Allen's test is for the patency of:

Allen's test is for the patency of: Radial and ulnar aery> ulnar aery> radial aery In the modified Allen test, one hand is examined at a time: The hand is elevated and the patient is asked to clench their fist for about 30 seconds. Pressure is applied over the ulnar and the radial aeries so as to occlude both of them. Still elevated, the hand is then opened. It should appear blanched (pallor may be observed at the finger nails). Ulnar pressure is released while radial pressure is maintained, and the colour should return within 5 to 15 seconds. If color returns as described, Allen's test is considered to be normal. If color fails to return, the test is considered abnormal - suggests that the ulnar aery supply to the hand is not sufficient- indicates, it may not be safe to cannulate or needle the radial aery.