The characteristics of the urinary bladder wall in infants during the first 6 months of age

Objectives: to determine by ultrasonograph the normal values of bladder wall thickness in healthy infants in the first 6 months of life and to observe the possible differences between sexes. Patients and Methods: Ultrasonograph screening was performed in 416 healthy term infants (216 males and 200 females) aged between 0.5 and 6 months. Bladder wall thicknesses were analyzed using a Sonoline Prima ultrasound machine with semi convex probe of 5.0 MHz, and linear probe of 7.5 MHz. Results: The mean bladder wall thickness was 2.32 ± 0.542 mm (95% confidence interval: 2.27-2.37). The minimal bladder wall thickness was 1.0 mm, and maximal 4.0 mm, respectively. The average bladder wall thickness was 2.42 ± 0.56 mm in males, and 2.21 ± 0.50 mm in females. We found a statistically significant difference between bladder wall thickness of male and female infants in the first 6 months of life. The bladder wall in the male infants was thicker than in female infants (t=3.97, p=0.00009, p<0.01). Conclusion: These results might be expected because the male urinary bladder needs somewhat higher pressure to expel the urine via the significantly longer and narrower urethra than the bladder in female infants. That relative hyperfunction of the male bladder results in a relatively thicker bladder wall, what contributes to physiologic variances between sexes in infancy.