51 Pediatric: Hirschsprung’s, Anorectal Malformations, and Other Conditions

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51

Pediatric: Hirschsprung’s, Anorectal Malformations, and Other Conditions

Alberto Peña and Marc Sher

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Hirschsprung’s Disease

Hirschsprung’s disease (congenital megacolon) is an anomaly characterized by functional partial colonic obstruction caused by the absence of ganglion cells. It occurs in approximately 1 in 5000 births. Boys are more frequently affected than girls and it is more common in Caucasians. A deletion in the long arm of chromosome 10 has been found.¹The functional disturbances in this condition are attributed to the absence of ganglion cells from the Auerbach’s myenteric plexus (located between the circular and longitudinal layers of smooth muscle of the intestine), the Henle’s plexus (located in the submucosa), and the Meissner’s plexus (in the superficial submucosa). The absence of these cells probably produces uncoordinated contractions of the affected colon. This is translated into a lack of relaxation of the colon that results in partial colonic obstruction.

The length of the aganglionic colonic segment varies. In the most common type, the aganglionic segment includes the rectum and most of the sigmoid colon. Nearly 80% of all patients have this type. In approximately 10% of the patients, the aganglionosis extends to the area of the splenic flexure or the upper descending colon. Total colonic aganglionosis occurs in another 8%–10% of the patients. In those cases, the absent ganglion cells sometimes extend to the distal terminal ileum.

In the so-called “ultrashort” aganglionosis, the ganglion cells supposedly are lacking only a few centimeters above the pectinate line of the rectum. This is a rather controversial condition.

Very rarely, one can see patients who have universal aganglionosis, meaning that the ganglion cells are absent in the entire gastrointestinal tract, which is a lethal condition.

The clinical manifestations are those of a partial colonic obstruction. In addition, these patients have a poorly characterized immunologic mucosal defect that may explain why they suffer from an inflammatory process called enterocolitis, which is the main cause of death. In addition, fecal stasis seems to promote the proliferation of abnormal colonic flora (Clostridium difficile) as well as production of endotoxins that contribute to the aggravation of the clinical condition.

Usually the patient becomes symptomatic during the first 24 – 48 hours of life. Delayed passage of meconium (more than 24 hours), abdominal distention, and vomiting are the most common symptoms. A rectal examination may produce explosive passage of liquid bowel movements and gas, which dramatically improves the baby’s condition. This clinical improvement only lasts for a few hours, after which the symptoms recur. If the colon is not decompressed, the infant usually suffers from sepsis, hypovolemia, and endotoxic shock.

Cecal perforation may occur. About 25%–30% of these babies die when unrecognized or not treated.²Patients that do survive unrecognized and without treatment, ultimately develop the classic clinical picture initially described for this condition. They have severe constipation, a huge megacolon, and an enormously distended abdomen. This clinical situation is extremely rare nowadays in developed countries.

Occasionally, these patients are misdiagnosed as having idio- pathic chronic constipation. In the latter condition, the patients are not seriously ill, and it is very common for them to have overflow pseudoincontinence (encopresis). A rectal examination discloses a rectum full of fecal matter. On the contrary, patients with Hirschsprung’s disease usually have malnutrition, lack of normal development, an empty aganglionic narrow rectum, and they do not have soiling.

The presence of the symptoms described in a newborn must alert the clinician to the diagnosis of Hirschsprung’s disease. An abdominal film shows massive dilatation of small bowel and colon. It is almost impossible to differentiate colon from the small bowel, in a plain abdominal film during the newborn period. A contrast enema is used in most institutions to clarify the diagnosis. The catheter should be introduced only a few centimeters into the rectum in order to be able to visualize the nondilated aganglionic segment of the rectosig- moid, followed by a transitional zone and then a proximal dilatation. These typical changes are often not obvious during the neonatal period. The older the patient, the more obvious the size difference between normal and aganglionic segment.

In patients with total colonic aganglionosis, the entire colon is not distended; the dilatation affects the small bowel only.

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A manometric study may show an absent rectoanal inhibitory reflex. However, this study is not considered reliable for this diagnosis early in life but more helpful in the adolescent or adult with unrecognized short segment disease.

The definitive diagnosis is based on both the histologic absence of ganglion cells, and the presence of hypertrophic nerves in a rectal biopsy. These can be taken as full-thickness rectal biopsies under direct vision. More recently, a suction biopsy has gained wide acceptance. The specimen, however, must include mucosa and submucosa. An important diagnostic alternative is the determination of acetylcholinesterase activity in the mucosa and submucosa.³

Medical Management

Colonic decompression and irrigation with saline solution is the most valuable tool for the emergency management of newborn babies. This maneuver may dramatically improve a very ill neonate. Irrigations should not be confused with enemas. An enema is a procedure in which an amount of fluid is instilled into the colon. It is expected that this fluid will be spontaneously expelled. Patients with Hirschsprung’s disease are, by definition, incapable of expelling this fluid and, therefore, enemas are contraindicated. A colonic irrigation, however, promotes the expelling of the rectocolonic contents through the lumen of a large rubber tube, which is cleared with small amounts of saline solution. Rectocolonic irrigations may save the baby’s life, but are not the ideal long-term form of treatment. Once the histologic diagnosis has been established, the baby must remain with nothing by mouth, and the irrigations must continue in preparation for the surgical treatment.

