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Isolated primary Hydatid cyst of kidney: A case report of asymptomatic patient


We report an isolated primary hydatid cyst of kidney in a pregnant asymptomatic woman. We also present salient diagnostic feature of asymptomatic patients of hydatid cyst. 



Introduction
Hydatid cyst of kidney is a very rare condition (2-3%) caused by the larval stage of echinococcus granolosus (Warren et al., 2002). It is endemic in parts of the Middle East, South America, Australia, New Zealand and Alaska (Vuitton, 1997). Isolated renal involvement is even rarer (Yaycioglu et al., 2006).We report a rare case of primary renal echinococcosis in an asymptomatic pregnant female with emphasis on cytological , histopathological and radiological diagnosis.

Case report
A 23-year old primi gravida, otherwise asymptomatic came for routine antenatal checkup. Per abdomen was within normal limits without lump/mass, tenderness and discomfort. Her blood investigations were normal with no eosinophilia. Renal function tests were normal. Her ultrasound (USG) showed lesion in left renal fossa arising from left kidney. Abdominal examination did not reveal any abnormal mass. Rest of systemic examination was normal. CT scan revealed a well defined round to oval hypodense well capsulated, non enhancing, retroperitoneal, cystic lesion measuring 111x109x90 mm showing multiple thin septi within, with daughter cyst like areas within. This lesion involving mainly upper/and part of mid pole of left kidney. The collecting system, ureter and bladder were devoid of any such lesions. Her routine blood investigations were normal with no eosinophilia and normal renal function tests. X-ray chest Paview was normal. Since patient was asymptomatic and renal functions were normal, it was decided to continue pregnancy. Kidney-sparing pericystectomy surgery was planned after 9 months of delivery. The resected specimen showed a large capsulated cyst with multiple whitish grape like daughter cysts of different sizes inside.
Showing well defined round to oval hypodense well capsulated non enhancing retroperitoneal, cystic lesion in left renal fossa showing multiple thin septi within with daughter cystlike areas. Lesion involve mainly upper and mid pole of left kidney. Collecting system devoid of the lesion on these sections displacing and compressing left adrenal gland, vessels peripherally in relation to the lesion.

Discussion
Echinococcosis is produced by larval stage of the echinococcus tapeworm, E. granulosus. Man is the intermediate host and acquires disease by ingesting water and vegetables contaminated with faeces of dogs. Dogs, fox, wolf and jackals are definitive hosts (Goel et al., 1995). After ingestion, the hexacanth embryos are hatched in duodenum. These embryos pass through intestinal wall to reach the portal venous system and the liver. Hence liver is the most commonly affected organ. Liver acts as the first filter as the embryos get arrested in sinusoidal capillaries. Those larvae that escape tie liver are next filtered by the lungs. Embryos which pass the pulmonary capillaries then enter the general blood stream and lodge in various organs (Strohmaier et al., 1990). Practically, all the organs spleen, brain, heart, kidney, genitor-urinary tract, muscles-can be invaded (Poulios, 1991).
Embryos forms a hydatid cyst, the young larva being transformed into a hollow bladder from the inner side of the cyst, brood capsules with number of scolices are developed. A single egg contain thousands of scolices. The fully developed scolex is an end product. A hydatid cyst consists of 3 layers-pericyst, exocyst, endocyst containing many daughter cysts, scolices, hooklets. (Buckley RJ 1985). Isolated hydatid cyst is a rare condition and can be challenging in absence of resources (Yaycioglu et al., 2006).Even though majority isolated cysts are primarily isolated, it may involve renal proper in peripheral tissues with involvement of kidney proper afterward spreading intra and infra capsular area.
Common presenting complaints are mass in flank, hematuria, pain, passage of 'grape shins' like material in urine, hypertension, renal colic. (Saidi, 1976) Routin blood examinationcan only help patient of hydatid cyst disease by showing eosinophilia. This is only in 40-50% of cases. (Poulios, 1991;Buckley et al., 1985;Aragona et al., 1984) Radiologically, plain flims are not specific and remendously revealing but Ultrasonography, CT scan and MRI are main mainstray in diagnosis of hydatid cyst (Haines et al., 1977). Even though accuracy is operator and radiologist dependant it has tremendous diagnostic utility. Treatment of choice in renal hydatid cyst is surgical removal. The type of surgerical management of renal echinococcosis changes of individual patient and type of removal may be nephrectomy,partial nephrectomy or marsupialization. (Poulios et al., 1991;Buckley et al., 1985). Risk of cyst rupture and dissemination, hypersensitivity reaction during dissection and removal is always there so careful meticulous care during removal is mandatory. Pre and postoperative administration of Albendazole for about one month decrease chances of anaphylaxis and risk of recurrence rate postoperatively. (Mongha et al., 2008). Laparoscopic removal is not widely practice yet due to fear of rupture of cysts, dissemination during dissection and removal.

Conclusion
In general, asymptomatic isolated patients can be accurately diagnosed with radiological, cytological and histopathological tools. Treatment of choice is surgical removal sparing kidney (cyst removal with pericystectomy).