Differential diagnosis
Large cysts in the liver, solitary or multiple, may be caused by a variety of diseases. Neoplasms [cystadenoma, cystadenocarcinoma, squamous cell carcinoma, hemangioma, metastases (of tumors of the colon, pancreas, ovary, or neuroendocrine tumors), hepatocellular carcinoma], non-neoplastic cysts (simple cyst, ciliated foregut cyst, polycystic kidney disease, biloma, Caroli's disease), and infections (pyogenic abscess, actinomycosis, amebiasis, and echinococciasis) are all part of the differential diagnosis of large cystic lesions in the liver [1].

Diagnosis
When the U/S findings became available, echinococciasis was strongly considered in the differential diagnosis and testing for the presence of echinoccocal antigens in the serum was performed. The results of this testing were negative. Still, the history, the clinical picture of the patient, as well as the U/S and CT imaging made this diagnosis highly possible. Thus, we proceeded to surgical resection of the cyst. Biopsy taken from the excised specimen confirmed the diagnosis of echinococciasis (Echinococcus granulosus).

Therapy
The patient was cured by surgical excision of the mass, combined with administration of albendazole 400mg, once a day by mouth, for 1 week prior and 2 weeks after the operation.

Teaching points

• Echinococcal cyst can lead to peculiar findings on different imaging techniques, depending on which of the parts are imaged and the stage of the disease. Although inferior and central CT sections of the lesion exhibited the typical well demarcated, hypodense cyst [2], the superior CT sections of the lesion exhibited hyperdense, separated, peripheral areas. They may represent calcified daughter hydatid cysts [3] separated by fibrous tissue or, more commonly, a redundant, folded, inner germinal wall of a cyst [1].
• Ultrasonographic and CT imaging represent the cornerstone for the diagnosis, classification of the stage of progression, and determination of best mode of treatment of hydatid cyst disease.
• Echinococciasis should always be included in the differential diagnosis, when a, symptomatic or asymptomatic, patient is found to have a mass in the right upper abdominal quadrant, especially in endemic areas [4].
• Sensitivity of testing of serum echinococcal antigens ranges from 80 to 95% for hepatic-limited echinococcal disease, and is even lower for solitary extra-hepatic echinococcal cysts. By this approach, needle biopsy and aspiration of the cyst, which carry the risk of cyst rupture, were avoided.
• Definite treatment is surgical and should be always considered in low risk patients.

References

1. Baden LR, Elliott DD. Case records of the Massachusetts General Hospital. Weekly Clinicopathological exercises. Case 4-2003. A 42-year-old woman with cough, fever, and abnormalities on thoracoabdominal computed tomography. N Engl J Med 2003; 348(5):447-455.
2. Tuzun M, Hekimoglu B. Pictorial essay. Various locations of cystic and alveolar hydatid disease: CT appearances. J Comput Assist Tomogr 2001; 25(1):81-87.
3. Sayek I, Onat D. Diagnosis and treatment of uncomplicated hydatid cyst of the liver. World J Surg 2001; 25(1):21-27.
4. Suwan Z. Sonographic findings in hydatid disease of the liver: comparison with other imaging methods. Ann Trop Med Parasitol 1995; 89(3):261-269.

Acknowledgements

1. This case was prepared for the website by I. Bliziotis, MD.
2. A modified version of this case report was accepted for publication in the journal American Family Physician [Bliziotis I, Kasiakou S, Baloyanni M, Falagas ME. A healthy woman with right upper quadrant discomfort on deep palpation. American Family Physician 2004 (in print)].