Human is an accidental host in the life cycle of Echinococcus granulosus. When infested, about 95% of the larvae are trapped in the liver or the lung, while only 5% of them escape into the systemic circulation to involve other organs .
A primary retroperitoneal hydatid cyst is extremely rare [4, 5]. It is a distinct entity that must be considered when caring for a patient with a retroperitoneal mass in endemic regions . In these cases, peritoneal involvement is seen in about 12% of cases , mainly because of secondary spillages due to rupture and other possible complications .
Clinical features include flank pain, abdominal mass, and nonspecific symptoms such as nausea and vomiting. Symptoms are usually due to compression as cysts increase in size . When rupture or secondary infection occurs, acute symptoms arise. The differential diagnosis of a cystic retroperitoneal mass includes abscess, chronic hematoma, necrotic malignant soft tissue tumor, cystic lymphangioma, pancreatic cyst, and hydronephrosis [4, 11]. Diagnosis is established based on the combination of many parameters, including patient origin, clinical findings, imaging, and serology.
The radiological appearance of the hydatid disease of musculoskeletal system mimics tumors and other inflammatory conditions. Therefore, preoperative diagnosis is sometimes difficult clinically and radiologically . Abdominal ultrasonography is a sensitive tool for diagnosing HC with characteristic findings such as floating membranes, hydatid sand, and daughter cysts. Presence of an undulating membrane and multiple daughter cysts within a mother cyst can suggest the diagnosis on CT and magnetic resonance imaging . As in our case, when characteristic radiological findings are present, diagnosis can be confidently made with high specificity.
Surgery is the cornerstone for treatment of hydatid cysts [12, 14]. Total cystectomy without contamination of the field is the procedure of choice. As in our case, when total cystectomy is not possible because of dense adhesions to important anatomical structures, partial cystectomy should be done . Furthermore, chemotherapy should always be considered in conjunction with surgery .
A retroperitoneal localization of the hydatid cyst is extremely rare. Rupture is a serious complication. The clinical symptoms can be confusing; therefore, preoperative diagnosis is sometimes difficult. In endemic regions, high suspicion for this disease is justified regardless of the localization affected, because delayed diagnosis increases the risk of impairment, recurrence, and sepsis.