Hydatid cyst is a parasitic disease caused by the tapeworm Echinococcus granulosus. The tapeworm stage is harbored in the intestine of a carnivore, called the “definitive host”. The tapeworm eggs are passed in the feces of an infected carnivore and are ingested by a herbivore (e.g., sheep), called the “intermediate host”. The eggs hatch in the intestine of the herbivore, penetrate the intestinal wall, and reach the liver using the portal vein, where they develop into a hydatid cyst. Sometimes they passed through the liver barrier and reach the lungs and all other viscera¹.

Hydatid disease is prevalent worldwide especially in countries with a warm climate (India, African countries, Turkey, South American countries and Middle Eastern countries). This parasitic illness is diagnosed commonly in the east and south-east regions of Turkey². Renal hydatidosis is an uncommon presentation echinococcal disease and occurs in only about %2 of all cases³.

Case 1- A 44-year-old female admitted to the hospital with the complaint of right flank pain. Physical examination revealed a smooth, nontender, mobile mass in the patient's right upper abdomen. Laboratory tests revealed an erythrocyte sedimentation rate of 31 mm/hr, normal blood cell count and normal serum creatinine levels, and no abnormalities on urinalysis. A chest x-ray film was unremarkable. Ultrasonography (US) was performed and the big cystic mass 15x15 cm in size was detected. The internal structure of the mass was purely anechoic, and the cystic wall was thin and regular. No alteration in the wall's structure, which could resemble a germinative membrane, was apparent. A computarized tomography (CT) examination verified the US findings; and well delineated the association between the mass and the right kidney (Figure 1). After all these radiological findings, the mass was diagnosed as a giant simple renal cyst. The operation was planned for a simple cyst; but was altered, after an intraoperative diagnostic needle sampling brought out the charasteristic fluid of hydatid cyst. It was like clear water (rock water), which was the key point for us to define the mass as a hydatid cyst. Hypertonic sodium chloride (3% NaCl) solution was injected into the cyst cavity for sterilization. The cyst wall was opened and the germinative membrane was extracted. The internal surface of the cyst wall was washed with pavidone iodine, and cystectomy was performed. Pathological examination confirmed the hydatid cyst. Immediate postoperative echinococcal antibody titration was negative. The postoperative period was uneventful, and the patient was prescribed albendazole 400 mg twice daily for 4 weeks to prevent metastatic cyst formation.

Figure 1: Computed tomography scan showing renal hydatid cyst presenting as a peripelvic cystic lesion without calcification, debris, or a solid component (Patient 1).

Case 2- A 27-year-old female admitted to the hospital with the complaint of right flank pain for three years and for a pain in right gluteal region for a year. Physical examination revealed a smooth, nontender, mobile mass in the patient's right gluteal region. Laboratory tests revealed an erythrocyte sedimentation rate of 25 mm/hr, normal blood cell count and normal serum creatinine levels, and no abnormalities on urinalysis. A chest x-ray film was unremarkable. Ultrasonography was performed and multipl renal cysts were detected. Abdominal computed tomography revealed two cysts in right kidney 12x12 cm and 5x5 cm in size (Figure 2). Also a cyst between internal and external oblique muscles 5x5 cm in size, and a cyst in the right gluteal region 12x12 cm in size were determined (Figure 3). Pretreatment with albendazole 400 mg twice daily for 4 weeks performed before operation. One month after albendazole treatment, renal and gluteal hydatid cysts were surgically removed.

Figure 2: Computed tomography appearance of the renal hydatid cyst (Patient 2).

Figure 3: Computed tomography appearance of the gluteal hydatid cyst (Patient 2).

The clinical presentation of renal hydatid disease is usually non-specific and related to the mass effect of the enlarging cyst. Abdominal and lumbal pain is the most frequent presenting symptom⁴. The only pathognomonic sign of renal hydatid disease is hydatiduria, which occurs when the cyst communicates with the collecting system; this has been reported in 5% to 28% of patients^5,6 Preoperative definitive diagnosis for renal hydatid disease is difficult even when all investigations were performed. The diagnosis is usually made with imaging and serologic studies.

There is no specific laboratory finding of renal hydatid disease. Moderate eosinophilia is non-specific, although present in 20-50% of cases. Indirect hemagglutination test and enzyme-linked immunosorbent assay are the most sensitive tests, although they commonly provide both falsepositive and negative results³. Recently counter immunoelectrophoresis against arch-5 gained wide acceptance⁷.

However, despite modern imaging methods, isolated renal hydatid disease might still cause diagnostic dilemma like mentioned as in our first case. Among imaging studies, CT is the most valuable diagnostic examination⁸. CT findings include a thick, calcified cyst wall, a unilocular cyst with detached membrane, multiloculated cystic formation with mixed density, and daughter cysts with lower density than the mother cyst⁹.

Medical management of renal hydatidosis is far from being a realistic alternative to surgery and should be considered as adjuvant therapy. Pretreatment with albendazole is very important as the cyst material becomes nonantigenic, decreasing the chance of anaphylaxis. Pretreatment also decreases tension in the cyst wall; thus, reducing the risk of spillage. The recommended dose of albendazole is 400 mg twice daily for 4 weeks². However, we administered albendazole after surgery in our first case

Surgical options include simple cystectomy, pericystectomy, partial or total nephrectomy. Cyst removal without contamining the patient is the goal of therapy because rupture of a cyst also causes alergic manifestations that vary from pruritus and urticaria to anaphylactic shock even death¹⁰ Before the main surgical procedure three different scolocidal agents can be injected into the cysts; 3% hypertonic saline solution, 10% povidon iodine solution, and 95% ethanol. A safely cleavage plane have been to obtained between cyst and normal renal tissue. Renal sparing surgery is possible in a significant proportion of cases - as in our cases. Total nephrectomy is inevitable in case of significantly destroyed renal parenchyma by pressure from cyst².

Gupta et al.¹¹ described a rare case of isolated renal hydatid cyst presenting as perinephric and iliopsoas abscess and discussed the dilemma in diagnosis. An another interesting case of a giant renal hydatid cyst is presented in our second case. Patient presented with the complaint of right flank pain for three years and for a pain in right gluteal region for a year. The big cystic mass detected at kidney and gluteal region.

A serologic survey is necessary for the follow-up of operated patients. It increases the efficiency of the treatment. Specific antibodies increase 4 to 6 weeks after surgery, after which they decrease slowly for the next 12 to 18 months. Persistently high specific antibody titers or a secondary increase in the antibody titers 6 to 12 months after surgery indicate a relaps¹².

Our conclusion is that not all hydatid cysts present with the charasteristic radiological findings and hydatid cysts can be found in unusual localization. In order to prevent iatrogenic echinococcal dissemination all precautions must be taken during operation.