BACKGROUND The adrenal gland plays a vital role in fetal growth. Many disease states such as congenital adrenal hyperplasia, hemorrhage and tumors can lead to morphological changes in the gland. Ultrasound measurements of normal adrenal sizes in the fetus reported in the literature have shown a trend of increasing size with gestational age. There is no literature available on standard fetal adrenal sizes or detailed appearance by fetal MRI. OBJECTIVE The purpose of this study was to provide MR data on the size and signal characteristics of the fetal adrenal gland throughout the second and third trimesters. MATERIALS AND METHODS In this retrospective review, we selected 185 prenatal MRIs obtained from Jan. 1, 2014, to May 31, 2017, with normal abdominal findings for inclusion. The adrenal glands were identified in coronal, sagittal or axial T2-W planes and coronal T1-W plane when available. We measured the length and thickness of the medial and lateral limbs of the right and left adrenal glands and recorded signal intensity on T1-W and T2-W sequences, gender and gestational age in each case. RESULTS The gestational age (GA) ranged 18-37 weeks. Visibility of the adrenal glands on T2-W images was high (90.3-97.2%) up to 30 weeks of GA but declined afterward (47.5-62.2% at 31-37 weeks). Visibility on T1-W images increased with GA, ranging from 21.4% visibility at 18-22 weeks and increasing to 40% at 35-37 weeks. Mean lengths of the adrenal gland limbs steadily increased from 8.2 mm at 18-22 weeks to 11.0 mm at 35-37 weeks. In the second trimester, adrenal glands were low in signal intensity on T2-W images and were surrounded by hyperintense perirenal fatty tissue. In the third trimester, the glands became less distinct, with increasing signal and obliteration of perirenal tissue. The glands were moderately hyperintense on T1-W images throughout pregnancy, with increasing visibility as pregnancy progressed. CONCLUSION Normal sizes and signal intensities for adrenal glands are reported. Visibility of adrenal glands on T2-W images was 90.3-97.2% up to 30 weeks but declined thereafter. Visibility on T1-W images increased in the third trimester. Adrenal gland sizes increased with gestational age.

中文翻译：

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产前磁共振成像显示胎儿肾上腺的正常大小。

背景技术肾上腺在胎儿生长中起着至关重要的作用。先天性肾上腺皮质增生，出血和肿瘤等许多疾病状态均可导致腺体形态改变。文献中报道的胎儿的正常肾上腺尺寸的超声测量结果显示，随着胎龄的增加，尺寸呈增加趋势。没有关于标准胎儿肾上腺大小或胎儿MRI的详细外观的文献。目的本研究的目的是提供整个中期和中期的胎儿肾上腺的大小和信号特征的MR数据。材料与方法在本回顾性研究中，我们选择了2014年1月1日至2017年5月31日获得的185例产前MRI，并将其腹部正常纳入。在冠状动脉中发现了肾上腺，矢状或轴向T2-W平面和冠状T1-W平面（如果可用）。我们测量了左右肾上腺的内侧和外侧肢的长度和厚度，并记录了每种情况下T1-W和T2-W序列，性别和胎龄的信号强度。结果胎龄（GA）为18-37周。T2-W图像上的肾上腺可见度很高（90.3-97.2％），在GA出现30周之前，但随后下降（31-37周时为47.5-62.2％）。GA可以提高T1-W图像的可见度，从18-22周的21.4％可见度到35-37周的40％可见度。肾上腺四肢的平均长度从18-22周的8.2毫米稳定增加到35-37周的11.0毫米。在中期中期，在T2-W图像上，肾上腺的信号强度较低，周围环绕着肾上腺高脂肪组织。在孕晚期，随着信号的增加和肾周组织的闭塞，腺体变得越来越不明显。在整个怀孕期间，T1-W图像上的腺体呈中等程度的高信号，随着怀孕的进行，可见度也逐渐增加。结论报告了肾上腺的正常大小和信号强度。到30周时，T2-W图像上肾上腺的可见度为90.3-97.2％，但此后下降。妊娠中期，T1-W图像的可见度增加。肾上腺的大小随胎龄的增加而增加。结论报告了肾上腺的正常大小和信号强度。到30周时，T2-W图像上肾上腺的可见度为90.3-97.2％，但此后下降。妊娠中期，T1-W图像的可见度增加。肾上腺的大小随胎龄的增加而增加。结论报告了肾上腺的正常大小和信号强度。到30周时，T2-W图像上肾上腺的可见度为90.3-97.2％，但此后下降。妊娠中期，T1-W图像的可见度增加。肾上腺的大小随胎龄的增加而增加。