Giant hepatic echinococcus cyst: a case report

Clinical History

A 24-years-old female patient from Albania with hepatomegaly, vulvar and lower limbs venous varixes, already subjected to saphenectomy, came to our Department complaining of worsening of chronic symptoms, such as right-hypochondriac pain, early satiety, sickness, and vomiting. Sierological exams were negative.

Imaging Findings

US-scan revealed a huge cystic formation, occupying the major part of hepatic dome, dislocating down and left of the whole liver, elevating the diaphragm and compressing the inferior vena cava, suprahepatic veins and intrahepatic biliary ducts (Fig.1a). The cyst appeared uniloculated, without internal septations, filled by anechoic fluid and surrounded by a three-layer wall (Fig.1b):
-inner layer (germinal) finely granular hyperechoic;
-intermediate layer (laminated membrane) hypo-anechoic;
-outer layer (adventitial) hyperechoic.
MR-scan (Fig.2) defined the exact edges of the lesion (maximum diameter 23cm; involvement of VII,VIII, part of IV,V,VI segment). Post contrastographic phases didn't show any enhancement (Fig.3).
After US-guided percutaneous drainage and alcoholisation, follow-up evaluation showed signs of hepatic abscess therefore the patient underwent urgent CT-scan with iodine ionic contrast administration through the drainage (Fig.4a). CT-examination showed a voluminous formation occupying right hepatic lobe (12x9cm) within layer of parenchimal-density tissue and air component (Fig.4b). Cyst-wall presented inhomogeneous contrast-enhancement (Fig.4c).
The patient underwent laparoscopic treatment (Video 5).

Discussion

Echinococcal cyst is a parasitic disease caused by the larvae of Echinoccocus, primarly E.Granulosum (EG), charaterised by a worldwide distribution. Mediterranean areas, Africa, South America, the Middle East, Australia and New Zealand are interested by an endemic distribution due to the transmission of EG by means of the dog-sheep cycle [1]. EG has a vital cycle that needs two hosts: definitive (dog) and intermediate (most commonly sheeps or rarely humans). This zoonotic infection is transferred to humans by ingestion of contaminated food by dog feces within parasite's eggs. Liver (>65%) and lung (25%) are the organs where humans mainly develop cystic disease [2]. The echinococcal cyst is an evolution of a oncosphere (a stage of asexual reproduction cycle of EG), coming from the bowel through mesenteric veins. This formation appears like a fluid-filled, spherical, unilocular cyst that consists of an inner germinal layer of cells supported by a characteristic acellular, laminated membrane of variable thickness. Each cyst is surrounded by a host-produced layer of granulomatous adventitial reaction [3].

The clinical manifestations are frequently variable due to site, size, and condition of the cysts. At first, patients are often asymptomatic because of the slow growth of the echinococcal cyst, until its size might cause organ dislocation and dysfunction. In the hepatic involvement common signs and symptoms include hepatomegaly (with eventual palpable mass), right hypocondriac pain, sickness and vomiting [3]. Lung echinococcal cysts, the second most frequent localisation, are clinically charaterised by fever, cough and chest pain, simulating a typical bacterial pneumonia, eventually with typical radiographic findings, but unresponsive to empiric antibiotic treatment [2]. Furthermore, the inner content, released if a cyst ruptures, causes allergic reactions ranging from mild to fatal anaphylaxis. Dissemination of protoscolices, floating in the cystic fluid, might result in multiple secondary echinococcosis disease [3].

Diagnosis requires an index of suspicion (endemic areas), typical radiographic findings and specific serological test, which has low sensitivity in extra-hepatic cases [2].
Traditional radiography allows detection of echinococcal cysts in the lung, appearing like a hyperdense mass, eventually with cyst-wall calcifications; in other sites, US, MR and CT are useful to identify the deep-seated lesions [3], showing single or multiple uniloculated cysts (EG), without internal septations, filled by fluid and surrounded by the typical three-layer wall.

Treatment is complicated and carries significant risks. Therapeutic options include the use of antihelmintic drugs, surgery and medico-surgical procedures such as PAIR (puncture, aspirate, injection of a scolicide, re-aspirate) [4].

Differential Diagnosis List

Final Diagnosis

Hepatic echinococcus cyst

URL:	https://www.eurorad.org/case/9892
DOI:	10.1594/EURORAD/CASE.9892
ISSN:	1563-4086