Change in the three-dimensional shape of the stomach in the developing human fetus

Fetal Physiologically Based Pharmacokinetic Models: Systems Information on the Growth and Composition of Fetal Organs

BACKGROUND

The growth of fetal organs is a dynamic process involving considerable changes in the anatomical and physiological parameters that can alter fetal exposure to xenobiotics in utero. Physiologically based pharmacokinetic models can be used to predict the fetal exposure as time-varying parameters can easily be incorporated.

OBJECTIVE

The objective of this study was to collate, analyse and integrate the available time-varying parameters needed for the physiologically based pharmacokinetic modelling of xenobiotic kinetics in a fetal population.

METHODS

We performed a comprehensive literature search on the physiological development of fetal organs. Data were carefully assessed, integrated and a meta-analysis was performed to establish growth trends with fetal age and weight. Algorithms and models were generated to describe the growth of these parameter values as functions of age and/or weight.

RESULTS

Fetal physiologically based pharmacokinetic parameters, including the size of the heart, liver, brain, kidneys, lungs, spleen, muscles, pancreas, skin, bones, adrenal and thyroid glands, thymus, gut and gonads were quantified as a function of fetal age and weight. Variability around the means of these parameters at different fetal ages was also reported. The growth of the investigated parameters was not consistent (with respect to direction and monotonicity).

CONCLUSION

Despite the limitations identified in the availability of some values, the data presented in this article provide a unique resource for age-dependent organ size and composition parameters needed for fetal physiologically based pharmacokinetic modelling. This will facilitate the application of physiologically based pharmacokinetic models during drug development and in the risk assessment of environmental chemicals and following maternally administered drugs or unintended exposure to environmental toxicants in this population.

Validation of ultrasound methods to monitor gastric volume changes in preterm infants

OBJECTIVES

The aim of this study was to validate 4 sonographic methods of estimating stomach volume for the purpose of monitoring changes in gastric volume over time and to describe the echogenic characteristics of milk feeds.

METHODS

Twenty-four infants were monitored during a single intragastric tube feed, with 2 ultrasound images of the entire stomach and an image of the antral cross-sectional area (ACSA) before, during, and after the feed. Raw measurements, 3 stomach volume calculations, and ACSA were tested for intra- and interrater agreement. Calculated stomach volumes and ACSA were compared with delivered feed volumes, and characteristics of stomach image echogenicity graded at each time point.

RESULTS

Spheroid calculation of stomach volume was the most reliable and valid measure of stomach volume. Fortified breast milk feeds were more echogenic than unfortified breast milk feeds. Residual stomach volumes (median 2.12 mL, range 0.59-9.27 mL) were identified in 18 of 24 infants.

CONCLUSIONS

Direct ultrasound stomach measurement (spheroid) will provide a useful research tool and a potential clinical tool for assessing gastric emptying and feeding intolerance in preterm infants.

Three-dimensional sonographic volume measurement of the fetal stomach

The objective of this study was to measure the fetal gastric volume using three-dimensional (3-D) ultrasound during pregnancy. Three-dimensional sonographic examinations were performed involving 35 pregnant women from 12 to 38 weeks of gestation. The fetal gastric volume was monitored every 5 min for a minimum of 40 min (40-60 min) in each woman. The rotational technique with Virtual Organ Computer-aided AnaLysis (VOCAL) was used to calculate the fetal gastric volume. Maximum and minimum gastric volumes were curvilinearly associated with the gestational age, respectively (R(2) = 0.611, p < 0.0001, and R(2) = 0.407, p < 0.0001, respectively). A curvilinear relationship was noted between the functional capacity (maximum volume - minimum volume) of the fetal stomach and gestational age (R(2) = 0.531, p < 0.0001). The maximum volume change [(maximum volume - minimum volume/maximum volume) × 100] did not change during pregnancy (mean and standard deviation, 64.1% ± 16.1%). However, gastric emptying cycles could not be determined in this study because of the short observation period and small number of subjects. Our findings suggest that the fetal gastric volume calculated by conventional two-dimensional ultrasound in previous investigations is approximately one-third of the maximum volume using 3-D ultrasound in the present study and that 3-D ultrasound is a superior means of evaluating the fetal gastric volume in utero. However, the data and their interpretation in the present study should be viewed with some degree of caution because of the small number of subjects. Further studies involving a larger sample size are needed to confirm these findings.

Nomogram of the fetal gastric size development in normal pregnancy

OBJECTIVE

To construct an ultrasonographic nomogram of the fetal gastric size with gestational age in normal singleton pregnancy.

PATIENTS AND METHODS

Out of 17 000 outpatient pregnant women who were admitted to our hospital, a total of 250 fetal measurements were randomly collected from routine ultrasonographic examinations performed in women with normal singleton pregnancies between 13 and 39 weeks of gestation without medical or obstetric complications. None of the fetuses had detectable fetal malformations. The ultrasound plane which provided the largest stomach area including the pylorus on a transverse and oblique section was used for definition and measurement of gastric longitudinal dimensions. The transverse section at the center of the gastric corpus was used for transverse and anteroposterior dimensions. Biparietal diameter, abdominal circumference were also measured.

