<s>[INST]Hi, GP suspected that my dad might have kidney stone. And he ordered him to get a CT scan done. My question is... is CT scan necessary to detect kidney stone? Would X-Ray and/or ultrasound not be sufficient enough to determine kidney stones existence, position and size?Thank you so much for answering my query[/INST]Hi, Plain CT scan without contrast is the investigation of choice for renal stone disease. Ultrasound is operator dependent and there is a lot of interference form bowel gas and sometimes difficult to localize the stone, and same goes with X-ray too.However, if the symptoms are very obvious to stone disease, ultrasound is preferred for sheer simplicity, economical and lack of radiation exposure. I go with ultrasound and then order for CT if required.</s>