<prompt> For doing CABG , Allen;s test is done to test which artery -UlnarRadial arteryAnt interosseousPostinterosseous  <response>: Ans. is a i.e.. Ulnar artery Ref: Schwartz 9the p. 636; Sabiston 18the p. 1813; o Allens test is used to assess collateral circulation in hand. In Allens test, the radial artery is occluded by pressure over it at the wrist, for several minutes and the color of hand is compared with other hand. This is the first step and it indicates the presence of circulation through ulnar artery. In step 2, the ulnar artery is occluded similarly at wrist and colour compared with other hand and this gives an indication about circulation through radial artery. Since Radial artery is harvested for CABG as a conduit; patency of ulnar artery should be tested beforehand by Allens test. 