Numerous conditions can cause left flank pain, or pain on the left side of the torso. According to the Clinical Methods website, flank pain is a sensation of pain or distress in the part of the torso between the ribs and the ilia, or hip bones, and the upper abdomen and back. Flank pain is often caused by kidney problems, but can also be due to problems with other tissues and structures.
According to the National Institute of Neurological Disorders and Stroke, or NINDS, shingles is an outbreak of skin rash or blisters that's caused by the varicella-zoster virus--the same virus responsible for chicken pox. MayoClinic.com states that, although shingles can manifest anywhere on the body, it usually appears as a band of blisters that wraps around one side of the torso, from the middle of the back to the sternum or breastbone. Common signs and symptoms associated with shingles include pain, burning, numbness and tingling in the affected area, a red rash that develops several days after the onset of pain, fluid-filled blisters that eventually burst and intense itching. In some cases, a person with shingles may also experience fever and chills, body aches--possibly including left flank pain--headaches and fatigue, according to MayoClinic.com.
The National Institute of Diabetes and Digestive and Kidney Diseases, or NIDDK, states that pyelonephritis, also known as kidney infection, is most commonly caused by bacteria that spread from the bladder to the kidney. Common signs and symptoms associated with pyelonephritis include back, flank and groin pain or discomfort, the urge to urinate, pain or burning with urination, fever, nausea, vomiting, and pus and blood in the urine. In some cases, pyelonephritis can cause serious health complications, such as acute renal failure, irreversible kidney damage and chronic kidney disease. In other cases, kidney infection can spread to the bloodstream, causing a life-threatening condition known as sepsis. A diagnosis of kidney infection is made following a positive urine test in which bacteria and white blood cell formations called casts are identified.
According to MedlinePlus, rib cage pain--including pain on the side of the torso, over the flank--includes any pain or discomfort in the rib area. Two of the most common causes of rib cage pain are fractured or bruised ribs. Symptoms include tenderness over the affected area, decreased trunk active range-of-motion due to pain and trunk muscle spasms, and pleuritic pain, or pain that's associated with deep breathing. A person who sustains a left-sided rib injury should be evaluated by a qualified health care professional for possible lung and spleen damage. In some cases, a chest X-ray may reveal a collapsed or bruised lung. MedlinePlus states that rest and temporary immobilization are helpful in treating rib cage injuries. Other possible treatments include instrument-assisted soft tissue mobilization, cold laser therapy and kinesio taping techniques.