Where Are All the Kidneys?

Most people have 2 kidneys.  Most people can function well with one.  Some people desperately need kidneys, but are unable to find a donor.  Why?  Speaking from experience--I attempted to donate one-- it is expensive to donate a kidney.  One has to undergo a number of tests, and pay for all costs except for the actual hospital visit. Legally the recipient is legally forbidden to help out.  The consequence: few donated kidneys and a profitable black market.