The examination was conducted by Dr Nat Cary, one of the UK's leading forensic pathologists, at Queen's Hospital in Romford, Dr Shah Abbas Khan's family said in a statement.
Assistance was provided by Scotland Yard's counter-terrorism command to enable the post-mortem to be conducted "as effectively as possible", the statement said.
"The coroner, with the family's consent, agreed upon this sensible course of action," it added.
It is not expected that the findings will be made public until they have been considered by the coroner.
His relatives have said he was the victim of a political murder, but the Syrian government said he committed suicide.
British Prime Minister David Cameron has called for those responsible for the death of the surgeon while in custody in Syria to be held to account.
He wrote a condolence letter to Dr Khan's mother Fatima on Friday, describing her son's death as an "appalling tragedy".
The letter reads: "Abbas' death is a sickening and appalling tragedy and it is right that the Syrian regime should answer for it.
The doctor working at the Royal National Orthopaedic Hospital (RNOH) in north-west London had entered Syria without a visa after bring moved by the plight of refugees and worked in camps in Turkey, his family said.
