Amebiasis: modern diagnostic imaging with pathological and clinical correlation

A 48-Year-Old Man with Fevers and Weight Loss

A 48-Year-Old Man with Fevers and Weight Loss48-year-old man presented for evaluation of fevers, night sweats, and a 20-pound unintentional weight loss over 3 months. He also had a dry cough over the same time, without dyspnea, chest discomfort, or hemoptysis. On examination, he was febrile and tachycardic, with tenderness in the right upper quadrant on abdominal palpation. What is the diagnosis?

Amoebic liver abscess in a COVID-19 patient: a case report

BACKGROUND

Amoebiasis is a parasitic disease caused by Entamoeba histolytica, which affects people living in low- and middle-income countries and has intestinal and extraintestinal manifestations. To date, knowledge on coronavirus disease 2019 (COVID-19) coinfection with enteric parasites is limited, and E. histolytica coinfection has not been previously described. Here we present the case of a patient with COVID-19 who, during hospitalisation, presented a clinical picture consistent with an amoebic liver abscess (ALA).

CASE PRESENTATION

A 54-year-old man, admitted as a suspected case of COVID-19, presented to our hospital with dyspnoea, malaise, fever and hypoxaemia. A nasopharyngeal swab was positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by reverse-transcription polymerase chain reaction. After 7 days, he developed diarrhoea, choluria and dysentery. An abdominal ultrasound showed a lesion compatible with a liver abscess; stool examination revealed E. histolytica trophozoites, and additional serology for E. histolytica was positive. After 12 days of treatment with metronidazole, ceftazidime and nitazoxanide, the patient reported acute abdominal pain, and an ultrasound examination revealed free liquid in the abdominal cavity. An emergency exploratory laparotomy was performed, finding 3000 mL of a thick fluid described as "anchovy paste". Computed tomography scan revealed a second abscess. He ended up receiving 21 days of antibiotic treatment and was discharged with satisfactory improvement.

CONCLUSION

Here we present, to the best of our knowledge, the first report of ALA and COVID-19 co-presenting. Based on their pathophysiological similarities, coinfection with SARS-CoV-2 and E. histolytica could change the patient's clinical course; however, larger studies are needed to fully understand the interaction between these pathogens.

Venous thrombosis and segmental hypoperfusion in amebic liver abscess: MDCT demonstration and its implications

PURPOSE

To report venous thrombosis and associated perfusion defect in amebic liver abscess (ALA) using MDCT.

METHOD

MDCT images of 62 patients with ALA were reviewed for venous thrombosis and associated perfusion abnormalities.

RESULT

The study found 43 (69%) patients with venous thrombosis: portal vein thrombosis (PVT) occurred in 39, hepatic vein thrombosis (HVT) in 37 and inferior vena cava (IVC) thrombosis in 4. Combined PVT and HVT occurred in 33 (77%) patients. The portal vein thrombi remained localized in subsegmental branches in 25 patients and extended to segmental branches in 14. The hepatic vein thrombi were confined to peripheral branches in 18 patients; they progressed to the main trunk in 19 and to the IVC in 4. A wedge-shaped hypoattenuating zone suggesting ischemia was identified in 33 (77%) patients in portal phase: 31 had combined PVT and HVT, 2 had HVT alone, but none had PVT alone. It occurred significantly more often with combined PVT and HVT than HVT alone (p = 0.05). Arterial phase enhancement occurred in 2 of 13 patients with multiphasic CT. All patients were symptomatic despite medical therapy and therefore required percutaneous drainage. About half of the patients were identified with ruptured abscesses. Segmental atrophy was observed in seven of nine patients who underwent follow-up CT.

CONCLUSION

Combined PVT and HVT commonly occur with ALA and often manifests as segmental hypoperfusion in portal venous phase, indicating ischemia. The detection of such events by CT may be indicative of severe disease that requires aggressive management involving percutaneous drainage.

Venous thrombosis and segmental hypoperfusion in amebic liver abscess: MDCT demonstration and its implications

PURPOSE

To report venous thrombosis and associated perfusion defect in amebic liver abscess (ALA) using MDCT.

METHOD

MDCT images of 62 patients with ALA were reviewed for venous thrombosis and associated perfusion abnormalities.

