Surgery for Toxic Megacolon



Surgery for Toxic Megacolon


David A. Rothenberger

Kelli Bullard Dunn



Toxic megacolon is an imprecisely defined term used to describe a life-threatening clinical syndrome arising in the setting of acute colitis or an acute exacerbation of chronic colitis. Toxic megacolon is characterized by non-obstructive segmental or total colonic dilation with resultant abdominal distension and pain accompanied by signs of systemic toxicity usually including tachycardia, fever, and leukocytosis. Depending on the acuity and severity of the colitis, hypoalbuminemia, anemia, and electrolyte imbalance may be observed. Mental status changes and hypotension progressing to shock are ominous signs of impending death from underlying sepsis.


Etiology and Epidemiology

In the past, toxic megacolon usually developed in the patients with chronic ulcerative or Crohn’s colitis. Today, this is a rare occurrence, probably because gastroenterologists carefully manage the patients with known idiopathic inflammatory bowel diseases and refer them to surgeons before toxic megacolon develops. If outpatient therapy of acute exacerbations of colitis fails to resolve the symptoms, patients are typically hospitalized for more intensive non-operative therapy. Failure to improve or development of signs of toxicity even in the absence of colonic distension (“toxic colitis”) triggers surgical consultation. In this way, intervention can prevent toxic colitis from progressing to toxic megacolon. Operative strategies for these two conditions are similar, though the presence of megacolon poses additional problems to the surgeon.

Today, toxic megacolon is more often seen in patients at their initial presentation
of ulcerative or Crohn’s colitis or in patients with other forms of colitis including pseudomembranous (Clostridium difficile) colitis, cytomegalovirus colitis, colitis associated with salmonellosis, Campylobacter jejuni and other bacteria, ischemic colitis, or drug-induced colitis including chemotherapy. C. difficile colitis has become increasingly problematic. Recent reports have documented both an increase in the incidence and severity of this disease. The emergence of a fluoroquinolone-resistant, highly toxigenic strain of C. difficile poses a new threat to effective antibiotic control of this form of colitis.

Acute colonic pseudo-obstruction does not generally progress to toxic megacolon, but can produce ischemia that leads to perforation. Although the etiology of this disease is poorly understood, it occurs most often in hospitalized patients with severe underlying medical and/or surgical disease. Early recognition and treatment are critical to avoid progression. The treatment consists of resuscitation, medical management of the underlying condition, and occasionally colonoscopic or pharmacologic (neostigmine) decompression. Progression to ischemia and perforation is associated with mortality of up to 40%.

The incidence of toxic megacolon has substantially decreased over the past 30 years. For example, in the patients undergoing colectomy for acute colitis, the incidence of toxic megacolon decreased from 71% between 1975 and 1984 to 22% between 1995 and 2005. In addition, mortality decreased from 10% to 2% over this period of time. These better results likely reflect improvements in critical care and a shift toward early operation in the patients with severe, but nontoxic, colitis.


Initial Evaluation and Resuscitation

Initial management of the patient with toxic colitis or toxic megacolon is the same. Clinical evaluation; baseline laboratory tests including blood, stool, and urine cultures; and flat and upright abdominal radiographs or CT scan are obtained concomitant with the stabilization of the patient by vigorous fluid resuscitation and prompt correction of electrolyte abnormalities. An indwelling urinary bladder catheter is useful to monitor the urine output and assess the adequacy of resuscitation. Transfusion of blood products may be needed. Broad-spectrum antibiotics tailored to treat colonic bacteria are begun. Other initial treatment includes bowel rest and nasogastric suction. If the patient has been on corticosteroids, stress-dose intravenous steroids are administered.


Indications for Emergency Surgery

Following stabilization of the patient’s vital signs, a decision is made to either operate emergently or to treat the patient aggressively in the hope of reversing the toxic state. Free air, diffuse peritonitis, localized peritonitis with associated increasing abdominal pain and/or acute distension of the colon greater than 10 cm, major hemorrhage, and uncontrolled sepsis are the primary indications for emergency laparotomy. The decision to operate for toxic colitis or toxic megacolon in the absence of these indications is more difficult. Table 1 lists the absolute and relative indications for surgery.

Advocates of aggressive medical therapy note that over half of the patients with flares of acute colitis from inflammatory bowel disease respond to high-dose corticosteroids, cyclosporine, and other drugs and can be spared the need for emergency colectomy. Conversely, advocates for early surgical intervention point out that mortality from operations for toxic megacolon or toxic colitis is usually the result of delays in operative intervention. This is especially tragic, they say, since most patients with toxic megacolon who initially improve without surgery eventually require colectomy.

The threshold to operate is dependent on the overall status of the patient’s health and the cause, duration, and extent of the patient’s colitis as well as the adequacy of prior therapy. In general, the sicker the patient, the lower is the threshold for operating in the setting of toxic colitis or megacolon. Severely malnourished, anemic patients with multiple co-morbidities will not tolerate a colonic perforation that occurs while undergoing well-intentioned but ill-advised medical therapy. Patients who are immunosuppressed from underlying diseases, such as human immunodeficiency virus infections, or from drug therapies, such as posttransplant regimens, are particularly at risk. For these patients, early intervention is advised.

