I felt lousy the night in June when I told Don St. Dennis that, after several weeks of successful tests, I had learned that day I was rejected as a kidney donor by a transplant-review surgeon who spotted a couple flaws with my 64-year-old plumbing system.

“That sucks, as we used to say on the North Side,” St. Dennis quipped with a chuckle. “I appreciate what you’ve tried to do for my health.”

St. Dennis had worked in management at Toro Co., and, until 2015, as business professor and external-affairs director at St. Mary’s University in Minneapolis.

They don’t come better than former Sgt. St. Dennis, 68, in his third year of kidney and heart disease. That’s due to U.S. spraying of the chemical-defoliant Agent Orange over the jungles of Vietnam that’s still sickening and killing Vietnamese and Americans 50 years later.

St. Dennis taught international business students that ethical commerce, cultural and educational relationships are much better investments than war. He’s not a pacifist, but a pragmatist and front-row student of history and war.

He wrote a letter to the editor in 2003 that advised against rushing into the ill-fated war in Iraq. “It is so irritating to hear people question my patriotism because I ask that the United States stop and think before it starts a chain-reaction war that may affect us for generations,” he wrote.

He was prescient.

I lost touch with St. Dennis after he retired in 2015, until I learned last winter of his declining health, including daily kidney dialysis.

I decided to donate a kidney. I’m blessed with good health and better luck.

I was buoyed to learn that kidney donors generally live longer than the general population and that one kidney is all we need. The surviving kidney actually grows to provide reserve capacity.

St. Dennis has been waiting for a new kidney at the V.A. Hospital or Mayo Clinic for two-plus years. We weren’t a “match,” but were admitted to the paired-donor program at Mayo. I would donate to the recipient pool. Don would get one that matches.

I passed three days of tests in May at Mayo. And then I was rejected, after conditional approval by a transplant committee, by the reviewing surgeon.

I was deflated, but for not for long.

St. Dennis, so grateful for life after surviving a helicopter being shot down, small-arms fire, rocket-propelled grenades and more in 1971, is stoically teaching me and others about grace and courage.

“Recently, [Star Tribune’s] Jim Souhan wrote about how Maya Moore of the Minnesota Lynx learned to ‘fix your face’ from a coach early in her career,” St. Dennis said. “When things get tough, don’t pout, fix your face. I try to be that. I have it better than most. Stay calm. Take life in the moment.

“In ’Nam, I never counted how many days I had left. I try not to count how long it might be until my transplant.”

According to the National Kidney Foundation, of the 123,000 Americans on the waiting list for a lifesaving organ transplant, more than 100,000 need a kidney. Only 17,000 receive one each year. Every day 12 people die waiting for a kidney.

St. Dennis faces tough odds as his health challenges increase. He relies on family and faith.

Don, a DeLaSalle High School student, met Sue St. Dennis, a Washburn High girl, in 1968, when they worked part-time at Dayton’s downtown store. They married in 1970. A month later, Don was shipped to Vietnam. They have two sons and four grandchildren.

“Family is the best part of my life,” St. Dennis said.

War was the worst.

St. Dennis was a University of Minnesota student in 1969, when a professor failed to record a passing grade on his transcript. That exposed St. Dennis, ironically who aced the class, to the Army draft. He opposed the war. Rather than risk a low number, he enlisted, hoping he could pick his duty. He trained as an Army correspondent. Stateside for a year. Then he was sent to Vietnam. He wrote for military publications, and, escorted civilian news crews, sometimes into combat zones. St. Dennis had better duty than many infantrymen, but he witnessed enough to know the horror of war.

St. Dennis returned to the U to complete his education.

His best business tour was at Toro, under CEO Ken Melrose, who took it from near-bankruptcy to top performer by 2003. St. Dennis ran communications and the Toro Foundation. He volunteered with nonprofits, starting in the Army when he volunteered nights at a GI drug-recovery center.

St. Dennis is sustained by family, humor, his curiosity and a “mashup” faith of liberal Catholicism “and a bit of the Zen Buddhism I learned about in Vietnam.”

More information about organ donations: United Network for Organ Sharing, or www.unos.org.

Neal St. Anthony has been a Star Tribune business columnist and reporter since 1984. He can be contacted at nstanthony@startribune.com.