Many conditions and injuries can cause left-sided low back pain. According to the National Institute of Neurological Disorders and Stroke, low back pain occurs most often among people 30 to 50 years of age. The location of low back pain largely depends on the cause of the problem and the tissues involved.
Muscle Strains
Muscle strains can cause left-sided low back pain. According to the website Sports Injury Clinic, a muscle strain--the partial tearing of muscle fibers--is usually caused by a sudden, unguarded movement or by trying to lift an object that's too heavy. Muscle strains can occur anywhere in the body, including the left-sided low back. One of the most commonly strained low back muscles is the quadratus lumborum muscle or QL.
Pain caused by low back muscle strains, including QL strains, may not manifest immediately after an injury. Instead, pain may develop gradually as the affected muscle or muscles tighten up. Common signs and symptoms associated with a low back muscle strain include sharp pain in the back, swelling or bruising in the affected area and reduced low back active range of motion. Low back muscle strains may be associated with trigger points--hyper-irritable nodules or knots within a tight band of muscle.
Left-sided Colitis
Left-sided colitis can cause low back pain on the left side. MayoClinic.com states that left-sided colitis is a type of ulcerative colitis. Ulcerative colitis is an inflammatory bowel disease that causes long-term inflammation of the digestive tract. The most common symptoms associated with ulcerative colitis are abdominal pain and diarrhea.
Ulcerative colitis can significantly affect a person's quality of life. In some cases, ulcerative colitis can progress, causing life-threatening complications. Along with left-sided colitis, ulcerative proctitis, proctosigmoiditis, pancolitis and fulminant colitis are forms of ulcerative colitis. Left-sided colitis is characterized by inflammation in the rectum, sigmoid colon and descending colon, which are all located on the left side of the body. Common signs and symptoms associated with left-sided colitis include pain on the left side and back, abdominal cramping, bloody stools and unexplained weight loss.
Kidney Stones
Kidney stones can cause left-sided low back pain. According to the National Institute of Diabetes and Digestive and Kidney Diseases, kidney stones are hard masses that form within the kidneys--two bean-shaped organs situated just below the ribs, toward the middle of the back. Kidney stones are made of crystals that separate from urine.
MayoClinic.com states that, although many stones pass undetected through the urinary system, some kidney stones can cause excruciating back, flank and groin pain. Common signs and symptoms associated with kidney stones include severe back and side pain, pain that shifts locations over time, pain on urination, bloody urine, nausea and vomiting, an ongoing urge to void the bladder and fever and chills if an infection is present. According to the NIDDK, the number of Americans with kidney stones has been increasing during the past 30 years.
