Pelvi-ureteric junction (PUJ) obstruction is an enigmatic condition. While in a reasonable majority it is clear cut, the diagnosis and the need for intervention in the remainder is still a challenge. We would like to share the details of two cases, one in a transplant recipient and the other in a living kidney donor, and propose an explanation as to why PUJ obstruction becomes manifest after such a long period of time. In this presentation, we would like to propose that forced drinking of fluids by patients who have an equivocal PUJ and a single kidney could tilt the balance resulting in overt PUJ obstruction.