Innovation in hepatic alveolar echinococcosis imaging: best use of old tools, and necessary evaluation of new ones

Hepatic alveolar hydatid disease (Echinococcus multilocularis), a mimic of liver malignancy: a review for the radiologist in non-endemic areas

Alveolar hydatid disease or alveolar echinococcosis (AE) is caused by the parasite Echinococcus multilocularis and is increasingly seen as an imported disease in non-endemic areas such as the UK. It is rare compared to cystic echinococcosis (CE), but like CE commonly affects the liver. AE does have imaging features that can aid in diagnosis, but is often initially misdiagnosed as liver malignancy. It is usually fatal if untreated, underscoring the importance of early diagnosis. This review highlights the role of imaging in AE diagnosis with the broader objective of increasing radiologists' awareness of this unusual, but increasingly prevalent disease.

The role of contrast-enhanced ultrasound in the diagnosis of hepatic alveolar echinococcosis

To evaluate the value of contrast-enhanced ultrasound (CEUS) compared with ultrasound (US) in the diagnosis of hepatic alveolar echinococcosis (AE).Thirty-one patients with 43 hepatic AE lesions between January 2010 and September 2017 were included in the study. All lesions which were histopathologically proven to be hepatic AE were retrospectively reviewed. Features of the lesions by CEUS were retrospectively studied.All lesions were detected by US and CEUS in the 31 patients (17 males and 14 females) with a mean age of 38.5 ± 10.6 years (range: 16-58 years). The size of the lesions ranged from 1.5 × 0.7 cm to 15 × 18 cm. By US, 3 lesions (7%, 3/43) were hypoechoic nodules, 21 (48.8%, 21/43) were hyperechoic, and 19 lesions (44.2%, 19/43) were of mixed echogenicity type (solid-cystic). 27 lesions (62.8%, 27/43) had calcifications. Only 1 lesion was detected blood-flow signals. With CEUS, 23 lesions (53.5%, 23/43) displayed no enhancement in the arterial phase, portal phase and delayed phase on CEUS. 11 lesions (25.6%, 11/43) displayed a slight ring-like hyper-enhancement in the arterial phase and displayed hypo-enhancement in the portal and delayed phase. 6 lesions (14%, 6/43) displayed hyper-enhancement in the arterial phase and hypo-enhancement in the portal and delayed phase. 2 lesions (4.7%, 2/43) showed iso-enhancement in the arterial, portal, and delayed phase. 1 lesion (2.3%, 1/43) showed slight hypo-enhancement in the arterial, portal, and delayed phase.CEUS is a more valid technique for diagnosing AE than US. It could be a reliable tool in the diagnosis of hepatic AE.

Hunting Poses Only a Low Risk for Alveolar Echinococcosis

The Austrian province of Tyrol belongs to the areas where the alveolar echinococcosis (AE) caused by the fox tapeworm Echinococcus multilocularis (E. multilocularis) is highly endemic. In Central Europe and since 2011 in Austria, a growing incidence of human cases of AE has been observed, presumably linked with increasing fox populations infected by the fox tapeworm E. multilocularis. Hunting and the related activities put hunters in a high-risk group, and they are considered particularly vulnerable for the contraction of an AE. In light of this risk and the increased number of AE cases made public in Austria, the objective of the study was to investigate the prevalence of AE in hunters and to provide a possible connection to the incidence increase. In 2015 and 2016, we examined 813 serums of active hunters from all nine districts of Tyrol and serologically tested them for E. multilocularis antibodies. Twenty-one (2.58%) positive results in ELISA were detected via Western blot (WB), and only one (0.12%) serum showed a low positive reaction. No lesion in the liver parenchyma could be detected by abdominal ultrasonography in this patient so far, but the risk of developing alveolar echinococcosis remains for this WB-positive hunter. Risk factor analysis of these 813 hunters revealed that 697 (85.7%) hunted red foxes regularly and 332 (40.8%) of those skinned them as well. Three hundred and eighteen (39.1%) out of the 813 hunters were owners of hunting dogs; 89 (10.9%) and 243 (29.9%) were owners of non-hunting dogs and cats, respectively. Our results indicate that hunters do not have a greater risk of infection with E. multilocularis compared to non-hunters in Austria. The cause of the unexpected increase in AE cases in Austria remains unclear.

