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Trends in evaluation, treatment of toxic megacolon
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Toxic megacolon, a life-threatening complication, occurs in about 1% of patients with ulcerative colitis, particularly among those with the most severe symptoms. The condition poses a high risk for colonic perforation and requires prompt management.
Researchers at the University of Bari Medical School in Italy summarized current trends in the evaluation, diagnosis and treatment of toxic megacolon.
Diagnosis
The condition is characterized by whole colon distention with a diameter of 6 cm or greater in the transverse tract and the absence of haustra and peristalsis, but the use of corticosteroids may mask the symptoms. Other disease indicators include thickening of the bowel wall, altered mucosa, and ulcerations near islands of normal mucosa. Patient symptoms may include abdominal pain and inconsistent stools. Hematological tests include white blood cell count, hemoglobin, hematocrit and blood-gas analysis to assess metabolic alkalosis. Inflammation tests should include albuminuria, serum electrolytes, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Auscultation can detect an absence of peristalsis.
X-rays or abdominal radiograms can be useful in identifying the condition, the researchers wrote, while ultrasound and abdominal and pelvic CT scans, especially spiral CT, can monitor the progress of UC and alert clinicians to indications of perforation.
Treatment
Researchers wrote that complete resection of the colon is necessary because of the likelihood of recurrence of toxic megacolon. Patients can be stabilized before surgery with up to 48 hours of intensive care and drug therapy unless massive rectal bleeding is present and the patient is unresponsive to drug therapy.
Early surgery was associated with a higher incidence of mortality, except when corticosteroids were used before megacolon developed. According to the researchers, emergency resection surgery is preferred when steroid use is apparent because perforation signs may be masked.
Complex and demolitive surgical procedures, which require lengthy operations, are to be avoided, according to the report. Regardless of when surgery is performed, the researchers wrote that the “gold standard” is total colectomy with ileostomy and rectal stump sinking in emergency procedures. Proctocolectomy may be preferred as an elective surgery after up to 48 hours of conservative therapy.
Three months after surgery, the researchers suggest evaluating bowel continuity restoration based on a patient-by-patient case as to performing ileorectal anastomosis or completing demolitive surgery via proctectomy and ileoanal pouch anastomosis. Researchers wrote that primary ileorectal anastomosis carries a high risk for dehiscence after emergency colectomy and should be considered only in patients exhibiting good local and systemic healing.
Early warning signs
A predictive factor of toxic megacolon risk is the distention of the jejunum and ileum. Researchers wrote that in their assessment of research including 1,182 UC patients — 18 diagnosed with toxic megacolon — jejunum and ileum distention was predictive in 40% of cases where conservative treatment failed. When shown in radiological exams, the onset of the condition is predictive with the presence of blood pH above 7.5, albuminuria up to 2.4 g/dL, serum chlorine below 95 mEq/L, serum calcium of less than 4.2 mEq/L and serum phosphorus up to 1.5 mEq/L. More than 50% of patients with severe UC with massive hemorrhage develop toxic megacolon, according to the researchers.
Surveillance for early diagnosis
Researchers recommend the surveillance protocol proposed by Kumar to monitor severe UC patients and quickly identify any presence of toxic megacolon. The protocol requires a physical exam twice daily, monitoring of vitals, frequency and characteristics of defecation, consideration of abdominal pain, tenderness and peristalsis, daily monitoring of hemoglobin and electrolytes, CRP and ESR every other day and daily abdominal X-rays.
Disclosure: Relevant financial disclosures were not provided by researchers.
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