Decision-making in the new born period

The decision to perform an anoplasty in the newborn period or to delay the repair and perform a colostomy is based on the infant's physical examination findings, the appearance of the perineum, and any changes that occur over the first 24 hours of life.

Meconium is not usually observed at the perineum in a baby with a rectoperineal fistula until at least 16-24 hours of life. Abdominal distension does not develop during the first few hours of life but is required to force meconium through a rectoperineal fistula, as well as through a urinary fistula. This is because the most distal part of the rectum in these children is surrounded by a funnellike voluntary muscle structure that keeps part of the rectum collapsed and empty. The intra-abdominal pressure must be high enough to overcome the tone of the muscles that surround the rectum if meconium is to be expected at the perineum or in the urine. Therefore, the decision of whether to perform a colostomy or an anoplasty must be delayed for 16-24 hours while the surgeon evaluates for clinical evidence of the baby's anorectal anomaly.

Not waiting at least 16-24 first hours of life and doctors can miss this important clinical clue.

Also, any method of trying to determine the location of the distal rectum before the above mentioned period, is flawed because of the lack of abdominal distention. Therefore, the distal rectum can be falsely located as high.

In fact, the only way to determine the patient's anorectal defect definitively is to perform distal colostography, which requires the presence of a colostomy. Yet we can say, that only in one case a definitive repair in the newborn period can be performed without a protective colostomy (and as a consequence without distal colostography test), and that is Anoplasty for Rectoperineal fistula (males & females).

Some authors have performed definitive repair in the newborn period. The advantage to this approach is avoidance of the colostomy and earlier repair of the malformation; however, with this practice, considerable risk to the urinary tract exists because the surgeon does not know the precise anorectal defect. As previously said, the only way to determine the patient's anorectal defect definitively is to perform distal colostography, which requires the presence of a colostomy. Without this information, an operation in the newborn period is essentially a blind perineal exploration. The surgeon may not be able to locate the rectum and may find and damage other unexpected structures, such as the posterior urethra, seminal vesicles, vas deferens, and ectopic ureters, during the search for the rectum. Finally, without fecal diversion, the risk of dehiscence and infection exists. These complications may compromise the chance of achieving bowel function.

In females, the presence of a single perineal orifice in a patient is clinical evidence of persistent cloaca. Patients with these anomalies also have small genitalia. Examination of the abdomen may reveal an abdominal mass that likely represents a distended vagina (hydrocolpos). Abdominal ultrasonography is helpful to determine the presence of an obstructive uropathy and hydrocolpos.

Unfortunately, a common error in diagnosis occurs during the perineal inspection when a female is thought to have imperforate anus with rectovaginal fistula; however, in actuality, all 3 structures (urinary tract, vagina, rectum) meet in a common channel, and the baby has persistent cloaca.

Making the correct determination of persistent cloaca is vital because 90% of babies with persistent cloaca have an associated urologic problem and 50% have hydrocolpos. This may be a source of urinary tract obstruction, and if undrained during the newborn period, it can become infected and lead to vaginal scarring . The urinary tract and the distended vagina both may need to be managed in the newborn period to avoid serious complications.

Missing the diagnosis of persistent cloaca frequently means that an obstructive uropthy is overlooked. The patient may then receive only a colostomy, and subsequently, sepsis, acidocis, and sometimes death may occur.

The other implication of missing the diagnosis of persistent cloaca involves repairing only the rectal component of the anomaly, leaving the patient with a persistent urogenital sinus.

Colostomy

A descending colostomy with separated stomas is recommended.

The advantages of this type of colostomy include the following:

1.  It defunctionalizes only a small portion of distal colon.

2.  In cases of large rectourinary fistulae in which the patient passes urine into the bowel, the urine comes out easily through the mucous fistula, avoiding problems of hyperchloremic acidosis caused by urine absorption. Urinary tract infections are also avoided.

3.  Washing and cleaning the portion of the colon distal to the colostomy is relatively easy.

4.  Distal colostography is easy to perform.

5.  The sigmoid loop is kept distal to the colostomy, which provides enough length to reach the perineum during the definitive pull-through procedure.

6.  The separated stomas prevent spillage of stool from proximal to distal bowel, which avoids impacted distal stool and urinary tract infections.

7.  A low incidence of prolapse exists with this technique. Proximal stoma prolapse in a normally rotated colon should not occur with this technique because the colon is well fixed to the retroperitoneum just before the colostomy rises to the skin level. The distal stoma may prolapse because it is in a mobile portion of the colon. To avoid this, the distal stoma must be made intentionally small because it is used only for irrigations and radiologic studies.

When performing the colostomy in the newborn, the distal bowel should be irrigated to remove all the meconium. This prevents formation of a megasigmoid, which may be responsible for the future development of constipation.

Colostomy errors include the following:

1.  Too-distal sigmoidostomy (the most common error): The colostomy is placed too distal and interferes with the pull-through procedure.

2.  Right upper sigmoidostomy: Cases of inadvertent sigmoid colostomy placed in the right upper quadrant during attempts to perform a transverse colostomy have been reported. Anchoring of the sigmoid in the right upper quadrant interferes with the pull-through procedure.

3.  Incomplete diverting of stool: An error occurs when a loop colostomy does not divert the stool completely and allows for distal stool impaction and urinary tract infections.

4.  Megarectum: Transverse colostomies can produce megarectum

Constipation

Constipation is the most frequent problem encountered after treatment for imperforate anus in which the rectum has been preserved.

Constipation is the most important problem to avoid after definitive repair for female patients with rectovestibular or rectoperineal fistula and for male patients with recto-bulbar urethral fistula, imperforate anus without fistula, and rectoperineal fistula.

Failure to avoid constipation can result in megarectum and megasigmoid, and it can lead to fecal impaction and overflow incontinence.