Similarly, early operative intervention is usually indicated for the patients with toxic colitis or toxic megacolon and a history of ulcerative or Crohn’s colitis that had progressed despite adequate therapy to the point that elective surgery was being strongly considered. There is little benefit from aggressive medical therapy with its attendant risks of progression to perforation in such patients who will almost certainly need surgery anyway even if the toxic state can be reversed.


Initial Nonoperative Management

In the absence of the need for emergency laparotomy, non-operative management is continued with antibiotics and bowel rest and the diagnostic workup is pursued. Barium enema is avoided because it may worsen the megacolon, and if perforation occurs, barium peritonitis is often lethal. Supportive measures including hyperalimentation are instituted. Antidiarrheal agents, opiates, belladonna alkaloids, and narcotics should be avoided as they may worsen the toxic megacolon. Specific medical treatment to induce remission is instituted based on the known or likely cause of the underlying colitis.

For the patients with severe colitis resulting from inflammatory bowel disease, intravenous corticosteroids have been the mainstay of medical therapy. More recently, immunomodulators such as cyclosporine and tacrolimus have been proposed as adjunct therapy. Some authors report success in avoiding colectomy when these drugs are used as a bridge to more conventional immunosuppression (6-mercaptopurine, azathioprin), but their role in toxic colitis and/or megacolon is undefined. For the patients with signs and symptoms of sepsis, immunosuppression should probably be avoided.








Table 1 Indications for Surgery




















Absolute Relative
Pneumoperitoneum Inability to promptly control sepsis
Diffuse peritonitis Increasing megacolon
Localized peritonitis with increasing abdominal pain and/or colonic distension >10 cm Failure to improve within 24–48 h
Uncontrolled sepsis Increasing toxicity or other signs of clinical deterioration
Major hemorrhage Continued transfusion requirements

Conversely, if there is a history suggestive of a specific infectious cause for the colitis
and no history of antecedent idiopathic inflammatory bowel disease, antibiotics or other non-operative therapy tailored to the likely causative agent is generally indicated. A medical “cure” may be achieved for many such patients with toxic colitis or megacolon from infectious colitis. Corticosteroids are generally contraindicated in this setting. Patients with probable pseudomembranous toxic megacolon are generally treated with a combination of intravenous metronidazole plus oral vancomycin supplemented by gentle vancomycin enemas. If oral intake is not possible, vancomycin is given per the nasogastric tube. The combination of infection and inflammatory bowel disease can be particularly problematic. C. difficile, in particular, can exacerbate colitis in these patients. It has been estimated that C. difficile may be an inciting factor in ulcerative or Crohn’s colitis in up to 5% of the patients. As such, C. difficile infection should always be considered in these patients.

A particularly difficult diagnostic dilemma is posed by the patient who presents with acute toxic megacolon and no known history of ulcerative colitis or Crohn’s disease and no history suggestive of infectious colitis such as recent use of antibiotics or foreign travel. Such patients may benefit from additional diagnostic workup including stool for Gram stain and cultures for pathogens as well as a limited proctoscopy examination. If performed gently and without air insufflation, such an examination can provide useful information to guide medical therapy without iatrogenic injury. The rectal mucosa is visualized and biopsied for histology. Diffuse mucosal granularity with friability may suggest a diagnosis of ulcerative colitis. Aphthous ulcers, rake ulcers, or skip areas of diseased mucosa with intervening normal mucosa may suggest Crohn’s disease. Pseudomembranes suggest the diagnosis of infectious colitis from Clostridium difficile.


Monitoring Medical Therapy

Mortality from toxic megacolon or toxic colitis most often arises because of the delays in the decision to operate, resulting in irreversible sepsis. This can occur even in the absence of free perforation. Bacterial translocation through the ulcerated mucosal surface can result in bacteremia and severe sepsis. Thus, frequent (two to four times per day) clinical evaluations coupled with serial monitoring of hemoglobin, white blood cell counts, and abdominal radiographs are essential to determine the patient’s response to medical therapy. The response to medical therapy determines the need for operative intervention and is categorized as an improvement, a plateau, or a deterioration.


Improvement

Medical management is continued if the patient’s condition is clearly improving as denoted by reversal of signs of toxicity including fever, tachycardia, leukocytosis, abdominal pain, and colonic distention. Return of bowel function and cessation of hematochezia are favorable signs. As improvement continues, treatment of the underlying cause of the colitis is maximized, oral intake is begun, and intravenous therapy is changed to oral agents. If tolerated, the patient is discharged and followed closely in the outpatient setting.


