end, unless the obstruction is rectosigmoid, in which case the distal end may be oversewn or stapled and left to drain transanally.
If the cause of the obstruction can be relieved nonsurgically, through procedures such as decompressing a volvulus, or if the obstruction is only partial, deferring surgery temporarily and supporting the patient while the large bowel is cleansed so that primary anastomosis may be performed more safely is preferable.
Oral laxatives are contraindicated if large bowel obstruction is suspected. If any evidence suggests simple constipation, patients should be managed with transrectal enemas. Tap water, isotonic sodium chloride solution, and a variety of other fluids may be used. In patients with renal insufficiency, the physician should be sensitive to the electrolyte content of the fluid.
Care after discharge focuses on surgical convalescence and, if relevant, the need to care for the disease that caused the obstruction. An obstructing colon cancer may require postoperative chemotherapy, depending on the stage of the disease. The patient who is chronically obstipated may need stool softeners.
If the patient has received a colostomy or ileostomy, a decision regarding whether it is temporary or permanent may have been made at the time of discharge, depending on the patient's diagnosis, comorbidity, and postoperative convalescence.
Most patients who retain a rectum are, at least in principle, candidates for reanastomosis at a subsequent stage. Generally, it is performed 2-3 months after the initial operation. Careful counseling and assessment are required before proceeding with the second procedure.
Counseling is directed at the risks of the second procedure because the patient must understand that this surgery is elective and that a colostomy or ileostomy is compatible with a reasonable lifestyle. Often, local ostomy support groups and meeting with other patients with ostomies are helpful at this time.
Patients who had stool incontinence before their first operation, those with substantial surgical risks, and patients with decreased mental status who are cared for in nursing homes may potentially be better off without a reanastomosis.
In addition, the remaining colon, both proximally and distally, must be evaluated radiographically or endoscopically to rule out synchronous colonic lesions, such as neoplasms, because the presence of the large bowel obstruction prevented this from being performed before the first procedure.
Pain medicines generally should be avoided preoperatively. If the pain is sufficiently severe to merit use of significant analgesics, peritonitis, rather than large bowel obstruction, should be considered as the first diagnosis.
Oral laxatives are contraindicated in patients with complete large bowel obstruction.
A slow preoperative mechanical bowel preparation is indicated for patients who have incomplete obstruction, provided the patient can tolerate it.
The author's preference is for polyethylene glycol solutions, such as GO-LYTELY, because they avoid issues of fluid and electrolyte imbalance. The fluid should be administered slowly (rather than given in the standard manner of 1 gal over 4 h), and the patient should be observed for abdominal cramping and intolerance.
Patients with an endoscopically reduced sigmoid volvulus should be offered elective surgical procedures, including sigmoid resection or fixation, because of the high risk of recurrence.
Aggressive screening for colorectal cancer in individuals who are older than 50 years or who have a strong family history of colorectal cancer, as indicated by current guidelines, should reduce the future incidence of malignant colonic obstruction.
See related CME at Guidelines Issued for Early Detection of Colorectal Cancer.
Peritonitis from bowel perforation secondary to overstrenuous attempts at reduction of volvulus or intussusception or injudicious attempts to dilate or stent an unsuitable colonic obstruction
Misdiagnosis of an ileus secondary to intra-abdominal infection as large bowel obstruction, with consequent delay in treatment
Prior to surgical decompression, the patient's overall medical condition and presence of any comorbidities that define surgical risk determine the prognosis.
After surgical decompression, prognosis is determined by the underlying disease.
Marc D Basson, MD, PhD, MBA, FACS, Professor, Chair, Department of Surgery, Assistant Dean for Faculty Development in Research, Michigan State University College of Human Medicine
Disclosure: Nothing to disclose.
Specialty Editors
Juan B Ochoa, MD, Assistant Professor, Department of Surgery, University of Pittsburgh; Medical and Scientific Director, HCN, Nestle Healthcare Nutrition
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Medscape Salary Employment
BS Anand, MD, Professor, Department of Internal Medicine, Division of Gastroenterology, Baylor College of Medicine
Disclosure: Nothing to disclose.
Alex J Mechaber, MD, FACP, Senior Associate Dean for Undergraduate Medical Education, Associate Professor of Medicine, University of Miami Miller School of Medicine
Disclosure: Nothing to disclose.
Chief Editor
Julian Katz, MD, Clinical Professor of Medicine, Drexel University College of Medicine