Causes of waist pain in the left side One of the most common causes for the incidence of this condition is an injury when one falls or has an accident, for example, or pulled muscle, which occurs when one lifts heavy things or twists awkwardly, for instance. However, there are also some other conditions that usually lead to the appearance of sharp pain that can be felt in the left side of the waist. These conditions are kidney diseases, irritable bowel syndrome, diverticulitis and ovarian cyst, as well as pregnancy, gastritis, urinary tract infection, ulcer, pancreatitis and pelvic inflammatory disease. Two most common kidney diseases are kidney stones, which are crystal formation of excess uric acid or calcium and bacterial kidney infection that starts in the urethra and reaches the kidneys. These two disorders can cause sharp pain in the lower abdomen that tends to spread to the back. Irritable bowel syndrome is a condition that manifests itself through the constant alternation of constipation and diarrhea, which may cause pain in the left or right side of the waist. Diverticulitis is a medical term for the inflamed diverticula of the colon. One of the symptoms of this condition is the pain that occurs in the left side of the lower abdomen. The benign tumor that forms in the ovary in the form of fluid-filled sac is called ovarian cyst. When a woman suffers from this disorder, she may experience pain in the waist along with many other symptoms that are characteristic for this condition. The pain in the left side of the waist, as well pain in the back are very common in pregnant woman because of the pressure that the body weight makes on the waist region.