Pulsing under right rib cage ?

Transmission: Normally one can perceive the pulse transmitted from the great vessels or heart in areas of the abdomen, chest or neck. Depends on body habitus. If impressive, have your doctor take a look at it. Vascular abnormalities can also present as pulsatile masses. A thorough exam aided by ct scans, mris, or ultrasounds can help determining the cause.

Need attention: When you say under rib you mean upper abdomen? You need to be examined.