Scientists make 'laboratory-grown' kidney

A kidney "grown" in the laboratory has been transplanted into animals where it started to produce urine, US scientists say.

Similar techniques to make simple body parts have already been used in patients, but the kidney is one of the most complicated organs made so far.

A study, in the journal Nature Medicine, showed the engineered kidneys were less effective than natural ones.

But regenerative medicine researchers said the field had huge promise.

Kidneys filter the blood to remove waste and excess water. They are also the most in-demand organ for transplant, with long waiting lists.