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Amoebic Colitis - Causes, Symptoms, Diagnosis, and Treatment

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Amoebic colitis is an invasive infection of Entamoeba histolytica which affects the colon primarily. The symptoms and treatment are explained in the article.

Medically reviewed by

Dr. Shubadeep Debabrata Sinha

Published At March 23, 2023
Reviewed AtMarch 23, 2023

Introduction

Invasive infection of Entamoeba histolytica results in amoebic colitis. It was first discovered in 1875 in the colonic ulcer autopsy performed by Losch. Entamoeba histolytica can enter the body by ingesting the amoebic cyst, which can be found in contaminated water and food. One more way of transmission is fecal-oral self-inoculation which can occur during oral-anal sexual contact with the infected partner. The symptoms include diarrhea with rectal bleeding, liver abscesses, colonic granulomatous masses, and colonic perforations. The treatment of the infection is a combined therapy of luminal agents with tissue amebicides. The surgical method has been opted for only when a liver abscess may need drainage.

What Causes Amoebic Colitis?

Entamoeba histolytica is a protozoan parasite that causes amebiasis. It colonizes the intestinal tract of almost 90 % of individuals and remains asymptomatic. In about 10% of the cases, the parasite crosses the mucosal barrier and invades the lamina propria. The parasitic cysts are ingested through contaminated food or water (especially in regions of poor sanitation) and in cases of oral sex contacting the anal region of the infected individual. If the organism remains untreated in the gut, it can cause many severe complications.

How Does Entamoeba Histolytica Enter the Gut Lining?

The protective barriers for Entamoeba histolytica are mucus and gastric acid; they do not let the microorganism enter the intestinal epithelium. The entry of the microorganism occurs at the terminal lining of the ileum or the colon, where the trophozoites enter the lumen of the gut. Some individuals tend to show invasive infection due to the interplay between the host defense mechanism and the virulence factor of Entamoeba histolytica. Gradually the protozoa cause inflammation of the colonic mucosa, edema, and necrosis which may lead to perforation in the colon.

What Are the Symptoms Seen in Amoebic Colitis?

  • Approximately 90% of the cases of Entamoeba infection are asymptomatic, as they present no symptoms and stay in the host body. However, such individuals are more dangerous as they are the egg carriers of protozoa. It becomes difficult to determine who is infectious, and that person can transmit the infection to many others.

  • The symptomatic cases of Entamoeba infection show symptoms such as diarrhea with blood in the stool and pain during bowel movements.

  • The physical examination of such infected individuals may have diffused or localized tenderness in the abdominal region.

  • In prolonged undiagnosed cases, there are chances of megacolon which can further lead to necrosis and perforations in the colon.

  • Although the symptoms of amoebic colitis are generally within the intestine, in about 1 % of cases, it shows extraintestinal symptoms, mostly liver abscesses. Patients with an abscess in the liver may show symptoms such as pain in the upper quadrant of the abdomen, fever, and chills.

  • Some other symptoms in cases of the infected liver include increased white blood cells in the blood weight loss. Jaundice is not seen in cases of Entamoeba infection.

  • In some rare cases, the trophozoites penetrate the diaphragm and cause lung abscesses. In cases of lung infection, the symptoms are chest pain with difficulty breathing and cough.

How to Diagnose Amoebic Colitis?

  • The most important process to diagnose amoebic colitis is the detection of trophozoites of Entamoeba histolytica in colonoscopy biopsies or by examining fresh stool. Patients with diarrhea likely have trophozoites in the stool, which can be easily seen in the direct wet mount or the trichrome (three colors) stained smears.

  • Colonoscopy: A thin tube with a camera is inserted in the colon through the rectum, which shows many ulcers in the cecum and the ascending colon. The histological appearance of ulcers shows flask-shaped structures. In severe cases, amoebic colitis resembles ulcerative colitis histologically.

  • Ultrasonography: It helps to detect abscesses in the liver. The abscess should be aspirated and tested, which may show the presence of motile trophozoites and necrosed tissues. These mobile trophozoites have the potential to penetrate the diaphragm and reach the lungs.

  • Serological Tests: These tests are performed to check the antibody level for Entamoeba histolytica in the body. Approximately 90 % of people show a positive result for this test. This antibody level rise happens after tissue invasion. Still, it is not relevant to differentiate whether the infection is new or old, as the antibodies can persist in the body for years even after the infection is cured.

  • Blood Test: WBCs (white blood cell) levels increase in amoebic colitis cases.

What Is the Treatment for Amoebic Colitis?

The primary aim of treating individuals with amoebic colitis is to cure the invasive disease as well as eradicate the presence of orginaism and its intestinal carriage. The treatment for amoebic colitis comprise of a combination of therapies including antimicrobial therapy, supportive care, and treatment of associated complications.

  • Antiamoebic drugs - there are two classes of antiamoebic agents with varying efficacy and site specific activity depending on the predominant sites of parasites' existence.

  • Luminal amoebicides - act primarily in the lumen of the bowl. These luminal amebicides kill the trophozoites present in the intestine and other organs like the liver or lungs.

  • The luminal agents include Diloxanide, Furoate, Iodoquinol, arbarsone, stovarsol, thioarsenite, quinfamide, mantomide, chlorphenoxamide, antibiotic amoebicides such as tetracycline, erythromycin, paromomycin, and fumagillin.

  • Tissue amoebicides - act primarily on the trophozites colonized in the bowel wall and in the liver tissues. These agents help in healing of the infected intestinal lining having multiple ulcers.

  • The tissue amebicides used include Nitazoxanide, Metronidazole, Erythromycin, and Chloroquine, emetine hydrochloride, and nimorazole.

  • Recent guidelines include administrating metronidazole 750 mg orally for 7 to 10 days or tinidazole 2 g (gram) orally once daily for three days, followed by a luminal agent for elimination of intraluminal cysts preferably paromomycin 25 to 30 mg/kg (milligram per kilometer) per day orally in three doses for seven days.

Treatment for Complications

  • Surgical intervention - surgical procedures is opted only in severe complications such as intestinal or liver abscess where the abscess needs to be drained. It can also be performed in cases of perforation and necrosis, as these conditions need quick treatments due to failure of medication therapies.

  • Image-guided percutaneous intervention such as needle aspiration and catheter drainage are done to drain the abscess.

  • Percutaneous catheter drainage enhaces treatment outcomes in severe cases of amebic empyema and is often life-saving in complications like amebic pericarditis.

  • Complications such as toxic megacolon is surgically operated by colectomy.

Conclusion

Amoebic colitis is an intestinal infection caused by Entamoeba histolytica protozoa. It is reported that almost 90 % of cases are asymptomatic, and only about 10% of cases show invasive symptoms such as diarrhea with blood in stool and pain in the upper right abdominal region due to liver abscess. Sometimes the trophozoites may penetrate the diaphragm and reach the lungs. The infection of trophozoites in the lungs leads to chest pain and difficulties in breathing. The treatment for amoebic colitis includes combined medical therapy with luminal agents and amebicides, and in severe cases like a liver abscess, surgeries can be performed.

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Dr. Shubadeep Debabrata Sinha
Dr. Shubadeep Debabrata Sinha

Infectious Diseases

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