D

If the balloon cannot be deflated by routine means, the safest next step is to puncture the balloon under imaging so that fragments are not left behind; ultrasound-guided transabdominal, transrectal or transperineal needle puncture is well-described and avoids the chemical or over-distension injuries associated with the other options [St Luce, 2005, PMID 15882746; Kumar, 2014, PMID 24395871].