In vivo visualization of trophozoites in patients with amoebic colitis by using a newly developed endocytoscope Naoki Hosoe, MD, PhD,* Taku Kobayashi, MD, PhD,* Takanori Kanai, MD, PhD, Rieko Bessho, MD, Tetsuro Takayama, MD, Nagamu Inoue, MD, PhD, Hiroyuki Imaeda, MD, PhD, Yasushi Iwao, MD, PhD, Seiki Kobayashi, PhD, Makio Mukai, MD, PhD, Haruhiko Ogata, MD, PhD, Toshifumi Hibi, MD, PhD Tokyo, Japan Background: 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. Objective: To determine the feasibility of ECS to directly detect the amebic parasites in vivo. Design: Prospective, single-center, pilot study. Setting: Tertiary-care university hospital. Patients: This study involved 5 patients who were suspected to have amebic colitis by conventional colonos- copy in our institute. Interventions: A super-magnifying ECS with 450  magnification. Main Outcome Measurements: We compared ECS findings with those of conventional methods—serum antibody tests and histology of colon biopsy specimens. Results: 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. Limitations: Pilot study with a limited number of patients. Findings were compared only with serology and histology findings. Conclusions: ECS would be a useful tool for the prompt diagnosis of amebic colitis via the real-time in vivo visualization of amebic trophozoites. Amebiasis is the second leading cause of death from parasitic disease worldwide. 1 Approximately 50 million people develop invasive disease, resulting in 10,000 deaths per year. 2 Amoebas are distributed worldwide, with the highest prevalence rates found in developing coun- tries. There are 6 known species of amoeba that can reside in the human GI lumen: Entamoeba histolytica, E dispar, E moshkovskii, E polecki, E coli, and E hartmanni. Entamoeba histolytica is the causative agent of amebiasis, however, E dispar and E moshkovskii are morphologically indistinguishable from E histolytica. Most individuals infected with E histolytica are asymptom- atic, and the infection is self-limited. Nevertheless, 4% to 10% of individuals infected with E histolytica go on to develop disease within a year of infection. 1 Patients typically present with subacute or chronic symptoms such as fever, bloody diarrhea, and abdominal pain, thus amebic colitis is often difficult to distinguish from other GI disorders including in- flammatory bowel diseases and other types of infectious enterocolitis. Patients may further develop intestinal and/or extraintestinal complications. Intestinal complications in- clude massive bleeding, perforation, and toxic megacolon, which may ultimately lead to surgical intervention. In pa- tients with fulminant amebic colitis, delayed initiation of treatment leads to higher mortality rates. 3 Moreover, many Abbreviations: ECS, endocytoscopy system; PCR, polymerase chain reac- tion. DISCLOSURE: T. Kobayashi is supported by a grant from the Japanese Foundation for Research and Promotion of Endoscopy. T. Kanai, H. Ogata, and T. Hibi are supported by grants from the Japanese Ministry of Education, Culture, Sports, Science and Technology; the Japanese Min- istry of Health, Labor and Welfare. No other financial relationships relevant to this publication were disclosed. *Drs Hosoe and Kobayashi contributed equally to this article. Copyright © 2010 by the American Society for Gastrointestinal Endoscopy 0016-5107/$36.00 doi:10.1016/j.gie.2010.04.031 Received March 16, 2010. Accepted April 19, 2010. Current affiliations: Division of Gastroenterology and Hepatology, Department of Internal Medicine (N.H., T. Kobayashi, T. Kanai, R.B., T.T., T.H.), Department of Tropical Medicine and Parasitology (S.K.), Division of Diagnostic Pathology (M.M.), Center for Diagnostic and Therapeutic Endoscopy (N.I., H.I., Y.I., H.O.), School of Medicine, Keio University, Tokyo, Japan. Reprint requests: Toshifumi Hibi, MD, PhD, Division of Gastroenterology and Hepatology, Department of Internal Medicine, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan. www.giejournal.org Volume 72, No. 3 : 2010 GASTROINTESTINAL ENDOSCOPY 643