Normally an with steganography adapted file / picture is only dectected by the tool which was used for the stego in the first place.

There are some tools who are able to detect files adapted with other stego-tools. You can try stegdectect ( http://www.outguess.org/detection.php ). It is free.

Also the professional forensics tools like FTK and Encase are capable of detecting steganography. But they are not free of charge!! ha ha

An other alternative is to get yourself a free HEX-editor, load the adapted file (in this case you have to know in front that the file is adapted) and look based on searching for the fileheaders in the file!!

Good luck!