A man posing as a doctor was exposed after telling a patient her gallbladder was in good condition – even though it had already been removed.
Wellington Augusto Mazini Silva set off alarm bells during an ultrasound when he made the claim.
The patient reported the incident to the Director of Public Health, who contacted the police.
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Silva, 28, was arrested on Wednesday (7 Jan).
Police discovered he had been using the medical registration of a partner in a clinic in São Paulo, Brazil.
The real doctor had been properly hired by the company managing the local health service in Cananéia, São Paulo state.
Silva, who presents himself as a medical student on social media, was also found with prescription pads from other clinics, police said.

When questioned, he insisted he was a doctor and claimed he expected to receive 2,000 BRL (£277) for his services.
He produced another registration number, which belonged to a second doctor, and officers also found a medical stamp belonging to a third.
His name does not appear anywhere in the São Paulo state medical registry, as reported by Need To Know.
Police said Silva had raised concerns with other patients, including telling a man he did not have fatty liver disease, despite being under treatment for it.
Others said reports he issued were copied from other documents.
Following a court hearing, Silva was remanded in custody. His lawyer said he will appeal the decision and prove his client’s innocence at trial.
The Cananéia City Council said: “It should be emphasised that the individual acted for only one day and used his own equipment.

“While ultrasound is a low-risk procedure, practising without the proper legal qualifications constitutes a serious ethical and legal breach.
“In line with the precautionary principle and to ensure patient safety, the City Council assures that no patient will be adversely affected.
“All those who underwent examinations on Tuesday, 6 January, are being recalled to repeat their tests on Tuesday, 13 January.
“This guarantees both accurate diagnoses and the continued provision of care with quality and safety.”
Silva is accused of practising medicine without a licence, using false documents, committing fraud to gain money or benefit, and acting in a way likely to endanger health.