Page 27 of 73 ANOMALIES OF THE STRUCTURE OF ANORECTAL AREA
Congenital anomalies of a rectum and anus meet rather often: insignificant anomalies — at 1 of 500 live-born, expressed — at 1 of 5000 live-born. These anomalies are combined with malformations of uric system, a gullet and, more rare, a duodenum. The most acceptable clinical classification divides anorectal anomalies on "low" and "high" depending on whether they are localized is higher or lower than a pelvic diaphragm.
Embryology and Pathogeny. The anus and a rectum are formed of dorsal part of a back gut, or a foul place when lateral outgrowths of a mesenchyma form on the average line the urorectal partition separating a rectum and the proctal channel from a bladder and an urethra. Between these two systems there is a kloakalny channel which is closed on the 7th week of pre-natal development. In process of growth of a mesoderm the kloakalny partition is divided on urogenital (ventrally) and proctal (dorsalno). On the 7th week of pre-natal development in urogenital part of primary foul place the outside opening appears; in proctal department of a foul place it forms later. Merge of proctal hillocks and invagination of the outside fabrics which are going deep in the direction of a rectum form an anus, or a proctodeum. The proctodeum and a rectum are divided by a temporary partition which is broken off on the 8th week of pre-natal development.
Disturbance of forming of anorectal structures at various stages leads to emergence of various inborn defects — from a stenosis of an anus, an incomplete rupture of a proctal partition and an atresia of an anus ("low" type) before not omission of a foul place and lack of invagination of a proctodeum ("upper" type). Not fusion of channels between uric and rectal parts of a foul place is shown by fistulas which are more often observed at boys. At girls fistulas connect a rectum more often to a vagina, than to uric system.
As the muscle of an outside proctal sphincter comes from an external leaf of a mesoderm, it usually is not broken at obstructive anomalies of an anus and a rectum.
Types of anomalies of anorectal area. "High" anomalies occur almost only at boys. One blind end of rectourethral fistula is in a rectum, and another — in prostatic part of an urethra. The gut blindly comes to an end above a pubic pryamokishechnoy of a muscle; outside and internal proctal sphincters are absent; pubic pryamokishechnaya the muscle rather poorly supports an anus and a rectum. This pathology is combined with a sacrum underdevelopment, total or its partial absence and, therefore, with disturbance of an innervation and functions of pelvic bodies. At girls "high" anomalies are provided by the fistular courses between a rectum and a back vault of the vagina.
The atresia of a rectum arises because normally developed proctodeum does not connect to a rectum; they can be at considerable distance from each other or be divided only by a mucous membrane. At a rectum atresia fistulas are absent. The malformation when the urethra and a rectum open in the general foul place is known. In this case there is the only kloakalny opening on a crotch and neither the urethra, nor a rectum are visible.
Ekstrofiya (ectropion) of a foul place. This heavy anomaly includes a bladder ectropion, a nonperforated anus, an underdevelopment or lack of a large intestine, sharp deformation of outside genitalias and sometimes small umbilical hernia.
At the "low" anomalies which are localized at the level of a pelvic diaphragm or below it outside and internal proctal sphincters are well developed and normally function. At boys the anus can be closed by a skin membrane — the so-called "the closed anus" from kpered on which average line there is a fistulous opening. It can be localized on a crotch, a scrotum, even on a penis. At girls the malrelated anus opens on a crotch, in anticipation of a vagina or in the vagina. The intermediate type of "low" defects is shown by rectourethral fistulas.
Diagnosis. Estimating the newborn's condition with a malformation of a rectum and an anus, first of all it is necessary to define what type of anomalies it treats ("low" or "high"). The choice of palliative or radical methods of treatment, and also the forecast depends on it.
The stenosis of the anorectal channel can be limited or total. Narrowing is diagnosed at manual and endoscopic research. The nonperforated proctal membrane looks as a thin transparent plate which easily stretches meconium.
Fig. 12-17. Identification of a sleny intestinal pocket at a nonperforated anus or total absence of a rectum (by the Wangensteen — Rice method).
The child is held headfirst, at the same time intestinal gas fills a blind pocket.
and. The roentgenogram of intestines p vertical position of the child (the head up), the horizontal level of gas is visible. Localization of impassability is not visible.
. The child is held headfirst. Impassability level is accurately visible. In proctal area there is a lead tag.
