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Colonoscopic diagnosis of amebiasis: a case series and systematic review
Abstract and Figures
Purpose:
Nonspecific gastrointestinal symptoms make diagnosis of amebiasis difficult. Certain colonoscopic findings predict amebic colitis while others suggest different diagnoses. We aimed to evaluate the diagnostic capability of colonic evaluation of amebiasis.
Methods:
We retrospectively reviewed data of all amebiasis cases admitted to our institution between 2003 and 2012. Cases were diagnosed by clinical presentation, laboratory examinations, and colonoscopy with biopsy and microscopic examination. Patients were stratified as right-sided colitis and proctosigmoiditis. A systematic review was conducted by searching Medline, Cochrane, EMBASE, and Google Scholar using key words amebiasis, amebic colitis, amebic proctosigmoiditis, colonoscopy, and Entamoeba histolytica. Data were extracted from articles meeting the inclusion criteria. Colonoscopic findings were described and studies were assessed for quality.
Results:
The current series included 20 patients (5 male, 15 female, median age 51), 7 with amebic liver abscess and 13 with amebic colitis. Colonoscopic findings of right-sided colitis included aphthae or erosions, ulcers, exudates, or edematous swollen mucosa in cecum, and findings for proctosigmoiditis were edematous swollen mucosa with bloody exudate. In 25 studies, colonoscopic findings of 41 patients (36 male, 5 female, median age 43.39 years) included mainly ulcers in the cecum and rectum, ulcerated mass, and edematous mucosa; and in fewer patients, submucosal invasion suggestive of colon cancer, bleeding ulcers, proctitis, and ulcers with aphthae in rectum.
Conclusions:
Colonic evaluation of suspected amebiasis is of diagnostic value when accompanied by biopsy and microscopic identification of Entamoeba species. Colonoscopic manifestations vary between right-sided colitis and proctosigmoiditis.
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... Nagata et al. investigated the sensitivity and specificity of endoscopic findings that were significantly associated with amebic colitis were: cecal lesions, multiple number of lesions, presence of aphthae or erosions and presence of exudate. Multivariate analysis revealed that the best combination of findings to predict amebic colitis was the presence of cecal lesions, multiple lesions, and exudates [9]. Lee et al. observed distinct differences in findings based on rightside amebic colitis versus proctosigmoiditis, the colonoscopic findings of right-sided colitis included aphthae or erosions, ulcers, exudates, or edematous swollen mucosa in cecum, and findings for proctosigmoiditis were edematous swollen mucosa with bloody exudate [21]. In our study, cecum was the most common site of amebic colitis, and the caecum and rectum were also involved in many lesions (11/16, 68.75%). ...
... In our study, cecum was the most common site of amebic colitis, and the caecum and rectum were also involved in many lesions (11/16, 68.75%). The features of the lesions in rectums had 2 types, in some patients, the irregular ulcer or erosions covered with white or yellow exudates were observed in rectum and cecum, and the bloody exudates in rectum were more severe than those in cecum; in other patients, rectal lesions were much less severe than those in cecum, the small superficial erosion or reddened mucosa were observed in the rectal ampulla, however, the irregular ulcer or erosion covered with white or yellow exudates were observed in the cecum, which was different from the report of Lee [21]. The features of the typical lesions in our study were similar to the previous reports [10,22], which included multiple irregular shaped ulcers and erosions with surrounding erythema, and the ulcers and erosions were covered by the white or yellow exudates which were named "dirty ulcer". ...
Background
The clinical features of amoebic colitis resemble those of inflammatory bowel disease (IBD), and therefore the risk of misdiagnosis is very high. The aim of this study was to analyse the characteristics of the endoscopic and pathological findings of amebic colitis and the lessons from our patients, which were useful for diagnosing the amebic colitis timely and avoiding the serious complication.
Methods
We retrospectively reviewed data of all amebic colitis admitted to Beijing Friendship Hospital from January 2015 to January 2020. Cases were diagnosed by clinical presentation, laboratory examinations, and colonoscopy with biopsy and histological examination, no ELISA stool antigen or PCR tests were used.
