What is Amebic Colitis?
Amebic colitis is an infection of the colon’s lining, caused by a micro-organism called Entamoeba histolytica (E histolytica). The first report of sickness caused by E histolytica dates back to 1875 by a scientist named Losch. He discovered the amebas in ulcers in the colon at an autopsy and proved that the disease can be artificially caused in living organisms through the introduction of human feces into the rectum. Other researchers have also confirmed that this ameba is what causes the illness.
While this micro-organism is found all over the world, it’s relatively rare in the United States. However, it is frequently observed in patients with AIDS and men who engage in sexual activities with other men. Symptoms of amebic colitis can range greatly and may include:
* Bowel discomfort with diarrhea and rectal bleeding, similar to symptoms of a condition called irritable bowel syndrome (IBS)
* Abscesses (infected, pus-filled areas) in the liver
* Masses in the colon that have an inflammatory reaction and can be mistaken for cancerous tumors
Complications can include perforation (a hole) in the colon, channels called fistulas forming between the intestines and other organs, or abscesses in the liver.
Finally, E histolytica can spread by swallowing the cyst (the dormant stage) of the ameba. These cysts can be found in contaminated water and food. It can also be spread through close contact that involves the mouth and the anus, often observed in some sexual behaviors.
What Causes Amebic Colitis?
E histolytica is a small organism known as a protozoan parasite that causes a disease called amebiasis. For most people who are vulnerable to it (about 90%), it just lives in the intestinal tract without causing any problems or symptoms. However, in around 10% of people, the parasite can break through the inner lining of the colon, an area known as the mucosal barrier, and invade a deeper part of the colon called the lamina propria.
If amebiasis isn’t treated, it can lead to severe inflammation in the colon and a potentially deadly infection. This mainly occurs if the parasite is ingested through contaminated food or water, which is usually a problem in areas with poor sanitation. This shows how crucial it is to drink clean water and consume safe food.
Risk Factors and Frequency for Amebic Colitis
E histolytica, a type of parasite, affects around 10% of the world’s total population. It causes over 100,000 deaths each year due to amebic dysentery and liver abscesses. This parasite is particularly prevalent in developing countries. However, it’s also seen in Western countries, among recent immigrants, travelers returning from places where the parasite is common, men who have sex with men, and people with weakened immune systems.
The E histolytica parasite is transmitted through either food or water that has been contaminated with human feces. This is usually due to poor sanitation conditions or inadequate personal hygiene.
Signs and Symptoms of Amebic Colitis
Most of the time, about 90%, people carrying the infection don’t show any signs or symptoms. However, these silent carriers can still spread the disease. When symptoms do occur, they normally show as a colon infection called amebic colitis. This type of infection causes diarrhea, often with blood in the stool. The symptoms can be quite vague and the onset of the disease is usually slower compared to a bacterial infection in the colon. The symptoms of amebic colitis can sometimes be mistaken for ulcerative colitis or Crohn’s disease.
In some cases, a physical exam may reveal tenderness in certain areas of the abdomen, and occasionally a lump can be felt. If left unaddressed, a serious condition called toxic megacolon can occur, which is a sudden widening of the colon. This is a critically dangerous situation as it can lead to the death of tissues and rupture of the colon.
Less than 1% of those with amebic colitis can also end up with an infection outside the intestines. Liver abscesses are most common amongst these extraintestinal infections, and can bring symptoms like fever, chills, and upper right abdominal pain, or show no symptoms at all. Other associated signs could include weight loss, elevated white blood cell counts, and increased liver enzymes. Jaundice, or yellowing of the skin and eyes, is usually not present. In some cases, the infection can penetrate into the lungs causing chest pain, shortness of breath, and a productive cough.
Testing for Amebic Colitis
The most reliable method for diagnosing amebic colitis, a type of intestinal infection, is by identifying a parasite called E. histolytica in the microscopic analysis of tissue samples taken during a colonoscopy, or less commonly, in a sample of fresh stool. The parasite is often found in patients with diarrhea.
This parasite typically affects the cecum and ascending colon areas of your intestine, creating many small ulcers separated by normal tissue. These ulcers often look flask-shaped under a microscope. In severe cases, these small ulcers can merge and resemble a condition called ulcerative colitis.
For amebic liver abscesses, which are infections in the liver caused by the same parasite, ultrasound or x-ray tests are commonly used for detection. If an abscess is found, doctors may take a sample and can observe active E. histolytica and dead cells inside.
There are also tests available that can detect antibodies for E. histolytica in your blood. These antibody tests are positive in over 90% of patients with the disease outside of the intestine. These antibody levels increase once the parasite invades tissue, but the presence of antibodies does not prevent the disease. However, these tests can’t tell the difference between a past infection and a current one because the antibodies can remain in your body for years after the infection has cleared.