More than 90% of "low" defects are fistulas which outside opening is on a crotch or in anticipation of a vagina. Such fistula can be not noticed until from it meconium does not begin to be emitted. Repeated careful surveys of the child in the first 24 h life allow to see meconium pieces at an outside fistular opening. Detection at the boy of meconium about an anus or a kpereda from it is a sign of "low" anomaly. It is possible to see the skin crossing points reminding by the form the handle from a bucket both at "high", and at a "low" atresia. Existence of perineal hillocks — the cystous accumulations of dense slime which are located on the average line of a kpereda from an anus and even passing to a scrotum, always testifies to the "closed" anus. At girls it is possible to confirm the diagnosis and to define the course of the proctal channel by the catheter entered into a malrelated anus. Retraction existence on site does not indicate an anus "low" anomaly yet. The diagnosis is confirmed radiological when a contrast agent through a thin catheter is entered into the fistular canal.
Point out "high" defect badly expressed proctal hollow eminating a crotch and defects of development of vertebrae. Release of meconium with urine — an important symptom of fistula between uric system and a rectum or atresias of the rectum which is located over a pelvic diaphragm. In most cases X-ray inspection is conducted right after stretching of intestines or within the first days (fig. 12-17) is revealed. Before making the roentgenogram, the child is held by several minutes headfirst; at the same time gas forces out meconium from the most distal departments of a large intestine. Stephens suggested to consider that the muscle lifting an anus is located on the line connecting a pubic symphysis to the last segment of a sacrum; if the gas bubble is visible proximal to this line, then anomaly is referred to "high" type. By other techniques the level of a gas bubble is correlated to the ischium having the comma form. Rectourethral fistula can be revealed by means of a retrograde uretrotsistografiya.
If any of the called methods does not allow to determine authentically rectum atresia level, then for the benefit of the child it is necessary to consider that it has a "high" anomaly. Blind opening of a crotch in hope to find low lying rectal bag is contraindicated.
Anorectal defects are often combined with other inborn pathology. The expressed changes in uric system and a backbone find at "high" defects in 50% of cases and at "low" — in 25%. It follows from this that the excretory urography needs to be carried out by all patient, especially at the solution of a question of radical treatment of "high" defects. Research of haunch bones can reveal anomaly of a structure of a sacrum which will have further significant effect on functions of intestines and uric system. Existence of rectourethral fistula is demonstrated by allocation with urine of meconium or gases.
Treatment. A stenosis of proctal dripped treat by method of manual or tool dilatation. Other forms of an atresia of an anus are subject to surgical correction.
As at "low" defects at girls the system of the muscles lifting an anus is kept, carry out only local intervention. At such children function of deduction of fecal masses completely remains and therefore unreasonable operation can do harm. There are no proofs that the shift of an anus of a kpereda approximately on 1 cm serves as the reason of infections of generative organs and uric system or conducts to difficulties at childbirth. In rare instances when there is rectovaginal fistula, the anus needs to be transplanted kzad. In case of the "closed" anus at boys and an anus, malrelated in an entrance of the vagina, at girls it is necessary to execute recovery operation at which the membrane closing an anus is cut in the dorsal direction, and the mucous membrane is hemmed to edges of the created anus. After operation can be required regular dilatation within 1 — 2 month.
At defects of "high" type the optimum result is reached when radical plastic surgery is preceded by imposing of a transverzostoma for 6 — 12 months. It is very important to place intestines in the corresponding opening of a pelvic diaphragm, and an anus — in the area of an outside sphincter. The fistular courses close.
The above there is an atrezirovanny rectum, the surgical intervention is more extensive and the postoperative period is heavier. Considerable anomalies of a sacrum usually lead to disturbance of nervous control of the act of defecation. However patient long education at the child of hygienic skills yields satisfactory physiological result. At a number of patients such postoperative complications as a stenosis and bad regulation of function of an outside sphincter are possible (an incontience a calla), but the main postoperative problem are locks. Absence of feeling of filling of a rectum leads to its overflow, emergence of "locking ponos", formation of the acquired megacolon. The timely measures promoting bowel emptying allow to avoid formation of dense fecal conglomerates. The child should be accustomed to defecation at the same time irrespective of, there is a desire or not. Sometimes it is necessary to do enemas daily.
Forecast. At "low" type of anorectal defect deduction function the calla remains. At "high" defect only in rare instances it is possible to achieve normal deduction; most of patients actually has perineal kolostoma. Such form of a kolostoma is more preferable abdominal at children of advanced age and teenagers.