Japanese scientists have successfully grown stem-cell generated kidneys that can excrete urine in pigs and rats, according to a study published in the Proceedings of the National Academy of Science of the United States, or PNAS. Previous attempts at urine excretion in stem-cell generated kidneys had failed.

The scientists created extra urine excretion pathways (created from cloacas), which they attached to bladders and connected to ureters, a technique they called the “stepwise peristaltic ureter.” The technique was successful and prevented hydronephrosis, the researchers reported.