Could SUVmax be an auxiliary parameter in the clinical management of pulmonary hydatid disease?

OBJECTIVE

The aim of this study was to investigate the role of 18F-fluorodeoxyglucose positron emission tomography/computerized tomography (FDG-PET/CT) in the diagnosis and treatment of pulmonary hydatid disease and also compare the morphological characteristics of the lesions with SUVmax values and identify complicated disease.

METHODS

Thirty-six patients with a diagnosis of pulmonary hydatid disease who underwent 18F-FDG PET/CT imaging were included in this retrospective study. The size of the lesions, morphological characteristics, accompanying parenchymal and pleural findings, SUVmax and HUmean values and FDG uptake in mediastinal lymph nodes were noted. The relationship between morphologic properties, SUVmax of the lesions and lymphatic FDG uptake was analysed.

RESULTS

A total of 99 lesions of 36 patients were classified as solid (7.1%), cystic (53.5%), semisolid (20.2%) and cavitary (19.2%). Thirty-two of the lesions were encapsulated, 38 of the lesions had border irregularity. Accompanying consolidation was present in 10 cases, bronchial obstruction in 9, pleural thickening in 28 and effusion in 3. There was positive correlation between lesions HUmean and SUVmax values (r = 0.285). SUVmax values were significantly higher in lesions with irregular borders, solid or semisolid type and presence of consolidation, bronchial obstruction and pleural thickening. Also more lymphatic FDG uptake was detected in this group.

CONCLUSION

Higher SUVmax values may be a useful parameter in the diagnosis of complicated pulmonary hydatid disease. FDG-PET may provide guidance for determining the priority of lesion for surgery in cases with multiple lesions and may be helpful to evaluate the response to medical treatment.

Biological characteristics of 18F-FDG PET/CT imaging of cerebral alveolar echinococcosis

This study aims to analyze the characteristics of F-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG PET/CT) for cerebral alveolar echinococcosis (CAE).Twenty-five CAE patients underwent F-FDG PET/CT, and the diagnosis was confirmed by clinical and surgical pathology. The F-FDG PET/CT results were subject to visual and semiquantitative analysis, and the difference in F-FDG SUVmax for lesions among the 3 types of CAE was evaluated.In the 25 CAE patients, 62 lesions were detected by F-FDG PET/CT, and these lesions were classified into 3 types, according to the characteristics of the lesion's uptake of F-FDG on PET images: type I, 17 lesions, FDG was concentrated into a mass radioactive distribution in the CAE foci; type II, 28 lesions, FDG presented a annular concentrated radioactive distribution around the CAE foci; type III, 17 lesions, FDG in the CAE foci presented a radioactive distribution with defects and sparse areas. The difference in F-FDG SUVmax between type I and type II CAE was not statistically significant (P > .05), the difference in F-FDG SUVmax between type I and type III CAE was statistically significant (P < .001), and the difference in F-FDG SUVmax between type II and type III CAE was statistically significant (P < .001);The F-FDG PET manifestations of CAE are classified into 3 types. Both type I and type II may have invasive activity, while the lesions of type III CAE show that the focus is relatively stable or at a stationary phase. If there are no definite alveolar echinococcus focus in other sites, these patients can temporarily delay the treatment. It is recommended that the patient should undergo whole body PET/CT once a year to dynamically observe the bioactivity and size of type III CAE lesions and assess the presence of new echinococcus lesions in the rest of the body.

Plasma IL-23 and IL-5 as surrogate markers of lesion metabolic activity in patients with hepatic alveolar echinococcosis

Fluorodeoxyglucose (FDG) uptake by alveolar echinococcosis (AE) liver lesions is a signal of their metabolic activity and of disease progression. In order to find a surrogate marker for this status, we investigated whether parameters of the peripheral and/or periparasitic immune responses were associated with metabolic activity in a prospective case-control study of 30 AE patients and 22 healthy controls. Levels of 18 cytokines and chemokines, representative of innate and adaptive immune responses, were assessed in plasma and peripheral cells of two groups of patients with (MAAE) and without (MIAE) metabolically active lesions, and in the liver of MAAE patients. Mixed cytokine profile was observed in the peripheral blood of AE patients, with a predominance of Th2, Th17 and Treg responses. Among the detected markers only plasma IL-5 and IL-23, more elevated in MAAE patients, were found discriminant. Discrimination between MAAE and MIAE patients obtained by using IL-23 was improved when IL-5 was used in combination. The combination of elevated levels of IL-5 and IL-23 is significantly associated with FDG uptake at PET scan. It offers a new tool for the follow-up of AE patients which could substitute to FDG-PET whenever non-available to assess disease progression.

