Volumetric growth of the lungs in human fetuses: an anatomical, hydrostatic and statistical study

[Preliminary Experimental Study of Establishing a Lung Development Model with Specific Pathogen Free Preterm Pigs]

OBJECTIVE

To determine the best time for conducting cesarean section for the establishment of an animal model of lung development with specific pathogen free (SPF) preterm Bama minipigs under the condition of not making medical interventions such as hyperoxia, mechanical ventilation, or medication.

METHODS

SPF Bama sows at gestational day (GD) 113, GD107, GD104, GD101, and GD98 were selected and cesarean sections were performed. Then, the viability of the preterm piglets were observed. Based on their general data, viability, and paraffin sections stained with hematoxylin and eosin, the best time for performing cesarean section in order to build a SPF preterm pig model of lung development was determined.

RESULTS

Cesarean sections were performed on a total of 7 sows and 55 piglets were delivered, among which 25 were still alive 3 hours after delivery. Seven piglets of GD104 and all piglets of GD107 and GD113 survived, while piglets of GD98 and GD101 all died. The survival rate of piglets of GD104 was 33.33% (7/21). Piglets of GD98 already possessed fully developed physical appearance and lung shape. Piglets from GD104 had better lung expansion and higher density of thin-walled alveoli. The lungs of GD107 piglets were basically fully expanded, and the density of thin-walled alveoli was almost the same as that of normal full-term piglets.

CONCLUSIONS

Findings of this study suggest that SPF preterm piglets of GD104 with no specific pathogen exposure and no medical intervention can be used to establish a SPF preterm pig model of lung development.

Morphometric study of the diaphragmatic surface of the liver in the human fetus

This study aimed to examine age-specific reference intervals and growth dynamics of the best fit for liver dimensions on the diaphragmatic surface of the fetal liver. The research material consisted of 69 human fetuses of both sexes (32♂, 37♀) aged 18–30 weeks. Using methods of anatomical dissection, digital image analysis and statistics, a total of 10 measurements and 2 calculations were performed. No statistical significant differences between sexes were found (p>0.05). The parameters studied displayed growth models that followed natural logarithmic functions. The mean value of the transverse–to–vertical diameter ratio of the liver throughout the analyzed period was 0.71±0.11. The isthmic ratio decreased significantly from 0.81±0.12 in the 18–19th week to 0.62±0.06 in the 26–27th week, and then increased to 0.68±0.11 in the 28–30th week of fetal life (p<0.01). The morphometric parameters of the diaphragmatic surface of the liver present age-specific reference data. No sex differences are found. The transverse–to–vertical diameter ratio supports a proportionate growth of the fetal liver. Quantitative anatomy of the growing liver may be of relevance in both the ultrasound monitoring of the fetal development and the early detection of liver anomalies.

Volumetric Growth of the Liver in the Human Fetus: An Anatomical, Hydrostatic, and Statistical Study

Using anatomical, hydrostatic, and statistical methods, liver volumes were assessed in 69 human fetuses of both sexes aged 18-30 weeks. No sex differences were found. The median of liver volume achieved by hydrostatic measurements increased from 6.57 cm(3) at 18-21 weeks through 14.36 cm(3) at 22-25 weeks to 20.77 cm(3) at 26-30 weeks, according to the following regression: y = -26.95 + 1.74 × age ± Z × (-3.15 + 0.27 × age). The median of liver volume calculated indirectly according to the formula liver volume = 0.55 × liver length × liver transverse diameter × liver sagittal diameter increased from 12.41 cm(3) at 18-21 weeks through 28.21 cm(3) at 22-25 weeks to 49.69 cm(3) at 26-30 weeks. There was a strong relationship (r = 0.91, p < 0.001) between the liver volumes achieved by hydrostatic (x) and indirect (y) methods, expressed by y = -0.05 + 2.16x ± 7.26. The liver volume should be calculated as follows liver volume = 0.26 × liver length × liver transverse diameter × liver sagittal diameter. The age-specific liver volumes are of great relevance in the evaluation of the normal hepatic growth and the early diagnosis of fetal micro- and macrosomias.

