Media playback is unsupported on your device Media caption Natalie Johnson suffered after she received illegal injections

A growing number of American women are getting plastic surgery to enhance their behinds. But with the costs running into the thousands of dollars, many are choosing cheap, illegal and life-threatening backstreet procedures.

She did it because she thought she'd look better, and be more desirable.

But getting injections for a bigger behind was the biggest mistake Natalie Johnson ever made.

At her home in a Miami suburb, she shows me pictures of her scarred body, bruised and blackened from decaying tissue.

"I didn't need it, I was perfect without it," she says. "I was in a lifestyle where I felt if I had a big old butt, I could make more money."

The pain she has to endure is so severe that it is hard for her to sit down for too long. Johnson relies on her nine-year-old daughter to help with the most basic of tasks.

Johnson was working as an exotic dancer when she met someone claiming to be a doctor who offered to perform a buttocks-enhancement procedure at a fraction of the price of a registered surgeon.

Image caption Johnson says her body deteriorated years after the injection

It did not seem out of the ordinary. Other friends had it done and plenty of young women in Miami desire a larger behind to look like the dancers in music videos, Johnson says.

She says a man named O'Neal Morris came to her house wearing white scrubs - "looking professional" - and injected a substance into her behind using plastic syringe.

At first the results were good: a firmer, rounder rear, bringing her closer to her goal of a "Coca-Cola bottle-shaped body".

She had two more rounds of treatment. Soon after, the problems began.

"It started making me really, really sick. I noticed it was starting to disintegrate and my butt turned wrinkly," she says.

Bottom's up

Surgical attention to the backside is on the rise. In 2013:

• 2,438 people got a buttock lift, an 80% increase over 2000.

• 7,281 people received a "lower body lift", which includes shaping the buttocks, thighs, hips and abdomen. That represents 3,417% increase over 2000 and the biggest growth measured by the American Society of Plastic Surgeons.

• 942 people got buttock implants, compared with 858 in 2012. Rates were not measured in 2000.

• 9,993 people in the US got a buttock augmentation with fat grafting, compared with 8,654 in 2012.

"I was getting dizzy, and feeling fatigued."

On one occasion Johnson was rushed to hospital after she stopped breathing.

Morris began a one-year jail sentence in January for practising medicine without a licence.

Women who came forward during the trial said Morris, who is not a qualified doctor, had injected them with a range of substances including cement, superglue and tyre sealant.

The Federal Bureau of Investigations says the numbers of cases of people posing as fake doctors to perform this kind of treatment are on the rise, especially in Florida, New York, California and Texas.

At his surgery in a Miami suburb, Dr Alberto Gallerani shows me vials containing things he has pulled out of patients' buttocks, including olive oil and super glue.

A certified plastic surgeon, Gallerani has been treating Johnson and hundreds of other women and men who come to him for corrective surgery after botched procedures.

Image caption Dr Gallerani says he suspects shame is keeping more women from coming forward

He shows me photos of what can go wrong. They are too horrific to post online, but in some cases the skin has changed colour and is badly scarred. Other more extreme images show how the body has become severely disfigured.

Gallerani says in many cases the symptoms can take several years to appear.

"What many of the people doing this don't realise is, they're putting a ticking time bomb in their body," he says.

He says he gets 100 calls a week from people asking for help.

Buttocks are an increasing target for surgical enhancement. In 2013, the numbers for this procedure doubled over the previous year, according to the American Association of Aesthetic Plastic Surgeons. It costs thousands of dollars to get it done properly, which is why many women are opting for cheaper, unregulated methods.

Hip-hop culture celebrates a larger rear, and the pressure on women to have a bigger behind is huge, says Tee Ali, a London-based casting agent.

Image caption Claudia Aderotimi died after an injected substance spread to her organs

His client and friend, 20-year-old Claudia Aderotimi, died in 2011 after she flew from London to Philadelphia to get injections from a woman she met online. Doctors believe the illegal silicone shots spread to her organs, killing her. The person accused of administering the procedure is due in court next year.

Ali says Aderotimi believed a bigger behind would help her make it in the music industry.

"When girls go out and one of them has a big rear, she gets all the attention. She'll get everything, free lifts, free drinks," he says. "It's well known, girls with bigger bums have more attention and they have big jobs and they're more in demand."

Ali says young women to whom he has spoken are afraid to discuss the issue openly, and won't admit they might want to get surgery in the first place, which also drives many to underground procedures. He says many women fly to the US to get the injections because they are harder to find in the UK.

Tragically, Aderotimi is not alive to warn others of the dangers, but Johnson believes by sharing her story she can save others from the same fate.

"Stick with what God gave you," she says.

"I tell girls, if it ain't broke don't fix it. You are beautiful the way you are."