A gravely ill Bronx man whose sister died on the operating table just two weeks ago trying to donate her kidney to him had yet another kidney transplant cancelled at the last minute tonight.

Dad of four Roberto Medina — who had spent all day at Montefiore Medical Center prepping for the scheduled surgery — had expected to undergo the life-saving operation sometime after 7 p.m. after the Bronx hospital and other hospitals agreed to vault him to the top of the kidney recipient list for compassionate reasons.

But close to that time, Medina, 39, and his family were informed that he wouldn’t be receiving that dead-donor kidney — which is now going to someone else — because the New York Organ Donor Network had not obtained required approval for the speeded-up donation from two federal organ-donation-oversight bodies, The Post has learned.

“There was not a good outcome,” a downcast Medina said via telephone from Montefiore this evening.

The stunning about-face was the second time since May 23 — when mom-of-three Yolanda Medina died while undergoing kidney-harvesting surgery on her brother’s behalf — that Medina has entered Montefiore expecting to receive a new kidney only to be thwarted at the last minute.

Helen Irving, president of the New York Organ Donor Network, said, “Unfortunately, the patient in question will not be able to receive an organ as soon as we had hoped.

“We hope to have all of the approvals in place shortly. I have been impressed by the unity, support and commitment of the transplant community in wishing to pursue this rare request. Our thoughts are with the patient and his family at this difficult time.”

It is not known when Medina will get a kidney that’s a match for him, but The Post has been informed it could be fairly soon, as those organs become available often.

Earlier in the day, Medina had expressed thanks for the expedited surgery.

Montefiore had told him to return to the hospital hours after The Post revealed how 41-year-old Yolanda’s death from having her aorta cut during the harvesting surgery had led to the shutdown of the prestigious live-donor program while the hospital and state health officials investigate the shocking incident.

“They went out of their way. They spoke to all the organizations in the area — they all agreed the next kidney was for me,” Medina told The Post with his wife Marybel, by his side. “Montefiore took the step.

“I know my sister is here through all this and she’s doing her thing from heaven. She wants to finish what she started — she’s an angel.”

Yolanda’s was the first-ever death of a live donor in more than 40 years of such surgery at Montefiore.

The hospital yesterday declined to comment on the stunning turn of events.