It’s a well-known truth in the public health world: African Americans run an elevated risk of kidney disease. And if they get it, a gene variant common among people of African descent makes the disease more likely to progress to kidney failure.

Retired NBC4 videographer Ron Minor knows this as well as anyone: His mother died of renal failure. His son went on dialysis four years ago, at age 38. And next month, Minor will mark five years since his own kidney transplant. Yet when he tells people what he has learned, he says the most common response is “I didn’t know.”

Now Minor, an African American who lives in Annapolis, is trying to do more than talk to friends. He and his wife, Kathy, have made a 44-minute documentary, “I Didn’t Know,” which will be shown on WHUT-TV at 9 p.m. Thursday, with repeat broadcasts at 2 p.m. Saturday and 5 p.m. on Sept. 28. It’s an impassioned survey of kidneys, kidney disease, dialysis and the sad, frustrating world of kidney transplants, where sick or dying patients vastly outnumber donors.

Beginning with America’s obesity epidemic, it points out that the high rates of related conditions such as diabetes, high blood pressure and heart disease among African Americans are all factors in developing kidney disease. With a grabbing-you-by-the-lapels sense of urgency, narrator James Brown of CBS Sports notes that more than 40 percent of black Americans have high blood pressure (many of them don’t know it), that early screening is key and that diet and lifestyle changes can literally save lives.

Scenes shift from overweight customers standing in fast-food lines to weakened patients hooked up to dialysis machines to worried doctors. With repeated up-close images of kidneys, dialysis needles and bruised veins, the show might be hard on the squeamish. But Minor isn’t trying to make it easy: He’s trying to make people listen.