CONGENITAL DEFORMITIES OF THE RECTUM (See Fisehl, Deformities in the Region of Rectum and Anus, vol. iii.) Pathological Anatomy.—A rather frequent arrest of development, reaching back into a very early period of embryonal life, consists in dis turbances connected with the physiological structure of the rectum.
From the preceding description of the history of abdominal develop ment, the close relations between the development of the rectum and that of the urogenital system are apparent. Although it is not an easy matter to explain these anomalies in each case from their natural history of development, I believe it is still clearer and more logical to explain the abnormal connection, positional changes and communications of the organs by assuming that, similarly to cranial processes, biological mnemonics have failed, whether from deficient power of fetal develop ment or from individual pathological conditions of the mother, instead of vaguely holding purely mechanical and 'indemonstrable causes respon sible,.such as the bursting of preformed organs and inflammations of the well-protected primitive nuclear structure. (Sec lAwen, Rotten.) Many experiments on the lower species of vertebrate animals have demonstrated to what kaleidoscopic changes, and subsequent sponta neous correction of growth, injuries to the ovum may lead.
An imperforate anal membrane leads to the condition called atresia ani. At the physiological site of the anus the skin is either quite smooth (Plate 4, Fig. 2S) or, as is usually the case, there is a small fossa or fold of the skin which points to the anal spot (Plate 4, Fig. 28; Plate 5, Figs. 30a and 30b). Above this closed anal membrane the rectum terminates like a cul-de-sac. Again, the external anal orifice may be present, the invagination of the ectoderm having taken place, while the deep part of the membrane has no orifice (atresia recti). If both structures are closed, the layer between the external integument and the blind rectum may attain considerable thickness. At the sacrum, and higher, the sigmoid flexure may terminate in the shape of an ampulla (atresia ani et recti).
(See Fig. 29, Plate 4.) In these serious forms the pelvic outlet. is likewise changed, the tuberosities of the ischium being approximate because of the absence of the rectum.
Through the relations of development at the pelvic extremity abnormal orifices and communications may occur; a persistent corn munication between the anterior and posterior spaces of the cloaca causes the rectum to end in the bladder (atresia ani vesicalis); or, if the rectum should be formed later at the normal place, there may be a congenital fistula between these two organs. If the perineum is insuffi ciently developed, the rectum inosculates into the vestibulum (atresia ani vestibularis) (Figs. 30a and 30b, Plate 5).
The insertion of the female genitals between the structures of the cloaca also leads to abnormal orifices and fistular formations (atresia ani vaginalis).
These anomalies may also complicate the structure of the male genital organs. The rectum may communicate with any part of the urethra either directly or by a fistula (atresia ani urethralis) (Fig. 31, Plate 5).
These fistular ducts may also open outward at atypical places, as for instance under the penis and at the scrotum. Stieda explains these as secondary formations.
The symptoms causing these anomalies vary with the gravity of the anatomical malformation. The complete superficial closure of atresia ani is usually noticed at once, since it leads shortly after birth to mani festations of intestinal occlusion, restlessness, and vomiting. The re tained meconium is soon infected from the mouth, decomposes and gives rise to general peritonitis.
If there are fistulae with an external opening, the conditions described may be less pronounced or entirely absent.
The most favorable conditions exist in anovestibular atresia (Fig. 30, Plate 5), the opening of the rectum into the vestibulum being of consider able width. Corresponding to the embryonal displacement there is a functioning sphincter interims, so that cases have occurred in which individuals only learned of the abnormal condition at an advanced period, perhaps on the occasion of childbirth.