Sentence:  An <WSD>artificial</WSD> kidney these days still means a refrigerator-sized dialysis machine. Such devices mimic the way real kidneys cleanse blood and eject impurities and surplus water as urine. But they are nothing like as efficient, and can cause bleeding, clotting and infection—not to mention inconvenience for patients, who typically need to be hooked up to one three times a week for hours at a time. 
Meaning of the word marked with <WSD> tags:  Man-made; of artifice.