Hi Mr IK ! Left nephrolithiasis with obstructive nephropathy means a stone in the urinary system may be in the pelvicalyceal system obstructing the flow of urine resulting in swelling of the drainage system of the urine. This might have caused pain in your left side kidney area for which you might have gone for an ultrasound. This is not a major problem as it is curable with some intervention by a qualified urologist. However, it should not be left untreated, as back pressure due to the obstruction of the urine outflow may cause damage to the kidney, and might land up in destruction of the kidney tissue. If it occurs in both kidneys, then renal failure may occur. I would advise you to consult a Urologist in your area at the earliest possible, and go as per his advice. Thanks and good luck.