# Toxic Megacolon and Severe Colitis

> Toxic megacolon and severe colitis for NEET-PG Medicine covering Truelove and Witts criteria, colonic dilatation, rescue therapy and when surgery is needed.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/toxic-megacolon-and-severe-colitis
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Harrison's Principles of Internal Medicine; Sleisenger and Fordtran's Gastrointestinal and Liver Disease; Davidson's Principles and Practice of Medicine
- How to cite: "Toxic Megacolon and Severe Colitis", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/toxic-megacolon-and-severe-colitis

## Direct answer

Toxic megacolon is acute, non-obstructive dilatation of the colon, usually above 6 cm on plain film, complicating severe colitis, most often ulcerative colitis. It is a surgical emergency because perforation and sepsis can follow quickly. Severe colitis is graded by Truelove and Witts criteria, and management is intravenous steroids, fluid and electrolyte correction, antibiotics and early review for rescue therapy or colectomy.

## What you must remember

- **Truelove and Witts severe criteria:** six or more bloody stools daily, plus at least one of pulse above 90, temperature above 37.8 °C, haemoglobin below 10.5 g/dL or ESR above 30 mm/h.
- **Dilatation threshold:** transverse colon diameter above 6 cm on a plain abdominal radiograph, though some use 5.5 cm.
- **Masked signs:** steroids and opioids blunt fever, tenderness and bowel sounds, so a falling pulse can mislead.
- **Precipitants:** opioids, loperamide and anticholinergics, plus infection such as Clostridioides difficile or cytomegalovirus.
- **Perforation site:** the transverse colon is the most common site, and perforation carries high mortality.
- **Rescue therapy:** intravenous ciclosporin or infliximab, reviewed at about 72 hours when steroids have failed.
- **Surgery:** emergency colectomy for perforation, peritonitis, uncontrolled sepsis or failure of medical therapy.

## A pathway for a flare that is getting worse

A 27-year-old with a flare of ulcerative colitis has eight bloody stools daily, a pulse of 112 and a distended abdomen with reduced bowel sounds. He started loperamide three days earlier for diarrhoea.

1. **Grade the severity:** Apply Truelove and Witts criteria, recording stool frequency, pulse, temperature, haemoglobin and ESR at the bedside.
2. **Image the abdomen:** A plain film measures the transverse colon, and CT is used to look for perforation or free gas.
3. **Stop the drugs that slow the bowel:** Loperamide, opioids and anticholinergics are withdrawn because they promote dilatation.
4. **Support and treat:** Correct fluids and electrolytes, keep him nil by mouth, decompress the stomach if distended and start broad-spectrum intravenous antibiotics.
5. **Send stool tests and start steroids:** Test for Clostridioides difficile and cytomegalovirus, start intravenous steroids and give thromboprophylaxis.
6. **Reassess at about 72 hours:** Failure to improve prompts rescue therapy, while perforation, peritonitis or deterioration calls for urgent colectomy.

## Where the exam tests the dangerous reassurance

Severe colitis is dangerous partly because treatment itself hides the signs of deterioration.

- **Trap:** using loperamide to settle the diarrhoea — **Correct:** antimotility drugs raise the risk of dilatation and perforation, so they are stopped.
- **Trap:** reading a normal temperature on steroids as improvement — **Correct:** steroids mask fever, so the pulse, haemoglobin and X-ray trends guide decisions.
- **Trap:** waiting for rescue therapy in a patient with peritonitis — **Correct:** perforation or sepsis requires prompt colectomy without further delay.

## Frequently asked questions

### What are the Truelove and Witts criteria for severe ulcerative colitis?

Severe ulcerative colitis by Truelove and Witts criteria is six or more bloody stools daily, plus at least one of pulse above 90, temperature above 37.8 °C, haemoglobin below 10.5 g/dL or ESR above 30 mm/h. Such patients need admission and prompt intravenous steroid therapy.

### What colonic diameter defines toxic megacolon?

Toxic megacolon is usually defined by transverse colon diameter above 6 cm on a plain abdominal radiograph, although some use a threshold of 5.5 cm. Dilatation with systemic toxicity is a surgical emergency that needs urgent senior review.

### Why are opioids and loperamide avoided in severe colitis?

Opioids and antimotility drugs such as loperamide slow colonic transit and increase the risk of dilatation and perforation in severe colitis. They are withdrawn as soon as toxic megacolon or severe disease is suspected.

### When is emergency colectomy needed in severe colitis?

Emergency colectomy is needed for perforation, peritonitis, uncontrolled sepsis or failure of medical therapy in severe colitis. Rescue therapy with intravenous ciclosporin or infliximab is considered first in suitable patients when steroids fail, but delay in surgery is dangerous.