MR Imaging of Normal Ovary in Menstruating Women: Detection Rate and Size of the Ovary and the Number and Size of the Follicle According to the Age

Shin, Myong Ho; Cho, Jae Ho; Kim, Gyung Tae; Chang, Jay Chun; Park, Bok Hwan

Abstract

PURPOSE
To determine the rates at which normal ovaries in women of reproductive age were observed at MRI, as well as differences in the size of a normal ovary and follicles, and the number of follicles, according to age.
MATERIALS AND METHODS
The MRI findings in 46 patients with normal ovaries were retrospectively analysed and proven grossly at surgery and/or pathologically. The detection rate and size of the ovaries, and the number of follicles and size of the largest were determined, and differences were analyzed according to age: under 30, 30-39, and 40 years or over.
RESULTS
Among 46 patients, bilateral ovaries were detected in 39 and unilateral ovary in seven. The overall detection rate was 92.4% (85/92), varying according to age. It was 100% (18/18) in those aged under 30, 95% (38/40) in the 30-40 age group, and 85.3% (29/34) among those aged 40 or over. Ovary size ranged between 15 and 50 (average, 24.3) mm and was most commonly 20-30 mm, regardless of age (60%). The average size was 28.8 mm under 30 years of age, 25.3 mm between 30 and 39, and 20.3 mm at age 40 or over (p<0.01). The number of follicles was recorded as 2, 3, 4, or 5 or more, with 10.6%, 23.5%, 18.8% and 47.1% of patients, respectively, assigned to these categories. Among those aged 30-39, ovaries containing five or more follicles were most common, with 83.3% of those under 30 and 47.4% of those aged 30-39 falling into this category. Among patients aged 40 or over, only 24.1% of ovaries contained five or more follicles; most (37.9%) contained three (p<0.05). The size of the largest follicle ranged from 2 to 30 mm and, regardless of age, 5-10-mm follicles were most common (43.5%). There were no significant differences according to age.
CONCLUSION
MRI is a useful tool for detecting normal ovaries in women of reproductive age. We found that most normal ovaries were 20-30 mm in size and contained five follicles or more, the largest follicle being 5-10 mm. The size of an ovary and the number of follicles decreased significantly with age.