There are 12 words that start with 'ureth'.
| urethan | urethra | 
| urethane | urethans | 
| urethrae | urethral | 
| urethras | urethanes | 
| urethritis | urethritises | 
| urethroscope | urethroscopes | 
Note: These 12 words that start with 'ureth' are found from the USA & Canada version of the tournament Scrabble word list.