Talk:Paper - Persistent opening of anterior cloacal depression (1938)

192

ANATOMICAL NOTES

PERSISTENT OPENING OF ANTERIOR CLOACAL DEPRESSION

By M. AMIN Assistant Professor of Anatomy, Cairo

Tue condition of parts described in this paper seems worthy of record. The subject was a 12-year-old girl, examined by me in March 1937. Physical examination revealed complete absence of a perineal anus (Fig. 1, 10), well-formed labia majora et minora (Fig. 1,5 and 3), an intact but abnormally situated hymen (Fig. 1,9), and an anomalous anal orifice (Fig. 1, 8) opening backwards from the vulval cleft and partially overlapped by the hymen. Through this anomalous anal opening the bowel discharged involuntarily. The urinary meatus (Fig. 1, 4) and clitoris (Fig. 1, 2) are normal, likewise the vaginal orifice (Fig. 1, 6); the posterior vaginal wall is interrupted by the unusual termination of the gut, the thick margin of tissue between this anomalous aperture and the vaginal opening is somewhat suggestive of the embryonic septum which divides the cloaca into rectum and urogenital sinus.

Fig. 1. Anomalous anal termination, showing (1) mons veneris, (2) clitoris, (3) labia minora, (4) urinary meatus, (5) labia majora, (6) vaginal orifice, (7) septum between vaginal and abnormal anal orifices, (8) abnormal anal opening, (9) fold regarded as hymen, (10) usual site of anus, imperforate and prominent.

The habitual involuntary discharge of bowel contents through this vaginal anus supports the views enunciated by Popowsky (1899) concerning the development of the perineal sphincteric musculature. Popowsky held that the m. sphincter ani externus and the m. sphincter sinus urogenitalis both derive from a common subcutaneous primordium, and that their differentiation is entirely dependent upon complete division of the cloacal aperture into anal and urogenital orifices. The absence, in the present case, of a perineal anus presumably prevented such differentiation, Anatomical Notes 193

recalling the condition of affairs typical of certain marsupials, where anal and urogenital apertures, opening into an ectodermal cloaca, are guarded by a common sphincter. Defective growth of the cloacal septum is held responsible for the present malformation: the septum has failed to reach the cloacal membrane, for had it done so either a normal or an imperforate anus would have resulted. The septum, and with it the anal canal, has grown forwards instead of backwards and so the latter has opened directly through the posterior wall of the urogenital sinus.

A similar case recorded by MacKenzie (1906) in a much younger child was interpreted by Robinson as an example of ‘“‘anal canal opening into a cloaca”: Keith (1933) regards such cases as examples of the ‘“‘ancient cloacal orifice of the reectum”’. Cases described by Reichel (1888) and others, however, differ somewhat from the present one: in them the rectum terminates normally, but a tendency towards an anterior cloacal termination is evidenced by a small canal connecting the rectum with the vestibule immediately behind the hymen. Somewhat similar are those further cases possessing a small but normally situated anal orifice, wherein the rectum communicates with the vestibule or the male urethra. In all such, a defective cloacal septum plays a causative part.

The curious position, in the present instance, of the fold regarded as hymen (Fig. 1, 9) is noteworthy, for its disposition might be held to suggest its derivation from the urogenital sinus only, or from surface mesoderm in good part. This view is supported by cases recorded by Pozzi (quoted by Wood Jones) which boasted a hymen but no vagina (the latter being represented by a small blind pocket derived from the urogenital sinus), and by cases described by Wood Jones (1927) of (a) single hymen with double vagina, (b) single hymen common to vaginal and urethal orifices. According to Wood Jones (1927) the hymen is formed from the mesoderm interposed between the surface and the bulbar apex of the downgrowing vaginal cords. Bloomfield and Frazer conclude, however, that the hymen is produced by the contact of vaginal and urogenital sinus structures. The presumptive hymen in the case herein detailed lies above the anomalous anal orifice, and thus separates it from the vaginal aperture: it is therefore unrelated to the contact site of Mullerian tubercle and urogenital sinus. Its attempted interpretation reveals a divergence of views con cerning hymeneal development and emphasizes the need for further research in this matter.

REFERENCES

Kerrtn, A. (1933). Human Embryology and Morphology, 5th ed. p. 434. MacKenzig, F. S. (1906). J. Anat. Physiol. vol. xi, pp. 409-11. Popowsk1, J. (1899). Anat. Hefte, Bd. xu.

REIcHEL, P. (1888). Geburtsh. Gynak. Bd. xiv, S. 82-94.

Woop Jonss, F. (1927). J. Anat., Lond., vol. Lxm, pp. 25-31.

Anatomy LXXIII 13