A Review and Reconsideration of Nonneoplastic Myometrial Pathology

Abstract

From 1861 to 1962, clinicopathologic research tried to explain the association of abnormal uterine bleeding with uterine enlargement. The etiology was theorized as metropathy, suggesting that myometrial dysfunction may predispose to abnormal uterine bleeding. Research reached a nadir in 1962, when a major review dismissed myometrial hypertrophy as a plausible explanation after prior rejections of the theories of chronic myometritis, fibrosis uteri, and subinvolution as causes of bleeding. Subsequent to this arose a crusade against unnecessary hysterectomies in the 1970s. Although myometrial hyperplasia was proposed in 1868, it is only in the past 25 years that tangible evidence has supported that idea. It now appears that clinically enlarged uteri are due to globoid outward bulging of the uterus, caused by increased intramural pressure-often unrelated to either uterine weight or myometrial thickness. Abnormal (dysfunctional) uterine bleeding may often be due to spontaneous rupture of thrombosed dilated endometrial vessels, due to the combined effects of obstructed venous drainage by increased intramural pressure, and Virchow's triad. Despite a century-old known association of parity with naturally occurring outer wall myometrial scars (fibrosis uteri with elastosis), it was not previously suggested that these may reflect healing reactions to muscle tears during labor and delivery. We now suggest that smaller, similar inner wall elastotic scars in the nerve-rich inner myometrium may explain many cases of pelvic pain. This review suggests that diverse pressure-related lesions may be present in clinically abnormal uteri that have been called "normal" since the crusade against unnecessary hysterectomy.

A Comparison of Hysterectomies for Bleeding With Hysterectomies for Pain

“…[4][5][6][7] First, the association of clinical enlargement and abnormal bleeding with uterine weight had been effectively discredited in hysterectomies <200 g. 4 In 1962, when 120 g was considered the upper limit of normal uterine weight, weight >120 g had been referred to as "myometrial hypertrophy," which had been the subject of considerable study in the first half of the 20th century. 1,4 Lewis et al reported that only 19% of uteri >120 g were "clinically enlarged" on physical examination, while only 58% of "clinically enlarged" uteri weighed over 120 g. 4 Thus, "myometrial hypertrophy" (increased uterine weight) did not correlate with uterine enlargement on physical examination.…”

“…For over 100 years, the research on the association of clinically enlarged uteri with abnormal bleeding (1861-1979) 1 rested on the basic premise that nonneoplastic myometrial pathology, like uterine atony, might cause abnormal bleeding. 1 This theory of "metropathy" has never been either proved or disproved. 1 The classic morphometric study of myometrium by Schwalm and Dubrauszky in 1966 included cases of "metropathic uteri."…”

“…1 This theory of "metropathy" has never been either proved or disproved. 1 The classic morphometric study of myometrium by Schwalm and Dubrauszky in 1966 included cases of "metropathic uteri." 2 It has been suggested that the virtual cessation of this research since 1980 was an unintended lingering consequence of the crusade against unnecessary hysterectomies, which escalated in the 1970s.…”

“…2 It has been suggested that the virtual cessation of this research since 1980 was an unintended lingering consequence of the crusade against unnecessary hysterectomies, which escalated in the 1970s. 1,3 Interestingly, it has never been suggested that clinically enlarged uteri correlate with pelvic pain.…”

“…History of hormonal treatment also had to be taken into account. 1 In the modern era, it has been suggested that "myometrial hypertrophy" applies only to nulliparous uteri >130 g, and to parous uteri (1-3 children) >199 g. 7 "Myometrial hypertrophy" did not apply to uteri with parity >3, at least partly because greater parity tended to correlate with increased uterine weight. [4][5][6][7] In 1979, Honore did a "pathology only" study of abnormal bleeding in hysterectomies >125 g, suggesting that enlargement on physical examination was due to a symmetrical outward bulging uterus.…”