Surgeons in the United Kingdom have reattached a man's penis nearly a day after it was cut off, the longest documented time the organ has been without a blood supply and still successfully replanted.

Six weeks after the operation, the young man's urethra was not only working once again, sensation had also returned to his penis. Thanks to a carefully reattached artery and vein, the patient was even able to achieve a full erection.

"The success of this case therefore should encourage surgeons to attempt penile replantation, even with prolonged ischaemia [loss of blood supply] time, due to possible success and the potential physical and psychosocial effects of organ loss for the patient," write surgeons from the University Hospitals Birmingham NHS Foundation Trust.

Penile reattachment, or replantation, is rare - only a hundred or so have been recorded in the medical literature. But when amputations occur, it's important to move quickly to give the replanted tissue the best chance of survival.

Successful reattachment is an emergency procedure that requires intricate microsurgery, with specialist input from urological and plastic surgeons, as soon as possible.

Unfortunately, treatment is often delayed, as few doctors are familiar with what to do and the emergency is not well documented in the literature.

A medical case reported more than two decades ago describes a 4-year-old's penis being successfully reattached 18 hours after the initial injury. Generally, after a day of being separated, the success rates of replantation are very low.

Surgeons in Birmingham just barely made it under the 24-hour mark. Their patient was a 34-year-old man with a history of paranoid schizophrenia who had tried to take his own life during a psychotic episode.

Discovered 15 hours later, the patient was immediately taken to hospital where he was resuscitated and wheeled to the operation room.

Major blood vessels running along the top of the penis were quickly identified, and found to be in working order; linking the vein back up required grafts from an arm vein. Unfortunately, one of the major severed nerves had retreated too far back to be reconnected, but the reconnected vessels returned blood to the penile tissue in the nick of time.

"Arterial flow was established a further 8 hours after arrival into hospital due to the patient's concomitant injuries, thus making the total ischaemia time 23 hours," the case report reads.

In the past, surgeons confronted with a total penile amputation would re-suture the structures without repairing the vessels or the dorsal nerve. Today, however, we know that this might lead to a failure of sensory recovery and scarring in the urethra.

Microsurgical replantation has improved a lot, to the point where many patients can once again achieve erections, but there's still plenty of issues we can improve on, and not only surgically.

Follow-up care is also hugely important, given that the vast majority of genital self-mutilations are penile amputations. Acute schizophrenic attacks are commonly associated, and there are various accounts of microsurgical replants of the penis among these patients in particular.

"These reports have noted the need for prolonged follow-up not only to assess the results of replantation, but also to identify those patients who are prone to re-inflict such injuries again," the authors of a 2013 analysis conclude.

Another long-term case study, published in 2015, argues for an "interdisciplinary approach with the involvement of urology, plastic surgery, endocrinology, and psychiatry."

The authors advise that after resuscitation, amputee patients should be transferred to a treatment centre where such expertise exists. Luckily, the young man in this newest case study arrived at such a hospital straight away.

The study was published in BMJ Case Reports.

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