Left-sided back pain is typically a result of ordinary pain that happens to manifest on one side of the body. In most cases, there is no specific reason for the pain to be focused on the left side. However, some anatomical differences in internal organs arguably make left-sided back pain more likely than right-sided pain.
The aorta is one example of such asymmetry. The body’s largest artery carries blood from the heart, traveling through the rib cage down the left side of the spine. If the aorta ruptures or tears it can cause left-sided back pain. This is a very rare cause of such pain, just as arterial dissection is a rare complication of chiropractic treatment.
The spleen can be another cause of left-sided back pain as it is located on the left of the body. Pain is usually felt in the upper left abdomen or upper lower back and is typically associated with a feeling of fullness. Pain is often vague and hard to place.
Our gut is mostly symmetrical and intestinal pain is usually felt in the stomach or abdomen, not in the back. Some gastrointestinal issues can cause pain on the left or right side of the body exclusively, however. For example, damage to a section of the gut on one side could create one-sided pain.
Situs inversus – when left-sided back pain gets confusing
One in every 10,000 or so people has a congenital condition called situs inversus (or tranversus or oppositus). In this condition a person’s internal visceral organs are mirrored. This means that the spleen is on the right of the body, the gallbladder is on the left, and so on.
As this condition is rare, a physician will not usually consider left-sided back pain a symptom of appendicitis or gall bladder problems initially. Equally, right-sided back pain is unlikely to be seen as a symptom of problems with the spleen or aorta.
Left-sided back pain is usually simple, ordinary pain that happens to be exclusively on the left of the body. If you have one-sided back pain and any red flag symptoms, such as fever, unexplained weight loss, numbness or weakness in your limbs, or respiratory problems, seek medical assistance. In most other cases, left-sided back pain will usually resolve within a few days with rest and conservative treatment.
For more on asymmetrical causes of back pain, check out this post on right-sided back pain.