Experiencing both lower back pain and diarrhea can be concerning. While these symptoms may occur together, lower back pain does not directly cause diarrhea. Their co-occurrence often indicates an underlying medical condition or a complex interplay of nerve signals. This article clarifies their relationship and identifies common conditions that manifest with both.
Understanding the Lack of Direct Causation
Lower back pain primarily involves the musculoskeletal and nervous systems, stemming from musculoskeletal or nervous system issues. Diarrhea is a digestive symptom characterized by loose, watery stools, indicating a gastrointestinal disturbance. These are distinct physiological processes; a strained back muscle or pinched nerve will not directly trigger intestinal upset. The presence of both symptoms suggests a shared root cause rather than a direct causal link.
Conditions That Cause Both Lower Back Pain and Diarrhea
Several medical conditions can simultaneously present with lower back pain and diarrhea. Inflammatory Bowel Disease (IBD), such as Crohn’s disease or ulcerative colitis, often causes chronic digestive tract inflammation, leading to diarrhea, abdominal pain, and sometimes lower back pain. About one in five people with IBD may also develop enteropathic arthritis, an inflammatory arthritis affecting the spine.
Irritable Bowel Syndrome (IBS) is another common condition characterized by abdominal pain, cramping, bloating, and altered bowel habits, including diarrhea. While the exact cause of IBS-related back pain is not fully understood, it is a common issue. Digestive symptoms like gas pressure and colon spasms can trigger pain that radiates to the lower back.
Gastrointestinal infections, or viral gastroenteritis, involve inflammation of the stomach and intestines. These infections cause watery diarrhea, abdominal cramps, nausea, and vomiting. They can also lead to systemic symptoms like muscle aches, headache, and a low-grade fever, which may be perceived as back pain.
Kidney stones and kidney infections (pyelonephritis) are causes of concurrent back pain and digestive issues. Kidney stones can cause severe, sharp pain in the back and side, radiating to the lower abdomen. While diarrhea is not a direct symptom of kidney stones, severe pain can sometimes lead to nausea and vomiting. Kidney infections, which result from a urinary tract infection spreading to the kidney, can cause sudden lower back pain, fever, chills, and gastrointestinal symptoms like diarrhea, nausea, and vomiting.
Pancreatitis, an inflammation of the pancreas, is another condition causing severe upper abdominal pain radiating to the back. Both acute and chronic pancreatitis can cause digestive issues, including nausea, vomiting, and diarrhea, especially in chronic cases where the pancreas produces fewer digestive enzymes.
In rare cases, certain types of cancer, such as colorectal cancer or pancreatic cancer, can manifest with both lower back pain and changes in bowel habits like diarrhea. For colorectal cancer, back pain usually occurs in later stages, often due to the tumor pressing on nearby structures or spreading to the spine. Pancreatic cancer can cause pain that spreads to the back and changes in stool consistency, including diarrhea. Ectopic pregnancy, where a fertilized egg implants outside the uterus, can cause abdominal and pelvic pain, which may include lower back pain, along with gastrointestinal symptoms like diarrhea.
Referred Pain and Nerve Connections
Referred pain explains why discomfort originating in abdominal or pelvic organs can be felt in the lower back. Visceral pain, which arises from internal organs, is often poorly localized and diffuse. This happens because sensory nerves from internal organs share pathways in the spinal cord with nerves that innervate the skin and muscles of the back. The brain, accustomed to interpreting signals from somatic (body surface) areas, misinterprets visceral pain as originating from more densely innervated somatic regions, such as the lower back.
The close proximity of the lower spine to the digestive and urinary systems also contributes to this perceived connection. For instance, an inflamed colon or an irritated kidney can directly affect adjacent structures or nerve roots, leading to discomfort felt in the back. Conditions like IBS, with symptoms such as gas pressure and colon spasms, can generate pain in the abdomen that radiates to the lower back due to these shared neural pathways.
When to Seek Medical Advice
Given the wide range of potential underlying causes for concurrent lower back pain and diarrhea, seeking professional medical advice is important. A healthcare professional can conduct proper tests to identify the root cause. Seek medical attention if symptoms are severe or worsening, or if accompanied by other concerning signs.
Immediate medical attention is warranted for red flag symptoms including severe or rapidly worsening pain, a high fever or chills, and bloody or black, tarry stools. Other concerning signs are unexplained weight loss, persistent vomiting, and signs of dehydration such as decreased urination or extreme thirst. Neurological symptoms like numbness, tingling, or weakness in the legs, or any loss of bladder or bowel control, also require urgent evaluation.