Plateau

Patients may reach a plateau after institution of medical therapy. This clinical scenario is characterized by initial reversal of some of the signs of toxicity but failure to resolve other parameters. For instance, the colonic distension may decrease, but tachycardia may persist despite adequate fluid resuscitation. Often a fluctuating clinical picture of possible improvement is followed by laboratory or clinical examinations suggesting worsening of the patient’s condition. When this pattern is observed, the decision to operate is difficult. Patients are sometimes reluctant to consent to a major operation on an urgent basis, but surgeons bear the responsibility of intervening before a life-threatening complication such as perforation occurs. In our experience, illusory improvement really is no improvement and is an important indication for urgent surgery. Our rule of thumb is to operate if the response to medical therapy has reached a plateau persisting more than 24 to 48 hours.


Deterioration

Immediate operative intervention is indicated for the patients whose clinical condition deteriorates. This may be denoted by increased leukocytosis, increased tachycardia, persisting fever, inadequate urine output, confusion, progression of colonic distension, or development of localized or generalized peritonitis.


Subtotal or Total Colectomy and Management of the Rectal Stump

The decision to operate for toxic megacolon or worsening toxic colitis is made to save the patient’s life. Table 2 lists the operative options. Almost always, the procedure of choice involves a subtotal or total colectomy with ileostomy. Controversy surrounds the preferred management of the rectosigmoid or rectum. Three options are available.








Table 2 Operative Choices






  1. Total or subtotal colectomy and ileostomy with

    • Hartmann pouch
    • Mucous fistula
    • Subcutaneous exteriorization of closed distal bowel

  2. Total proctocolectomy and ileostomy
  3. Diversion procedures

    • Ileostomy
    • Cecostomy
    • Ileostomy with transverse decompressive colostomy (Turnbull “blowhole” procedure)

  4. Restorative procedures

    • Total colectomy and ileorectal anastomosis
    • Restorative proctocolectomy with ileal pouch–anal anastomosis


Mucous Fistula

The proximal end of the rectosigmoid colon is exteriorized to decompress the remaining colon and rectum. This second stoma is placed either at the inferior edge of the midline incision or in a separate lower abdominal site. This avoids placement of a high-risk suture or staple line in the pelvis and makes subsequent colostomy closure technically easier because the distal bowel is easily identified and pelvic tissue planes are left undisturbed. Advocates say this makes mucous fistula the safest and preferred option. But, this approach leaves the patient with a second stoma and is associated with an increased incidence of wound infection, especially if the mucous fistula is placed in the midline wound.


Subcutaneous Exteriorization of the Closed Distal Bowel

To avoid a second stoma while maintaining the advantages of minimizing the risk of pelvic sepsis and easier subsequent reoperation to restore bowel continuity, some surgeons advocate a modification of mucous fistula in which the closed end of the distal bowel is placed in a subcutaneous location at the site of the ileostomy, the inferior aspect of the midline wound, or a remote site. In the event of a suture line dehiscence, the bowel opens in a controlled, subcutaneous location, thus creating a mucous fistula.



Hartmann Pouch

While mucous fistula or subcutaneous exteriorization of the bowel may be technically easy to perform in the patients with a relatively healthy sigmoid colon, many patients requiring emergent colectomy for toxic megacolon will have severe disease throughout the abdominal colon. The diseased bowel and mesentery are foreshortened, edematous, and dramatically inflamed, making it technically difficult to mobilize the distal bowel to the abdominal wall. More importantly, the need to preserve enough length of the rectosigmoid to reach the abdominal wall to create the mucous fistula risks persisting toxicity, perforation, or hemorrhage from the severely diseased, albeit defunctioned, rectosigmoid. It is for these reasons that we generally close the rectum and leave it in situ as a Hartmann pouch. Neither sutured closure nor stapled closure has proved to be superior, although, in reality, the edematous bowel is rarely amenable to stapled closure only. We generally oversew the staple line. Despite the presence of a high-risk suture or staple line, the risk of rectal stump leak (“stump blowout”) remains relatively low (between 2% and 12%) and can be minimized further if a few simple precautions are followed. Placement of the suture or staple line intraperitoneally, as opposed to low in the pelvis, may decrease the rate of leakage and avoids a pelvic dissection. Prior to closing the abdomen, the Hartmann pouch can be decompressed via proctoscopy and a drain (usually a soft red rubber catheter or Foley catheter) can be placed transanally to maintain decompression of the rectal stump. In the event of a stump leak, the resulting pelvic abscess can often be managed by percutaneous catheter drainage.


Other Operative Choices

Today, diversion procedures alone (ileostomy, cecostomy, or an ileostomy with transverse decompressive colostomy, the so-called Turnbull “blowhole” operation) are almost never used because of their high rates of mortality and morbidity and their failure to allow the patient to regain health. A total proctocolectomy and ileostomy is sometimes performed for toxic megacolon or toxic colitis if the rectum is the source of life-threatening hemorrhage or if the rectal disease is severe and/or there is no consideration of subsequently performing a restorative ileal pouch–anal anastomosis procedure. This particularly applies to the patients with severe rectal Crohn’s disease. Before a proctectomy is included as part of the emergency operation, the surgeon must be certain that the patient can tolerate the added morbidity from the additional dissection and additional anesthesia time required to complete the proctectomy.

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Aug 2, 2016 | Posted by in GENERAL SURGERY | Comments Off on Surgery for Toxic Megacolon

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