Results
16 patients were diagnosed with amebic colitis by the colonoscopy accompanied by biopsy and microscopic examination. At first time, 12 (75%) patients were misdiagnosed as IBD. Cecum was the most common site of amebic colitis (100%), and the caecum and rectum were also involved in many lesions (68.75%). Multiple lesions of erosion and/or ulcer were recognized in all patients (100%).The endoscopic findings included multiple irregular shaped ulcers and erosions with surrounding erythema, and the ulcers and erosions were covered by the white or yellow exudates. The intervening mucosae between the ulcers or erosions were normal. The features of rectums can be divided to 2 types: in 6 patients (54.5%), the irregular ulcer or erosions covered with white or yellow exudates were observed in rectum and cecum, and the bloody exudates in rectum were more severe than those in cecum; in other 5 patients (45.5%), rectal lesions were much less severe than those in cecum, the small superficial erosion or reddened mucosa were observed in the rectal ampulla. All patients were diagnosed as detection of amebic trophozoites from HE-stained biopsy specimens. The number of trophozoites ranged from 1/HPF to > 50/HPF. Among 16 cases, mild architectural alteration of colon crypt were observed in 10 cases (62.5%), and serious architectural alteration of colon crypt was found which had crypt branch in 1 case (16.7%). Cryptitis was observed in 12 cases (75%) and its severity was mild or moderate. No crypts abscess was observed in all cases.
Conclusions
The colonoscopy with histological examination are very important to diagnose the amebic colitis. Detect the amoebic trophozoites in the exudates by histological examination is the vital. Sometimes a negative biopsy does not rule out amebiasis, repeated biopsies may be needed to make the diagnosis.
... To distinguish between present and past infections in asymptomatic individuals with positive serological test results, PCR of stool samples is commonly performed. Moreover, colonoscopy has a high diagnostic value (35,(54)(55)(56)(57). In asymptomatic cases, visible infective ulcers can be found but usually limited within the proximal side (from cecum to ascending colon), whereas ulcers are distributed to the multiple sites of large intestine (from cecum to rectum) in symptomatic colitis cases (58,59). ...
Amebiasis, which is caused by Entamoeba histolytica (E. histolytica), is the second leading cause of parasite-related death worldwide. It manifests from asymptomatic carriers to severe clinical conditions, like colitis and liver abscesses. Amebiasis is commonly seen in developing countries, where water and food are easily contaminated by feces because of the poor sanitation. However, a recently challenge in many developed countries is the increase in domestic cases of invasive amebiasis as a sexually transmitted infection (STI amebiasis). In contrast to food-/waterborne transmission of E. histolytica in developing countries, transmission of STI amebiasis occurs directly through human-to-human sexual contact (e.g., men who have sex with men and people who engage in oral-anal sex); in this setting, asymptomatic infected individuals are the main reservoir of E. histolytica. The Development of screening methods for the early diagnosis of asymptomatic E. histolytica infection is the key to epidemiologic control. Moreover, delay in diagnosis of severe cases (e.g., fulminant amebiasis) leads to death even in developed countries. It is also important to increase clinical awareness of domestically transmitted STI amebiasis in the clinical settings. This review considers the changing epidemiology and clinical manifestations of STI amebiasis, and finally discusses the future strategies for the better practice.
... Entamoeba muris resides in the large intestine at 5 days postinfection. E. histolytica is thought to replicate in the colon and has been found during diagnostic colonoscopies (25). As our model uses the natural oral route of infection, we aimed to determine where E. muris is located during primary infection. ...
