Abstract
Dilatation of foetal urinary collecting system is common. But cause of obstruction, if any, arise from soft tissues or developmental abnormalities of urinary tract or other paradox. A prenatal diagnosis of a 'calculus' inside ureter producing obstruction and ultimate back pressure changes in collecting system of a foetus is not reported so far. Other than inborn error of metabolism, what aetiological factors lead to this, are a matter of concern and great research. Here kidneys are not dysplastic. Amniotic fluid volume remains normal. Antenatal administration of calcium either orally or parenterally could be a contributory factor as it promotes nephrocalcinosis; and uretric calculus has it's origin in kidneys as believed. There is no maternal symptom related to this entity. Here we report a unique case of foetal ureterolithiasis producing hydroureter and hydronephrosis.