RESULT

The study found 43 (69%) patients with venous thrombosis: portal vein thrombosis (PVT) occurred in 39, hepatic vein thrombosis (HVT) in 37 and inferior vena cava (IVC) thrombosis in 4. Combined PVT and HVT occurred in 33 (77%) patients. The portal vein thrombi remained localized in subsegmental branches in 25 patients and extended to segmental branches in 14. The hepatic vein thrombi were confined to peripheral branches in 18 patients; they progressed to the main trunk in 19 and to the IVC in 4. A wedge-shaped hypoattenuating zone suggesting ischemia was identified in 33 (77%) patients in portal phase: 31 had combined PVT and HVT, 2 had HVT alone, but none had PVT alone. It occurred significantly more often with combined PVT and HVT than HVT alone (p = 0.05). Arterial phase enhancement occurred in 2 of 13 patients with multiphasic CT. All patients were symptomatic despite medical therapy and therefore required percutaneous drainage. About half of the patients were identified with ruptured abscesses. Segmental atrophy was observed in seven of nine patients who underwent follow-up CT.

CONCLUSION

Combined PVT and HVT commonly occur with ALA and often manifests as segmental hypoperfusion in portal venous phase, indicating ischemia. The detection of such events by CT may be indicative of severe disease that requires aggressive management involving percutaneous drainage.

Ileocecal thickening: Clinical approach to a common problem

Ileocecal thickening (ICT) is a common finding on radiological imaging. It can be caused by a variety of inflammatory, infectious, or neoplastic conditions, and evaluating a patient of ICT can be a challenging task. Intestinal tuberculosis (ITB), Crohn's disease (CD), and adenocarcinoma are the most common causes. Enteric bacterial infections, cytomegalovirus, histoplasmosis, amebiasis, systemic vasculitis, lymphoma, etc. should be suspected in appropriate clinical settings. However, it could often be a spurious or nonspecific finding. A thickness of more than 3 mm in a normally distended small bowel is usually considered abnormal. Detailed evaluation of imaging of the site and extent of thickening; the degree and pattern of thickening; and the associated findings, such as degree of fat stranding, fibrofatty proliferation, adjacent lymph nodes, and solid organ involvement, should be performed. Ileocolonoscopy is an important tool for diagnosing and obtaining samples for tissue diagnosis. Histopathology is usually the gold standard for diagnosis, although—not uncommonly—findings could be nonspecific, and reaching a definitive diagnosis is difficult. As such, a systematic approach with the integration of clinical, biochemical, radiological, endoscopic, histological, and other laboratory tests is the key to reaching a diagnosis. In this article, we review the causes of ICT and present a clinical approach for the management of ICT.

Ultrasound-guided percutaneous catheter drainage of various types of ruptured amebic liver abscess: a report of 117 cases from a highly endemic zone of India

OBJECTIVE

To determine the efficacy and safety ultrasound-guided percutaneous catheter drainage (US-PCD) in management of various types of ruptured amebic liver abscess including free rupture (FR) with diffuse intraperitoneal fluid collections (DIFC).

METHODS

This study analyzed 117 patients with ruptured ALA who underwent US-PCD. The indication for US-PCD was failure to respond to conservative treatment and/or percutaneous needle aspiration.

RESULTS

Majority of patients were locally fermented alcohol abusers (95%), and malnourished (75%). Ninety-eight patients had intraperitoneal rupture including 66 contained rupture (CR) with localized intraperitoneal fluid collection (LIFC) and 32 FR with DIFC. Pleuropulmonary complication was found in 19 patients including 13 pleural and 6 pulmonary. A total of 333 catheters were used to drain 202 abscess cavities and associated fluid collections. US-PCD was technically and clinically successful in all cases. Multiple sessions (median 2; range 2-5) of PCD required with upsizing the catheter (median 14 F; range 14-20 F) and placement of additional catheter in 26 (22%) patients. The patients with FR with DIFC required more number of catheters (p = 0.01) and had longer hospital stay (p = 0.01). No major procedure related complication was observed. Six patients developed secondary bacterial infection; two of them presented with cavito-cutaneous fistula at catheter insertion site, and one with cholangitis due to biliary stricture formation necessitating subsequent endoscopic treatment. Post-procedural death occurred from sepsis in a patient with FR.

CONCLUSION

US-PCD is a safe and effective mode of treatment for ruptured ALA including FR with DIFCs. We recommend PCD as a first-line therapy for ruptured ALA.

