Gender Specific Chronological and Morphometric Assessment of Fetal Bladder Wall Development

Morphology of the fetal renal pelvis during the second trimester: Comparing genders

OBJECTIVES

Many studies of neonates have shown that renal pelvis ectasia is more common in boys. The aim of this study was to determine whether there are structural differences in the renal pelvis between male and female fetuses in the second trimester of gestation.

MATERIAL AND METHODS

We studied 34 renal pelvises obtained from 34 human fetuses (17 males and 17 females), ranging in age from 13 to 23 weeks postconception. The renal pelvis tissue was stained with Masson's trichrome to quantify connective and smooth muscle cells (SMC). The tissue also was fixed for scanning electron microscopy (SEM) in a modified Karnovsky solution. The images were captured with an Olympus BX51 microscope and Olympus DP70 camera. The stereological analysis was done with the Image-Pro and ImageJ programs, using a grid to determine volumetric densities (Vv). Means were statistically compared using simple linear correlation and the Mann-Whitney test (p<0.05).

RESULTS

Quantitative analysis indicated differences (p=0.0275) in Vv of connective tissue in male renal pelvises (mean=55.3%) compared to female ones (mean=51.46%). Quantitative analysis indicated a significant difference (p=0.0002) in SMC in male renal pelvises (mean=12.57%) compared to female ones (mean=16.22%). When we compared the SMC at different ages, we did not find any correlation in male (r²=0.2657, p=0.3027) or female fetuses (r²=0.3798, p=0.1326). When we compared the connective tissue at different ages, we did not find any correlation in female fetuses (r²=0.3798, p=0.2870), but we did observe a positive correlation between the connective tissue and age in male fetuses (r²=0.8308, p<0.0001). SEM showed that the collagen fibers had no differences between male and female.

CONCLUSION

The renal pelvis presents significant structural differences between male and female fetuses. The renal pelvis in males had less SMC and presented a positive correlation of connective tissue with age and the renal pelvis in female had less connective tissue without correlation with the age.

LEVEL OF EVIDENCE

III.

Morphology of the fetal bladder during the second trimester: comparing genders

OBJECTIVES

The aim of the present study was to determine, by histological and stereological analysis, whether there are between-gender structural differences in the bladder in the second gestational trimester in human fetuses.

MATERIAL AND METHODS

Forty bladders, which were obtained from 40 human fetuses (20 males and 20 females) ranging in age from 13 to 23 weeks post-conception (WPC), were studied. The fetuses were macroscopically well preserved, without anomalies of the urinary and genital systems; the cases with syndromes were abandoned. The bladders were dissected and embedded in paraffin, from which 5-μm thick sections were obtained and stained with: Masson's trichrome, to quantify connective and smooth muscle tissue; Weigert's resorcin fuchsin, to observe elastic fibers; picrosirius red with polarization, to observe collagen; and anti-beta III tubulin antibody, to observe the bladder nerves. The images were captured with an Olympus BX51 microscope and Olympus DP70 camera. The stereological analysis was performed with the Image Pro and Image J programs, using a grid to determine volumetric densities (Vv). Means were statistically compared using simple linear regression and the paired t-test (P<0.05).

RESULTS

The fetuses weighed between 60 and 490 g, and had crown-rump lengths between 9.5 and 20.4 cm. No elastic system fibers were observed in any bladders. Quantitative analysis indicated no differences in the Vv of the smooth muscle cells in the male bladders (26.19-50.16%; mean=35.66%) compared to the female ones (30.60-45.63%; mean=38.73%) (P=0.740) and there were also no differences in the Vv of the connective tissue in females (40.52-60.40%; mean=50.69%) and males (38.84-70.16%; mean=57.04%) (P=0.0506). There were no differences observed in the distribution of the nerves and collagen between the genders.

CONCLUSION

The histological analysis of the smooth muscle, collagen, nerves and connective tissue of the developing bladders revealed that there are no gender differences during weeks 13-23 of gestation.

Lower urinary tract function in childhood; normal development and common functional disturbances

This review aims to provide researchers and clinicians involved with the adult lower urinary tract with background knowledge regarding the early development of bladder function and its most common disturbances in childhood. Bladder development begins in weeks 4-6 and the detrusor muscle is formed during weeks 9-12 of gestation. Higher CNS centres are involved in micturition at birth, and the infant usually wakes up, at least briefly, to void. Voiding during the first years of life is often incomplete, owing to detrusor-sphincter dyscoordination, but this disappears when bladder control is attained. Approximately 5-10% of 7-year-old children suffer from daytime incontinence and/or nocturnal enuresis, and a few per cent of them will not outgrow it. Daytime incontinence in childhood is usually attributable to detrusor overactivity, although it is unclear to what extent it is the detrusor or the micturition reflex per se that is overactive. Enuresis - nocturnal incontinence - is caused by either nocturnal polyuria and/or nocturnal detrusor overactivity, in both cases combined with high arousal thresholds. Bladder problems in childhood constitute a risk factor for the development or persistence of bladder problems in adulthood.

[Fetal bladder development. A current overview]

Human fetal bladder development starts in the 9th to 10th week of gestation. Smooth muscle cell formation is induced by Hedgehog proteins and their signaling in the surrounding mesenchyma of the fetal bladder cavity. Bladder wall thickness increases significantly with advancing gestation, mediated by linear growth patterns irrespective of the related sex. lt is the aim of this article to address new insights into bladder development to enhance our knowledge about normal and pathological conditions that occur when developmental processes are disturbed.