Low-flow priapism is caused in children mainly due to sickle cell anemia, while in adults it is caused by taking drugs (antidepressants, anabolics, antihypertensives, α-blockers, antipsychotics) and by idiopathic causes (metastatic tumors, hematological diseases, neurological diseases, inflammations). It is characterized by painful erection without swelling and hardness of the glans. The treatment is the bleeding of the cavernosum with various surgical methods within 4 hours of the onset of symptoms because beyond 4 hours the erectile dysfunction becomes permanent.

High-flow priapism is mainly caused by penile or perineal injuries and usually resolves after ejaculation. The damage appears 2-3 weeks after the injury and its treatment is not urgent. Treatment is either conservative or surgical.

References:

http://uroweb.org/guideline/male-sexual-dysfunction/#3

https://www.huanet.gr/wp-content/uploads/2017/12/02_PRIAPISM_Zachariou.pdf