Fulminant amoebic colitis in the era of computed tomography scan: A case report and review of the literature

Amoebic colitis, caused by ingestion of water or food contaminated with the protozoan Entamoeba histolytica, can progress to a fulminant colitis. Computed tomography (CT) findings reported in the literature on this type of colitis are sparse. We present a 59-year-old male patient with a one-week history of progressive abdominal pain, abdominal distension and associated watery and bloody diarrhoea. A CT scan revealed deep ulcerations with submucosal and intramural tracking of contrast. Colonoscopy and biopsy confirmed a diagnosis of Amoebic colitis. The patient required a laparotomy and demised. Deep ulcerations with submucosal and intramural tracking of contrast on CT are diagnostic of fulminant amoebic colitis. Although not demonstrated at CT in this case, discontinuous bowel necrosis, omental wrapping (seen at laparotomy in our case) and neovascularisation of the bowel wall may be other features to look out for.

Serodiagnosis of Extraintestinal Amebiasis: Retrospective Evaluation of the Diagnostic Performance of the Bordier® ELISA Kit

Soluble antigens from an axenic culture of Entamoeba histolytica were used to develop a commercial ELISA kit to quantify anti-E. histolytica antibodies in sera of patients with extraintestinal amebiasis in non-endemic settings. The diagnostic specificity and sensitivity of the test were assessed retrospectively using 131 human serum samples with amoebic serologic status available. They were selected according to their results in immunofluorescence (IFAT) and were separated in 2 sample categories: 64 sera with positive results by IFAT and 67 with negative results by IFAT. The sensitivity and specificity of the ELISA kit were assessed at 95.0% and 94.0% compared to the IFAT. The test can be useful to exclude a potential diagnosis of amebiasis and could be used as a screening method since ELISA is an automated technique.

Amoebic liver abscess: an unusual cause for a right iliac fossa mass: a case report

Background

Amoebic liver abscess is the most common extra intestinal manifestation of amoebiasis in tropical countries. It usually presents with right hypochondrial pain, fever and anorexia. Amoebic liver abscess has gained clinical significance due to the wide variety of clinical presentations which can cause diagnostic dilemmas and high mortality in untreated cases.

Case presentation

We report a case of a 63-year-old male with a history of anorexia for 3 weeks, fever for 4 days and examination findings of tender hepatomegaly with a liver span of 15 cm in the mid clavicular line and a firm irregular mass in the right iliac fossa. Ultrasound scan of the abdomen showed two large liver abscesses with one of them leaking into the peritoneal cavity causing a localized pus collection, which had been walled off in the right iliac fossa. He was treated with metronidazole and liver abscesses were drained percutaneously under ultrasound scan guidance. The diagnosis of Entamoeba histolytica infection was confirmed with the serology and subsequently by PCR from the aspirated material. He made an uneventful recovery with resolution of the symptoms and right iliac fossa mass.

Conclusion

Recognition of variable presentation of amoebic liver abscess is vital, considering the curable nature of this disease and potentially fatal outcome of untreated abscess. An intra-abdominal mass in a patient with amoebic liver abscess should raise the suspicion of a localized collection of pus and impending generalized peritonitis. Early diagnosis and prompt intervention can prevent the dreaded complication of peritonitis and toxemia, and hence reduce the consequent morbidity and mortality.

A review of amoebic liver abscess for clinicians in a nonendemic setting

Amoebic liver abscess (ALA) is an uncommon but potentially life-threatening complication of infection with the protozoan parasite Entamoeba histolytica. E histolytica is widely distributed throughout the tropics and subtropics, causing up to 40 million infections annually. The parasite is transmitted via the fecal-oral route, and once it establishes itself in the colon, it has the propensity to invade the mucosa, leading to ulceration and colitis, and to disseminate to distant extraintestinal sites, the most common of which is the liver. The authors provide a topical review of ALA and summarize clinical data from a series of 29 patients with ALA presenting to seven hospitals in Toronto, Ontario, a nonendemic setting, over 30 years.

Amebic infection in humans

Clinical human infections with the protozoa Entamoeba histolytica is still estimated to occur in 50 million people worldwide, of which approximately 100,000 die annually. Although most clinical symptoms are due to involvement of the large intestine, 1 % present with involvement of the liver in the form of a liver abscess, a potentially fatal condition. Distinguishing an invasive form (E. histolytica) from a morphologically identical non-invasive one (E. dispar) requires molecular or enzymatic characterization. Further, the pattern of infection, interpretation of presence of antibodies in the host, manifestations of disease, approach to investigations and strategies for management remain complex. This article also provides a comprehensive review of the parasite and host factors that govern the complex relationship of the prozoa and humans, and tries to explain why some develop a particular form of the disease in endemic zones. Application of modern imaging and image guided therapy seems to be playing a major role in diagnosis and management of the potentially most serious form of the disease, amebic liver abscess. Despite lack of controlled studies there is a tendency to lower the threshold of their use in clinical practice, and indeed in-hospital mortality rate seems to be falling for amebic liver abscess. In a world getting increasingly swamped by non-infectious metabolic diseases, awareness of amebic infections, its bed-side diagnosis, the use of appropriate laboratory tests, and decision making in management are shrinking. This review tries to update the scientific developments in amebiasis.

