Overview 21g olive tipped needles are perfect for flushing of the small male feline urethra in cases of obstructive FLUTD. The blunt tip prevents trauma to the sensitive urethral lining. Rather than forcing struvite plugs back into the bladder with saline, it is suggested that J0153w Walpole’s solution is infused to dissolve away any crystal formation. Then a J0153 series Jackson catheter is inserted to ensure urethral patency.