<s>[INST] MY FATHER has a stone of 1.8mm in right kidney, since last few days he is suffering from trenenduos pain,may be b'coz of stone but stone is extremely small.x ray report was normal....which diagnostic test should he opt for confirmation of the cause of pain? [/INST] Hello and welcome to HCM. As an Urologist, i can understand your anxiety.Your father should undergo an a plain CT scan-KUB,or a CT-IVU.A 1.8mm stone is a too tiny,to cause severe pain,as you describe.A CT-IVU is the best single test. It will also show,if the kidney is affected.According to the reports,treatment can be advised.Tell him to drink about 3 liters of fluids daily.He may take analgesic,for pain.If you've any doubts,send the reports to me,as a direct question.Dr.Matthew J. Mangat. </s>