Surgical Treatment

The basis of the surgical treatment consists of the resection of the aganglionic segment and pullthrough of a normoganglionic segment to be anastomosed to the rectum, immediately above the pectinate line. This should guarantee the preservation of bowel control. There are several ways to achieve these basic goals. The surgical treatment has evolved significantly since 1948 when the first surgical technique was described.⁴

Originally, these patients were subjected to a staged treatment. The first stage consisted of the opening of a diverting colostomy. The second stage included the resection of the aganglionic segment and pullthrough of the normoganglionic bowel, and the third stage was the colostomy closure.

Subsequently, surgeons adopted a two-stage modality that included the opening of the colostomy during the newborn period. The second stage consisted of the pullthrough, leaving the patient without a colostomy.

More recently, the treatment most often used consists of a neonatal primary procedure without a protective colostomy.^5,6 This approach is less invasive and avoids the morbidity of a

stoma and multiple surgeries. However, approaches may vary from country to country as with the surgeon’s experience. In addition, a primary procedure, without a protective colostomy, requires the presence of an experienced clinical pathologist, familiar with the interpretation of frozen sections. Also, in the case of a very ill, low-birth-weight newborn, or a very sick baby, a colostomy is still the optimal way to protect the patient.

In the presence of an experienced pathologist, the colostomy must be open in a normoganglionic portion of the colon. In the absence of an experienced pathologist, the surgeon must open the colostomy, proximal to the transition zone. If the transition zone is not evident, the colostomy should be done in the right transverse colon. In the event of a nondilated entire colon, the patient should receive an ileostomy.

The definitive procedure (resection of the aganglionic segment and pullthrough of the normal ganglionic colon) can be done in different ways. Swenson and Bill⁴described an operation consisting of an intraabdominal resection of the aganglionic segment including a part of the normoganglionic dilated colon, and pullthrough of a normoganglionic bowel, with a perineal anastomosis of the normoganglionic bowel to the rectum, above the pectinate line.

Duhamel⁷described an operation designed to avoid pelvic dissection and potential nerve damage. He proposed to preserve the aganglionic rectum, dividing the colon at the peritoneal reflection. The normoganglionic colon is then pulled through a presacral space, created by blunt dissection and anastomosed to the posterior rectal wall above the pectinate line.

Soave⁸ designed an ingenious and appealing procedure consisting of an endorectal (submucosal) dissection of the aganglionic colon, leaving a seromuscular cuff. He carried this dissection down to the rectum above the pectinate line.

The normally innervated colon is passed through the muscu- lar cuff and anastomosed to the rectum. The purpose of this operation, again, was to avoid the perirectal dissection and its potential negative effects caused by denervation of pelvic organs.

The original Soave procedure was performed in two stages.

During the first stage, the colon was pulled down, but was not anastomosed to the rectum; it was left protruding outside the rectum. In the second stage, a week later, the protruded bowel was resected and the anastomosis was performed.

Subsequently, Boley⁹proposed a primary anastomosis.

The abdominal portion of all of these operations can be done laparoscopically. This has been advocated by a number of pediatric surgeons recently.^10–12 Georgeson and col- leagues^10,11 described their technique of laparoscopically obtained seromuscular biopsies in 80 patients to successfully determine the transition point. They preserved the marginal artery establishing a colonic pedicle for anastomosis through four ports, laparoscopically.

In 1998, De la Torre-Mondragon and Ortega-Salgado¹³ and subsequently Langer et al.¹⁴ reported a novel, transanal approach for the management of this condition.

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They demonstrated that the whole procedure can be done transanally provided that the patient does not have a long segment type of aganglionosis. A special retractor (LoneStar™;

Lone Star Medical Products Inc., Houston, TX) is used to expose the dentate line as well as the rectal mucosa.

We recommend the use of multiple fine sutures taking the rectal mucosa 1 cm above the pectinate line. These allow the surgeon to exert a uniform traction on the rectal mucosa.

