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I married my wife on May 29. Three weeks later, I was lying in a New York City hospital recovery room. My new mother-in-law was a few beds away, my kidney flushing toxins from her body.

When my wife, Shelly Banjo, and I began dating six years ago, I learned that polycystic kidney disease ran in her family. It is a genetic disease where cysts grow on kidneys, eventually destroying them. Shelly’s mother, Batya Banjo, would eventually need a kidney transplant. Some day, Shelly also might need one.

Now, Batya refers to me affectionately as her new son and “kidney buddy.” I’ll be thinking about her, recovering back at her home in Texas, as I run the New York City Marathon on Sunday.

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A year and a half ago, I proposed to Shelly on a bench in Central Park, where we have trained together for marathons. Soon after, I decided to get tested to see if her mother and I were the same blood type, the first round in qualifying as a kidney donor.

Batya is 69 years old and grew up in Israel. She met her husband, Chaim, at Hebrew University, where they were biochemistry lab partners. They got married, moved to Canada for medical school and then to Dallas, where they started a medical practice and raised three daughters.

In the summer of 2013, the whole family flew to Israel, where we piled in a van and toured the state for two weeks. Only then did I truly understand who kept the family ticking. Batya chimed in when Shelly’s dad forgot the punch line of a joke, sewed torn backpacks and jeans for her daughters, and never ceased giving her family advice—even when it wasn’t sought. That trip was the last time Batya felt healthy. Soon after, her kidneys started failing.

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