Richards, 50, who lost her mom, Kathleen Richards, to breast cancer in 2002, was understandably anxious about the procedure — while Rinna, 55, tried her best to soothe her worried friend.
"This test gives me so much anxiety. But the reason my mom died of breast cancer is because she didn't go get a mammogram for five years," she explained during the episode.
"So if my mom had gone (to the doctor), maybe she would still be here, and I'm haunted by that thought all the time."
Luckily, her results eventually came back looking "fantastic."
Once it was all over, Richards broke down in tears from the stress, as Rinna comforted her. "It's OK, you're clear. You're clear. It's all good," Rinna told her.
After the episode aired, Richards took to Twitter to urge women everywhere to schedule regular mammogram appointments.
The American Cancer Society recommends women begin having yearly mammograms by age 45. They can switch to having mammograms every other year beginning at age 55.
"I lost my Mom to Breast cancer in 2002," Richards wrote in her tweet. "The fact that she hadn’t had a mammogram in 5 years haunts me. I really wanted to show this to bring awareness re early detection and as a reminder to get checked."
She also thanked fans who said she was brave for undergoing the procedure on TV.
"I was scared to do this with cameras," Richards shared, "but felt it was important."