Some of these are local and fall under their special sections, but there is one form which has more general results.
Up to the fifth week of embryonic life there are no external openings for the intestine and urino-genital organs. The rectum is still closed below, but communicates with the allantois, which forms a common opening for the intestinal, urinary, and genital passages, and is itself still open through the imperfect abdominal wall in front. This condition may persist in a greater or less degree.
The most extreme form is where, along with imperforate anus, there is fissure of the abdomen and bladder, a combination of the conditions described in last section with that now under consideration. In some cases the colon is deficient, and the ileum may communicate with the extroverted bladder. Such conditions are hardly compatible with life.
In the simpler forms there is imperforate anus and the intestine communicates with urinary or genital passages. The communication may be with the vagina (anus vaginalis), or with the urethra (anus urethralis), or with the urinary. bladder (anus vesicalis). The communications may be very small, so that continuance of life is impossible from accumulation of faeces, but there may be fuller communication, and sometimes the condition is surgically remediable.
Fig. 12. - Imperforate anus, a, Anus and anal part of rectum, b, Dilated rectum separated from anal part by a complete septum, c, Urinary bladder.
Simple imperforate anus may be a simple absence of the aperture, but in many cases there is also a defect of a portion of the rectum. The latter condition may exist while the anus is perfectly formed (Fig. 12). (See further on under Intestine).