THE NORMAL UTERUS

The uterus is a thick, pear-shaped muscular organ located between the two layers of the broad ligament laterally, the urinary bladder anterior and the rectosigmoid colon posteriorly.

  • The fundus is the superior area above the entrance of the fallopian tubes.
  • The body (corpus) is the expanded portion and forms the major bulk of the uterus.
  • The isthmus is the slightly constricted lower portion that separates the body from the cervix.
  • The cervix is the lowermost portion that undergoes progressive thinning during pregnancy but maintains a constant length of about 3 cm.
  • The vaginal canal lies in the midline and rums from the cervix to the external genitalia.

 

The myometrium has a homogeneous echotexture with smooth borders. The transition between the endometrium and myometrium is delineated by an echo poor line, which is thought to represent the deeper more vascular layer of the inner myometrium. Normal arcuate vessels may be seen in the periphery of the uterus. These vessels bifurcate into radial branches, which supply blood throughout the uterus.

 

The endometrium appears as a central line whose appearance and density are related to the phases of the menstrual cycle. After menstruation, when the majority of the decidual inner layer of the endometrium has been shed, only a fine cavitatory line present. As the endometrium thickens in the proliferative phase of the cycle, it becomes more prominent but remains echo poor. The endometrium continues to thicken and become more reflective as it enters the secretory phase presumable due to the glands filling with mucin and becoming tortuous. Towards the end of the cycle the endometriual shadow (which includes both the anterior and posterior endometrium) may reach 10 mm.

Pre-menarchal uterus

 

 

 

Prior to menarche the uterine body is about half the length of the cervix.

In nulliparas the body and cervix have the same dimensions, while in multiparas the body is approximately double the length of the cervix.

Age

Longitudinal

Diameter of Uterus (cm)

Antero-posterior Diameter of Uterus (cm)

Antero-posterior Diameter of Cervix (cm)

Uterine Volume (cm3)

2

33.14.4

7.03.4

8.32.0

1.981.58

3

32.44.3

6.41.3

7.62.2

1.630.81

4

32.93.3

7.61.8

8.61.8

2.100.57

5

33.15.5

8.02.8

8.41.8

2.361.39

6

33.24.1

6.72.9

7.51.8

1.801.57

7

32.33.9

8.02.2

7.72.5

2.321.07

8

35.87.3

9.02.8

8.41.7

3.121.52

9

37.14.4

9.73.0

8.82.0

3.701.62

10

40.36.4

12.85.3

10.72.6

6.543.78

11

42.25.1

12.83.1

10.72.6

6.662.87

12

54.38.4

17.35.3

14.35.2

16.189.15

13

53.811.4

15.84.5

15.02.4

13.185.64

Early proliferative phase

 

Late proliferative phase

 

Secretory phase

 

Uterine Diameter versus Parity

    

 

LONGITUDINAL DIAMETER

ANTEROPOSTERIOR DIAMETER

TRANSVERSAL DIAMETER

VOLUME

PREPUBERTAL

1-3 cm

0,5-1 cm

0,5-1 cm

10-20 ml

MULTIPAROUS

8 cm

4 cm

5 cm

60-80 ml

NULLIPAROUS

6 cm

3-4 cm

3-4 cm

30-40 ml

POSTMENOPAUSAL

4-6 cm

2-3 cm

2-3 cm

14-17 ml

 

 

Anatomical segments of the uterus.

 

 

 

Anteflexion

 

 

Retroflexion

 

 

 

 

Retroversion + Retroflexion

 

 

 

 

 

 

 

 

REFERENCES

 

  1. Harris RD, Barth RA. Sonography of the gravid uterus and placenta: current concepts. AJR 1993;160:455-465.