Doctors in Hubei province have successfully transplanted kidneys from a prematurely born donor baby into a 47-year-old woman suffering from kidney failure.

The donor weighed only 1.3 kilograms, the lightest kidney donor ever reported, Wuhan Union Hospital said on Wednesday.

The woman, surnamed Wang, from Duchang county, Jiangxi province, was diagnosed with uremia in June last year and transplant surgery performed a month later.

Without the transplant, she would have had to rely on blood dialysis for the rest of her life.

The kidneys used in the surgery were from a baby born prematurely, whose parents decided to donate the organs after the infant died, the hospital said.

Following a year of follow-up treatment, the baby's kidneys, which were between 3 and 4 centimeters long when transplanted, have grown to 6.9 cm and 7.6 cm in the patient's body, closer to the usual size of 10 cm for an adult.

The two kidneys are functioning normally and Wang's health has recovered, the hospital said.

Transplant surgeries using kidneys donated by infants are very difficult compared with kidneys donated by adults. Generally, infants that weigh less than 5 kg are not considered as sources of organs for transplant surgeries abroad, the hospital said.

Wang Zhendi, a transplant surgeon in the hospital and the woman's doctor, said the blood vessels and ureter, a tube that carries urine from the kidney to the urinary bladder, are very thin in infants' kidneys. This makes precise surgery very difficult, with higher chances of post-surgery complications. It is also more difficult for such kidneys to function in an adult's body as they are not fully developed.

"The less the weight of the donor, the slower the kidney recovers functioning in the body where it is transplanted," he said.

Although an adult can survive with just one kidney, usually two kidneys are transplanted from an infant to improve the chances of a healthy outcome, he said.

The success of the surgery means sources for kidney transplant surgeries can be expanded to include infant donors. This will ease the gap between the number of organs donated and the number of patients with terminal kidney disease waiting for transplant surgery in China, the hospital said.

In Wuhan Union Hospital alone, more than 500 registered patients with kidney failure are waiting for suitable organs for transplantation, the hospital said.