Smooth muscle in the female pelvic peritoneum: a clinicopathological analysis of 31 women.

AIM

To study the presence and morphological features of smooth muscle in the subcoelomic mesenchyme with the aim of establishing both a normal range for the female pelvis, and its possible relationship to endometriosis, diffuse peritoneal leiomyomatosis (LPD) and other forms of 'müllerianosis'.

METHODS

Seventy laparoscopically obtained pelvic peritoneal biopsies accessioned over a 16-month period were examined from 31 women clinically suspected of endometriosis. These biopsies were selected for the presence of assessable, appropriately oriented peritoneum, sufficiently distant from focal endometriosis to allow a presumption of 'normality'. The histological features and morphometric measurements of smooth muscle in these biopsies were documented. Pathological changes, where present, were recorded.

RESULTS

Focal endometriosis was identified in 28 (40%) of the biopsies, nine (12.9%) displayed other manifestations of 'müllerianosis', 11 (15.7%) showed focal chronic inflammation or fibrosis only, and 22 (31.4%) displayed no specific pathological changes. Of 70 biopsies, 52 contained smooth muscle within the subcoelomic mesenchyme, directly below the peritoneal mesothelium. Biopsies in which smooth muscle was identified were predominantly from the region of the uterosacral ligaments (16/18) and pelvic side wall (22/25). The biopsies without a smooth muscle layer were predominantly from the pararectal area (7/8) or the rectal serosa (2/4). Where present, smooth muscle varied in prominence, depth, thickness of the layer and organisation of muscle bundles. Patterns ranged from thin, widely spaced and wispy fibres to a more or less continuous band of either horizontally and/or vertically organised fibres. Both focal and diffuse arrangements were evident. 'Neovascularisation' was observed laparoscopically in some areas that corresponded with prominent smooth muscle development.

CONCLUSIONS

Smooth muscle occurs sufficiently frequently immediately beneath the peritoneum of the female pelvis, and with a sufficiently predictable anatomical distribution, to be regarded as a normal component of the microanatomy of this tissue in the patients studied.