I went to Nepal via abu dhabi 3 months ago...u won't need a transit visa, but u'll have to stay within the airport even if u have a long transit...mine was 17 hours and i spent it hanging around in the lobby and shopping in the duty free stores...it wasn't bad...if u have a long transit, i highly recommend you to ask your travel agent to reserve a room for u at the airport hotel...they can provide u with room and meal free of cost provided that your travel agent makes a reservation for u early enough...hope this helps.