Spine fractures or arthritis, gastrointestinal disease, shingles, muscle spasms or infection of the spine can cause left flank pain near the kidneys, notes MedlinePlus. Problems that cause pain in a single kidney include cancer, tumors, polycystic kidney disease and hydronephrosis, says Mayo Clinic.
Problems in the back or in other organs are more likely to cause left flank or back pain than the actual left kidney, according to Mayo Clinic. Fever, frequent urination, chills or blood in the urine usually accompanies left flank pain caused by kidneys, explains MedlinePlus.
Urinary tract or kidney infections may also cause left kidney discomfort, states Mayo Clinic. Other more serious problems, such as hardening of arteries supplying blood to the kidney, blood clots in the kidney's veins and hemorrhaging into the kidney, also cause pain.
Although kidney stones may cause kidney pain, usually they are not painful until they travel from the kidneys, notes Mayo Clinic. However, kidney stones can cause hydronephrosis, which occurs when urine backs up into the kidneys, according to the National Kidney Foundation.
Depending on the cause, doctors often treat back, muscle or spine pain in the left flank with nonsteroidal anti-inflammatory drugs and physical therapy. Doctors treat infections affecting the kidney with antibiotics, but severe infections may require fluids and a short hospital stay, explains MedlinePlus.