Abstract

We present a rare cause of rib destruction by hydatid disease, extending along the sixth rib. To the best of our knowledge, there is no previous report of hydatid cyst involving a whole rib without apparent clinical symptoms.

Case Presentation

He had no history of previous symptoms associated with the lesion. On physical examination, there was no fever, and arterial pressure was within normal limits. Chest examination showed diminished expansion of left thoracic cage on inspiration, dull to percussion and diminished breath sounds over the left middle hemithorax on auscultation. His chest X-ray revealed a pleural based, well-circumscribed and lobulated mass lesion which nearly filled the left hemithorax, with absence of the sixth rib ipsilaterally (Figure 1a). The computed tomography scan of chest showed a sharply demarcated cystic lesion benign in nature extending along the sixth rib trace by destructing it (Figure 1 c-f). Routine laboratory tests were normal. However, indirect hemaglutination test for hydatid disease was positive (1/512).

Fig 1: (a) Pre- and (b) postoperative chest X-rays and (c-f) preoperative thorax computed tomography images of the case. (a, b) The cyst, which is located around the 6th rib of left chest wall, was totally removed surgically. Thorax computed tomography images show extension of the cyst along the sixth rib trace, as well as rib destruction.

Because of high suspicion of hydatid disease for the cystic lesion with benign nature, surgical removal was planned without further investigation, and postero- lateral thoracotomy was performed. Beyond the m. latissimus dorsi and m. serratus anterior, extrathoracic protrusion of the lesion extending along the 6^th rib (Figure 2a) was seen. The 6^th rib was completely removed by disarticulation from the costo-vertebral joint. The lesion was 7x26 cm in diameter. The thoracic wall was reconstructed by using prolene mesh; to prevent lung herniation, since the thoracic wall defect was too large (7x26 cm in diameter) following removal of the mass lesion causing rib destruction. When the capsule of the specimen was incised, the daughter vesicles were revealed (Figure 2b). Histopathological examination of the specimen also confirmed the diagnosis of hydatid cyst. No complication occurred postoperatively (Figure 1b). Albendazole at a dose of 10 mg/kg per day was administered after the operation for three months. At the 10 month follow-up, the patient was healthy.

Fig 2: (a) Intra- and (b) postoperative images of the cyst. The daughter vesicles were revealed after incision of cyst capsule.

Discussion

Although hepatic and pulmonary localization is the most frequent, it may be determined in any part of the body from head to toe.[6] However, bony localization particularly in the rib(s), is exceptional. When costo-vertebral echinococcosis occurrs, patients usually are admitted with complaints, sometimes with neurological complaints according to localization of the cyst.[7] In some cases, concomitant lesions elsewhere, especially in the lungs, may be detected.[8] In our case, there was neither any other lesion nor any symptom including neurological and non-neurological ones. Although nearly the whole rib was destroyed in the case, no extension of the cyst to adjacent tissues was detected. Sometimes size of hydatid cyst may increase without apparent clinical symptom, however, an osseous involvement without symptoms is exceptional.

The exact incidence of rib echinococcosis is unknown. In 2004, less then 50 cases of costal echinococcosis had been reported.[8] A retrospective study by Thameur et al, found eight cases (0.49%) with costal involvement out of 1619 cases with thoracic hydatid disease.[9]

Osseous involvement in hydatid disease is seen in the spine, pelvis, femur tibia, humerus, skull and ribs. In the cases with osseous hydatidosis, absence of pericyst formation allows aggressive proliferation of the parasite along the lines of least resistance, especially along the bone canals. The posterior end of rib is most commonly involved in costal echinococcosis. Cysts grow along the long axis of the rib causing expansion of the cortex where it meets more resistance from the solid cortical portion of the rib.[5,8-10]

The typical appearance of hydatid disease in chest X-ray and CT of thorax are mostly sufficient for the diagnosis, and diagnostic difficulties in non-complicated cases are very limited in our clinical experience since the disease is endemic in our country, especially in our region, eastern Anatolia. However, we usually confirm our preoperative diagnosis with histopathological examination of surgical specimens as it was done in our case.

The treatment of choice of this disease is the radical resection of the rib(s) involved. However, medical treatment is limited to cases with inoperable disease. It may be use as an adjuvant therapy in operable cases. Use of antihelminthic drugs for both preoperative treatment and postoperative prophylaxis helps in the reduction of recurrence of this disease. We gave a medical treatment for prophylactic purpose (10 mg/kg/day albendazole) for three months in postoperative period without observing any recurrence or side effect associated with the treatment.

The present case depicts an unusual presentation of hydatid disease with rib involvement.

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
The authors received no financial support for the research and/or authorship of this article.

References

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