Sir.—We read with interest the letter by Choi et al in the May issue of the Journal (131:595, 1977) describing
Bubble of fluid in catheter (arrow). Suture was originally tied at this position. two neonates with broken umbilical arterial catheters. We recently encountered a catheter that began to leak fluid at the point of a tightly tied suture. Oftentimes there will be leakage before the catheter completely breaks, and careful observation may prevent a serious complication. The Figure demonstrates a bubble of fluid. Originally, the suture was tied at this position.