If this is from the vent area it may be a cloacal or rectal prolapse.
You can read about this here
http://www.ahc.umn.edu/rar/MNAALAS/Snakes.html
where it says
" A prolapse occurs when an organ inverts itself inside out and protrudes through the usual external opening of that organ. Prolapses of the cloaca and reproductive organs are not uncommon among captive snakes. Often the cause cannot be determined. Prolapses can be precipitated by straining during egg-laying or straining related to uric acid stones. Parasitic infections or other intestinal disease may also result in prolapses. Veterinary assistance is essential in these cases to treat the prolapse and determine the underlying cause, if possible."
Hope this helps you!
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