Comparison of Intravoxel Incoherent Motion Diffusion-Weighted Magnetic Resonance (MR) Imaging to T1 Mapping in Characterization of Hepatic Alveolar Echinococcosis

BACKGROUND The aim of this study was to compare intravoxel incoherent motion diffusion-weighted magnetic resonance imaging (IVIM DW MRI) to T1 mapping for characterization of hepatic alveolar echinococcosis (HAE). MATERIAL AND METHODS Eighteen HAE patients confirmed by surgery were examined with conventional MRI, IVIM DWI MRI with 10 b values (range: 0-1,000 sec/mm²), and longitudinal relaxation time (T1) mapping. Diffusion coefficient (D), perfusion fraction (f), pseudo-diffusion coefficient (D*), and T1 relaxation time were calculated in solid components, perilesional components, and background liver parenchyma of HAE patients. The correlation between T1 relaxation time and IVIM-derived parameters was assessed by using the Pearson correlation test. RESULTS T1 relaxation times were significantly higher in solid components (820.58±331.24 ms) compared to background components (551.52±182.93 ms) of HAE patients (p<0.05). IVIM-derived D values were significantly higher in solid components (1.30±0.28×10^-3 mm²/sec) compared to perilesional components (0.88±0.28×10^-3 mm²/sec) and background liver parenchyma (0.97±0.27×10^-3 mm²/sec) of liver parenchyma. There were significant differences in f values between solid components (13.70±7.66%), perilesional components (23.59±10.73%) and background liver parenchyma (30.78±10.18%). IVIM derived D* values were significantly lower in solid components (14.32±10.85×10^-3 mm²/sec) than in background liver parenchyma (30.06±15.68×10^-3 mm²/sec). Importantly, IVIM-derived f values were significantly correlated with T1 relaxation time: r=-0.337 (p<0.05). CONCLUSIONS Based on our image comparison, IVIM DWI MRI might be better than T1 mapping, and IVIM-derived f values might be a valuable index for characterization of HAE.

Screening of antigenic vesicular fluid proteins of Echinococcus multilocularis as potential viability biomarkers to monitor drug response in alveolar echinococcosis patients

PURPOSE

The only drugs available to treat alveolar echinococcosis (AE) are mostly parasitostatic and in many cases prescribed for life. Decision criteria for discontinuation rely on the absence of parasitic viability. The aim of the present study is to search for candidate proteins that may exhibit good potential as biomarkers for viability.

EXPERIMENTAL DESIGN

Sixteen serum samples (five healthy controls, 11 patients with AE), are used. AE-patients are classified into three groups "Cured" (n = 2), "ABZ-responders" (n = 4) and "ABZ-nonresponders" (n = 5). Immunoreactive proteins from vesicular fluid (VF) are identified and quantified by LC-MS/MS analysis after immunoprecipitation (IP) using all 16 serum samples.

RESULTS

Shotgun analysis of VF lead to the identification of 107 E. multilocularis proteins. Comparative proteomics reveal nine proteins more abundant in IP eluates from ABZ-nonresponder patients (cathepsin b, prosaposin a preprotein, actin modulator protein, fucosidase alpha L1 tissue, gluthatione-S-tranferase, beta galactosidase, elongation factor 2, H17g protein tegumental antigen, and NiemannPick C2 protein).

CONCLUSIONS AND CLINICAL RELEVANCE

Detection of antibodies against these proteins by ELISA could be helpful to monitor the course of alveolar echinococcosis under albendazole (ABZ) treatment.

Potential risk factors associated with human alveolar echinococcosis: Systematic review and meta-analysis

Background

Human alveolar echinococcosis (AE) is a severe zoonotic disease caused by the metacestode stage of Echinococcus multilocularis. AE is commonly associated with a long incubation period that may last for more than ten years. The objective of this systematic literature review was to identify and summarize the current knowledge on statistically relevant potential risk factors (PRFs) associated with AE in humans.

