Lateral distribution of benign ovarian cysts

Abstract

It is well known that the frequency of endometriotic cysts is higher in the left ovary. Previous studies suggested that ovarian dermoid cysts have a predisposition to a right lateral distribution. In this study we investigated the left- and right- sided distribution of benign ovarian cysts in large series of women undergoing surgery at our institution. Retrospective database review. We examined the clinical records of 1099 consecutive women of reproductive age (range: 15–54 years) with benign ovarian cysts who underwent surgical treatment. Age of patients at time of surgery, sites and sizes of ovarian cysts were recorded. Cyst diameter was assessed by ultrasound examination in the month before surgery. The data were abstracted from a continuously updated database of women undergoing surgery in our institution. Women who had undergone previous abdominal surgery, except appendectomy, were excluded. ANOVA and one-way analysis of variance on ranks were used as appropriate. The χ2-test was used to compare observed and expected events. Forty-four women with cyst of different histology in the same ovary or bilaterally were excluded from the analysis. Accordingly, the final study population included 1055 women. Patients with serous cysts were significantly older that those with endometriotic, dermoid, and paraovarian cysts (p<0.001). Dermoid cysts were unilateral in 202 (91.4%) women and bilateral in 19 (8.6%) patients. Among the women with unilateral dermoid cysts, 55.0% had left-sided cyst and 45.1% had right-sided cyst (not significant, p=0.159). Torsion occurred in 6 women with dermoid cysts; cysts undergoing torsion were significantly larger (p=0.004) than those that did not undergo torsion. Unilateral endometriotic cysts were found more frequently on the left ovary (n = 275, 59.9%) than on the right ovary (n = 184, 40.1%) (p<0.001; 18.041, χ2). Serous, mucinous, and paraovarian cysts were equally distributed on both sides. Bilateral cysts were significantly more frequent in women with endometriotic cysts (19.3%, 95% CI 16.2–22.8%) than in subjects with non-endometriotic cysts (8.4%, 95% CI 6.1–11.3%) (p<0.001, OR 2.60, 95% CI 1.78–3.80). No significant difference was observed in the cyst diameter in right and left-sided cysts in each histologic group. Dermoid cysts as well as serous, mucinous, and paraovarian cysts are equally distributed on both sides. This finding is in contrast with previous reports suggesting a predisposition of dermoid cysts to a right lateral distribution. The presence of bilateral lesions should always be investigated in women with ovarian endometriosis.