<prompt> Most common investigation done for obstructive jaundiceCT scanUSGX-RayERCP  <response>: B i.e. Ultrasonography - USG is most sensitive in detecting gall stone is the first screening method and investigation of choice for gall stone obstructive jaundiceQ. - Most common cause of obstructive jaundice is stone in gall bladder or CBD. And the stones are best visualized by USG. Other advantage of USG is that its a noninvasive cheap procedure, easily available every where. - If asked obstructive jaundice dt tumours condition, then investigation of choice will be CT Scan. Though CT Scan may yield similar information, is more expensive and is not good as ultrasound when the stones are concerned. 