Toxic Megacolon Workup

  • Author: Deepika Devuni, MBBS; Chief Editor: Julian Katz, MD   more...
 
Updated: Mar 29, 2012
 

Approach Considerations

Complete blood count (CBC)

Patients with toxic megacolon (toxic colitis), or TM (TC), may develop leukocytosis with a left shift. Patients can also present with leukemoid reaction. Additionally, bloody diarrhea results in anemia.

Although the presence of an increased white blood cell count contributes to the diagnosis of TM (TC)—and most investigators believe that the absence of a high white blood cell count makes defining a disease as toxic megacolon difficult—an abnormally low count, or even a white blood cell count that is within normal limits, does not rule out toxic megacolon. This is because in immunosuppressed or extremely toxic patients, the white blood cell count actually may be normal or low.

Chemistry panel

Electrolyte disturbances are very common in TM (TC) secondary to inflammatory diarrhea, steroid use, and ongoing gastrointestinal losses. The inflamed colon is unable to reabsorb salt and water.

Nutrition and coagulation panel

A coagulation panel should be ordered in the event that surgery is required. A nutrition panel, in accordance with the physician's practice, is helpful in determining treatment (eg, albumin vs prealbumin) and in assessing nutritional status.

ESR and CRP

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels are usually elevated. Although these findings may support the diagnosis of TM (TC), they are not specific.

Histology

Pathology in cases of TM (TC) demonstrates acute inflammation involving all layers of the colon. Variable amounts of necrosis and degeneration are present. Infiltration by inflammatory cells (neutrophils, macrophages, and lymphocytes) is noted. The myenteric and submucosal plexuses are usually preserved.

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Radiography

Plain abdominal radiographs are essential for the diagnosis and management of toxic megacolon (toxic colitis), or TM (TC). Repeated abdominal plain films are necessary to evaluate the efficacy and progress of treatment.

Radiographic findings include the following:

  • Dilated (>6 cm) transverse colon (see the image below)A 22-year-old man presented with abdominal pain, pA 22-year-old man presented with abdominal pain, passage of blood and mucus per rectum, abdominal distention, fever, and disorientation. Findings from sigmoidoscopy confirmed ulcerative colitis. Abdominal radiographs obtained 2 days apart show mucosal edema and worsening of the distention in the transverse colon. The patient's clinical condition deteriorated over the next 36 hours despite steroid and antibiotic therapy, and the patient had to undergo a total colectomy and ileostomy.
  • Loss of colonic haustrations, possible "thumbprinting" (see the image below)Plain abdominal radiograph from a patient with knoPlain abdominal radiograph from a patient with known ulcerative colitis who presented with an acute exacerbation of his symptoms. This image shows thumbprinting in the region of the splenic flexure of the colon.
  • Presence of intraluminal soft-tissue masses (ie, pseudopolyps)
  • Free intraperitoneal air - Possible finding, best seen on upright chest radiograph or left lateral decubitus abdominal film

Comparison with old baseline films, if these are available, is helpful. Avoid barium studies in a patient who is severely toxic; the potential for perforation is considerable.

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Ultrasonography

Maconi et al found intestinal ultrasonography potentially to be a diagnostic test for toxic megacolon.[16] The investigators demonstrated similar findings in 4 cases. The findings, including the following, need further evaluation by more studies:

  • Complete loss of haustra coli of the colon
  • Hypoechoic and thickened bowel walls with irregular internal margins in the sigmoid and descending colon
  • Marked dilation of the transverse colon (>6 cm), a finding that correlated well with the plain radiograph of the abdomen
  • Hypoechoic and thin (< 2 mm) bowel walls without haustra coli in the dilated colon; in patients who underwent surgery, the postoperative pathohistologic findings of the bowel walls correlated with the ultrasonographic features observed before surgery
  • Slight dilation of ileal bowel loops (diameter >18 mm) with increased intraluminal gas and fluid
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CT Scanning

A computed tomography (CT) scan should probably be obtained in patients for whom the diagnosis of toxic megacolon (toxic colitis), or TM (TC), is being considered. A CT scan may identify a local or contained perforation.

If the diagnosis remains unclear or the cause of toxicity is thought to be an abscess, a CT scan may be helpful. There is little literature on the role of CT scanning in TM (TC), but additional studies may help to further define the role of this imaging modality in diagnosing and deriving a prognosis for TM (TC). (See the image below.)

Computed tomography scan from a patient with pseudComputed tomography scan from a patient with pseudomembranous colitis demonstrating the classic accordion sign.
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Endoscopy

If the diagnosis of toxic megacolon (toxic colitis), or TM (TC), is in doubt and the patient's condition is not toxic or unstable, endoscopy may be attempted by appropriately trained personnel.

