A MAN was left unable to pee for four days after a 30-minute kinky spanking session.

The unnamed 61-year-old turned up at hospital covered in red lacerations and bruises across his bum and thighs after being hit more than 1,000 times with a wooden cane and whip.

He told doctors at the Klinikum Stuttgart Hospital in Germany that the BDSM session lasted 30 minutes, and that he was struck while being tied down to a wooden bench.

Medics believe blunt force trauma to his kidneys and a surge of creatine in his bloodstream caused his symptoms, according to the British Medical Journal case report.

The day after his fetish session, the man, who enjoys BDSM on a regular basis, noticed he couldn't pee at all.

Three days later he spotted blood in his urine and went to hospital.

The patient, who consented to share his experience, said: "I have been engaging in bondage and discipline, dominance and submission, sadism and masochism (BDSM) for some seven years now.

"I take part in sessions like the one described in this report roughly once every three months.

"I had observed my urine turned dark red afterwards in the past so I wasn't worried at first, when it happened again this time.

"However, the next day I could not urinate at all, which had never happened before."

The man's GP ran blood tests and phoned later in the day to tell him to go to hospital.

There, medics warned him if the damage to his kidneys was that bad he might have to be put on dialysis - which filters the blood in the place of the kidneys.

"That really scared me," the patient added.

"The whole situation felt strange because I didn't feel ill at all but of course, I realised that something was wrong with my kidneys.

"I had been aware all the time that BDSM can be harmful but this event convinced me to reduce the intensity with which I do it.

"I take joy in BDSM but of course, I do not want any serious harm to occur to me."

Doctors told the man they believe the force of the spanks caused a build up of tension in his muscles.

This caused a rise in creatine levels in his blood.

When muscles tense, more creatine - chemical waste - is produced by the body.

Creatine is then filtered from the blood by the kidneys, and peed out in the urine as a waste product.

But too much creatine can damage the kidney's ability to function.

Doctors also believe abdominal compartment syndrome - caused by too much pressure on the man's tummy - could have played a role in his symptoms.

The doctors noted he had been strapped down "very firmly with the ropes cutting into his back and thighs and his organs being squeezed against the wooden bench".

After four days his kidneys "spontaneously" began to produce normal amounts of urine again - and his creatine levels returned to normal.

Doctors believe this is the first case of acute kidney injury resulting from BDSM.

"As outlined above, the patient reported to have been strapped very fiercely onto a wooden bench, that is, a hard surface," Dr Fabian Echterdiek, who treated the man, said.

"He explained that this position resulted in his organs being squashed vigorously onto the bench.

"We believe that this situation may have led to an intermittent abdominal compartment syndrome with critically reduced kidney perfusion."

They noted auto-erotic activities, like strangulation, are more prevalent in medical literature as they are more likely to result in serious injury or death.