In the rectum we frequently encounter valve like structures. They make it difficult to perform rigid sigmoidoscopy whereby the scope has to negotiate a slalom course formed by these structures. During colonoscopy or flexible sigmoidoscopy, the valves provide a hiding place for polyps, and unless one is careful, a lesion can easily be missed. The attached video shows two such cases of "near miss" (see video). --
Giovanni Morgagni (1682–1771) is credited with the first description in the 18th century of rectal valves. However, it was John Houston (1802–1845), an Irish anatomist and surgeon, who presented the seminal study of the structures in 1830 [1]. A medical graduate of the University of Edinburgh, he was a demonstrator of anatomy at the Royal College of Surgeons Ireland and curator of the Dublin College of Surgeon’s Museum [2].
Houston described the valves' obliquity, upward orientation, and concave surfaces. Because the valves were located successively on opposite sides of the rectum, they formed “a sort of spiral tract down its (rectum) cavity.” Hence, they came to be known as "spiral valves of Houston". According to Houston, the valves were attached to one-third to one-half the rectal circumference. The thickest parts of them were their midportions, where they measured 1.3–1.9 cm.
In the mid-nineteenth century, a single mid-rectal valve was described by the Hanoverian, Otto Kohlrausch, creating confusion with the established eponym "Houston's Valves.” [2].
Amongst mammals, the rectal valves appear to be unique to humans. Modern anatomy texts and atlases usually describe three rectal folds. However, in a sigmoidoscopic study of 400 adults, Abramson determined that the number of valves varied from zero to seven [3]. More than 3/4 of patients had two or three. Average length of valves in this in vivo study was 3 cm (range: 1.6–5.6 cm). Valve thickness was 1.4 cm (range: 0.8– 1.6 cm), similar to that recorded by Houston.
Many hypotheses about rectal valves have been discredited; and their physiologic functions are still largely unknown. No one has proved either the precise purpose of rectal valves or identified their etiologic role in rectal disease. Houston suggested their spiral arrangement enhanced the rectum’s reservoir function. They were necessary “to support the weight of faecal matter, and prevent its urging toward the anus” [1].
REFERENCES
[1] Houston J. 1830. Observations on the mucous membrane of the rectum. Dublin Hosp Rep 5:158–165.
REPRINTED: Dis Colon Rectum. 1987 Nov;30(11):906-8. John Houston 1802-1845. Observations on the mucous membrane of the rectum. 1830.
[2] Ikard RW, Clin Anat. 2015 May;28(4):436-41. Spiral rectal valves: Anatomy, eponyms, and clinical significance.
[3] Abramson DJ. 1978. The valves of Houston in adults. Am J Surg, 136:334–336.
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