Isolated renal hydatid presenting as a complex renal lesion followed by spontaneous hydatiduria.

Echinococcosis is a zoonotic disease. Liver is the most common site of involvement. Renal involvement is seen in 2% to 3% of patients. Computed tomography findings in renal hydatid typically include: a cyst with thick or calcified wall, unilocular cyst with detached membrane, a multiloculated cyst with mixed internal density and daughter cysts with lower density than maternal matrix. Rarely type IV hydatid cysts may mimic hypovascular renal cell carcinoma. We report a case of previously asymptomatic middle aged female who presented with mild intermittent pain and a complex renal lesion on imaging which was considered to be a hypovascular renal carcinoma or urothelial neoplasm. However, by serendipity, the patient had spontaneous hydatiduria and later was definitively diagnosed and stented. Hydatid disease should always be considered amongst the top differential diagnosis of an isolated "complex" renal lesion which remains indeterminate on imaging.