The man, whose name is unknown, was diagnosed with nonischemic priapism — a condition resulting from the inability of blood to exit the penis. His case was detailed in the latest issue of the Journal of Sexual Medicine.

“In our case, most probably, the handheld needle penetrated the penis too deep, creating an arteriovenous fistula,” wrote the study authors from Kermanshah University of Medical Sciences in Kermanshah, Iran. A fistula is a connection between two organs or vessels — in this case an artery and a vein — that normally don’t connect.

“For eight days after tattooing, the penis was painful, and thus there were no erections,” the authors wrote. “After that, the patient noticed longer-than-usual sleep-related erections. This progressed, within a week, to a constantly half-rigid penis, day and night.”

Men are advised to seek medical attention for an erection lasting more than four hours.

During a normal erection, blood rushes into the penis through the arteries to build up pressure and later leaves through the veins. But in nonischemic priapism, blood continues to enter faster than it can leave, causing persistent pressure and a permanent erection. The problem resolves naturally 62 percent of the time, the researchers reported. And when it doesn’t, men have the option of selective arterial embolism — a procedure that blocks the offending artery.

Instead, the Iranian man chose to have a shunt implanted to drain the excess blood, according to the report.

“Predictably, the procedure was unsuccessful,” the authors wrote. “Because of the painless nature of erections, moderately good preservation of erectile function during intercourses, and disappointment with former surgery, the patient has declined to undergo further therapies, and lives with his condition.”

Despite his permanent erection, the man has no regrets over his penis tattoo, according to the report. Nevertheless, the report authors advise against the practice.

“Based on our unique case, we discourage penile tattooing,” they wrote.