Use of ultrasound bladder monitoring in children after caudal anaesthesia

Urinary retention occurring after caudal anaesthesia in children has a low incidence. Most children will void within 12 h of surgery, although the incidence of retention is higher after hypospadias repair. However, overdistention causing bladder atony that is temporary, or may become permanent, is described in adults. Long-term effects of overdistention in children have not been described. Urine volume, used to describe overdistention, is traditionally measured after catheterization. We report two children suffering from urine retention after caudal anaesthesia (bupivacaine 0.25%) was used to supplement a general anaesthetic. Ultrasound bladder monitoring was used to assist with the clinical diagnosis of bladder distension in the postanaesthesia care unit (PACU) and subsequent management. In-out catheterization was required in a 1-year-old-girl with a bladder volume of 12 ml·kg^-1 after external manual compression over the bladder was unable express urine. Spontaneous micturation occurred within the subsequent 8 h. A 10-year-old boy suffered distress in PACU with a bladder volume, measured by ultrasound, of 5 ml·kg^-1. Catheterization relieved distress and spontaneous micturation returned 18 h after surgery. Measured urine volumes were similar to those estimated by ultrasound. Ultrasound bladder monitoring is a simple, noninvasive technique that can be used to assist with the diagnosis and management of urinary retention in children. It may replace catheterization as the prefered technique to measure urine volume. The correlation between measured bladder volumes and urine volume appears reasonable. A volume of approximately 10 mg·kg^-1 may be considered as causing overdistension.