Methodology/Principal findings

Six bibliographic databases were searched, generating a total of 1,009 publications. Following the removal of duplicate records and the exclusion of papers that failed to meet the criteria of a previously agreed a priori protocol, 23 publications were retained; however, 6 of these did not contain data in a format that allowed their inclusion in the meta-analysis. The remaining 17 publications (6 case-control and 11 cross-sectional studies) were meta-analysed to investigate associations between AE and PRFs. Pooled odds ratios (OR) were used as a measure of effect and separately analysed for case-control and cross-sectional studies. In the case-control studies, the following PRFs for human AE showed higher odds of outcome: “dog ownership”, “cat ownership”, “have a kitchen garden”, “occupation: farmer”, “haymaking in meadows not adjacent to water”, “went to forests for vocational reasons”, “chewed grass” and “hunting / handling foxes”. In the cross-sectional studies, the following PRFs showed higher odds of outcome: “dog ownership”, “play with dogs”, “gender: female”, “age over 20 years”, “ethnic group: Tibetan”, “low income”, “source of drinking water other than well or tap”, “occupation: herding” and “low education”. Our meta-analysis confirmed that the chance of AE transmission through ingestion of food and water contaminated with E. multilocularis eggs exists, but showed also that food- and water-borne PRFs do not significantly increase the risk of infection.

Conclusions/significance

This systematic review analysed international peer-reviewed articles that have over the years contributed to our current understanding of the epidemiology of human AE. The identification of potential risk factors may help researchers and decision makers improve surveillance and/or preventive measures that aim at decreasing human infection with E. multilocularis. More primary studies are needed to confirm potential risk factors and their role in the epidemiology of human AE.

Human alveolar echinococcosis is a severe zoonotic disease caused by the metacestode stage of the tapeworm Echinococcus multilocularis. The objective of this systematic literature review was to identify and summarize the current knowledge on potential risk factors associated with human alveolar echinococcosis. The categories of potential risk factors included dog-related factors such as dog ownership or play with dogs; vocational factors like being a farmer or handling foxes; human habits such as chewing grass; gender (being female) and socio-cultural factors like being Tibetan or having a low income or poor education, which may be relevant only in particular endemic areas. The identification of potential risk factors may help identify strategies that aim to decrease human infection with E. multilocularis.

Multimodality imaging in diagnosis and management of alveolar echinococcosis: an update

Alveolar echinococcosis is a parasitic disease limited to the northern hemisphere. The disease occurs primarily in the liver and shows a profile mimicking slow-growing malignant tumors. Echinococcus multilocularis infection is fatal if left untreated. It can cause several complications by infiltrating the vascular structures, biliary tracts, and the hilum of the liver. As it can invade the adjacent organs or can spread to distant organs, alveolar echinococcosis can easily be confused with malignancies. We provide a brief review of epidemiologic and pathophysiologic profile of alveolar echinococcosis and clinical features of the disease. This article focuses primarily on the imaging features of alveolar echinococcosis on ultrasonogra-phy, computed tomography, magnetic resonance imaging, diffusion-weighted imaging and positron emission tomography-computed tomography. We also reviewed the role of radiology in diagnosis, management, and follow-up of the disease.

To see or not to see: non-invasive imaging for improved readout of drug treatment trials in the murine model of secondary alveolar echinococcosis

Alveolar echinococcosis (AE) is an emerging zoonotic disease caused by the cestode Echinococcus multilocularis. The secondary infection model of AE is based on intraperitoneal injection of disease-causing metacestodes into the peritoneal cavity of mice, which allows investigations on novel drugs or immunotherapeutical treatment options in vivo. So far, such in vivo studies assessed exclusively the parasite weight at the endpoint of a given treatment period. We here developed an ultrasound (US)-based scoring system that allows to follow-up parasite development in the living animal, and provides insights into parasite growth during the treatment phase. By this method a statistically significant difference between untreated and medicated mice with E. multilocularis infection was observed at 2 months post-infection, and the growth curve of the parasite load was described by a linear mixed model. High correlation and similar levels of variation were observed for the standard method based on parasite weight measurement, the novel US-based scoring system, as well volume segmentation by post-mortem magnetic resonance imaging. Thus, US-based scoring in the live animal has the potential to assist the 3R concept by contributing to the refinement and reduction of animal use in experimental echinococcosis.

