Section: Colorectal Sub-section: Acute colorectal
Definition
- Toxic mеgаϲоlоո is total or segmental nonobstructive colonic dilatation that occurs in the context of systemic toxicity
-
6 cm non-obstructive segmental or complete dilatation of the colon, and signs of systemic toxicity.
- Classic finding of > 6 cm of transverse +
- Any 3 of the following:
- Fever
- Tachycardia
- Leucocytosis
- Anaemia
- Any 1 of the following:
- Dehydration
- Altered mental status
- Electrolyte imbalances
- Hypotension
- Any 3 of the following:
- Classic finding of > 6 cm of transverse +
Aetiology
Most common:
- IBD
- Pseudomembranous colitis Other infectious
- Salmonella
- Shigella species
- Campylobacter
- Yersinia
- Entamoeba
- Cryptosporidium
- Cytomegalovirus Other causes
- COPD
- Diabetes
- Immunosuppression
- Kidney failure
- Chemotherapeutic drugs
- Kaposi’s sarcoma
- Colonoscopic overdistension
- Cystic fibrosis
Pathophysiology
- On histopathology there is inflammation which spreads to the smooth muscle layer – this causes paralysis of the SM and subsequent dilatation.
- Increased production of NO synthase by macrophages and smooth muscle cells inhibits muscle tone which contribute to dilatation.
- It is equivocal as to whether the myenteric plexus is affected.
Clinical presentation
- Critically ill (fever, tachycardia and leucocytosis) with abdominal distension, tenderness and diarrhoea.
- High index of suspicion – symptoms may be masked by medications (steroid, immunosuppressants, opioids) or other factors (elderly, debilitated).
Management
Initial:
- Aggressive resuscitation, correction of electrolyte derangements. Serial xrays. Critical care unit. Stop medications that slow colonic motility and function. Transfuse if significant GI bleed.
- CT may be useful to determine aetiology and evaluate for pneumatosis, subclinical perforation and abscesses.
Medical:
- IBD
- Can trial aggressive medical therapy for 5-7 days. MDT approach
- Clostridium difficile
- Vancomycin 500mg PO Q6H and metronidazole 500mg IV Q8H.
- If unable to tolerate oral, can have NG
- If ileus, could have vancomycin via enema
- Unknown
- If presenting without history of IBD, should empirically treat for C. difficile colitis until proven otherwise.
- Limited lower GI scope may be helpful in obtaining biopsies and evaluating for pseudomembranes.
Surgery:
- Indications for surgery:
- Emergency: peritonitis, perforation, uncontrolled sepsis, ischaemia, ACS or end-organ failure
- Urgent: increasing abdominal pain +/- colonic distension, physiological deterioration, lack of objective improvement within 24 – 72 hours and transfusion requirements.
- Early intervention if: immunocompromised, malnourished, severely debilitated or multiple comorbidities
- Approach
- Open total or subtotal colectomy + end ileostomy
- Rectal stump – can be closed or exteriorised as mucous fistula. No difference in outcomes. Always leave a rectal tube.