The man heard a snap, felt his penis become immediately flaccid, and noticed a rush of blood from the tip.

He was rushed to the A&E department of a Boston hospital as he was suffering severe pain, according to a case report in the New England Journal of Medicine.

Doctors found he had torn his tunica albuginea, the watertight and fibrous outer sheath of one of the penis’ inner chambers, the corpus cavernosa.

The corpus cavernosa runs along the length of the penis and is filled with spongy tissue, into which blood flows to create an erection.

The tunica albuginea helps to trap the blood in the corpus cavernosa, maintaining an erection.

The snap had led to a tear in the corpus cavernosa’s sheath, which meant blood leaked out, creating swelling.

It was forced out of his body through the urethra, the tube by which a man passes urine, which is why he saw blood coming out of the end of his penis.

When he arrived at hospital, he was taken straight to the operating room for emergency repair.

In the United States, the majority of cases are the result of traumatic coitus, usually from thrusting an erect penis against the symphysis pubis or perineum. In Japan, only 19% of cases are attributed to sexual intercourse, with the majority of cases reported as the result of masturbation and rolling over in bed onto an erect penis. A majority of the cases in Mediterranean countries are the result of patients kneading and snapping their penis during erection to achieve detumescence. In Iran, only 8% of the cases were attributed to sexual intercourse; the remaining cases were due to self-manipulation and potentially fabricated events, such as a donkey bite to the erect penis, a man falling from a mountain onto his erect penis, and a brick falling onto an erect penis. Other rare reports in the world literature include cases resulting from banging an erect penis against a toilet, masturbating into a cocktail shaker, and placing an erect penis into tight pants. –Rev Urol. 2004 Summer; 6(3): 114-120.