"The kidney was successfully removed and transplanted into the donor's niece, and both patients are doing fine. As far as we know, no one has ever applied this type of procedure to a donor kidney," said Dr Robert Montgomery of Johns Hopkins University School of Medicine, who led the surgical team.

The three-and-a-half-hour surgery, performed Thursday, eliminated the need for a five- to six-inch incision in the abdomen of the patient -- a 48-year-old woman from Lexington Park – who donated her kidney to her niece. Instead, she has only a few small scars on her abdomen.

"(In fact) doctors made a smile-shaped incision in the back of her vagina and inserted an inflatable bag through a tube to hold the incision open. The kidney was then pulled out intact," Montgomery said.

According to the doctors, the patient had less pain and a shorter recovery time – benefits that could encourage more kidney donations.

"It's another step toward really reducing the impact of the operation on the donor. We are all trying to reduce the disincentives to donation," Dr Montgomery was quoted as saying by the US media.

Transvaginal kidney removals have been done previously to remove cancerous or non-functioning kidneys that endanger a patient's health, but not for healthy kidney donation.

"Because transplant donor nephrectomies are the most common kidney removal surgery – 6,000 a year just in the US – this approach could have a tremendous impact on people's willingness to donate by offering more surgical options.

"Since the first laparoscopic donor nephrectomy was performed at Johns Hopkins in 1995, surgeons have been troubled by the need to make a relatively large incision in patient's abdomen after completing the nephrectomy to extract the donor kidney.