When various rings are inserted into the penis they first affect the venous return, the arterial blood flow is still normal, the penis distal to the ring swells rapidly, the ring is pushed to the root of the penis, the penis becomes thick at the distal end and small at the proximal end, and the ring is then difficult to withdraw.
With time, the swelling of the penis increases and the pressure on the urethra causes urinary retention. Prolonged entrapment can cause arterial blood flow obstruction leading to penile strangulation and the development of a urinary fistula. Eventually the distal penis becomes necrotic.