There are several Entamoeba species that colonize humans, but only Entamoeba histolytica causes severe disease. E. histolytica is transmitted through the fecal-oral route to colonize the intestinal tract of 50 million people worldwide. The current mouse model to study E. histolytica intestinal infection directly delivers the parasite into the surgically exposed cecum, which circumvents the natural route of infection. To develop a fecal-oral mouse model, we screened our vivarium for a natural murine Entamoeba colonizer via a pan-Entamoeba PCR targeting the 18S ribosomal gene. We determined that C57BL/6 mice were chronically colonized by Entamoeba muris. This amoeba is closely related to E. histolytica, as determined by 18S sequencing and cross-reactivity with an E. histolytica-specific antibody. In contrast, outbred Swiss Webster (SW) mice were not chronically colonized by E. muris. We orally challenged SW mice with 1 Â 10 5 E. muris cysts and discovered they were susceptible to infection, with peak cyst shedding occurring between 5 and 7 days postinfection. Most infected SW mice did not lose weight significantly but trended toward decreased weight gain throughout the experiment compared to mock-infected controls. Infected mice treated with paro-momycin, an antibiotic used against noninvasive intestinal disease, do not become colonized by E. muris. Within the intestinal tract, E. muris localizes exclusively to the ce-cum and colon. Purified E. muris cysts treated with bovine bile in vitro excyst into mobile , pretrophozoite stages. Overall, this work describes a novel fecal-oral mouse model for the important global pathogen E. histolytica. IMPORTANCE Infection with parasites from the Entamoeba genus are significantly underreported causes of diarrheal disease that disproportionally impact tropical regions. There are several species of Entamoeba that infect humans to cause a range of symptoms from asymptomatic colonization of the intestinal tract to invasive disease with dissemination. All Entamoeba species are spread via the fecal-oral route in contaminated food and water. Studying the life cycle of Entamoeba, from host colo-nization to infectious fecal cyst production, can provide targets for vaccine and drug development. Because there is not an oral challenge rodent model, we screened for a mouse Entamoeba species and identified Entamoeba muris as a natural colonizer. We determine the peak of infection after an oral challenge, the efficacy of paromo-mycin treatment, the intestinal tract localization, and the cues that trigger excysta-tion. This oral infection mouse model will be valuable for the development of novel therapeutic options for Entamoeba infections.
... Fulminant necrotizing amoebic colitis (FulNAC) is an uncommon presentation of invasive amoebic colitis (less than 0.5-3% cases), which is more aggressive, life threatening, complicated and is associated with high mortality and morbidity [6,7]. FulNAC may cause large bowel gangrenous necrosis, perforation, and peritonitis [8,9], observed in the endoscopic examination as mucosal and/or submucosal ulcers [4]. Due to their low incidence and similar clinical and endoscopic findings with inflammatory bowel disease (IBD), intestinal amoebiasis is easily misdiagnosed. ...
Intestinal amoebiasis is a parasitic infection caused by Entamoeba histolytica. It is commonly found in developing countries with poor hygiene. A rare, life-threatening complication of amoebiasis is fulminant necrotizing amoebic colitis (FulNAC). We report a 59-year-old male with acute lower right abdominal pain. Before coming to our institution, he was diagnosed with acute appendicitis. Extensive necrosis near the caecum involving the appendix and colon was observed intraoperatively. The patient underwent a right hemicolectomy, followed by an ileostomy and colostomy. Histopathologic examination confirmed the diagnosis of FulNAC. After the surgery, the patient was transferred to the high care unit and treated with metronidazole after histopathologic findings confirmed the etiology. The patient showed excellent response to the antibiotic prescribed, and the symptoms subsided. He was discharged from the hospital on day nine. Additionally, we reviewed fifty-one existing case reports on invasive intestinal amoebiasis worldwide, confirmed by histopathological examination following their preoperative diagnosis, surgery, pharmacology treatment, and outcomes. The learning point of this case is that intestinal amoebiasis should be considered a differential diagnosis for patients around fifty years old with bowel symptoms and travel history or living in tight quarters. Blood tests, radiological examinations, and serological evaluations are valuable diagnostic modalities. Metronidazole should be given as early as possible, and health promotion is recommended to prevent this disease in the population.