RESULTS

The fetal gastric longitudinal, anteroposterior and transverse dimensions were significantly correlated with gestational age (r values 0.74, 0.71, and 0.49, respectively). There was a significant correlation measurements between gastric size and AC. The correlation coefficents for gastric dimensions with gestational age was larger than those with AC (r=0.732, 0.702 and 0.489, respectively). The ratio of fetal gastric anteroposterior dimension to fetal AC was a constant parameter calculated as 1/3.

CONCLUSION

Fetal stomach dimensions in normal pregnancy correlate with gestational age and nomogram of fetal gastric development appears to be useful in assessment of normal fetal growth.

Three-dimensional morphometry in ultrasound

The clinical use of three-dimensional (3D) ultrasound has rapidly spread to many specialities over the last ten years. The reason is easy to see, namely that single two-dimensional (2D) scans are often difficult to interpret and the mental correlation of multiple 2D scans to form a 3D image of anatomical morphology is taxing and uncertain. The rapid development of techniques for the realtime tracking of the spatial position and orientation of ultrasound probes and the development of computer graphics techniques for the presentation of anatomical images have made 3D ultrasound a realistic diagnostic tool. The authors describe the range of methods of data acquisition and display and provide illustrations of some current clinical applications.

Rhythmic changes in the stomach movement of the human fetus with congenital duodenal obstruction during the third trimester of pregnancy

In order to reveal whether or not rhythmic changes exist in fetal stomach movement (FSM), in utero FSM was assessed in three fetuses between 27 and 33 weeks' gestation with congenital duodenal obstruction. A total of four observations, one each at 27, 29, 31 and 33 weeks' gestation, was obtained. The longitudinal transection of each fetal stomach was continuously observed for 60 min using real-time ultrasound. The configuration and the area of the stomach were analyzed for each 15-s epoch. The complexity of the stomach configuration was quantified and defined as stomach complexity. For each case, the chronological changes of the stomach complexity were analyzed using the least median square of regression. The correlation between changes of the stomach complexity and the area of the stomach was analyzed using the cross-correlation method. (1) For gestational ages of 27, 29, 31 and 33 weeks, the 240 sequential measurements of the stomach complexity were significantly stratified into outlying and non-outlying points. The outlying points were 13.3% (32/240), 30.8% (74/240), 32.9% (79/240) and 36.3% (87/240) of the total observation points, respectively. (2) The percentages in which outlying points lasted 3 min (12 points) or more were 0% (0/240), 5.0% (12/240), 28.3% (68/240) and 30.4% (73/240) of the total observation points, respectively. (3) For each gestational age, no significant time series correlation was found between the stomach complexity and the area of the stomach. These findings suggest that: (1) two different conditions emerge in the FSM, at the latest at 27 weeks' gestation, and begin manifesting from 29 weeks' gestation onwards. (2) These chronological changes cluster into 'active' and 'quiet' phases from 31 weeks' gestation onwards. (3) FSMs are not related to the changes in the stomach area throughout the observation periods. The underlying mechanism of this rhythmicity may represent the development of ultradian rhythm of the stomach movement, generated by the central nervous system.

Three-dimensional ultrasound imaging

The objective of this article is to provide scientists, engineers and clinicians with an up-to-date overview on the current state of development in the area of three-dimensional ultrasound (3-DUS) and to serve as a reference for individuals who wish to learn more about 3-DUS imaging. The sections will review the state of the art with respect to 3-DUS imaging, methods of data acquisition, analysis and display approaches. Clinical sections summarize patient research study results to date with discussion of applications by organ system. The basic algorithms and approaches to visualization of 3-D and 4-D ultrasound data are reviewed, including issues related to interactivity and user interfaces. The implications of recent developments for future ultrasound imaging/visualization systems are considered. Ultimately, an improved understanding of ultrasound data offered by 3-DUS may make it easier for primary care physicians to understand complex patient anatomy. Tertiary care physicians specializing in ultrasound can further enhance the quality of patient care by using high-speed networks to review volume ultrasound data at specialization centers. Access to volume data and expertise at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment.

Three-dimensional ultrasound image of the fetal stomach: congenital duodenal obstruction in utero

To quantitatively characterize the stereographic stomach configuration in utero, 11 fetuses (subject-group) with congenital duodenal obstruction, diagnosed antenatally, between 29 and 37 weeks' gestation were studied. Also included were 879 uncomplicated fetuses between 20 and 40 weeks' gestation as a control-group. Applying the algorithm which we devised: "Modeling a three-dimensional shape from a silhouette by detecting symmetry", we reconstructed the three-dimensional stomach configuration from a two-dimensional ultrasound image for each case. The statistical differences in two parameters, stomach volume and sphericity, between subject- and control-group fetuses, were analyzed using the Grubbs-Smirnoff's test at corresponding gestational ages. From 29 to 37 weeks' gestation, the stomach volume in the subject-group fetuses was found to increase greatly with advancing gestation, having significantly higher values than the control-group fetuses, whereas the stomach sphericity remained unchanged with no significant differences from the control-group fetuses. These findings indicate that the fetal stomach with duodenal obstruction maintains almost the same three-dimensional portrayal in utero as that seen in uncomplicated fetuses, although the stomach becomes extremely enlarged.