Foley catheter balloon puncture and the risk of free fragment formation.
 The incidence of free fragment formation following balloon puncture or spontaneous bursting was examined in 294 Foley catheters immersed for 48 h in urine.
 The catheters were divided into 3 groups: 100 were inflated to the manufacturer's recommended volume, 100 to twice the volume and 94 to 3 times the recommended volume.
 The catheter balloons were punctured by pricking with a hypodermic needle.
 The overall incidence of free fragment formation was 27.3%.
 For both types of catheter examined, increasing balloon volume was not associated with an increased risk of free fragment formation following puncture.
 However, increasing volume was associated with increased free fragment formation when the balloon burst spontaneously.
 In view of the high risk of free fragment formation, cystoscopy should be performed in all cases of spontaneous catheter balloon rupture or after percutaneous balloon puncture.
