A Rare Autochthonous Case of Hepatic Hydatid Cyst in the Non-Endemic Region of Taiwan

Introdcution

Hydatid cyst disease, or cystic echinococcosis (CE), is a parasitic disease caused by Echinococcus granulosus. It is mainly transmitted by ingestion of the ova of the parasite. The completion of its life cycle requires an intermediate host (usually sheep, goat, or cattle) and a definitive host (usually dog, wolf, or other carnivore); therefore, the endemic regions of hydatid cyst correlate with rural areas where cattle- and sheep-raising activities are common, such as Central Asia, Northern China, the Middle East, and Central and South America. Cases in East Asia outside Mainland China are rare and consist almost exclusively of imported cases, except for Hokkaido, Japan [1,2].

Humans are an accidental host in its life cycle; therefore, only hydatid cysts and/or oncospheres but no adult worms or ova (ie, the infective agent) of Echinococcus granulosus are be found in human patients. The pathogen affects the liver in most cases, while involvement of the lungs, spleen, and central nervous system have also been reported [3].

Echinococcosis is rare in Taiwan; over the past 40 years, only 4 imported cases [3–6] (1 case was alveolar echinococcosis [6]) and 1 was autochthonous [7] have been reported. Here, we present a patient who has had no international travel history for more than 40 years, with the objective to raise the awareness of the diagnosis of hepatic hydatid cysts, since it can be easily missed in asymptomatic patients, especially when treating ones in non-endemic areas without significant relevant history.

Case Report

The 91-year-old Taiwanese woman presented to our Emergency Department with a 2-day history of melena. One episode of coffee-grounds vomitus 8 h before arrival was also reported. She was afebrile and mildly tachycardic on arrival. She has long-standing hypertensive heart disease and dementia, for which she was taking bisoprolol, amlodipine, and valsartan. She denied use of alcohol, tobacco, or illicit substances. She used a wheelchair and lived on the fourth floor of an apartment without an elevator or escalator. Physical examination findings were insignificant other than mildly pale conjunctiva and moderate epigastric tenderness. Laboratory workup revealed leukocytosis with neutrophil predominance, borderline low erythrocyte count, impaired renal function (creatinine=2.0 mg/dl; blood urea nitrogen=49 mg/dl), and elevated C-reactive protein level (9.1 mg/dl). Stool analysis was negative for occult blood, parasite, ova, mucus, and leukocytes. Liver enzyme levels were elevated (asparagine transferase=249 U/L, alanine transferase=199 U/L), while a coagulation panel and albumin level were both within normal limits. Further survey of the cause of suspected upper gastrointestinal tract bleeding yielded no significant findings, and she refused esophagogastroduodenoscopy. Computed tomography (CT) was thus arranged, which revealed a 14×10×12 cm homogeneous cystic lesion occupying the right hepatic lobe with partially calcified wall (Figures 1, 2). A subsequent sonographic study was compatible with the above finding, showing a 10.4×9.6 cm cystic lesion with isoechoic-to-hypoechoic internal septa occupying the hepatic segments 5, 7, and 8 (Figure 3). The “water-lily” sign was visible. Magnetic resonance imaging (MRI) was refused because it would involve additional visits after discharge. No E. granulosus antibody testing was readily available in Taiwan. After discussion with the patient, aspiration, biopsy, and surgical resection were refused due to old age. Regarding anthelmintic regimens, the first-line agent, albendazole, was unavailable in Taiwan and could be imported only for patients with larva migrans. We thus recommended mebendazole to the patient and her family, but this was also declined after explaining the required life-long treatment duration, the follow-up plans, pros and cons, recurrence rates, and the prognostic outlooks. The family also expressed a strong will to “let nature take its course” after the acute episode due to socioeconomic factors. Supportive care including tranexamic acid, intravenous high-dose pantoprazole, antacids, and routine follow-ups were thereby implemented. She was discharged 4 days after admission with improved symptoms, including melena and hematemesis. No recurrent symptoms have since been reported at 1 year after discharge, but the cyst remained unchanged on sonograms.

Discussion

It takes 20–25 years on average for the cysts to grow large enough to cause symptoms. In fact, most patients are asymptomatic and are diagnosed with hydatid cysts incidentally. Our 91-year-old patient, whose initial presentation of melena was believed to be related only remotely to hydatid cysts given the clinical course, was later found to be infested with E. granulosus with further workups. This also explains why imported cases can sometimes be misclassified as autochthonous if a detailed travel history is not taken. The patient and her family lived in the urban area of Taipei City and denied any international travel over the past 40 years, which meets the criteria of an autochthonous case. However, the source of infestation was unknown. Obtaining feces samples from stray dogs in nearby areas may be valuable in determining the routes of transmission.

The initial diagnostic workup for hydatid disease is ultrasonography; CT and MRI studies can provide ancillary evidence. Preoperative diagnosis is reached based on the combination of pathognomonic features on sonograms and positive serology results. In areas with extremely low prevalence and limited access to serology tests, as in Taiwan, findings on sonography and CT images can suffice for accurate diagnosis [3,8]. Typical sonographic findings depend on the activity of the disease. The sonographic findings of our case – detachment of the walls of daughter cysts from the main cyst wall, also called the “water-lily” sign” – were characteristic of the CE3A pattern on the 2001 World Health Organization Informal Working Groups on Echinococcosis (WHOIWGE) classification of hepatic hydatid cysts [9]. CE3A pattern indicates that the disease is in the transitional stage.

Uncomplicated small-to-medium-sized CE4 or CE5 hydatid cysts can be managed with active surveillance or anthelmintics in selected patients [10]. Of all the anthelmintics, albendazole and mebendazole are the agents of choice. Otherwise, surgical excision is recommended. Puncture, aspiration, injection, and re-aspiration (PAIR) is minimally invasive and can be an alternative to surgeries [9]. If invasive procedures cannot be performed, as in our patient, life-long anthelmintics were recommended, although concurrent prognostic tools should be applied to lower the recurrence rate [11].

A significant limitation to the present case report is that no surgical specimen was obtained for the confirmation of hydatid cyst due to the patient’s age and functional status. In addition, no further epidemiological evidence (for example, ova found in the stools of stray dogs) is currently present to support the route of transmission hypothesized above. However, the case is still valuable given the typical sonographic pattern, points for education (especially for gastroenterologists and radiologists practicing in non-endemic regions), and the inspiration for further epidemiological studies.

Conclusions

In areas with extremely low incidence rates, diagnosis of hydatid disease could be reached based on pathognomic findings with 2 or more imaging modalities, especially when definite invasive procedures are not possible and/or specific tests are not readily available. Through this report, we aim to raise the awareness of Echinococcus infestation in non-endemic regions and emphasize the integral role of sonography and its pathognomic signs in the diagnosis of hydatid disease.