Never trust a plastic surgeon from a hardware store
"In 2009, there was a patient presented to the emergency room in Rhode Island. She had had some form of 'HydroGel' (she called it that) injected in large volume, approximately 2 liters (which is a very large quantity), one into each buttock. I believe by 'HydroGel,' she meant some sort of silicone-based product like silicone bathroom caulk. The patient said that she was injected by someone in Miami who claimed to be a nurse, and who performed the procedure in their home.
"When she came to the ER, she had a high fever and was draining pus on both buttocks, which were red, swollen, painful, and infected. We took her to the operating room, and because the external substance was so integrated into the tissue within and around the fat cells, we had to make multiple large incisions on both buttocks' fat. Afterwards, her buttocks looked like she had been attacked by a bear. The only way to get rid of the infection was to fully remove the external substance. We left the incisions opened and packed them with gauze.