Amebiasis

Amebiasis is an important cause of death from parasitic disease worldwide. The causative organism is Entamoeba histolytica, which has an infective cyst stage and a pathogenic and motile trophozoite stage. The clinical presentation can vary from an asymptomatic carrier state to fulminant colitis and colonic perforation. The majority of patients can be managed medically. However, a small percentage of patients require urgent exploration and resection with an associated high mortality rate. Early recognition and initiation of medical therapy including treatment of asymptomatic carriers are vital to preventing catastrophic outcomes.

Reassessment of the epidemiology of amebiasis: state of the art

The epidemiology of amebiasis has dramatically changed since the separation of Entamoeba histolytica and Entamoeba dispar species, and the worldwide prevalence of these species has not been estimated until recently. The most cited data regarding prevalence, morbidity, or mortality due to amebiasis is the 1986 Walsh report, in which 100,000 deaths are reported to occur worldwide each year due to medical complications of invasive amebiasis. However, the prevalence values of Entamoeba histolytica infection could be completely erroneous since the estimations were performed prior to the molecular characterization of E. histolytica and E. dispar species. Moreover, Entamoeba moshkovskii, another morphologically indistinguishable human parasitic Entamoeba, was not mentioned or considered as a contributor to the prevalence figures in endemic areas. However, recent available prevalence and morbidity data obtained through molecular techniques allow the construction of a more reliable map of endemic regions of amebiasis all over the world [the Asian subcontinent (India, Bangladesh), Africa, Asian Pacific Countries (Thailand, Japan), South and Central America (Mexico, Colombia)]. The epidemiology of infectious diseases focuses on identification of factors that determine disease distribution in time and space, transmission factors responsible for the disease, clinical manifestations, and progression in the host, with the goal being the design of realistic intervention and prevention strategies in a reasonable period of time. In the present review, we will describe how molecular tools have made actual knowledge regarding the epidemiology of amebiasis possible. We will also analyze the most relevant available data on prevalence, morbidity, geographic distribution, patterns of transmission, exposure, and risk factors for infection in the human host. Our intention is to emphasize the recent molecular typing methods applied in genotyping Entamoeba species and strains, and to assess their value and limitations. Finally, we will discuss those areas of the host-parasite relationship that are still not fully understood, and the scientific challenges to approach this important public health problem in the future.

Prevalence and importance of amebic infestation in patients with ulcerative colitis in two regions in Turkey

We investigated the prevalence of amebiasis in patients with ulcerative colitis residing in two geographical regions with different socioeconomic status and climatic conditions, and its effect on the age of onset, duration, localization, and activity of disease. Ninety patients from a high socioeconomic location (group I) and 28 cases from a low socioeconomic location (group II) were enrolled. Median age at disease onset was significantly higher in group I compared with in group II. Prevalence of amebiasis in group I was significantly lower than in group II. A considerably number of patients with amebiasis in group I had a history of travel to the cities with a lower socioeconomic level, mainly located in the east of Turkey. There was a strong relationship between presence of amebiasis and history of travel to eastern parts of Turkey among residents from the northwestern part of Turkey. Median age and age at time of diagnosis were significantly lower in patients with amebiasis compared with those without infection. In patients with mild disease activity, prevalence of amebiasis was significantly lower compared with those with moderate or severe disease activity. In conclusion, prevalence of amebiasis was markedly higher in the southeast compared to the northwest of Turkey. Travel to regions with low socioeconomic status may be considered a risk factor for amebiasis in patients with ulcerative colitis. Amebiasis enhances disease activity in ulcerative colitis.

Parasitic lung infection and the paediatric lung

Human parasitosis is still prevalent worldwide and causes significant morbidity and mortality in developing countries. The involvement of the lung is variable depending on the characteristics of the parasites and hosts. In malnourished and immunodeficient children, the consequences of lung parasitosis may result in significant morbidity and mortality.