Tests that can detect the presence of the parasite in stool samples can show an active infection. Some tests are designed to identify the parasite in stool samples, and others can detect antibodies in the blood. One downside to these tests is that they require fresh, unpreserved stool samples. Tests that can be done quickly are being developed to help speed up the diagnosis process.
Treatment Options for Amebic Colitis
Amebic colitis, an intestinal illness caused by a parasite, often requires a two-pronged approach to treatment. This involves using two types of medications: luminal agents and tissue amebicides. Luminal agents are drugs that act upon the intestine, and these include medicines such as iodoquinol, diloxanide furoate, and paromomycin. Tissue amebicides, on the other hand, fight the parasites in body tissues and include drugs like metronidazole, nitazoxanide, erythromycin, and chloroquine.
Surgery might be necessary in some cases. For instance, if the patient also has an inflamed pouch of pus, known as an abscess, in the liver that requires drainage. Likewise, immediate surgery is needed if the individual develops a dangerous condition known as toxic megacolon, where the colon suddenly expands or perforates (develops a hole).
What else can Amebic Colitis be?
When trying to figure out if someone has a certain disease, doctors need to consider other conditions that have similar symptoms. This process is what we call ‘differential diagnosis’. For example, if someone has symptoms that might suggest they have amoeba affection (caused by E. histolytica), doctors are likely to consider a list of conditions including:
- Appendicitis
- Inflammatory Bowel Disease (IBD)
- Pseudomembranous colitis (a type of inflammation in the colon)
- Tuberculosis
Though rare, it’s possible that the amoeba infection could reach the appendix, usually extending from an infection in the right part of the colon.
There are ways to distinguish between these conditions, based on their unique features. For instance, typical IBD doesn’t show any signs of fibrinous material (a type of clot) containing organisms. Ulcerative colitis and Crohn’s disease, the two main varieties of IBD, have characteristic symptoms: pervasive colonic involvement with twisted mucosa (lining of the colon) and a type of cell called basal plasma infiltrating the layer beneath, distinguishing ulcerative colitis; Crohn’s disease, on the other hand, is represented by sporadic mucosal ulcers that appear more like fissure-like ulcers rather than flask-shaped, and they usually grow sideways rather than along the length of the bowel.
In the case of colon tuberculosis, ulcers and widespread fibrosis (scarring) extend into the wall of the colon, which can cause narrowing and blockage. In rare cases, this condition may coexist with tuberculous peritonitis (a severe infection in the lining of the abdomen). Upon microscopic examination, typical granulomas (a kind of inflammation) are usually present.
What to expect with Amebic Colitis
Medication can eliminate the illness known as amebiasis within a few weeks. However, in developing countries, this infection can be deadly among young children, particularly those under five years old.
Globally, amebiasis ranks third in causing death as a result of parasitic infections, following malaria and schistosomiasis. At least 5 people die from this condition in the United States every year.
Possible Complications When Diagnosed with Amebic Colitis
Amebic colitis can lead to several complications such as severe inflammation of the colon, large bowel enlargement, holes in the intestine, inflammation of the membrane lining the abdominal wall, bleeding, formation of narrow regions in the bowel, or blockages. “Fulminant colitis” is one such complication and it happens in 0.5% cases. Patients typically show symptoms such as severe diarrhea, fever, an increase in white blood cells, and vague stomach pain. It can also lead to death of the bowel lining causing holes in it that can then cause inflammation of the abdominal lining. The treatment usually consists of nitroimidazole drugs and early surgery. If the intestine raptures, broad-spectrum antibiotics are chosen for treatment. The condition where the large bowel enlarges, called “Toxic megacolon”, occurs in around 0.5% cases and is usually fatal, often needing surgery. It is characterized by complete or partial enlargement of the colon without any blockage, along with overall sickness.
Most Common Complications
- Severe inflammation of the colon
- Large bowel enlargement
- Holes in the intestine
- Inflammation of the membrane lining the abdominal wall
- Bleeding
- Formation of narrow regions in the bowel
- Blockage in the bowel
In terms of conditions outside the intestine caused by amebiasis, liver abscesses occur in around 3% to 9% of the cases. Another manifestation of amebiasis outside the intestine is pleuropulmonary amebiasis, which is the second most common condition after amebic liver abscess.
Preventing Amebic Colitis
If you’re traveling to areas where amebic infection – an infection caused by a parasite – is common, you can protect yourself by avoiding drinking unfiltered water and eating raw food, like fruits and vegetables, that may have been washed with that water. Even though the tiny particles, or cysts, of this parasite can survive the chlorine usually used to clean water, treating the water with a substance called iodine could kill them.
If you do get infected, your doctor will provide you with medicine. It’s important to understand any side effects these drugs might cause. You must also follow the complete treatment plan, which includes a second type of medicine called a luminal agent. This is used to completely get rid of the parasites from your body and alleviate the symptoms and the negative effects they could cause.
