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Toxic Megacolon - Causes, Symptoms, and Treatment

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Toxic megacolon is a rare, life-threatening complication of irritable bowel disease. Read the article below to know more about it.

Medically reviewed by

Dr. Ghulam Fareed

Published At January 23, 2023
Reviewed AtJune 2, 2023

What Is a Toxic Megacolon?

The large intestine is the lowermost part of the digestive tract that includes the appendix, colon, and rectum. The large intestine completes the digestive process by absorbing the excess water and helping in passing the stools. Certain diseased conditions lead to abnormal dilation of the colon and can cause the large intestine to malfunction.

A rare, life-threatening complication that results due to colon disease and infection is toxic megacolon. This can lead to a series of conditions that leads to dehydration and shock. Toxic megacolon is a condition that needs immediate medical care.

What Causes Toxic Megacolon?

Inflammatory bowel disease is the main cause of toxic megacolon. This condition leads to irritation and swelling of the digestive tract, which can be very painful and cause permanent damage to small and large intestines. Inflammatory bowel disease leads the colon to dilate, distend and expand. Due to this, it becomes tough for the colon to remove gas and feces; thus, gas and feces build up in the colon and then eventually rupture. Ruptures of the intestine can be life-threatening. Causes of toxic megacolon can be mainly of two types:



  • Clostridium difficile.

  • Shigella.

  • Entamoeba.

  • Salmonella.

  • Cytomegalovirus.

  • Escherichia coli.

  • Campylobacter colitis.

Cytomegalovirus can cause the condition in HIV (human immunodeficiency virus) and AIDS (acquired immunodeficiency virus) patients, and entameba is the least common cause of toxic megacolon. Other systemic conditions like diabetes, ischemia, organ transplants, surprised immunity, chronic obstructive pulmonary disease, and kidney failure also can be causes of toxic megacolon. Other precipitating factors for toxic megacolon include:

  • Barium enema.

  • Medications like opiates, antimotility agents, antidepressants, and anticholinergics.

  • Hypokalemia.

  • Colonoscopy and bowel preparations.

What Are the Signs and Symptoms of a Toxic Megacolon?

The large intestine rapidly expands when a toxic megacolon occurs. There is a sudden onset of the symptoms that include:

  • Abdominal tenderness.

  • Abdominal pain.

  • Fever.

  • Shock.

  • Tachycardia (rapid heart rate).

  • Bloating in the abdomen.

  • Painful bowel movements.

  • Bloody diarrhea.

How Is Toxic Megacolon Diagnosis Done?

Diagnosis of the toxic megacolon is done by:

  • Medical History and Physical Examination: A detailed medical history is taken, and a physical examination of the individual is done.

  • Blood Tests: A complete blood count is taken into consideration as a part of the diagnostic method.

  • X-ray: Images of the affected organs are taken. High-energy electromagnetic radiation is used to create images of body parts, especially bones.

  • CT Scan (Computed Tomography): A diagnostic procedure that uses a combination of computer technology and X-rays to produce body images.

  • Colonoscopy: A diagnostic test that allows looking for changes like irritated tissues, colon, intestine, and rectum. A flexible tube with a camera-headed tube is inserted into the rectum for examination.

What Is the Treatment for Toxic Megacolon?

Treatment of megacolon depends on the severity of the condition, the age of the individual, and other medical conditions associated with it. Treatment of toxic megacolon includes two approaches:

1) Medical Approach:

Treatment focuses on supportive care along with medical management. The patient needs to be admitted to ICU (intensive care unit ) to manage cases of unexpected deterioration. Initially, every 12 hours checking of abdominal films, electrolytes, and complete blood count is done. Medications like opioids and anticholinergics are stopped as they can aggravate megacolon.

Intravenous fluids are started to provide adequate hydration. Individuals are frequently placed on antibiotics to avoid infections. The most commonly used antibiotics are Metronidazole and Vancomycin. Suppose cytomegalovirus is suspected as the cause, Ganciclovir is recommended. Oral Vancomycin, oral Fidaxomicin, and oral Metronidazole are also drugs of choice.

In cases associated with ulcerative colitis, steroids are recommended. Generally, Hydrocortisone or Methylprednisolone is given. Also, using Cyclosporine and Infliximab in such cases shows benefits.

Surgical Approach:

If there is bleeding, perforation, or clinical deterioration in the patient, a surgical approach is unavoidable. The current treatment of choice for toxic megacolon is subtotal colectomy with ileostomy (a surgical procedure that removes damaged part of the ileum) and either a sigmoidoscopy (minimal invasive examination method for the large intestine and parts of the colon, the sigmoid colon), rectostomy (surgery performed to form a permanent opening of rectum), or Hartmann pouch (a procedure that removes part of colon sometimes rectum). Previously proctocolectomy and Turnbull methods were used. The Turnbull method was essential for patient preparation for colectomy; it is a colon compression technique.

What Are the Conditions Where You Need to Seek Immediate Care?

Conditions and symptoms that require immediate attention are:

  • Rapid heart rate.

  • Bloody diarrhea.

  • Increased frequency of diarrhea.

  • Fever.

  • Swelling in the belly, along with severe abdominal pain.

  • Weak pulse, clammy skin, dilated eyes, shallow breathing, confusion (shock).

How to Prevent Toxic Megacolon?

Toxic megacolon is a complication of colorectal infections, gastrointestinal tract infections, and irritable bowel disease. Prevention of this condition can be done by making lifestyle changes and taking regular, timely medical help. Controlling the symptoms of irritable bowel disease and preventing further infection can help to reduce the risk of developing toxic megacolon.

What Is the Differential Diagnosis of Toxic Megacolon?

The differential diagnosis of toxic megacolon is:

  • Acquired megacolon (a condition that involves persistent dilation and lengthening of the colon).

  • Colonic pseudo-obstruction (a disorder that is caused by acute dilation of the colon in the absence of an anatomic lesion that obstructs the flow of intestinal contents).

  • Diffuse gastrointestinal dysmotility (a condition in which muscles of the digestive system become impaired and thus result in loss of coordination and strength of digestive organs).

  • Hirschsprung disease (a condition of the large intestine that makes stool passing difficult).


Toxic megacolon is a rare but potentially life-threatening condition that requires immediate attention and emergency medical treatment. Failure to diagnose the condition at the right time can lead to high mortality and morbidity. Early diagnosis can increase the rate of survival. Aggressive hydration, replacement of electrolytes, and antibiotics are essential to avoid the signs of peritonitis. In most cases of toxic megacolon, individuals recover with medical therapy, but some require surgery. A high risk of colon perforation and abdominal compartment syndrome is a condition where surgery is required to avoid further complications.

Dr. Ghulam Fareed
Dr. Ghulam Fareed

Medical Gastroenterology


toxic megacolonirritable bowel syndrome
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