Not only should you delete clinical photos from your phone's gallery, but you also need to remove any messages that were used to send the photos.
Delete an SMS/MMS on iOS.
Delete and SMS/MMS on Android.
Unfortunately, on Android messages are not permanently deleted. When files are “deleted” on Android, really all that happens is the operating system labels the disk space that stores the file as free space. The data is still there, and off-the-shelf data recovery tools can easily recover it. What do we do about this? There are numerous free apps in the Google Play Store, Secure Eraser, that will allow you to delete these files properly. Tools like Secure Eraser write over the so-called free space with random data. You should probably install and use a tool like this to remove all “deleted" data.
Another complicating issue is, if you're using an iPhone, SMS messages are being bundled together with iMessage messages (Apple's messaging platform). By default, if you are sending a message from an iPhone to a recipient with an iPhone it is sent through iMessage. That means Apple servers store patient data and it has travelled overseas. You should turn off iMessage if you wish to use SMS for sending patient data.
Turn off iMessage and send via SMS only.
Finally, we also have the issue of messages being stored indefinably on the recipient's device. For this, we don't have a solution other than avoiding sending unencrypted patient data via text message. By sending a photo to a colleague, you are: