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, 206 (6), 525-34

Anatomy of the Lactating Human Breast Redefined With Ultrasound Imaging

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Anatomy of the Lactating Human Breast Redefined With Ultrasound Imaging

D T Ramsay et al. J Anat.

Abstract

The aim of this study was to use ultrasound imaging to re-investigate the anatomy of the lactating breast. The breasts of 21 fully lactating women (1-6 months post partum) were scanned using an ACUSON XP10 (5-10 MHz linear array probe). The number of main ducts was measured, ductal morphology was determined, and the distribution of glandular and adipose tissue was recorded. Milk ducts appeared as hypoechoic tubular structures with echogenic walls that often contained echoes. Ducts were easily compressed and did not display typical sinuses. All ducts branched within the areolar radius, the first branch occurring 8.0 +/- 5.5 mm from the nipple. Duct diameter was 1.9 +/- 0.6 mm, 2.0 +/- 90.7 mm and the number of main ducts was 9.6 +/- 2.9, 9.2 +/- 2.9, for left and right breast, respectively. Milk ducts are superficial, easily compressible and echoes within the duct represent fat globules in breastmilk. The low number and size of the ducts, the rapid branching under the areola and the absence of sinuses suggest that ducts transport breastmilk, rather than store it. The distribution of adipose and glandular tissue showed wide variation between women but not between breasts within women. The proportion of glandular and fat tissue and the number and size of ducts were not related to milk production. This study highlights inconsistencies in anatomical literature that impact on breast physiology, breastfeeding management and ultrasound assessment.

Figures

Fig. 1
Fig. 1
Artist's impression of the lobes of the breast. The ducts were injected with coloured wax prior to dissection (from Cooper, 1840).
Fig. 2
Fig. 2
(A) Ultrasound image of milk duct in the lactating breast. The duct appears as branching hypoechoic structure within echogenic glandular tissue. (B) The ducts focused on in this scan are outlined in white. The duct is traced from the nipple (N) to the periphery of the breast. The walls are echogenic (↑) and the lumen hypoechoic (asterisk). The first branch of this duct (→) is imaged almost directly under the nipple.
Fig. 3
Fig. 3
Diagram of the milk duct coursing deep into the breast from the nipple (N). Measurements were made of the depth (thin solid line) and diameter (dotted line) of the main milk duct (MMD) and the distance of the first branch (BR, thick solid line) from the base of the nipple. The diameter (double line) and depth from the skin (dashed line) of the first branch (BR) of the duct were also measured.
Fig. 4
Fig. 4
(A) The right breast divided into sectors according to the face of the clock. (B) The arrows show the four images documented along the 3 o’clock axis. The number of images was dependent on the size of the breast, the axis measured and the extent of the glandular tissue.
Fig. 5
Fig. 5
(A) Ultrasound image of tissues of the lactating breast. (B) The skin (SK) is shown as an echogenic (bright) line at the top of the image. The subcutaneous fat (SF) is less echogenic and situated below the skin. The intraglandular fat (IF) is of similar echogenicity to the subcutaneous fat. The glandular tissue is echogenic (G) while the milk duct (arrow) appears as a hypeoechoic (low echo) tubular structure. The retromammary fat (RF) is a thin hypoechoic band along the chest wall.
Fig. 6
Fig. 6
Distribution of different tissues through the right breast of two different lactating mothers. Cumulative totals of each tissue were calculated by summing all of the measurements made in the breast at 0, 3, 6, 9 and 12 cm distances from the base of the nipple. (A) Mother 1 had a total tissue sum of 1465 mm and a 24-h milk production of 299 g. (B) Mother 9 had a total tissue sum of 790 mm and a 24-h milk production of 176 g.
Fig. 7
Fig. 7
Drawing of the gross anatomy of the lactating breast based on ultrasound observations made of the milk duct system and distribution of different tissues within the breast.

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