There are several Entamoeba species that colonize humans, but only Entamoeba histolytica causes severe disease. E. histolytica is transmitted through the fecal-oral route to colonize the intestinal tract of 50 million people worldwide. The current mouse model to study E. histolytica intestinal infection directly delivers the parasite into the surgically exposed cecum, which circumvents the natural route of infection and does not produce infectious cysts. To develop a fecal-oral mouse model, we screened our vivarium for a natural murine Entamoeba colonizer via a pan- Entamoeba PCR targeting the 18S ribosomal gene. We determined that C57BL/6 mice were chronically colonized by Entamoeba muris . This amoeba is closely related to E. histolytica , as determined by 18S sequencing and cross-reactivity with an E. histolytica -specific antibody. In contrast, outbred Swiss Webster (SW) mice were not chronically colonized by E. muris . We orally challenged SW mice with 1×10 ⁵ E. muris cysts and discovered they were susceptible to infection, with peak cyst shedding occurring between 5-7 days post-infection. Most infected SW mice did not lose weight significantly but trended toward decreased weight gain throughout the experiment when compared to mock-infected controls. Infected mice treated with paromomycin, an antibiotic used against non-invasive intestinal disease, do not become colonized by E. muris . Within the intestinal tract, E. muris localizes exclusively to the cecum and colon. Purified E. muris cysts treated with bovine bile in vitro excyst into mobile, pre-trophozoite stages. Overall, this work describes a novel fecal-oral mouse model for the important global pathogen E. histolytica .
Importance
Infection with parasites from the Entamoeba genus are significantly underreported causes of diarrheal disease that disproportionally impact tropical regions. There are several species of Entamoeba that infect humans to cause a range of symptoms from asymptomatic colonization of the intestinal tract to invasive disease with dissemination. All Entamoeba species are spread via the fecal-oral route in contaminated food and water. Studying the life cycle of Entamoeba , from host colonization to infectious fecal cyst production, can provide targets for vaccine and drug development. Because there is not an oral challenge rodent model, we screened for a mouse Entamoeba species and identified Entamoeba muris as a natural colonizer. We determine the peak of infection after an oral challenge, the efficacy of paromomycin treatment, the intestinal tract localization, and the cues that trigger excystation. This oral infection mouse model will be valuable for the development of novel therapeutic options for Entamoeba infections.
Crohn's disease is a chronic inflammatory disease that can affect any portion of the gastrointestinal tract. Associated symptoms can vary based on the severity of disease, extent of involvement, presence of extraintestinal manifestations, and development of complications. Diagnosis is based on a constellation of findings. Many diseases can mimic Crohn's disease and lead to diagnostic conundrums. These include entities associated with the gastrointestinal luminal tract, vascular disease, autoimmune processes, various infections, malignancies and complications, drug- or treatment-induced conditions, and genetic diseases. Careful consideration of possible causes is necessary to establish the correct diagnosis.
Intestinal amoebiasis is caused by Entamoeba histolytica (E. histolytica) and is characterized by cecal lesions, multiple lesions, aphthae, and multiple exudative erosions. Intestinal Behçet’s disease (BD) is a chronic inflammatory disorder that is characterized by multiple ulcers. Although the etiologies of these two bowel diseases are unrelated, they are difficult to distinguish because they present similarly with inflammation and ulcers, especially if evidence of specific pathogens is not detected. Herein, we report a case of intestinal amoebiasis in a patient with BD. The patient underwent colonoscopy four times before intestinal amoebiasis was diagnosed. As intestinal BD was initially suspected, she received high-dose glucocorticoid therapy, which exacerbated her condition. Following exacerbation, she underwent colonoscopy, and E. histolytica was revealed. Deliberate care should be taken to distinguish between intestinal amoebiasis and intestinal BD, as the appropriate treatments for these diseases are entirely different.
A 43‐year‐old man underwent total colonoscopy for colorectal cancer screening. Colonoscopy revealed multiple erosions on the cecum. Biopsy specimens revealed multiple entamoeba trophozoite unexpectedly.
