Renal cystic echinococcosis; an unusual localization of echinococcosis

Clinical History

A 12-year-old girl with history of right flank pain was referred to the radiology department of FMIC for imaging workup.

Imaging Findings

Renal ultrasound was done and it revealed a cystic lesion containing a detached membrane with internal debris in the lower pole of the right kidney extending to the collecting system resulting in mild dilatation of the caliceal system. No vascularity was detected by Doppler in the lesion.
Then abdomen CT was done for further characterization of the lesion. Abdomen CT showed a well-defined thickened wall low attenuating mass in the antero-inferior aspect of the right kidney with internal floating membranes extending to the renal pelvis resulting in dilatation of the collecting system. The lesion showed rim enhancement of IV administration of non-ionic contrast media. There were also two small well-defined low attenuating lesions with calcification in the right lobe of the liver.

Discussion

Cystic echinococcosis is a parasitic disease which is endemic in many parts of the world. It is caused by either Echinococcus granulosus or, less frequently, Echinococcus alveolaris. [1, 4]
Cystic echinococcosis can occur almost anywhere in the body; liver and lungs are the most common sites. CE may be rarely seen in other sites such as kidneys, heart, orbit and bone. [1, 4, 5]
Involvement of the kidney is rare (2-3%). [5, 7] Usually the patients with renal CE have no symptoms and are diagnosed incidentally. Symptomatic patients may present with a loin mass, flank pain, dysuria, fever, pyuria or haematuria or renal colic and hydatiduria. [2, 3, 4, 6]
CE demonstrates a variety of imaging features according to growth stage, associated complications, and affected tissue. [1]
The WHO classification of CE in ultrasonography:
- CL; unilocular cystic lesion without internal echoes and septations
- CE1; uniformly anechoic cyst with fine echoes settled in, representing hydatid sand
- CE2; cyst with multiple septations (multivesicular, rossette or honeycomb appearances)
- CE3; unilocular cyst with daughter cysts with detached laminated membranes (water lily sign)
- CE4; mixed hypo and hyperechoic contents with absent daughter cysts (ball of wool sign)
- CE5; arch-like thick partially or completely calcified wall. [8]
Curvilinear or heterogeneous calcifications may be visible on plain films.
CT and MR imaging can show both intact and ruptured cysts. CT is best for detecting calcification and revealing the internal cystic structure posterior to calcification. CT shows fluid density cyst, with septations and daughter cysts. Ring enhancement may be seen on contrast enhanced CT. [1, 4]
On MRI, CE is seen as hypointense on T1 WI and as marked hyperintense lesions on T2 WI images. MRI displays a low-signal-intensity rim that surrounds the cyst (“rim sign”). [6]
Complications of renal CE include infection and rupture, in either the renal sinus or the perinephritic tissues. [1] 18% of renal CE can rupture into the collecting system, leading to acute colic and hydatiduria. [1, 2, 6]
Treatment of renal CE is primarily surgical and consists of total or partial nephrectomy. [7]
Percutaneous treatment of the cyst by using one of the three techniques can be an alternative treatment for the renal CE which are not related to the collective system and for protection of renal parenchyma. [9]
Some imaging findings of cystic echinococcosis are characteristics. Radiologists, especially those who work in endemic areas, need to be familiar with these findings and should consider this disease in the differential diagnosis. [4]

Differential Diagnosis List

Final Diagnosis

Right renal cystic echinococcosis

URL:	https://www.eurorad.org/case/13646
DOI:	10.1594/EURORAD/CASE.13646
ISSN:	1563-4086