Myles Bradbury admitted 25 offences in September, including sexual assault, voyeurism and possessing more than 16,000 indecent images while working at Addenbrooke's Hospital in Cambridge between 2009 and 2013.
The judge at Cambridge Crown Court told him his offences were a "gross and grotesque breach of trust".
It's also emerged Bradbury, 41, went on a church mission to an African orphanage just days before he abused two young cancer patients.
He travelled with KingsGate Christian Evangelical Church from Peterborough, Cambridgeshire in 2012 to help children whose parents had died from Aids, as part of a 15-strong group that went to Swaziland to help orphaned children in 2012.
However a spokesperson for KingsGate told Premier he only attended the church for a limited time.
In a statement, the church said: "We are shocked and deeply saddened at the actions of Dr Myles Bradbury and at the devastating impact that these have had on the lives of many.
"As soon as the charges against him were revealed in early July 2014 we promptly contacted Bulembu.
"Bulembu then instituted a detailed investigation to make sure that he had not had any one-to-one contact with children during that time.
"They found no evidence that he had any unsupervised involvement with children and was always accompanied by community development project staff."
According to reports Police said they had no evidence to suggest Bradbury offended on the trip to Bulembu but others on the team confirmed he was left alone with the orphans.
Each volunteer was allowed to be alone with up to six children in the afternoons for two to three hours, they said.
Bulembu Ministries, Swaziland has also claimed it was "confident" none of the children in their care had been abused by Dr Bradbury.
A statement seen by Premier said: "As an organization dedicated to the welfare of children, Bulembu is both saddened and sickened by the admissions of Dr Bradbury. Saddened for his vulnerable victims and their families and sickened at his ultimate betrayal of trust.
"Bulembu has stringent protocols in place which limit the potential for this kind of predatory behaviour. After extensive investigations we are confident that similar atrocities were not perpetrated by Dr Bradbury against any children in our care.
"Due to the nature of our work, we have to view every visitor with some caution, not granting freedom nor access to the children. Therefore, our policy on interaction and supervision is stringent and grows even more stringent, year by year.
"We also work with volunteer teams and team leaders to better assess prospective teams and team members."
