Is Constipation Linked to Back Pain?

Constipation and Back Pain: What’s the Link?

Back pain is typically caused by musculoskeletal issues, but constipation can also contribute to back pain, says gastroenterologist Sameer Berry, MD, a clinical assistant professor of medicine at the NYU Grossman School of Medicine in New York City and the chief medical officer of Oshi Health, which provides multidisciplinary gastrointestinal (GI) healthcare.

The overlap of symptoms may be because of what’s called referred pain, which occurs when pain originating in one part of the body is felt elsewhere.

“It’s the same reason why people with a heart attack can have pain in their arm or their shoulder. Your body’s not good at telling where internal pain exists,” Dr. Berry says.

Because pain signals from the colon enter the spinal cord alongside signals from the lower back and flank, the brain may misinterpret where the discomfort is coming from, says Simon Mathews, MD, a Baltimore-based gastroenterologist and spokesperson for the American Gastroenterological Association, where he chairs the Committee for GI Innovation and Technology.

As stool builds up in the colon, Dr. Mathews says that the stool stretching the walls of the colon can trigger visceral (internal) pain. “The brain sometimes misreads a poorly labeled colon signal as coming from the back. A distended colon can be felt as a dull ache across the low back,” he says.

In more severe cases, chronic or untreated constipation can lead to fecal impaction, which is when dry, hardened stool becomes stuck in the rectum and can’t be passed normally.

“It shows up as abdominal distension, cramping, nausea, loss of appetite. Back or pelvic discomfort can come with it,” he says.

A more likely scenario was documented in a study of more than 1 million people with lower back pain, however. Researchers note that factors such as reduced physical activity and taking constipation-causing medications may help explain why the conditions can occur together.

“Sometimes it’s much more likely that what you’re doing for your low back pain, like the medications and being sedentary, are more likely driving the constipation than the constipation actually driving the back pain,” Berry says.

It’s a vicious cycle, says Joe Betz, a doctor of chiropractic and the president of the International Chiropractors Association, who is based in Boise, Idaho. “Pain can reduce movement, and reduced activity may worsen both spinal stiffness and bowel motility,” he says.

Opioid pain medications are a well-known cause of constipation, while other medications and supplements — including nonsteroidal anti-inflammatory drugs (NSAIDs), drugs that block the neurotransmitter acetylcholine, antidepressants, calcium-channel blockers, antacids, and iron supplements, among others — may also contribute. NSAIDs and opioids in particular are frequently used for lower back pain, while the rest are often taken for other common health concerns.

Dr. Betz says that muscle strain, joint irritation, pelvic dysfunction, and prolonged sitting can also cause lower back, flank or pelvic pain that’s often interpreted as related to the digestive system. “Straining during a bowel movement may aggravate an existing back condition without being its original cause,” he says.

One clue that constipation may be contributing to back pain is that the discomfort builds when bowel movements slow down and eases up after a bowel movement, Mathews says.

Back pain that’s not caused by constipation is more likely to change with movement, posture, lifting, prolonged sitting, or specific physical activities, Betz says.

Mathews says that people can often point to the specific location of musculoskeletal back pain with one finger. But internal organ pain, also called visceral pain, is associated with a vaguer sense of location. “And it is more likely to be associated with GI symptoms like bloating, fullness, gas, and a sense of incomplete emptying,” he says.

If you’re unsure if your back pain is caused by constipation, or if what you’re doing to manage it is causing constipation, speak to your doctor, Berry says.