Quantitative Anatomy of the Growing Lungs in the Human Fetus

Using anatomical, digital, and statistical methods we examined the three-dimensional growth of the lungs in 67 human fetuses aged 16-25 weeks. The lung dimensions revealed no sex differences. The transverse and sagittal diameters and the base circumference were greater in the right lungs while the lengths of anterior and posterior margins and the lung height were greater in the left lungs. The best-fit curves for all the lung parameters were natural logarithmic models. The transverse-to-sagittal diameter ratio remained stable and averaged 0.56 ± 0.08 and 0.52 ± 0.08 for the right and left lungs, respectively. For the right and left lungs, the transverse diameter-to-height ratio significantly increased from 0.74 ± 0.09 to 0.92 ± 0.08 and from 0.56 ± 0.07 to 0.79 ± 0.09, respectively. The sagittal diameter-to-height ratio significantly increased from 1.41 ± 0.23 to 1.66 ± 0.18 in the right lung, and from 1.27 ± 0.17 to 1.48 ± 0.22 in the left lung. In the fetal lungs, their proportionate increase in transverse and sagittal diameters considerably accelerates with relation to the lung height. The lung dimensions in the fetus are relevant in the evaluation of the normative pulmonary growth and the diagnosis of pulmonary hypoplasia.

Three-dimensional growth dynamics of the liver in the human fetus

Purpose

The fetal liver is indubitably the earliest and the most severely affected organ by abnormal fetal growth. The size of the fetal liver assessed by three-dimensional ultrasonography is indispensable in determining the status of fetal growth, nutrition and maturity, and in the early recognition and monitoring fetal micro- and macrosomias. The aim of the present study was to measure the human fetal liver length, transverse and sagittal diameters to establish their age-specific reference intervals, the 3rd, 10th, 50th, 90th, and 97th smoothed centile curves, and the relative growth of the liver calculated for the 50th centile.

Materials and methods

Using anatomical, digital (NIS-Elements AR 3.0, Nikon) and statistical methods (one-way ANOVA test for paired data and post hoc RIR Tukey test, Shapiro–Wilk test, Fisher’s test, Student’s t test, the Altman-Chitty method), length, transverse and sagittal diameters of the liver for the 3rd, 10th, 50th, 90th, and 97th centiles were assessed in 69 human fetuses of both sexes (32 males and 37 females) aged 18–30 weeks, derived from spontaneous abortions or stillbirths.

Results

No male–female differences (P > 0.05) concerning the three parameters studied were found. During the study period, the fetal liver increased tri-dimensionally: in length from 19.51 ± 1.02 to 39.65 ± 7.05 mm, in transverse diameter from 29.44 ± 3.73 to 53.13 ± 5.31 mm, and in sagittal diameter from 22.97 ± 3.79 to 43.22 ± 5.49 mm. The natural logarithmic models were found to fit the data with gestational age (P < 0.001) in the following five cutoff points: 3rd, 10th, 50th, 90th and 97th centiles. The values of liver parameters in relation to gestational age in weeks were calculated by the following logarithmic regressions: y = −82.778 + 35.752 × ln(age) ± Z × (−2.778 + 0.308 × age) for liver length, y = −123.06 + 52.668 × ln(age) ± Z × (3.156 + 0.049 × age) for liver transverse diameter, and y = −108.94 + 46.052 × ln(age) ± Z × (−0.541 + 0.188 × age) for liver sagittal diameter. For the 50th centile, at the range of 18–30 weeks, the growth rates per week were gradually decreasing from 1.93 to 1.21 mm for length, from 2.85 to 1.79 mm for transverse diameter, and from 2.49 to 1.56 mm for sagittal diameter of the liver (P < 0.05). During the study period both the length-to-transverse diameter ratio and the sagittal-to-transverse diameter ratio of the liver changed little, attaining the values of 0.71 ± 0.11 and 0.87 ± 0.12, respectively.

Conclusions

The fetal liver does not reveal sex differences in its length, transverse and sagittal diameters. The fetal liver length, transverse and sagittal diameters grow logarithmically. The regression equations for the estimation of the mean and standard deviation of liver length, transverse and sagittal diameters allow for calculating any desired centiles according to gestational age. The three-dimensional evolution of the fetal liver follows proportionately. The age-specific reference intervals for evolving liver length, transverse and sagittal diameters constitute the normative values of potential relevance in monitoring normal fetal development and screening for disturbances in fetal growth.