Endoscopy may take the form of flexible sigmoidoscopy or colonoscopy. If clinical concern of TM (TC) exists, the examination should not progress beyond sigmoidoscopy, if at all. The scope should be advanced only as far as is needed for diagnosis. Air insufflation should be a minimal.

According to some experts, colonoscopy is generally justified only if the patient has no or minimal inflammation of the sigmoid or rectum. Perforation is an obvious potential complication of this approach.

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Contributor Information and Disclosures
Author

Deepika Devuni, MBBS  Resident Physician, Department of Internal Medicine, University Of Connecticut School of Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

Lisa M Rossi, MD  Fellow, Department of Gastroenterology-Hepatology, University of Connecticut School of Medicine

Disclosure: Nothing to disclose.

George Y Wu, MD, PhD  Professor, Department of Medicine, Director, Hepatology Section, Herman Lopata Chair in Hepatitis Research, University of Connecticut School of Medicine

George Y Wu, MD, PhD is a member of the following medical societies: American Association for the Study of Liver Diseases, American Gastroenterological Association, American Medical Association, American Society for Clinical Investigation, and Association of American Physicians

Disclosure: Springer Consulting fee Consulting; Gilead Consulting fee Review panel membership; Vertex Honoraria Speaking and teaching; Bristol-Myers Squibb Honoraria Speaking and teaching; Springer Royalty Review panel membership; Merck Honoraria Speaking and teaching

Clifford Y Ko, MD, MS  Professor, Department of Surgery, University of California, Los Angeles, David Geffen School of Medicine

Clifford Y Ko, MD, MS is a member of the following medical societies: American College of Surgeons, American Medical Association, American Society of Colon and Rectal Surgeons, Association for Academic Surgery, California Medical Association, and New York Academy of Sciences

Disclosure: Nothing to disclose.

Chief Editor

Julian Katz, MD  Clinical Professor of Medicine, Drexel University College of Medicine

Julian Katz, MD is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Geriatrics Society, American Medical Association, American Society for Gastrointestinal Endoscopy, American Society of Law, Medicine & Ethics, American Trauma Society, Association of American Medical Colleges, and Physicians for Social Responsibility

Disclosure: Nothing to disclose.

Additional Contributors

Douglas M Heuman, MD, FACP, FACG, AGAF Chief of GI, Hepatology, and Nutrition at North Shore University Hospital/Long Island Jewish Medical Center; Professor, Department of Medicine, Hofstra North Shore-LIJ School of Medicine

Douglas M Heuman, MD, FACP, FACG, AGAF is a member of the following medical societies: American Association for the Study of Liver Diseases, American College of Physicians, and American Gastroenterological Association

Disclosure: Novartis Grant/research funds Other; Bayer Grant/research funds Other; Otsuka Grant/research funds None; Bristol Myers Squibb Grant/research funds Other; Scynexis None None; Salix Grant/research funds Other; MannKind Other

Terence David Lewis, MBBS, FRACP, FRCPC, FACP Program Director, Internal Medicine Residency, & Assistant Chairman, Associate Professor, Department of Internal Medicine, Division of Gastroenterology, Loma Linda University Medical Center

Terence David Lewis, MBBS, FRACP, FRCPC, FACP is a member of the following medical societies: American College of Gastroenterology, American College of Physicians, American Gastroenterological Association, American Medical Association, California Medical Association, Royal College of Physicians and Surgeons of Canada, and Sigma Xi

Disclosure: Nothing to disclose.

Jerome H Liu, MD Staff Physician, Department of Surgery, University of California at Los Angeles Medical Center

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

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A 22-year-old man presented with abdominal pain, passage of blood and mucus per rectum, abdominal distention, fever, and disorientation. Findings from sigmoidoscopy confirmed ulcerative colitis. Abdominal radiographs obtained 2 days apart show mucosal edema and worsening of the distention in the transverse colon. The patient's clinical condition deteriorated over the next 36 hours despite steroid and antibiotic therapy, and the patient had to undergo a total colectomy and ileostomy.
A 72-year-old woman presented with vomiting and abdominal distention. The supine (right) and erect (left) plain abdominal radiographs show gross dilatation of the colon with multiple air-fluid levels. On further questioning, the patient revealed that she was taking diuretics for hypertension. Blood biochemical tests revealed markedly lowered potassium levels. After potassium replacement therapy, the patient's pseudo-obstruction completely resolved.
Gross pathology specimen from a case of pseudomembranous colitis demonstrating characteristic yellowish plaques.
Computed tomography scan from a patient with pseudomembranous colitis demonstrating the classic accordion sign.
Plain abdominal radiograph from a patient with known ulcerative colitis who presented with an acute exacerbation of his symptoms. This image shows thumbprinting in the region of the splenic flexure of the colon.
Increased postrectal space is a known feature of ulcerative colitis.
 
 
 
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