The Echinococcoses: Diagnosis, Clinical Management and Burden of Disease

The echinococcoses are chronic, parasitic diseases that are acquired after ingestion of infective taeniid tapeworm eggs from certain species of the genus Echinococcus. Cystic echinococcosis (CE) occurs worldwide, whereas, alveolar echinococcosis (AE) is restricted to the northern hemisphere, and neotropical echinococcosis (NE) has only been identified in Central and South America. Clinical manifestations and disease courses vary profoundly for the different species of Echinococcus. CE presents as small to large cysts, and has commonly been referred to as 'hydatid disease', or 'hydatidosis'. A structured stage-specific approach to CE management, based on the World Health Organization (WHO) ultrasound classification of liver cysts, is now recommended. Management options include percutaneous sterilization techniques, surgery, drug treatment, a 'watch-and-wait' approach or combinations thereof. In contrast, clinical manifestations associated with AE resemble those of a 'malignant', silently-progressing liver disease, with local tissue infiltration and metastases. Structured care is important for AE management and includes WHO staging, drug therapy and long-term follow-up for at least a decade. NE presents as polycystic or unicystic disease. Clinical characteristics resemble those of AE, and management needs to be structured accordingly. However, to date, only a few hundreds of cases have been reported in the literature. The echinococcoses are often expensive and complicated to treat, and prospective clinical studies are needed to better inform case management decisions.

Current status of diagnosis and treatment of hepatic echinococcosis

Echinococcus granulosus (E. granulosus) and Echinococcus multilocularis (E. multilocularis) infections are the most common parasitic diseases that affect the liver. The disease course is typically slow and the patients tend to remain asymptomatic for many years. Often the diagnosis is incidental. Right upper quadrant abdominal pain, hepatitis, cholangitis, and anaphylaxis due to dissemination of the cyst are the main presenting symptoms. Ultrasonography is important in diagnosis. The World Health Organization classification, based on ultrasonographic findings, is used for staging of the disease and treatment selection. In addition to the imaging methods, immunological investigations are used to support the diagnosis. The available treatment options for E. granulosus infection include open surgery, percutaneous interventions, and pharmacotherapy. Aggressive surgery is the first-choice treatment for E. multilocularis infection, while pharmacotherapy is used as an adjunct to surgery. Due to a paucity of clinical studies, empirical evidence on the treatment of E. granulosus and E. multilocularis infections is largely lacking; there are no prominent and widely accepted clinical algorithms yet. In this article, we review the diagnosis and treatment of E. granulosus and E. multilocularis infections in the light of recent evidence.

Alveococcosis of the liver - strategy of surgical treatment with special focus on liver transplantation

BACKGROUND

Echinococcosis is a zoonosis caused by infestation with any of 4 (of the 16) members of the Echinococcus genus, namely Echinococcus granulosus, Echinococcus multilocularis, Echinococcus oligarthus, and Echinococcus vogelii. The aim of this retrospective analysis was to present the outcomes of patients undergoing liver resection and liver transplantation (LT) for E. multilocularis infection.

METHODS

A total of 44 patients who underwent surgical treatment of E. multilocularis infection in the period between 1989 and 2014 were included in the study cohort and retrospectively analyzed.

RESULTS

LT was performed in 22 patients (50.0%), including 4 of 26 patients undergoing initial non-transplant management. Non-transplant procedures comprised liver resection in 23 patients (88.5%), diagnostic laparoscopy in 2 (7.7%), and left adrenalectomy in 1 patient (3.8%). Post-transplantation survival rates were 90%, 85%, and 75% at 1, 5, and 10 years, respectively.

CONCLUSION

In conclusion, LT for E. multilocularis infection is a safe and effective treatment method.

Hepatic Alveolar Hydatid Cyst: A Brief Review of Published Cases from Iran in the Last 20 Years

CONTEXT

Echinococcus multilocularis is the cause of alveolar hydatid disease, which most commonly involves the liver in more than 90% of cases. This disease is endemic in northern Iran. However, there are very few published cases from Iran. In this article, we will review all of the published cases of hepatic alveolar echinococcosis from Iran regarding all aspects, including clinical, paraclinical, and treatment protocols.

