The patient was consulted by an infectious diseases specialist and a general surgeon. To exclude involvement of another organ, chest X-ray and abdominal ultrasonography were ordered. No cystic mass was observed in thorax or abdomen. The patient took daily 2 × 400 mg albendazol oral for 3 months. After 2 months, the splint was removed and wrist exercises were started. Two months after the surgery, swelling in fossa radialis terminated. Wrist movements were painless and complete. The patient was evaluated by clinical examination, serological tests, and radiological imaging at 3rd, 6th, and 12th month follow-up visits. No finding related with local or systemic hydatic cyst was detected at 12th month follow-up. Recurrence was not observed at 12th month follow-up visit and serological tests were negative.
Hydatic cyst has a main and an intermediate host and it is transmitted to humans by direct contact or consumption of contaminated food. After ingestion, Echinococcus eggs reach portal venous circulation after passing through duodenal mucosa and cause disease after arriving to liver and the lung. Liver and lung function as filters for the parasite. On the other hand, some eggs may localize to peripheral organs after passing from lung. The parasite is transformed to larval stage in which it develops hydatic cyst in the end organ its egg stays.8
Involvement of many bones and soft tissues other than liver, lung, or spleen have been reported previously.9–14 Although hydatic cyst in bones may form due to hydatic cyst of liver or lung, it generally occurs as primary bone involvement in the absence of liver or lung involvement.15,16 Involvement of carpal bones is rare and only 1 case has been reported in proximal pole of scaphoid bone.9 Interestingly although size of the lesion was different in that case its localization was same with ours.
Differential diagnosis of a cystic lesion in carpal bones includes infections due to typical and atypical agents (including tuberculosis, brucellosis, and parasitic infections), fibrous dysplasia, simple bone cysts, osteosarcoma, intraosseous gangliomas, or osteomyelitis.17,18 Osseous hydatic is the name given to unilocular cysts in a bone. As seen in our patient, these patients usually present with complaints of pain and swelling. Deformity, pathological fractures, and secondary infections are also among symptoms.19,20
Diagnosis of cyst hydatic is difficult due to lack of a biochemical or radiological finding specific to cyst hydatic. Definite diagnosis can be established by histopathological examination of cyst material. Although sclerosis or periost reaction is not prominent at early stages of the disease, lytic lesions accompanied by sclerosis may occur at later stages. Our case also had a lytic lesion accompanied by sclerosis. Although computed tomography gives additional information regarding localization and calcification of the cyst, magnetic resonance imaging gives information about the severity of bone and soft tissue involvement.5,18
Eosinophilia is an important laboratory finding; however, it is elevated only in 25% of all cases. Additionally, positivity of IHA test is also important in hydatic cyst diagnosis but negative IHA test result does not exclude the diagnosis.21,22 In our case, IHA test was negative although eosinophilia was present.
There is not an accepted treatment protocol for cyst hydatic localized to bone. This is mainly due to inadequate number of cases.9 Early diagnosis and treatment is important to prevent complications. Main principal of the treatment is abundant irrigation of cyst pouch22 with a scolocidal agent such as 5% silver nitrate,23 hypertonic saline,21 or povidone iodine solution after excision and curettage. Formed bone defects may be filled with polymethylmetacrylate,11 autograft, or allograft.21 To decrease recurrence rate antihelminthic treatment should be given both preoperatively and postoperatively. Recommended treatment course is approximately 3 months.24,25
In conclusion, primary cyst hydatic in scaphoid bone is very rare. Simple cystic structures in carpal bones are frequent and in patients with clinical symptoms, especially if they live in an endemic region for E granulosus, hydatic cyst should be considered in the differential diagnosis of these cystic structures.
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