Retrovesical hydatid cyst

Clinical History

A 28-year-old male patient presented with a two-year history of frequent episodes of burning micturition. A physical examination revealed pelvic tenderness.

Imaging Findings

A 28-year-old male patient presented with a two-year history of frequent episodes of burning micturition. He lived in a rural area, and he had been in close contact with dogs. There were no abnormal findings on physical examination except pelvic tenderness. Routine blood test and the eosinophil count results were found to be normal. His renal function and plain X-ray scans were also normal, and in particular there was no calcification. We did not find any calculus in the urinary tract on doing an ultrasonographic examination. An intravenous pyelography (IVP) was performed, which showed a mass distorting and displacing the bladder and ureters. An ultrasound (US) investigation revealed a cystic mass 104 x 80 mm in size in the pelvic region, including multiple small cysts with an internal echo (Fig. 1). On computed tomography (CT), a septated cystic mass with a thin capsule that was sharply demarcated from the bladder was seen. The lesions contained multiseptated cysts within the cyst (Fig. 2). No cystic lesion was seen in the liver or spleen. The chest films were also found to be normal. The patient had been operated, and a total cyst excision was done. He had a smooth postoperative course. No reccurrence of the pelvic cyst was noted with a follow-up of two years.

Discussion

Hydatic disease of the urinary tract is known to be uncommon, accounting for only 2%–3% of all such cases (1). RVHC is rare even in endemic areas and accounts for 0.1%–0.5 % of hydatic cases (2). Hydatid disease is known to be a zoonosis that afflicts people worldwide produced by the larval stage of the Echinococcus tapeworm. The disease is prevalent in most parts of the world. Its pathogenesis remains controversial. According to the classical theory of Déve, RVHC is a result of fissuring or rupture of an intraperitoneal hydatic cyst and seeding of its contents in the Douglas pouch known as secondary echinococcosis (3). The clinical symptoms appear after a long course of the cyst. There is no specific sign in the pelvis except hydaturia when the cyst sometimes fistulizes into the bladder. The most frequently presenting symptoms are frequency, urgency, burning miction and possibly urinary retention. Other symptoms vary depending on the site of the hydatid cyst. Serology may be helpful in the diagnosis of HD. If the serology test result is negative, the diagnosis must not be rejected. It must be confronted with radiological findings. Plain X-ray scans usually reveal a mass in the pelvis or the abdomen. Linear calcification could be observed. A loss of renal outline and loss of the renal-psoas line have also been described. IVP demonstrates extrinsic compression and provides a good preoperative impression of the degree of vesical and ureteral displacement. The anterior displacement of the bladder is observed frequently. Ultrasonography is the key diagnostic tool in cases of HD. Five different stages may be recognized (4). Stage I: lesions are purely cystic. Stage II: when the laminated membrane has been detached from the pericyst. Stage III: lesions contain multiseptated daughter cysts within the cyst. Stage IV: complex heterogeneous mass. Stage V: lesions are calcified causing a well-defined, cone shaped acoustic shadow. CT more easily reveals calcification and daughter cysts and is more sensitive and accurate than ultrasonography in the differential diagnosis. It usually allows recognition of lesion extension and the precise assessment of relationships to neighboring structures. On MRI, the cyst wall shows a rim of a low signal intensity on both T1- and T2-weighted images (5). Treatment of RVHC is surgical. The aim of surgical therapy is to completely remove the cyst without contamination of the field. Ideally a total cyst excision is to be conducted.

Differential Diagnosis List

Final Diagnosis

Retrovesical hydatid cyst.

URL:	https://www.eurorad.org/case/3055
DOI:	10.1594/EURORAD/CASE.3055
ISSN:	1563-4086