In this case report we present a family cluster of amoebiasis in a nonendemic region. A 46-year-old women, diagnosed with Crohn's disease for which she received no maintenance therapy, was evaluated for the suspicion of a flare. At colonoscopy however, atypical findings for Crohn's disease were seen. Histopathologic examination revealed micro-organisms compatible with amoebiasis. Interestingly, 4 years before this event she started a new relationship with a 38-year-old man who was diagnosed with liver-amoebiasis 3 months after the start of their relationship. On top of this, her 18-year-old daughter was diagnosed with amoebiasis 2 years after her diagnosis. The source of the infection remains unknown, but we speculate that the infection was transmitted feco-orally between the different members of this family. These cases illustrate that we should be aware of parasitological causes of colitis, especially in patients with atypical endoscopic images or when a close "relative" is diagnosed with amoebiasis.
We determined yearly change in prevalence and risk factors for amebic colitis caused by intestinal invasive amebiasis among persons who underwent endoscopy and assessed differences between HIV-positive and HIV-negative persons in Japan. A total of 10,930 patients were selected for analysis, of whom 54 had amebic colitis. Prevalence was in 2009 (0.88%, 12/1360) compared with 2003 (0.16%, 3/1904). Male sex (odds ratio [OR] 8.39, 95% CI 1.99-35.40), age <50 years (OR 4.73, 95% CI 2.43-9.20), history of syphilis (OR 2.90, 95% CI 1.40-5.99), and HIV infection (OR 15.85, 95% CI 7.93-31.70) were independent risk factors. No differences in risk factors were identified between HIV-positive and HIV-negative patients. Contact with commercial sex workers was a new risk factor among HIV-negative patients. Homosexual intercourse, rather than immunosuppressed status, appears to be a risk factor among HIV-positive patients.
To diagnose amebic colitis (AC), serologic tests have the advantage of being inexpensive, noninvasive, and easy to perform, but few studies have investigated their utility, especially in a non-endemic country. A total of 299 symptomatic patients (165 HIV-infected patients) who underwent endoscopy and indirect immunofluorescence (IF) assay were analyzed between 2003 and 2009. The diagnosis of AC was defined as detection of amebic trophozoites from biopsy specimens or intestinal fluid sample via endoscopy. Forty-five patients (29 HIV-infected patients) were diagnosed with AC. The area under the receiver-operating characteristic curve (ROC-AUC) for the IF assay was excellent (0.90), and a cut-off value of 100 provided 89% sensitivity and 87% specificity. ROC-AUC was slightly lower in patients with HIV infection (0.88) than in those without HIV infection (0.94). Among HIV-infected patients, ROC-AUC showed no significant differences between different CD4+ cell counts. The IF assay is useful for diagnosing AC in symptomatic patients with and those without HIV infection.
Entamoeba histolytica infection (amoebiasis) is the second leading cause of death from parasitic diseases. Epidemiological studies from developed countries have reported an increasing prevalence of amoebiasis and of invasive infections, such as amoebic colitis, among men who have sex with men (MSM) who engage in oral-anal sex. Although most infections with E histolytica are asymptomatic, clinical manifestations of invasive amoebiasis mainly include amoebic colitis and amoebic liver abscess, which are associated with substantial morbidity and medical cost. Laboratory diagnosis of amoebiasis should be based on detection of E histolytica by use of tests with high sensitivity and specificity, such as specific amoebic-antigen or PCR-based assays. Microscopy used in routine clinical laboratories is not sensitive or specific enough for detection of E histolytica. Metronidazole or tinidazole remains the mainstay of treatment for invasive amoebiasis, followed by treatment with luminal agents to prevent relapse and transmission of E histolytica to sexual partners or close contacts.
This chapter discusses the parasites Entamoeba histolytica, E. dispar, E. coli, E. polecki and E. nana and their clinical importance, disease presentations and contribution to human illness. Of these amoeba species, E. histolytica is the most medically relevant parasite and causes the greatest human disease, and will therefore receive the greatest emphasis.
