This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': "Penile angiography is reliable only after intracavernosal injection of vasoactive substances. All are indications for penile angiography, EXCEPT: \nSelect and explain. \nA. Painful priapism, B. Peyronie's disease, C. Erectile dysfunction, D. Aeriovenous malformation", 'role': 'user'}, {'content': "Answer: A \nExplanation: Priapism is a prolonged, unwanted erection not associated with sexual stimulation. It is classified as low-flow (venous) and high-flow (aerial) priapism. Doppler US can distinguish the type of priapism, with low-flow priapism showing decreased or no blood flow in the cavernosal aeries. The most reliable method, however, involves testing aspirated blood from the corpus cavernosum for blood gas analysis. Ref: Liu D.R. (2011). Chapter 127. Urologic and Gynecologic Problems and Procedures in Children. In J.E. Tintinalli, J.S. Stapczynski, D.M. Cline, O.J. Ma, R.K. Cydulka, G.D. Meckler (Eds), Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e.", 'role': 'assistant'}]