EVIDENCE ACQUISITION

In this brief review, the published cases of hepatic Alveolar Echinococcosis (AE) from Iran were retrieved for review via a search in PubMed, Scopus, Google Scholar, IranMedex, scientific information database (SID), Magiran, and Irandoc (1995 - 2015) using the keywords Echinococcus multilocularis and Iran, Alveolar hydatid cyst and Iran, liver and Alveolar hydatid cyst and Iran, and Hepatic alveolar hydatid cyst and Iran. The following inclusion criteria were employed: 1, articles must be written in English or Farsi; 2, articles must have been published between 1995 and 2015; 3) cases must have been confirmed by pathological diagnosis.

RESULTS

There were 24 published cases of liver-involved alveolar hydatid cyst from Iran. The disease was more common in young- to middle-aged women in northeast Iran. The most common presenting signs and symptoms were abdominal pain with hepatomegaly and liver mass. Most of the patients were treated by surgery and albendazole. The few unresectable liver masses were treated by medical therapy. No liver transplantation for this disease was reported from Iran.

CONCLUSIONS

Hepatic alveolar hydatid cyst should be considered one of the important differential diagnoses of liver masses, especially in endemic areas of the world.

Efficacy of ultrasound-guided core-needle biopsy in the diagnosis of hepatic alveolar echinococcosis: a retrospective analysis

Background: This study retrospectively analyzed the clinical data, laboratory results, imaging findings, and histopathological features of 28 patients who underwent ultrasound-guided core-needle biopsy from a hepatic lesion and were diagnosed with alveolar echinococcosis. Results: Among 28 patients included in the study, 16 were females and 12 were males. The mean age of the studied population was 53 ± 16 years, and the age range was 18–79 years. The most common presenting symptom was abdominal pain, which was observed in 14 patients. A total of 36 lesions were detected in the patients’ livers, out of which 7 had a cystic appearance. Hepatic vascular involvement, bile duct involvement, and other organ involvement were depicted in 14, 5, and 7 patients, respectively. The average number of cores taken from the lesions was 2.7, ranging between 2 and 5. In histopathological evaluation, PAS+ parasitic membrane structures were visualized on a necrotic background in all cases. Regarding seven patients, who were operated, the pathological findings of preoperative percutaneous biopsies were in perfect agreement with the pathological examinations after surgical resections. None of the patients developed major complications after biopsy. Conclusion: Ultrasound-guided core-needle biopsy is a minimally invasive, reliable, and effective diagnostic tool for the definitive diagnosis of hepatic alveolar echinococcosis.

Proposal of an ultrasonographic classification for hepatic alveolar echinococcosis: Echinococcosis multilocularis Ulm classification-ultrasound

AIM: To establish an ultrasonographic classification based on a large sample of patients with confirmed hepatic alveolar echinococcosis (AE).

METHODS: Clinical data and ultrasonography (US) findings of 185 patients (100 males; 85 females; mean age at diagnosis: 51.4 ± 17.6 years; mean age at time of US examination: 58.7 ± 18.2 years) were retrospectively reviewed with respect to the US morphology of hepatic AE lesions. The sonomorphological findings were grouped according to a five-part classification scheme.

RESULTS: Application of the new classification resulted in the following distribution of sonomorphological patterns among the patients examined: hailstorm (54.1%); pseudocystic (13.5%); ossification (13.0%); hemangioma-like (8.1%); and metastasis-like (6.5%). Only 4.9% of lesions could not be assigned to a sonomorphological pattern.

CONCLUSION: The sonomorphological classification proposed in the present study facilitates the diagnosis, interpretation and comparison of hepatic alveolar echinococcosis in routine practice and in the context of scientific studies.

Navigation liver surgery for complex hydatid cyst with biliary tree communication

INTRODUCTION

Today, liver surgery navigation is utilized only in high-specialized centers for patients affected by malignant diseases. However, navigated surgery may also be of great interest for benign diseases such as hydatidosis in particular if the hydatid cyst is communicating with the biliary tree. With navigation we know exactly in each moment during the surgery the relationship of the cyst with the vascular/biliary structures around it.

PRESENTATION OF CASE

Herein, we report a case of a 20-year-old W/M affected by hepatic hydatid cyst communicating with the right bile duct, causing recurrent cholangitis. The diagnosis was confirmed by endoscopic retrograde cholangiography and magnetic resonance imaging. The liver cystectomy was easily performed using a navigation system incorporating instrument tracking and three-dimensional CT-reconstruction, thus permitting a selective suture of the bile duct communicating with the cyst.

CONCLUSIONS

The navigated system may guide the surgeon in patients with severe and complicated hydatid cysts.