Hi. I had gone through your query. Appendix surgery does not lead to any problem in erection of penis. But due to psychological stress of operation might be affect your sexual functions. Repeat ultrasound is advisable to diagnose any trauma or pressure in abdomen that occurred due to surgery. Penile Doppler to know blood flow and chance of erection with medications etc. erectile problem has many origins 1st is life style stress and busy life style make u fatigue and secondry to this it makes less desire in sex and erectile problems 2nd is relationship free communicative and mutual understanding will help sex is mutual act so try to do mutually and tell your problem to partner this will reduce your anxiety and able to erect easily so stress free lifestyle and mutual communication will help Third is physical health Routine check up and fit physical health is necessary Psychological soundness is must and sun set focus method for erection is very useful Medicines like sildenafil,, tadanafil, tetrafol plus etc Do take advise from doctors Get well soon thank you Take care