Hydatid disease of the kidney is rare and constitutes only 2 to 4% of all cases of hydatid. Its occurrence in children is even more rare. It ranks third after liver and lung. In the urinary tract, kidneys are generally affected, usually together with multiple organ involvement. An isolated renal hydatid cyst of the kidney without other organ involvement is very rare. We hereby present a case of pure hydatid cyst of the left kidney in a child presenting with left flank swelling and renal colic. She also had episodes of fever on and off for 2 months. On the basis of imaging studies, a diagnosis of hydatid cyst of the left kidney was established. The patient was successfully managed by simple nephrectomy. The patient is doing well at an 8-month follow-up.
Sanjay Kumar Gupta, Ranjit Kumar, Mahendra Singh, Vijoy Kumar, Rajesh K Tiwary, Atul Khandelwal, Vinod Priyadarshi
Submitted December 5, 2011 - Accepted for Publication January 9, 2012
KEYWORDS: Renal, hydatid cyst, simple nephrectomy, floating membrane
CORRESPONDENCE: Sanjay Kumar Gupta, Department of Urology, Indira Gandhi Institute of Medical Sciences, Bihar, India ().
CITATION: UroToday Int J. 2012 June;5(3):art 20. http://dx.doi.org/10.3834/uij.1944-5784.2012.06.07
INTRODUCTION
A 9-year-old female presented with swelling in her left flank and colicky pain that increased with time for 2 months. There was also associated dysuria. On abdominal examination, there was a smooth, mobile lump with a well defined margin in the left lumbar region. A routine blood investigation and renal function tests were normal except for mild eosinophilia. The indirect hemagglutination test was negative. The ultrasonography of the abdomen revealed an enlarged left kidney with a large thick-walled cyst, with a floating membrane and fine-floating echoes. An intravenous urogram showed an enlarged left kidney with calyceal distortion and pooling of the contrast, which is persistent in post-void film (Figure 1). A computed tomography (CT) scan revealed a large cyst rising from the mid and upper poles of the anterior surface of the left kidney. The cyst was thick-walled with a modulating membrane located in the center of the cyst (Figure 2). On exploration, the kidney was edematous, friable, and hugely enlarged in size, and it crossed the midline with marked and dense perinephric adhesion (Figure 3). Simple nephrectomy was performed. A thick-walled, single-layer cyst was seen on the cut section of the nephrectomy specimen (Figure 4). In the postoperative period, the patient was kept on albendazole (400 mg daily) for 3 months. The histopathological examination was consistent with hydatid disease.
DISCUSSION
A hydatid cyst is a parasitic infection caused by a larval form of Echinococcus granulosus. The adult worm is present in a dog’s small intestine. Humans are an intermediate host of Echinococcus granulosus through the ingestion of water or vegetables contaminated by its eggs [1]. The ovum is digested in the duodenum and the parasitic embryo pass through the intestinal wall to reach the portal venous system [1].
The liver acts as the first line of defense and is therefore the most frequently involved organ. In humans, the hydatid involves the liver in 75% of cases and the lung in 15% of cases. Hematogenous dissemination may be seen in almost any anatomical location [2]. Kidney involvement in echinococcus is extremely rare (2 to 3% of cases), even in areas where hydatid is endemic [3]. Hydatid is rarely seen in children and is usually encountered between patients aged between 30 and 50 years old [6]. Primarily, hydatid of the kidney occurs via the passage of embryos into the kidney by retroperitoneal lymphatics [2]. A hydatid cyst is closed if it contains all 3 layers of the cyst: pericyst, ectocyst, and endocyst. If the third layer, pericyst, is lost, it becomes an exposed cyst. When the layers of the cyst rupture, resulting into free communication with the pelvicalyceal system, it is called a communicating cyst [7]. Renal hydatid cysts usually remain asymptomatic for many years. Presenting complaints are typically flank mass, hematuria, and pain. Hydatiduria occurring due to the rupture of a cyst in the pelvicalyceal system is a pathognomonic clinical sign [4,5]. Microscopic hydatiduria occurs in 10 to 20% of cases of a renal hydatid. Gross hydatiduria is very uncommon [4]. There is no serological and immunological pathognomonic test for hydatid disease. Eosinophilia, the Casoni test, the complement fixation test, and an indirect hemagglutination test may be helpful for the diagnosis of renal hydatidosis [8].
On a plain radiograph, a ring-shaped calcification can be seen, which may be linear, multilaminated, or amorphous. In our case, there was no calcification on a plain radiograph but a renal shadow was enlarged and extended from T11 to l5. Excretory urography may demonstrate calyceal distortion, caliectasis, and a nonfunctioning kidney, possibly due to a mass effect of the cystic lesion [9]. An intravenous urography revealed calyceal distortion with caliectasis and pooling of the contrast in calyces, which persisted even in the post-void film. Ultrasonography is usually the primary radiological investigation. Although abdominal sonography is helpful with the diagnosis, CT is more accurate and sensitive [10]. Sonographic findings may show anechoic lesions with well defined margins, while a CT may demonstrate a cyst with a thick or calcified valve, a unilocular cyst with a detached membrane, a multiloculated cyst with a detached membrane, or a multiloculated cyst with mixed internal density and a daughter cyst with lower density than the maternal matrix [2,11,12]. Computed tomographic findings in this case demonstrated a unilocular cyst with a floating membrane typical of hydatid disease. Magnetic resonance imaging delineates the cyst more accurately but offers no advantage over CT, and it is also expensive.
Treatment of a renal hydatid cyst is essentially surgical. Kidney sparing surgeries such as cystectomy and pericystectomy are carried out whenever possible. Nephrectomy is the treatment of choice for renal hydatid cysts but it should be reserved for destroyed kidneys (25%) [13]. In this case, nephrectomy was done because the kidney was hugely enlarged, edematous, and friable, and during manipulation the kidney parenchyma ruptured and extruded pus. In addition, the upper ureter was suspected to have a daughter cyst due to its thick wall and beaded feeling on palpation along with the presence of hooklets in the pelvis. The surgeon must be careful to totally remove the cyst and avoid spilling its contents. There should be delicate manipulation with the use of abdominal packs soaked with hypertonic saline to reduce the risk of dissemination and prevent recurrence [14]. Preoperative treatment with albendazole decreases the tension in the cyst wall and renders the cyst nonantigenic.
The technique of percutaneous injection, aspiration, and re-aspiration has been described as a safe and effective treatment modality for a renal hydatid [15]. Cysts do not completely disappear with this technique but it can be useful for high-risk patients with symptomatic hydatid cysts [16].
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