Introduction

Toxic megacolon is a very uncommon and potentially life-threatening condition marked by complete or partial abnormal widening of the colon that does not cause colon obstruction (blockage). The widening of the colon is the result of inflammation of the innermost tissues, including the muscles, which is most commonly associated with inflammatory bowel disease (IBD). Consequently, the muscles become unable to propel substances inside the colon leading to their build-up, which can cause sepsis.¹

Despite IBD being the most common cause of toxic megacolon, toxic megacolon can be a complication of any disorder that causes colonic inflammation or infects the bowel. In addition, various factors that lead to ischemia (inadequate blood supply to a local area) can cause toxic megacolon, with cytomegalovirus (CMV) being the most common.¹

People with IBD are most likely to develop toxic megacolon and are typically affected between the 4th and 6th decade of their life. However, toxic megacolon can occur in a male and females of all ages. There is a correlation between toxic megacolon and Clostridioides difficile (C. difficile), formerly known as Clostridium difficile; however, the number of people suffering from this complication is unknown.^1,2

In this article, the clinical presentation and diagnosis of the disorder will be briefly discussed, with emphasis placed on the initial medical management of toxic megacolon. 

Signs and symptoms

There are no specific signs or symptoms that are characteristic of toxic megacolon.² However, the combination of the following symptomatology and an adequate work-up can induce suspicion of the condition. Non-specific symptoms include:

• Bloody diarrhoea (most common)³
• Swollen belly (abdominal distention)
• Abdominal pain
• Bloody stools (hematochezia)
• Vomiting (emesis)

As the disorder progresses rapidly, symptoms that indicate toxicity can develop. These can be:

• Fever (>38 °C)
• Rapid heart rate (tachycardia)
• Low blood pressure (hypotension)
• Altered mental status (lethargy, confusion)^1,3

Diagnosis

Diagnosis of toxic megacolon occurs from a combination of a detailed medical history, clinical and laboratory evaluation, and imaging.² Specifically, this contains:

• Medical history: the presence of risk factors, such as irritable bowel disease, Clostridioides difficile infection, HIV, or medications that can mask the condition or worsen it, including NSAIDS, and opioids, are suggestive of toxic megacolon
• Clinical and laboratory evaluation: the nonspecific symptomatology combined with signs and symptoms that suggest a toxic megacolon suggests the possibility of a toxic megacolon. In addition, laboratory tests usually exhibit anaemia, leukocytosis (>10,500/μL in adults), neutrophilia, hypokalemia (low potassium levels), increased inflammatory markers (including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), and hypoalbuminemia^1,2
• Imaging: abdominal X-ray is the most common modality used for diagnosis of toxic megacolon, however, the use of abdominal CT scans with contrast is increasing. Colon distention of >6 cm is characteristic of a toxic megacolon. CT scans are usually used to assess for potential complications, with specific signs including a thickened colon wall, changes in the fat surrounding the colon (pericolic stranding), and thickened submucosal folds (accordion sign)^1,3

Colonoscopy is not recommended because it can cause holes inside the colon (colonic perforation).^1,3

Initial stabilisation

The main aim of the toxic megacolon management plan is to prevent further complications and restore colonic function. Surgeons should be consulted very early regarding the treatment plan.¹ The first steps of managing toxic megacolon medically entail:

Resuscitation and supportive care

Restoring haemodynamic stability (blood pressure and heart rate) with intravenous (IV) administration of fluids (treatment of dehydration) and correcting electrolyte abnormalities, for example, hypokalemia, along with the cessation of medications, including NSAIDS and opioids, that affect the colon, are important in this management step.

In addition, continuous monitoring of the vital signs and abdominal examinations should be performed to monitor the disease and associated complications.^1,2

Bowel rest and decompression

Eating is avoided until the patient improves (bowel rest). A nasogastric (NGA) tube is used to decompress the stomach (not the colon) in the presence of severe distention. Evidence suggests the colon is decompressed through rolling manoeuvres, which move the air to the descending colon and rectum. Enteral (tube) feeding is recommended as soon as the patient improves.¹

Medication

Based on the specific case and underlying cause, the following medications can be administered:

• Broad-spectrum antibiotics: antibiotics are used to decrease the risk of septic complications. If CMV is suspected, ganciclovir should be administered. For C. difficile infections, oral vancomycin or fidaxomicin are the antibiotics commonly prescribed
• Anti-inflammatory therapy: administration of IV corticosteroids is necessary in cases of acute ulcerative colitis (UC); hydrocortisone or methylprednisolone are usually recommended. If the patient does not respond to steroids or demonstrates an intolerance, cyclosporine or infliximab could be considered
• Immunosuppressive therapy: Tacrolimus could be taken into consideration since some clinical responses were observed. Intravenous immunoglobulin (IV IG) can be used in severe cases of refractory (unresponsive) C. difficile infection¹

Prevention of complications

With severe colitis, medicines for venous thromboembolism prophylaxis should be administered. The continuous monitoring of toxic megacolon is necessary for intervening early with potential complications that could arise and require urgent surgical intervention, including bowel perforation and peritonitis. There should be monitoring for potential adverse drug reactions.¹

Surgical care

The gold standard surgical treatment of acute toxic megacolon is subtotal colectomy (removal of the colon) with ileostomy (creation of a stoma in the abdomen). In other words, a big part of the colon is removed with the ileum being kept and brought on the surface of the abdomen to allow stool to pass into an external bag.

In addition, a Hartmann pouch, sigmoidostomy, or rectostomy is performed depending on the severity of the disease, i,e. either the rectum can be preserved for future anastomosis or permanent diversion.¹

FAQs

What is the prognosis of toxic megacolon?

Early diagnosis and intervention are associated with high chances of survival. However, complications are correlated with poorer prognosis. Early surgical intervention demonstrates mixed findings, with some cases presenting favourable outcomes while others present poorer survival.¹

When should I contact my healthcare provider?

If you have been recently diagnosed with inflammatory bowel disease and experience any of the symptoms characteristic of toxic megacolon, contact a healthcare professional. Additionally, if you have recently been inflicted with an acute infection and your symptoms seem to worsen, contact a medical professional.⁴

Summary

Toxic megacolon is a rare, life-threatening disorder characterised by abnormal distention of the colon.

The most common causes include inflammatory bowel disease, infections, and ischemia. Sepsis can occur and affect all individuals irrespective of age or sex. Clinical presentation is marked by non-specific symptoms, with bloody diarrhoea being the most common sign of toxic appearance.

Diagnosis is reached through a combination of medical history, clinical evaluation, laboratory testing, and imaging. Initial stabilisation focuses on resuscitation, supportive care, and the administration of broad-spectrum antibiotics, anti-inflammatory, and immunosuppressive drugs. 

Surgical intervention includes subtotal colectomy with ileostomy and a Hartmann pouch, sigmoidostomy or rectostomy. Lastly, venous thromboembolism prophylaxis and continuous monitoring are essential to manage complications.