A 42-year-old thought blood in the toilet was pregnancy-related hemorrhoids. She had colorectal cancer.

• A woman in her early 40s thought the blood she saw in the toilet was hemorrhoids.
• More than a year later, she was diagnosed with stage 3b colorectal cancer.
• Experts say rectal cancer is on the rise in people under 50, and destigmatizing toilet talk is key.

Laura Behnke did not have time to worry about cancer when she first saw blood in the toilet.

She was trying in vitro fertilization for the fourth and final time, and her focus was on getting pregnant after three failed rounds with no healthy embryos. Everything else could wait.

A few days before the implantation was scheduled, she saw a kind of red mucus coating her stool, and thought: "'I have been under an immense amount of stress. I know I've been straining. This has to be hemorrhoids, right?'"

"I just told myself, 'You know what? Calm down, take some deep breaths, stop straining, and this will all go away, and it'll be fine, and you can go on and have a baby,'" Behnke told Business Insider.

It would be over a year before she discovered she had rectal cancer, joining a growing cohort of younger adults being diagnosed with the disease decades earlier than expected.

Cancer was not on her radar

After that fourth round of IVF, at age 41, Behnke did get pregnant. At first, she was shocked. Hearing a heartbeat at five weeks made it finally feel real. She was overjoyed.

Behnke continued to see some blood in the toilet intermittently, but it was easy to brush off because hemorrhoids are common during pregnancy. She didn't know the difference between the drops of blood typical for hemorrhoids, and the red mucus she saw that she now knows was characteristic of colorectal cancer.

"Nobody at any point asked me: 'What's the bleeding like? How often is it happening?'" Behnke said. "We all just said, 'Oh, hemorrhoids, cool. Moving on. We have other things to worry about.'"

In her third trimester, Behnke did develop a swollen external hemorrhoid, which made it hurt to sit down. For two days, she tried not to put any pressure on her bottom. In the car, she sat on a donut pillow. On the couch, she laid on her side. This bleeding looked and felt different, like bright red food dye coloring the toilet bowl. She took medication to manage the pain, and got on with the business of getting ready to be a new mom. A few months later, her daughter was born.

After six months of sleepless nights and newborn feedings, Behnke was finally starting to feel like herself again. She was regaining her strength, losing weight, and feeling in control of her body after years of IVF treatments and a pregnancy.

By now though, Behnke saw bloody mucus in the toilet even when she didn't have a bowel movement, which she attributed to that pesky external hemorrhoid. Her bowels were also changing shape, and her stools sometimes coming out pencil thin.

Behnke decided to see a colorectal surgeon to get the swollen hemorrhoid removed. The doctor asked her about all of her symptoms, sparing no details about the blood or the poop, and then, to her surprise, told Behnke she urgently needed a colonoscopy.

"It could be a whole lot of things other than cancer, but we need a colonoscopy to find out for sure," Behnke remembers her doctor saying.

After over a year of bloody stools, that was the first time Behnke heard the word "cancer" uttered.

Rectal cancer is on the rise among people in their 40s

When the doctor told Behnke she had late-stage 3b colorectal cancer, she broke down crying. "But we have a seven-month-old!" she wailed into her husband's shoulder.

"How could I be that sick and feel that good?" she wondered. "I had just had a completely normal and healthy pregnancy." Suddenly, she felt a debt of gratitude to that annoying little hemorrhoid that led to her diagnosis.

The colonoscopy revealed that cancer had spread to some of the lymph nodes around her rectum, and was edging closer to other parts of her body. She was thankful that the prognosis was still relatively good. With radiation, then chemotherapy, and surgery afterwards to remove part of her colon and rectum, doctors were confident they could wipe the organ clean.

At 42-years-old, Behnke was diagnosed with what has quickly become the deadliest cancer for people under 50 in America.

"The landscape of colorectal cancer is changing rapidly," Rebecca Siegel, an epidemiologist and the senior scientific director of surveillance research at the American Cancer Society, told Business Insider.

Experts don't know why, but many of these new, young-onset colon cancer cases are rectal, prompting bloody stools. Other common symptoms in this age group include persistent stomach cramping or severe abdominal pain, low iron levels, and changes to bowel movements, including the narrower stools Behnke saw.

Research suggests that bloody stools are an early warning sign for about 40% of rectal cancer patients. "There's an opportunity for earlier diagnosis, but the problem is, especially for younger people, they're not aware of the symptoms and they don't want to talk about the symptoms," Siegel said. "And sometimes they even do go to the doctor with these symptoms, and they're diagnosed with hemorrhoids or something else."

A couple of weeks after Behnke had her first dose of radiation, she stopped bleeding into the toilet. After 25 sessions of radiation, then four months of chemotherapy, and finally, surgery that removed parts of her colon and rectum, she landed in diapers alongside her daughter for a few weeks. Doctors said every visible trace of the cancer was gone.

Slowly, over time, her colon has healed and she's readjusted to a more normal bathroom routine, but she says things will never be quite the same down there. She prioritizes getting plenty of fiber in her diet from colorful vegetables, and also takes fiber pills twice a day, to help with the lingering symptoms.

"I am alive and I am healthy and all of this is workable," she said.

This is not an 'old man's disease' — talk to your doctor about bloody stools or unexplained stomach pain

Colorectal cancer, Behnke said, is not an "old man's disease" anymore. After her diagnosis, she urged her younger brother to get a colonoscopy, and doctors discovered he had precancerous polyps developing. Her young daughter, she said, will start having colonoscopies in her early 30s, because of her increased risk of developing colorectal cancer.

Behnke said she's grateful she met "the right surgeon at the right time," a doctor who asked the right questions, and didn't dismiss her symptoms because she was too young or postpartum.

"No rectal bleeding is okay," she said. "If you do have any sort of symptoms, any sort of concerns, anything that doesn't feel right, you have every right to go ask a doctor about it and to demand some answers."