Back pain is usually due to muscle sprains or strains in the lower back, arthritis in the vertebrae, or a slipped disk. In other words, musculoskeletal conditions are the most common causes of back pain.
Diarrhea, on the other hand, is mostly associated with digestive conditions such as stomach flu, IBS, or Crohn’s disease. Rather than causing low back pain around the spine, diarrhea is mostly associated with cramps, discomfort, and pain in the abdomen.
There will be situations when low back pain and diarrhea may overlap short-term. For example, someone with chronic back pain could get stomach flu. In this case, diarrhea will resolve once the infection is gone.
In other cases, someone with digestive problems may get a back injury and experience back pain for a week or two. Again, the back symptoms will improve as the person recovers from the injury. Back pain associated with diarrhea or constipation is also experienced by pregnant women but will improve after delivery.
However, there are people who experience long-term both back pain and diarrhea. Often they go through many tests and investigations, as the underlying condition may be hard to find. Why is that? How are back pain and diarrhea connected, why do some people experience both? Let’s get into more details in this article.
Irritable Bowel Syndrome (IBS)
Affecting up to 20% of the adults in the US, IBS goes often underdiagnosed. Many people experience bloating, abdominal discomfort, diarrhea, and/or constipation yet do not seek medical advice and learn to live with it. Other signs and symptoms suggestive for IBS include clear or white mucus with the stool and bowel movements that feel urgent, difficult to pass, or incomplete. Overall, IBS is mostly characterized by digestive symptoms. Yet, fatigue, joint pains, and back pain- especially at night- are often associated with this condition/
Back pain is extremely common in those with IBS- occurring in 68% -81% of individuals, according to a research paper published in 2004 in the Journal “ Gastroenterology”.In some cases, X-rays studies found degenerative changes of the spine that could explain the back pain. However, researchers believe that the back pain does not come from the pain, but is a “referred” pain from the gut. Unlike many cases of back pain that get worse over time, this back pain tends to mirror the symptoms of IBS- it rarely aggravates over time and somehow correlates with IBS flare-ups.
Inflammatory Bowel Disease (IBD)
Inflammatory bowel diseases (IBD) include Crohn’s disease and ulcerative colitis. Symptoms vary in intensity and include diarrhea (sometimes with blood), abdominal pain, decreased appetite, weight loss, as well as fatigue.
Musculoskeletal conditions- including back pain, arthritis, fibromyalgia are the most common extraintestinal manifestations of IBD. Pain affecting the muscle and joints develops either before or at the same time with digestive symptoms. One study found that smokers, females, and IBD disease activity were independent factors associated with IBD joint/back pain.
Having a body mass index (BMI) over 30 is associated with an increased risk to develop chronic diarrhea, according to research. Dietary factors, inflammation, and changes in gut flora may all play a role. Excess weight is also a well-known risk factor for low back pain. According to an extensive review of multiple studies, being overweight or obese are risk factors for low back pain in men and women. On the other hand, maintaining a healthy body weight helps prevent the development of low back pain.
Side effects from drugs or surgeries
According to the National Institutes of Health, nearly all medicines may cause diarrhea as a side effect. However, antibiotics, antacids, some immunosuppressants and chemo drugs, nonsteroid anti-inflammatory drugs (NSAIDs), and the anti-diabetes drug metformin are more likely to cause diarrhea. This means that it is possible that some individuals get diarrhea due to using NSAIDs like Advil to manage back pain. Another person with diabetes, on metformin, may also get diarrhea due to the diabetes medication.
Drugs can also cause back pain. For example, gabapentin has both diarrhea and back pain listed as potential side effects.
Surgeries on the digestive tract– for example, bariatric surgeries, or other parts of the intestine, liver, or pancreas can lead to chronic diarrhea.
The bottom line
Both issues- back pain and diarrhea should be investigated by the doctor. Your family doctor may refer you to a neurologist, gastroenterologist, or another specialist for further testing. There are other medical conditions that can cause back pain and diarrhea- for example, celiac disease, lactose or other food intolerances, appendicitis (which requires urgent care), kidney infections, pancreatic cancer or other cancers.
Keep a journal and share the details with your doctors. Try to find any triggers for back pain and diarrhea flare-ups. Do they occur at the same time? Notice any relation with the foods you consume, stress levels, recent weight gain, after taking a medication, or changes in the medicine you take. Also notice things that can improve the pain or bowel movements.