Chemical colitis
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Synonyms and keywords: Disinfectant colitis, Corrosive colitis, Iatrogenic colitis.

# Overview
Chemical colitis is inflammation of the large intestine or colon, caused by the introduction of harsh chemicals to the colon by an enema or other anorectal procedures. Chemical colitis can resemble ulcerative colitis, infectious colitis and pseudomembranous colitis endoscopically. Prior to 1950, hydrogen peroxide enemas were commonly used for certain conditions. This practice will often result in chemical colitis. Soap enemas may also cause chemical colitis. Harsh chemicals, such as compounds used to clean colonoscopes, are sometimes accidentally introduced into the colon during colonoscopy or other procedures.  This can also lead to chemical colitis. Chemical colitis may trigger a flare of ulcerative colitis or Crohn's disease.

# Historical Perspective
- The first description of chemical colitis was by Pinnock (1937), Murray (1937), and Gabriel (1937) when they reported deaths following use of soapsuds enemas.
- In 1945, Barker described acute colitis from soapsuds enema.
- In 1945, Bendit reported rectal gangrene following soap enema. Turrell further described that xray findings may be confusing following chemical colitis.
- Sheehan and Bryjolfsson in 1960, reported ulcerative colitis following self-administration of hydrogen peroxide enema.
- Since the earlier description, several cases of chemical colitis have been reported from glutaraldehyde or hydrogen peroxide used for cleansing endoscopes.

# Classification
There is no established classification system for chemical colitis. However, chemical colitis may be classified based on the mechanism or the causative chemical.

## Classification based on the mechanism
Based on the mechanism, chemical colitis can be classified into:
- Accidental (most common) or non-accidental

## Classification based on the causative chemical
Chemical colitis can be classified based on the causative chemical such as:
- Glutaraldehyde-induced chemical colitis
- Hydrogen peroxide-induced chemical colitis
- Soap-induced chemical colitis
- Radio-contrast (e.g Renografin-76) induced chemical colitis
- Alcohol-induced chemical colitis

# Pathophysiology

## Pathogenesis
Chemical colitis usually results from accidental or intentional rectal introduction of chemicals such as endoscopy cleaning solutions (glutaraldehyde and hydrogen peroxide), radiologic contrast material, hydrogen peroxide, soaps, formalin, hydrofluoric acid, alcohol, ammonia, lye, hot water, and herbal substances. Rarely it could occur following accidental ingestion of chemicals, such as accidental swallowing of hydrogen peroxide mouthwash during oral procedures.
- The most common implicated chemical agents in the pathogenesis of chemical colitis are glutaraldehyde and/or hydrogen peroxide disinfectants. The improper cleaning of the endoscopes allows the disinfectants to remain on the endoscopes, subsequently causing a chemical proctocolitis when the endoscopes are used.
- The main mechanism for developing chemical colitis is the direct contact of the chemical agent with the mucosa, subsequently causing corrosive injury to the mucosa and activation of the inflammatory pathway. Reactive oxygen formation, lipid peroxidation and vascular smooth muscle contraction also occur in hydrogen peroxide-induced chemical colitis.
- The primary mucosa toxin in glutaraldehyde is not fully known. However, it may be related to aldehyde. In addition to direct damage, glutaraldehyde is thought to activate arachidonic acid pathway and recruitment of inflammatory cells and substances. 
- The symptoms of chemical colitis typically develop within 48 hours, often less than 12 hours after introduction of the chemical, but may sometimes take days to weeks when frequent small dilute amount is ingested.

## Genetics
There are no identified genetic factors associated with chemical colitis.

## Gross Pathology
Gross pathology findings in most cases shows predominant superficial mucosa involvement. The mucosa is erythematous, friable, edematous with areas of necrosis. Also, multiple shallow mucosal ulcers with fibrinous and/ or purulent exudate and hemorrhage are present. In addition, in hydrogen peroxide-induced colitis, gas may be seen in the colonic wall.

## Microscopic Histopathology
- Microscopy shows loss of superficial glands and epithelium, mucosa congestion, capillary hemorrhage and erosions and presence of polymorphonuclear inflammatory infiltrates in the crypts. Chronic inflammatory infiltrates (lymphoplasma cells) may also be seen in formalin-induced colitis. In hydrogen peroxide-induced colitis, the goblet cells in the mucosa appear as empty vacuoles, so-called pseudolipomatosis". 
- Pseudomembranes composed of necrotic tissue and exudates may occasionally be seen lining the crypt.

# Differentiating chemical colitis from other Diseases
Chemical colitis must be differentiated from other causes of bloody diarrhea, especially acute causes and abdominal pain. Although the symptoms of chemical colitis may overlap with other causes of colitis, history of prior use of enema containing a known chemical agent shortly before onset of symptom will help in distinguishing the cause.
- The symptoms of colitis such as diarrhea especially bloody diarrhea and abdominal pain are seen in all forms of colitis. The table below lists the differential diagnosis of common causes of colitis:

# Epidemiology and Demographics
The overall prevalence and incidence of chemical colitis is not known.

## Epidemiology
The overall prevalence and incidence of chemical colitis are not known. Although, most reports of chemical colitis have been related to inadvertent residual contamination of endoscopes with the disinfectants glutaraldehyde and/ or hydrogen peroxide or following radio-contrast studies.
- The incidence of glutaraldehyde-induced colitis ranges from 0.1% to 4.7%.

