A 61-year-old woman presented with fever and right upper quadrant discomfort of 4 weeks' duration. She lived on a farm with her husband, and they had several dogs. The husband hunted wild animals, and they ate garden-grown vegetables. A physical examination revealed hepatomegaly. Computed tomography of the abdomen (Panel A) showed a large cystic lesion in the right hepatic lobe with internal septations. Laboratory studies showed peripheral eosinophilia and abnormal liver chemistries (less than 2 times the upper limit of normal). Serology for echinococcosis was equivocal.
Echinococcusgranulosus was strongly suspected because of the unilocular nature of the cystic lesion. Other infectious cystic diseases of the liver include Echinococcusmultilocularis and Echinococcusvogeli. These two infections were considered less likely on the basis of cyst characteristics, with E.multilocularis causing multilocular cysts and E.vogeli causing polycystic lesions. Therapy for cystic echinococcosis is based on considerations of the size, location, and manifestations of the cysts. Surgery has traditionally been the principal definitive method of treatment. In this case, surgical resection was considered; however, it was determined that because of the large size of the cyst, right hepatectomy would be required.
For uncomplicated echinococcal lesions, puncture, aspiration, injection of a scolicidal agent, and re-aspiration (PAIR) constitute an alternative to surgery. PAIR is indicated for univesicular hepatic cysts greater than 5 cm in diameter, cysts with daughter cysts, and cysts with detached membranes. The main contraindications for PAIR are superficially located cysts (because of the risk of rupture), cysts with multiple, thick internal septations, and cysts communicating with the biliary tree.1 The cyst in this case did have a relative contraindication to PAIR with a somewhat superficial location (which increased the risk of intra-abdominal spillage of cyst contents). The initially suspected internal septations were actually detached cyst membranes; thus, a complication was less likely. Furthermore, the risk of PAIR seemed less in comparison with the risk of right hepatectomy. Therefore, PAIR was performed, and the aspirated cyst fluid showed hydatid sand consisting of a protoscolex with prominent hooklets (Panel B) and free-floating, calcific hooklets (Panel C) from the degeneration of protoscolices. A diagnosis of E.granulosus was confirmed by the characteristic appearance of the protoscolex in the cyst fluid.
E.granulosus is a tapeworm infection found in areas in which dogs are used to raise livestock. Adult tapeworms develop in definitive hosts, which include dogs and other carnivores. Dogs are infected through the consumption of organs of sheep or cattle with hydatid cysts. In intermediate hosts (sheep and cattle) and humans, the larval forms penetrate the intestinal mucosa and enter the portal circulation, through which they travel to the liver and form hydatid cysts. Humans acquire the infection through the consumption of vegetables contaminated by dog feces containing parasite eggs.
Most individuals with hydatid liver cysts are asymptomatic. As the cyst enlarges, they may develop a fever, pain, tender hepatomegaly, and eosinophilia. The diagnosis relies on epidemiological data, clinical manifestations, radiological imaging, and serological tests. However, the detection of protoscolices or hooklets in cyst fluid, as in this case, is diagnostic.2
Daughter cysts develop from the inner germinal layer of hydatid cysts, as do cystic structures called brood capsules. New larvae, which are called protoscolices, develop in large numbers within the brood capsule. Protoscolices bud off from the cyst wall and have the potential to form other cysts or to develop into adult tapeworms if they are ingested by a host (usually a dog).
Surgery by which the cyst is removed without leakage of the cyst contents is the preferred definitive treatment. Cyst leakage during removal can cause fatal anaphylactic reactions, and because of this complication, percutaneous aspiration of these cysts has been contraindicated. However, in expert hands with the use of concomitant antihelminthic therapy, percutaneous aspiration for both diagnosis and therapy has been shown to be safe.3 PAIR is a procedure that can be performed safely with long-term control of echinococcal cysts.4
Our patient was treated with a prolonged course of albendazole and underwent four sessions of re-aspiration and ethanol injection into the cyst cavity. Six months after the treatment, a follow-up ultrasound examination showed nearly complete resolution of the cyst. This case illustrates the effectiveness of the PAIR procedure as a nonsurgical alternative for the management of hydatid cysts and emphasizes the importance of considering the extent and type of the hydatid lesion when the choice is being made between surgical and nonsurgical approaches.