Jason didn't want a "Coke can" - that's the nickname for a penis that has been enlarged with so much filler it resembles a stubby drink can. "Some people go really overboard," Jason tells us in Manchester. His procedure increased his girth by 16%, which he and his partner are thrilled about. It gave him a "self-confidence boost," and "everything still functions" as normal, just with "that extra little bit of width."

How many men are doing this? Nobody knows. There's no regulation, no official records, and anyone can start offering the procedure. It's the Wild West of cosmetic enhancements, but instead of tumbleweeds, there are syringes. Penis fillers even sparked a bizarre conspiracy theory at the last Winter Olympics, where male ski jumpers were rumored to be using them to increase the surface area of their suits for longer jumps. Because nothing says "Olympic glory" like a strategically enhanced jumpsuit.

Some men, however, have ended up in A&E with penises turning black and skin "sloughing off" after botched procedures. The British Association of Urological Surgeons has issued warnings. But why do men do it, and what are the risks? We visited a private clinic, met a man who's had it done, and chatted to a surgeon dealing with the consequences when it goes wrong.

Jason, who spoke anonymously, was happy with his length but wanted "a bit more symmetry" and girth for "that nice, balanced look." He spent a year weighing options, ruled out surgery, and chose hyaluronic acid filler because it's temporary and would "eventually just dissolve" if he hated it. He insists he's not motivated by alpha masculinity - "I don't subscribe to 'how big your dick is, is how big of a man you are'" - but rather by shifting expectations of male beauty. "It's not just women that need to keep up, men need to keep up as well," he says. "It's literally just society changing. The way the media portrays everything has a massive impact on everyday life now. You can't actually go anywhere without seeing some picture-perfect somebody."

Clinic websites tap into this insecurity with questions like "are you embarrassed by the size of your penis?" The most common procedure involves injecting hyaluronic acid, the same gel used in lip fillers, which acts as a "moisture magnet." Dr Javed Hussain has been offering penis fillers for over a year at his clinic in Prestwich, Greater Manchester. He trained as a doctor, but legally, no medical training is required to perform these injections. Demand is increasing, with clients ranging from mid-20s to 72 years old.

The procedure involves injecting the filler three times - on the top and sides - through a cannula that enters at the base and travels along the shaft. Costs up to £3,500 for a 10% to 20% girth increase lasting six to nine months. Risks range from minor soreness and bruising to serious infections and damage to vital structures and blood vessels needed for erections. Hussain says he "totally understands" surgeons' concerns, noting that "more and more evidence is growing" and he has an "immediate action plan" with drugs to dissolve filler if things go wrong. He claims he's never needed it, though the BBC can't independently verify that.

But he recalls a patient who came to him after treatment elsewhere that "really gone wrong." The wrong filler had been used, and the "shaft of the penis was starting to become black" as the procedure damaged blood vessels and the skin was dying. The man was sent straight to A&E.

Prof Vaibhav Modgil, an andrologist and consultant urological surgeon for the NHS in Manchester, has seen these men. "When it does happen, it can be devastating," he says. He recalls men with "skin necrosis, where an area of the skin dies off it turns very black and then it sort of sloughs off. So, men will go in thinking, 'Oh, it's gonna be brilliant,' but they might come out actually being even more dissatisfied than when they went in."

Alex, who used a pseudonym, traveled to Germany for a different procedure: surgery to cut the ligament attaching the penis to the pubic bone, plus fat cells harvested and injected into his penis. When he woke up, he was in so much pain he couldn't stand. "I sustained a lot of bruising and all my upper legs turned yellow," he says. "I couldn't walk properly for about a month." He was treated in Modgil's clinic and eventually got the all-clear, but says, "Many people do not get that luxury. I got off lucky." He admits he was "never small in the first place," but society and porn convinced him bigger was "masculine and the best."

Despite no official data, Modgil says online search trends, advertising, and social media suggest numbers are rising. This led the British Association of Urological Surgeons to issue new recommendations against these procedures. "We cannot recommend that any of these procedures should take place because the evidence is so poor," Modgil says. They reviewed 36 studies involving 3,750 men but still couldn't determine the "safety profile." There's a lack of long-term data, and no qualifications are needed to perform the procedure. Modgil says an outright ban is "probably too severe," but the industry "massively needs regulation." He calls for a national registry to record procedures and collect long-term data so men can make informed decisions.

Back in Manchester, Jason is happy with his results and plans to do it again when his fillers wear off. Because why not? It's only his penis.