Leg pain has a ton of causes, and sure enough, colon cancer is one of them.

But how is this possible? And if you have unexplained leg pain, should you worry about colon cancer?

“Patients with stage IV colon cancer can experience leg pain if they develop edema (fluid in the legs),” says Benjamin Levy, MD, board certified gastroenterologist who’s provided clinical care to patients at Mount Sinai Hospital, Schwab Rehabilitation Hospital, and Sinai Medical Group Touhy Refugee Clinic.

Dr. Levy explains, “This sometimes occurs if the colon cancer spreads to the liver and causes liver dysfunction or fluid backup.”

A major vein in the liver transports de-oxygenated blood back to the heart.

If the liver is malfunctioning, this vein is unable to clear the de-oxygenated blood fast enough – leading to the fluid backup which can extend into a leg.

At this point, the stomach, too, may be carrying excess fluid. The person with advanced colon cancer may notice a growing belly (despite no increase in food intake) along with the mysterious pain in their leg.

“In the United States, approximately 20 percent of patients may have colon cancer metastasis at the time of diagnosis, which means the cancer spreads to other organs, bones, lymph nodes or the bloodstream,” continues Dr. Levy.

“The most common places where colon cancer spreads include the liver, lungs, the lining of the abdomen and bones.”

If a bone in a leg is affected by metastasis, this can be another mechanism of pain from colon cancer.

A third mechanism could be a metastasis pressing against the sciatic nerve (which runs down the leg) or against another spinal nerve that leads to the leg.

  • The primary tumor, located inside the colon, would not be causing the leg pain.
  • It is the spread of the original mass that would, in the mechanisms just described.

“If colon cancer spreads to the bone, it may weaken the bone strength, cause pain, constipation, nausea, poor appetite and numbness,” says Dr. Levy.

“For these reasons and many more, routine colon cancer screenings are incredibly important.”

If your only symptom is leg pain (with or without numbness or tingling), and it’s truly your only new symptom (e.g., bowel habits and appearance have always been normal) – then chances are very unlikely that colon cancer is the cause.

Dr. Levy’s research and clinical projects have focused on health care disparities, GERD, the early detection of pancreatic cancer and the development of colon cancer screening campaigns.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.