A 62-year-old man was admitted to our hospital with complaints of abdominal pain and rectal bleeding. Although the colonoscopic examination was highly suggestive of a carcinoma, the histopathological examinations were consistent with chronic inflammation. CT examination revealed a solid lesion from cecum to the ascending colon with right urethral invasion. Percutaneous right nephrostomy was performed for grade 2-3 hydronephrosis. Three days after hospitalization, ileus developed and right hemicolectomy was performed. During surgery we observed that the lesion had invaded the middle part of ureter. So the middle part of ureter was removed with side-to-side urethral anastomosis and 6F double-J catheter was placed. The histopathological findings of resected specimen were consistent with ameboma. Reviewing the literature unilateral hydronephrosis due to colonic amebiasis has not been reported.
Entamoeba histolytica is a well-recognized cause of infectious colitis and disseminated amebic abscesses. Most prevalent in the tropics and subtropics, E. histolytica infections may also occur in the developed world. We describe a case of a North American traveler with intestinal amebiasis, a diagnosis first made by colonic biopsy. We review the available diagnostic tools and the role of the surgical pathologist in the detection of this infection.
Endoscopic diagnosis of amebic colitis can be difficult because its appearance may mimic other forms of colonic disease. The aim of this study was to identify predictive endoscopic findings for amebic colitis. Patients with suspected amebic colitis based on distinctive endoscopic findings such as aphthae or erosions, ulcers, exudates, or a bump, were included in the study. A total of 157 patients were selected, 50 of whom had amebic colitis. The sensitivity and specificity of endoscopic findings that were significantly associated with amebic colitis were: cecal lesions (80% and 54%), multiple number of lesions (96% and 29%), presence of aphthae or erosions (84% and 37%), and presence of exudate (88% and 74%). Multivariate analysis revealed that the best combination of findings to predict amebic colitis was the presence of cecal lesions, multiple lesions, and exudates, which corresponded to an area under the receiver operating characteristic curve of 0.89 (95% confidence interval 0.82-0.95).
This case-control study aimed to characterize the factors associated with amebiasis, defined as presence of anti-Entamoeba histolytica antibody titers of ≧ 128 by indirect hemagglutination assay, among persons seeking voluntary counseling and testing (VCT) for human immunodeficiency virus (HIV) infection. Between April 2006 and September 2009, 57 of 4,802 persons (1.2%) seeking VCT services were seropositive for E. histolytica infection. Compared with 228 seronegative controls, case subjects were older (odds ratio [OR] for per 1-year increase, 1.098; 95% confidence interval [CI], 1.036, 1.165), less likely to hold bachelor degree or higher (OR, 0.359; 95% CI, 0.152, 0.846), and were more likely to be men who have sex with men (MSM) (OR, 8.382; 95% CI, 2.050, 34.266) and have oral-anal sex (OR, 4.016; 95% CI, 1.711, 9.427) in multiple logistic regression analysis. The MSM, fecal-oral contamination, lower educational achievement, and older age were associated with increased risk for amebiasis among persons seeking VCT for HIV infection.
The endocytoscopy system (ECS) is a new method to provide real-time super-magnifying microscopic imaging in vivo. Routine diagnosis of amebic colitis requires multiple tests that are both time consuming and costly.
To determine the feasibility of ECS to directly detect the amebic parasites in vivo.
Prospective, single-center, pilot study.
Tertiary-care university hospital.
This study involved 5 patients who were suspected to have amebic colitis by conventional colonoscopy in our institute.
A super-magnifying ECS with 450 x magnification.
We compared ECS findings with those of conventional methods-serum antibody tests and histology of colon biopsy specimens.
We successfully visualized the amebic trophozoites in all 5 cases. In contrast, 3 specimens had positive results on serology, and 3 had positive histology results on hematoxylin and eosin staining.
Pilot study with a limited number of patients. Findings were compared only with serology and histology findings.
ECS would be a useful tool for the prompt diagnosis of amebic colitis via the real-time in vivo visualization of amebic trophozoites.