Novel patterns for the growing main bronchi in the human fetus: an anatomical, digital and statistical study

Abstract

PurposeIntensive progress in prenatal medicine results in performing airway management in the fetus affected by life-threatening congenital malformations. This study aimed to examine age-specific reference intervals and growth dynamics for length, proximal and distal external transverse diameters, and projection surface areas of the two main bronchi at varying gestational ages, including their relative growth in length and projection surface area.Materials and methodsUsing anatomical dissection, digital image analysis and statistics, length, proximal and distal external transverse diameters, and projection surface areas of the right and left main bronchi were examined in 73 human fetuses (39 males, 34 females) aged 14–25 weeks, derived from spontaneous abortions and stillbirths.ResultsStatistical analysis showed no sex differences. Between the 14 and 25th week of gestation, the lengths of the right and left main bronchi increased from 1.43 ± 0.18 to 3.18 ± 0.39 mm, and from 2.97 ± 0.16 to 7.58 ± 1.95 mm, in accordance with the functions: , respectively. The proximal external transverse diameters of the right and left main bronchi varied from 2.13 ± 0.41 to 4.24 ± 0.20 mm, and from 1.84 ± 0.06 to 3.67 ± 0.66 mm, following the logarithmic models: , respectively. The distal external transverse diameter rose from 2.09 ± 0.47 to 4.24 ± 0.20 mm, as for the right main bronchus, and from 1.85 ± 0.04 to 3.67 ± 0.66 mm, like for the left one. On either side, there were no statistically significant differences between values of the proximal and distal transverse diameters of the main bronchus. The projection surface areas of the right and left main bronchi ranged from 2.95 ± 0.19 to 13.34 ± 2.12 mm2, and from 5.57 ± 0.21 to 28.52 ± 5.24 mm2, as and . The two main bronchi revealed a proportionate increase in both length and projection surface area, since the right-to-left bronchial length ratio and the right-to-left bronchial projection surface area ratio were stable, 0.41 ± 0.07 and 0.47 ± 0.08, respectively, throughout the analyzed period.ConclusionsThe main bronchi show no sex differences. The right and left main bronchi grow logarithmically in length and external transverse diameter, and linearly in projection surface area. The right and left main bronchi evolve proportionately, with the right-to-left bronchial ratios of 0.41 ± 0.07 for length, and 0.47 ± 0.08 for projection surface area.

Quantitative anatomy of the liver visceral surface in the human fetus

“…According to the professional literature, shrinkage in formalin did not exceed 1% with reference to any linear dimension of the liver. [18][19][20][21][22][23][24][25][26][27] Furthermore, the size of the liver in situ was virtually unfettered by formalin solution, since some liver linear dimensions, i.e., height, as well as transverse and sagittal diameters, achieved in the present series, accurately corresponded with those obtained by Chang et al, when measuring in utero fetuses of the same age with the use of 3D-ultrasound. 3 Thirdly, in order to measure the liver parameters, an optimized digital image system (NIS-Elements AR 3.0.; Nikon) was used.…”

“…Fetal age determination was based on the crown-rump length (CRL), known date of the 1 st day of the maternal menstrual period, and the 5 fetal anthropometric measurements (head circumference, bi-parietal diameter, occipitofrontal diameter, abdominal circumference, and femur length) assessed by early 2 nd trimester ultrasound scans. [18][19][20][21][22][23][24][25][26] As a prerequisite, we excluded fetuses with chromosomal abnormalities or intrauterine growth restriction, as well as from multiple pregnancies, from diabetic mothers and those with severe infections.…”

Z scores of the fetal trachea and bronchial dimension

“…The diameter of the RPB was slightly larger than that of the LPB throughout pregnancy, which is in accordance with observations in fetal autopsy examinations. 5 Although the fetal trachea diameter has been reported previously, 6 The visualization of trachea and main bronchi in our study was much higher than those in previous studies 6,7 in late of 1990s narrowing and shortening of the main stem/lobar bronchi on the affected side. Experimental CDH rat models 10 using nitrofen showed tracheal narrowing, tracheal ring number decrease, and the presence of fragmented tracheal rings.…”

“…Between gestational weeks 20 and 40, the inner diameters of the LPB and RPB increased from 0.8 to 2.2 mm and 0.9 to 2.3 mm, respectively. The diameter of the RPB was slightly larger than that of the LPB throughout pregnancy, which is in accordance with observations in fetal autopsy examinations . Although the fetal trachea diameter has been reported previously, those findings were based on a small number of cases.…”

Quantitative Anatomy of the Growing Lungs in the Human Fetus

“…Advances in perinatal medicine result in the early recognition and prompt implementation of corrective procedures in the fetus with life-threatening congenital malformations of the respiratory system [ 16 ]. As a prerequisite, a widespread understanding of fetal quantitative anatomy is clearly required so as to produce both normative and pathological criteria adapted to fetal and neonatal respiratory structures [ 9 , 17 ]. Thus, the current research refers to morphometric analysis of the fetal lungs, providing the existing medical literature with innovative quantitative data.…”