Flow characteristics of urethral catheters of the same caliber vary between manufacturers

BACKGROUND

Clean intermittent catheterization (CIC) is frequently prescribed for bladder dysfunction, either per urethra or via a continent catheterizable channel. Small catheters may be required for infants or continent channels. Success with CIC is highly dependent upon patient and family compliance. The urinary flow rate through the catheter is an important factor, which can decrease CIC time and improve quality of life. There is little objective information regarding flow rate through urinary catheters to guide catheter recommendation or prescription. Clinically, we noted that there was a difference in flow among catheter brands, and we questioned if catheters of the same-labeled diameter exhibit the same flow characteristics, which could have implications for catheter selection.

METHODS

Twenty-one commercially available male pediatric urinary catheters from nine brands were tested (11 straight tip, 10 coude tip). Nine of the 21 tested catheters had a hydrophilic coating. All tested catheters shared a 10F outer diameter. For each, microscopic imaging and a precision caliper were used to measure the inner diameter and tip inlet area. A hydraulic system modified from ASTM standard testing specifications was used to simulate bladder catheterization. Measurement of each catheter was repeated five times using three different static hydraulic pressures (20, 40 and 50 cmH₂O). Catheter flow rate and structural measurements were identified and the fastest and slowest of the catheters are presented in the table. The variable flow rates between brands were due to the differences in catheter structural characteristics such as the inner diameter (ID) and the tip inlet area to inner lumen area ratio (AR). The maximum variation of flow rate of all tested 10F catheters was 48%, ID varied up to 22%, from 1.71 to 2.11 mm or 5.13-6.33F. AR varied up to 166%. The table delineates the fastest and slowest rates at three measured pressures. The outer diameter labeled 10F on packaging was true to size.

CONCLUSIONS

Based on packaging information, providers, and patients are unable to predict urinary flow through a catheter and thus use information regarding flow rate to guide catheter selection. This information cannot be calculated based on ideal flow calculations and could be listed on packaging to assist physicians and families in selecting the optimal urinary catheter for CIC.

Free voiding patterns in preterm and full-term newborn infants are different between males and females

AIM

The neonatal period is critical in bladder development, encompassing the transition from foetal bladder contractions to voluntary infant urination. The aim of this study was to investigate different voiding parameters between male and female newborn infants.

METHODS

We studied 102 healthy, single birth newborn infants - 54 preterm and 48 full-term - without lower urinary tract diseases, hospitalised in the neonatal intensive care unit from March 2011 to March 2012. Free voiding was observed from 9 a.m. to 9 p.m., and the free voiding parameters and fluid intake were recorded and compared between male and female newborn infants using the Student's t-test and chi-square test.

RESULTS

Male preterm newborns demonstrated larger mean postvoid residual volumes and lower bladder emptying rates than female preterm newborns (p < 0.05), and male full-term newborns had lower bladder emptying rates than female full-term newborns (p < 0.05). The bladder emptying rates of newborns defecating simultaneously with voiding were not statistically different between males and females of the same gestational age (p > 0.05).

CONCLUSION

Male newborns were more likely to have larger postvoid residual volumes than females, and defecating simultaneously with voiding may promote bladder emptying in male newborns.