## Demography

### Age
Patient of all age group can develop chemical colitis. However, the incidence of may be higher in elderly due to increased frequency of diagnostic and/ or therapeutic endoscopy in this age group.

### Gender
The prevalence and incidence of chemical colitis does not vary by gender.

### Race
There is no racial predilection to chemical colitis.

# Risk Factors
The common risk factors for developing chemical colitis include:
- Bowel obstruction
- Population with high prevalence of use of enemas for treatment of constipation.
- Persons with mental health problems especially suicidal persons, munchausen disease setting and those with schizophrenia.

# Screening
There are no established screening guidelines for chemical colitis

# Natural History, Complications and Prognosis

## Natural History
The symptoms and course of chemical colitis is highly variable. The severity and extent chemical colitis depend on the type of chemical agent, the concentration of the chemical agent, the quantity and duration of use the chemical agent. The symptoms often develop insidiously within 48 hours of the procedure and resolve following a period of bowel rest and symptomatic treatment.

## Complications
Complications of chemical colitis include
- Perforation
- Peritonitis
- Fecal incontinence following loss of rectal function
- Stricture
- Gangrene of the colon
- Fistula
- Anemia

## Prognosis
The prognosis of chemical colitis varies with the type of chemical. However, prognosis is generally good with resolution of symptoms following treatment. 

# Diagnosis

## Diagnostic Criteria
There is no definitive diagnostic criteria for chemical colitis. Diagnosis of chemical colitis is primarily clinical, based on detailed history, physical examination and endoscopic findings.

## History and Symptoms
Obtaining a complete history including any anorectal procedure done and recent use of enemas is important in making a diagnosis of chemical colitis. Symptoms of chemical colitis are not specific, and the severity depends on the type of chemical. Therefore, diagnosis of chemical colitis should be suspected in any individual who presents acutely (typically within 12 hours) with intestinal symptoms and has a prior history of endoscopy and/ or administration of enema. Common symptoms of chemical colitis include.
- Sudden onset of Abdominal pain which is colicky
- Anorectal pain
- Diarrhea
- Rectal bleeding
- Fecal incontinence
- Tenesmus
- Mucus discharge
- Vomiting

## Physical Examination
Physical examination findings in patients with chemical colitis may reveal:
- Abdominal tenderness  which may be more prominent in lower abdominal quadrants due to involvement of the distal sigmoid colon and/ or rectum
- Signs of dehydration such as lethargy, Tachycardia and Hypotension
- Fever due to dehydration or in individuals who have developed sepsis
- Pallor
- Toxic appearance in those with bowel perforation and sepsis

## Laboratory Findings
There are no specific laboratory findings associated with chemical colitis. Initial investigations should include hematological, biochemistry profiles and stool examination.

### Hematology
- Anemia
- Leukocytosis with left shift may be seen with sepsis (most common), but leukopenia can be seen.

### Electolytes
- Hyponatremia

### Stool Examination
Stool analysis may show
- Fecal blood
- Fecal leukocytes
- Stool culture is negative.

## Endoscopy
Endoscopy is required for confirmation of chemical colitis. Endoscopic features of chemical colitis include.
- Friable, hyperemic, edematous mucosa with/ or without ulcers of varying degree and patchy necrotic areas.
- White plaques may be seen in glutaraldehyde and hydrogen peroxide chemical colitis.
- Pseudomembranes may also be seen.
- Blanching of the mucosa can also be seen on flushing the with hydrogen peroxide (snow white sign).

## Other Diagnostic Studies
Other diagnostic test include

### CT scan
Abdominal CT scan may show characteristic homogenous thickened colonic wall  (target sign) in glutaraldehyde-induced chemical colitis

### Xray
There is no specific Xray feature of chemical colitis. However, it may help to rule out complications such as intestinal obstruction and perforation.

# Treatment
Majority of patients with chemical colitis can be managed medically.

## Medical Therapy
Medical treatment involves
- Stopping further exposure to the offending chemical
- Resting the bowel
- Correction of dehydration and electrolyte derangements by giving intravenous fluids or oral rehydration therapy whenever it is feasible
- Broad-spectrum antibiotic is given as an adjunct therapy
- Steroid therapy may be be needed, especially when severe

## Surgical Therapy
Surgical intervention may occasionally be required in chemical colitis. It is usually reserved for management of complications such as bowel perforation and stenosis.

# Prevention

## Primary prevention
There is presently no established method of prevention for chemical colitis. However, endoscopy probes should be properly rinsed after cleansing with disinfectant to avoid inadvertent exposure that may cause chemical colitis.

## Secondary prevention
There are no secondary prevention methods for chemical colitis.