The dictionary definition for the word "custodian" is someone who has responsibility for or looks after something. This past summer, one fortunate Minnesota grade-school custodian learned there was an unexpected custodial someone who was not only looking out for him but destined to save his life.

Patrick Mertens, 64, was in dire need of a kidney transplant. The generous staff at Kimball Elementary School had already spearheaded fundraisers to help him pay for ongoing dialysis treatment.

Even with their aid, Mertens' condition continued to deteriorate. His daughter, Kayla, posted a Facebook plea for potential donors to come forward. Someone did-and it was someone they knew, third-grade Kimball Elementary teacher Erin Durga.

Durga and Mertens were more than nodding acquaintances. In addition to working at the same school, Durga's three children attended the daycare facility run by Mertens' wife, Lynda.

The co-workers often chatted about their families with one another after school. Durga also got to know and like Lynda, with whom she bonded at the daycare center while picking up her kids.

Even so, it was a huge leap from swapping casual stories about your families to donating a kidney, but Durga knew it was something she was simply had to do.

"I felt in my heart, from the very beginning, that this was my thing," Durga told The Washington Post. "Once I decided that, yes, I'm going to donate to Pat, I felt really good about it, and I was at peace with it throughout the entire thing."

After tests confirmed she was a match, Durga drove to Mertens' home to break the news. But she didn't have to utter a word. The tee-shirt she wore emblazoned with "DONOR" said it all.

The procedure was scheduled for this past July. Mertens was nervous going in, but Durga reassured him just prior to surgery she was certain everything was going to be all right. Buoyed by her positive attitude, Mertens felt ready to face the coming ordeal.

Both patients emerged from the operation with flying colors and were well enough recovered to return to their jobs when the school year began in August.

Mertens says since the operation, things have truly turned around for him. As thankful as he is to be able to spend time with his loved ones and resume enjoyment of his favorite pastimes, the thing he and his wife are most grateful for is the amazing woman who was willing to make sure that he could.

"She's our miracle, our angel," Lynda Mertens said. "We'll forever be grateful for her."

Whether or not Durga is a real-life guardian angel isn't our call, but one thing's for sure-when you look up the word "custodian" in the dictionary, if her picture's not there, it definitely should be.

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