目的:導尿管常在醫療過程被用來引流尿液。但是有時候我們會碰到無法將導尿管前端的水球抽掉的情形。目前已經有很多的方法可以將水球破，但到底是什麼原因道致水球無法被抽除，卻無法得知。回顧整個使用導尿管的過程，我們懷疑是不是因為潤滑用的凝膠阻塞了抽除水球的通道而道致水球無法抽除。材料及方法:我們收集500支導尿管並將之分成三組，第一組的400支16F導尿管，在注水的通道口抹上薄薄一層的凝膠，第二組的70支導尿管則是將1毫升的凝膠注入注水的通道中第三組的30支導尿管則為對照組。然後注入7毫升的蒸餾水打起水球，再將這些導尿管置於生理食鹽水中放置七天之後再將水球抽除。結果:在第一組中，約有32支暫時阻塞，但在我們利用5毫升的生理食鹽水沖洗後，水球仍可被抽除;而在第二組中則有27支出現這種情現;第三組則無此情形發生。在總數500支導尿管中則沒有完全阻塞的情形發生。結論:根據我們實驗的結果，我們仍無法找出水球無法抽除的原因。但是可以推論，凝膠並不是造成水球無法抽除的主因。

Objective: Foley catheters are widely used for urinary diversion. Occasionally we have had the unpleasant experience of difficulty in deflating the catheter balloon, Several methods have been recommended for deflation of a retained Foley catheter, however, there seems to be no definite cause producing this phenomenon. We wondered if the lubricant jelly might be one of the causes for an undeflatable catheter balloon. Materials and Methods: A total of 500 two-way silicon-coated 16-Fr latex Foley catheters with a 10-ml balloon, which were all tested to be easily deflatable, was divided into 3 groups. There were 400 catheters in group I. All orifices of their inflating channels were covered by a thin film of 2%lidocaine jelly (Astra, Japan), and then the balloon was inflated with 7 ml of distilled water. In group II, 70 balloon channels were injected with 1 ml of jelly and then inflated with 7 ml of distilled water. The other 30 catheters which served as the control group (Group III) were inflated with 7ml of distilled water only. All balloons were immersed in normal saline, and were deflated with a 10-ml syringe 7 days later. Results: All balloons in the control group (Group III) deflated smoothly. In group I catheters, 368 deflated smoothly. The remaining 32 catheters were temporarily blocked but deflated after further inflation with 5 ml of distilled water. In group II catheters injected with 1 ml of jelly into the balloon channel, 43 could be deflated smoothly. Temporary undeflation was noted in 27 catheters, but they deflated after irrigation with an additional 5 ml of distilled water. Conclusion: The true cause of undeflatable catheter balloons has still not been identified. However, we suggest that lubricant jelly is not a major cause of undeflatable Foley catheters.