Not sure if URI is the same as RI, but one of the telltale signs of RI is mucus from the mouth and nose, or mucus bubbles when a snake breathes. You can check for mucus by keeping a snake's head still, then coaxing the mouth to open, then slipping something like a card in there to keep it open. Then you can freely inspect the mouth with relatively less risk. Of course, this is very stressful for the snake involved, so try not to do this for too long.

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