Amebic liver abscess

Amebic liver abscess is the most common extraintestinal manifestation of infection with Entamoeba histolytica, and it is associated with significant morbidity and mortality. In this article the most recent available information is reviewed relating to epidemiology, pathogenesis, presentation, diagnosis, and treatment. We reviewed thousands of cases of amebic liver abscess in the medical literature and present that information as it pertains to mortality, gender, anatomic location of abscesses, and clinical signs and symptoms.

Practice guidelines for evaluation of Fever in returning travelers and migrants

BACKGROUND

Fever upon return from tropical or subtropical regions can be caused by diseases that are rapidly fatal if left untreated. The differential diagnosis is wide. Physicians often lack the necessary knowledge to appropriately take care of such patients.

OBJECTIVE

To develop practice guidelines for the initial evaluation of patients presenting with fever upon return from a tropical or subtropical country in order to reduce delays and potential fatal outcomes and to improve knowledge of physicians.

TARGET AUDIENCE

Medical personnel, usually physicians, who see the returning patients, primarily in an ambulatory setting or in an emergency department of a hospital and specialists in internal medicine, infectious diseases, and travel medicine.

METHOD

A systematic review of the literature--mainly extracted from the National Library of Medicine database--was performed between May 2000 and April 2001, using the keywords fever and/or travel and/or migrant and/or guidelines. Eventually, 250 articles were reviewed. The relevant elements of evidence were used in combination with expert knowledge to construct an algorithm with arborescence flagging the level of specialization required to deal with each situation. The proposed diagnoses and treatment plans are restricted to tropical or subtropical diseases (nonautochthonous diseases). The decision chart is accompanied with a detailed document that provides for each level of the tree the degree of evidence and the grade of recommendation as well as the key points of debate. PARTICIPANTS AND CONSENSUS PROCESS: Besides the 4 authors (2 specialists in travel/tropical medicine, 1 clinical epidemiologist, and 1 resident physician), a panel of 11 European physicians with different levels of expertise on travel medicine reviewed the guidelines. Thereafter, each point of the proposed recommendations was discussed with 15 experts in travel/tropical medicine from various continents. A final version was produced and submitted for evaluation to all participants.

CONCLUSION

Although the quality of evidence was limited by the paucity of clinical studies, these guidelines established with the support of a large and highly experienced panel should help physicians to deal with patients coming back from the Tropics with fever.

Amoebiasis

Amoebiasis is the second leading cause of death from parasitic disease worldwide. The causative protozoan parasite, Entamoeba histolytica, is a potent pathogen. Secreting proteinases that dissolve host tissues, killing host cells on contact, and engulfing red blood cells, E histolytica trophozoites invade the intestinal mucosa, causing amoebic colitis. In some cases amoebas breach the mucosal barrier and travel through the portal circulation to the liver, where they cause abscesses consisting of a few E histolytica trophozoites surrounding dead and dying hepatocytes and liquefied cellular debris. Amoebic liver abscesses grow inexorably and, at one time, were almost always fatal, but now even large abscesses can be cured by one dose of antibiotic. Evidence that what we thought was a single species based on morphology is, in fact, two genetically distinct species--now termed Entamoeba histolytica (the pathogen) and Entamoeba dispar (a commensal)--has turned conventional wisdom about the epidemiology and diagnosis of amoebiasis upside down. New models of disease have linked E histolytica induction of intestinal inflammation and hepatocyte programmed cell death to the pathogenesis of amoebic colitis and amoebic liver abscess.

Amebic Liver Abscess

Amebic liver abscess should be suspected in travelers returning from endemic areas or in immunocompromised patients who present with fever, right upper quadrant pain, hepatomegaly, and a liver lesion on an imaging study. Rapid initiation of therapy without serologic confirmation of infection, if necessary, is important to minimize complications. Metronidazole is given orally or intravenously for 14 days. The drug is generally well tolerated and leads to resolution of symptoms in most patients within 2 to 3 days. It is effective against luminal cysts in only 50% of patients and, therefore, must be followed by a course of treatment with paromomycin (Humatin; Parke-Davis, Morris Plains, NJ) or another luminal antiamebic agent to eradicate the parasite. Image-guided drainage of an amebic liver abscess is indicated in patients who do not respond to antimicrobial therapy or who are at risk of abscess rupture. Surgery is reserved for patients with a ruptured abscess. Although medical therapy is generally successful in the treatment of infection caused by Entamoeba histolytica, the development of potent vaccines will be needed for worldwide eradication of disease attributable to E. histolytica.

