A large abdominal cyst as a manifestation of pelviureteric junction obstruction in a neonate.

Intraabdominal cystic lesions diagnosed during antenatal period are uncommon. They are found to have varying origins, with renal tract being the most common site. Rarely, a large unilateral cystic lesion of renal origin is caused by Pelviureteric junction obstruction, crossing the midline, leading to compression of the contralateral kidney. We present a case of a neonate who was diagnosed with a large abdominal cyst in the antenatal period. The cyst persisted and crossed the midline causing hydronephrosis on the contralateral side. This is an unusual presentation of a commonly occurring condition, usually such large cyst at birth origins from alimentary tract rather renal system. It is important to understand unusual presentations of intraabdominal lesions and the associated pathology. It is mandatory to rule out renal obstruction, if there is any decompression of renal function, it is mandatory to save renal function till the time of definitive surgery.