FETAL ADRENAL GLANDS

Adrenal length – left and right side (Table) – Bronshtein et.al. 1993

Adrenal length – right side (Graph)– Bronshtein et.al. 1993

EMBRYOLOGY

Link to Embryology

ULTRASOUND

• Large echolucent cortex surrounding an echogenic medulla. The normal appearance of the adult adrenal gland is the reverse.
• May be confused with the kidneys at 9 weeks GA as they are of similar size and in the same area of the abdomen.
• They can be imaged at the end of the first trimester but are only reliably visualized after 20 weeks gestational age (1,2).
• Their size increases linearly from 12-17 weeks of gestation (3).
• They lie superior and medial to the corresponding kidney, with the medial border adjacent to the aorta (on the left) and inferior vena cava (on the right).
• Width of adrenal limb <4mm
• Smooth surface
• Echogenic central stripe with surrounding hypoechoic rim (6-8).
• Echogenic central stripe – represents the congested sinusoids of the inner part of the fetal adrenal cortex, the central vein and small medulla.
• Peripheral hypoechoic area represents the less congested adrenal coetex and probably the definitive cortex.
• Shape.
• Oval or pyramidal shaped in a longitudinal plane.
• In a transverse plane they have been compared to radially oriented rice grains (lentiform or discoid).

• The internal echogenic area may be quite bright in two thirds of fetuses and may get even brighter in the last 5 weeks of pregnancy (1,2).
• Length increases with age, and it maintains a constant relationship to kidney length (2).
• 1.4 to 2.2 cm or 48-66% of the renal length (4).
• The adrenal gland constitutes 0.2% of total body weight at birth (this is 20 times it's relative size in the adult) (4).
• Renal agenesis.
• The adrenals assume a reniform shape making the early diagnosis of renal agenesis difficult.
• Adrenals may completely fill the renal fossa.
• The adrenal glands may appear more globular and simulate small but present kidneys. Autopsy studies have shown this phenomenon to be caused by a change in the normal-sized adrenal’s shape, rather than adrenal hypertrophy (9). Looking at orthogonal images may avoid this problem (10).
• Hoffman et al (11) reported a flat or "lying down" adrenal in 48% of 23 fetuses and 6 neonates retrospectively studied by US because of apparent renal agenesis or ectopia and suggested that the normal shape of the adrenal gland which usually "caps" the kidneys is affected by presence of an ipsilateral kidney.

Discoid adrenal gland in unilateral renal agenesis

REFERENCES

1. Jeanty P, Chervenak F, Grannum P et.al. Normal ultrasound size and characteristics of the fetal adrenal glands. Prenat Diagn 1984;4:21.
2. Lewis E, Kurtz A, Dubbins P et.al. Real time ultrasonographic evaluation of normal fetal adrenal glands. J Ultrasound Med 1982;1:265.
3. Bronshtein M, Tzidony D, Dimant M et.al. Transvaginal ultrasonic measurements of the fetal adrenal glands at
4. weeks of pregnancy. Am J Obstet Gynecol 1993;169:1205-1210.
5. Lee W, Comstock CH, Jurcak-Zaleski S. Prenatal diagnosis of adrenal hemorrhage by ultrasonography. J Ultrasound Med 1992;11:369-371.
6. Hauffa BP, Menzel D, Stolecke H. Age related changes in adrenal size during the first year of life in normal newborns, infants and patients with congenital adrenal hyperplasia due to 21-hydroxylase deficiency: comparison of ultrasound and hormonal parameters. Eur J Pediatr 1988;148:43-49.
7. Scott EM, Thomas A, McGarrigle HHG, Lachelin GCL. Serial adrenal ultrasonography in normal neonates. J Ultrasound Med 1990;9:279-298.
8. Kangarloo H, Diament MJ, Gold RH et.al. Sonography of adrenal glands in neonates and children: changes in appearance with age. J Clin Ultrasound 1986;14:43-47.
9. P. Dubbins, A. Kurt, R. Wapner et al., Renal agenesis: spectrum of in utero findings. J Clin Ultrasound 9 (1981), pp. 189–193.
10. S. Droste, J. Fitzsimmons, J. Pascoe-Mason et al., Size of the fetal adrenal in bilateral renal agenesis. Obstet Gynecol 76 (1990), pp. 206–209.
11. C.K. Hoffman, R.A. Filly and P.W. Callen, The "lying down" adrenal sign: A sonographic indicator of renal agenesis or ectopia in fetuses and neonates. J Ultrasound Med 11 (1992), pp. 533–536.