Amebiasis

Human amebiasis is caused by the protozoan parasite Entamoeba histolytica. Invasion of the colonic mucosa by the trophozoite form of this parasite generally results in the clinical syndrome of amebic dysentery, although there is a wide range of clinical presentations. Some patients will progress to disseminated disease, with resulting amebic liver abscesses. Although it is estimated that 10% of the world's population is infected with E. histolytica, only 1% of these patients will manifest disease. The diagnosis is usually made by microscopically identifying the microorganism in a stool specimen. The antibiotic of choice for treatment of amebiasis is metronidazole, 750 mg, three times daily for 10 days.

Specific detection of Entamoeba histolytica DNA by hemolysin gene targeted PCR

Diagnostic differentiation of pathogenic Entamoeba histolytica from non-pathogenic Entamoeba dispar is of great clinical importance. We have developed and evaluated a new polymerase chain reaction (PCR) assay (haemo-PCR) based on the novel E. histolytica hemolysin gene HLY6. The specificity of this assay was confirmed by analyzing different Entamoeba species, faeces samples, human and bacterial DNA, and digestion of amplification products with appropriate restriction enzymes. The sensitivity was confirmed by serial dilutions of E. histolytica HM-1:IMSS DNA in the excess of human DNA. Totally, 45 clinical samples were analyzed by the haemo-PCR assay including amoebic liver abscess (ALA) fluids from 23 patients suspected for amoebiasis, four faeces samples containing E. histolytica and E. dispar, and positive and negative controls. The results were compared with those obtained with PCRs for cystein-rich surface protein (P30) and small subunit ribosomal RNA (ssu rRNA) genes. The haemo-PCR gave a positive result in 18 (89%) ALA fluids compared with 14 (77%) and five (28%) by PCR for p30, and ssu rRNA, respectively. PCR products were obtained only from specimens containing E. histolytica DNA. The haemo-PCR assay was therefore found to be a valuable diagnostic tool for identification of E. histolytica infections both in faeces and ALA samples.

Amebic abscess of the liver presenting as acute cholecystitis

A case report is presented of a 37-year-old active duty Navy petty officer with amebic abscess of the liver presenting as acute cholecystitis. He was admitted with severe right upper quadrant pain and a positive Murphy's sign, but sonogram and computed tomography (CT) scan demonstrated an abscess in the right lobe of the liver. "Anchovy paste" material was obtained on percutaneous drainage, and he was placed on metronidazole administration with a tentative diagnosis of amebic abscess. This was confirmed on enzyme-linked immunosorbent assay. Symptoms resolved within a few days, and the abscess progressively decreased in size. Amebic abscess of the liver is discussed, with emphasis on pathogenesis, diagnosis, and treatment. Although uncommon, the condition is still seen in various population groups including the United States military. Difficulty in diagnosis is not unusual, and as in the herein-reported case, amebic abscesses of the liver may be confused with acute cholecystitis and other intra-abdominal infections. Abdominal sonogram and CT examination will identify a process in the liver, but the presence of amebiasis must be confirmed by laboratory studies on serum or contents of the abscess. Amebicidal agents are effective in many cases, but there remain roles for aspiration of the abscess, percutaneous drainage, and even open surgical drainage. Failure to establish an early diagnosis may result in rupture of the abscess, with catastrophic results.

Amebic liver abscess

Amebiasis is a widespread parasitic disease caused by Entamoeba histolytica. This protozoan organism is the third leading parasitic cause of death in the developing world and is an important health risk to travelers in endemic areas. Amebiasis most commonly results in asymptomatic colonization of the gastrointestinal tract, but some patients may develop intestinal invasive disease or extraintestinal disease-amebic liver abscess being the most common extraintestinal manifestation. This article reviews epidemiologic features, pathophysiology, clinical features, diagnostic tests, imaging studies, treatment of amebic liver abscess, and prevention measures.

Florid computed tomographic appearance of acute Campylobacter enterocolitis

A 28-year-old male presented with severe abdominal pain and bloody diarrhoea. Computed tomographic scan showed marked swelling of the distal ileum and entire colorectum. The patient recovered and Campylobacter jejuni was subsequently grown from his faeces.

Intestinal parasitic infections

Our understanding of the biology of several intestinal parasites has progressed considerably in the past year, especially in the area of molecular biology. Information from molecular and genetic analyses has been used increasingly to improve understanding of pathogenesis, to apply improved diagnostic methods, and to seek new vaccination strategies. There were fewer relevant clinical studies than in previous years, but some are notable. Control of helminth infections by mass chemotherapy in school age children appears an achievable goal in many communities. Vaccine trials against some protozoan infections continue to show promise in animal models.