Peripheral to this series of silk stitches, an incision is performed with cautery and a circumferential dissection of the rectum is performed applying uniform traction. The dissection can actually be performed submucosally or full thickness, depending on the experience of the surgeon. As the surgeon progresses in the dissection, full-thickness biopsies are taken to determine the place where the normoganglionic portion of the colon is reached. The peritoneal reflection is soon found. It is recommended to continue the dissection until one reaches an area 4 cm above the transition zone to be sure that normoganglionic bowel is pulled down. The normoganglionic bowel is transanally anastomosed to the anal canal, 1 cm above the pectinate line. Because the majority of patients have a transition zone in the sigmoid colon, it is possible to repair the entire defect using this technique, without a laparotomy or laparoscopy.^13,14 When the transition zone is located higher, the surgeon determines when he or she needs a laparoscopic-assisted procedure or a laparotomy. We specifically recommend resecting not only the aganglionic segment of the colon, but also the very dilated part of the colon because we have learned that a very dilated colon also has very poor peristalsis.

De la Torre-Mondragon and Ortega-Salgado¹³and Langer et al.¹⁴perform the rectal dissection submucosally, in a simi- lar way to the reoperative ileoanal pouch repairs for pouch- vaginal fistulas in adults described by Fazio and Tjandra.¹⁵

Complications and postoperative sequelae can be divided into two categories: preventable and nonpreventable.

Preventable complications should not occur because they are caused by technical errors. A feared preventable sequela is fecal incontinence. This is likely related to injury to the con- tinence mechanism. All these procedures were originally designed to prevent this from happening, provided they are performed correctly. Dehiscence, retraction, stricture, abscess, and fistula are all considered preventable because they are usually caused by technical errors. During the pullthrough, the surgeon must be familiar with the manipula- tion of the blood supply and the arcades of the colon to guarantee a good blood supply in the pullthrough colon. The anastomosis should be done without tension.

A nonpreventable complication is enterocolitis. This is also unpredictable, and a rather mysterious condition. Despite receiving a technically adequate operation, patients may have this condition. The frequency of this condition varies¹⁶and its etiology is unknown. We believe that fecal stasis is the most important predisposing factor. Fecal stasis occurring in the colon in a normal individual produces constipation.

In patients with Hirschsprung’s disease, stasis frequently results in proliferation of abnormal bacteria, ulcerations of the colon, absorption of endotoxins, shock, and sometimes perforation. These patients respond to colonic irrigations;

occasionally they require a colostomy and a secondary pullthrough.

Constipation may also occur after these procedures. It is more common in patients in whom the aganglionic segment was resected, but a dilated portion of the colon was pulled down. This is a partially preventable condition. Most cases of constipation can be avoided by resecting not only the aganglionic segment but also the dilated portion of the colon.

Each one of the techniques described has its own advocates. The analysis of different series shows that the most important factor that affects the clinical results is the experience and familiarity of the surgeon with each one of those procedures. Some surgeons claim that the Swenson operation exposes the patient to nerve damage that may provoke urinary and sexual disturbances. The Duhamel procedure is frequently followed by severe problems of constipation and dilatation of the aganglionic piece of colon left in place. In the Soave operation, patients may experience fecal incontinence, as well as perianal fistulas and abscesses because of the presence of islets of mucosa left in place during the endorectal dissection.

Advocates of a transanal approach cite the decreased morbidity and enhanced recovery as a consequence of a procedure without the intraabdominal dissection.^17,18 In addition, this approach permits early postoperative feeding, shorter length to stay, faster recovery, and possibly less chance for postoperative adhesions. Langer^17,18 compared the standard open approach to transanal Soave versus selective laparoscopic visualization and reported a shorter hospitalization and significantly less overall cost to the healthcare system. There was a trend of lower complication rates, specifically less incidence of adhesive bowel obstruction. They recommended only selective laparoscopy for children with long segment disease.

Surgical Management of Total Colonic Aganglionosis

We believe that the ideal treatment for this very serious condition has not yet been found. The current treatment consists of resection of the entire aganglionic colon and pullthrough of the normal aganglionic terminal ileum to be anastomosed to the rectum. To avoid fluid losses and in an attempt to decrease the number of bowel movements per day, as well as to promote water absorption, Martin¹⁹proposed to leave a part of the rec- tosigmoid and descending aganglionic segment in place. The normoganglionic terminal ileum is anastomosed in a latero- lateral manner to this colon and finally connected to the posterior aspect of the rectum as in the Duhamel procedure. Kimura et al.²⁰proposed the use of a right colon patch with the hope of creating a reservoir for water absorption. Another option is the ileoanal J-pouch anastomosis; however, risks associated with a

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pelvic dissection are obviously higher. All these approaches have proved to be rather simplistic. The stasis of stool in the small bowel produces bacterial proliferation and enterocolitis.

Rather than absorbing water, very often the intestine secretes fluid into the lumen, producing a secretory diarrhea. Therefore we, as others, believe that a straight ileorectal anastomosis is the preferred option, acknowledging that all patients with this condition will have a poor quality of life.

Surgical Treatment of Ultrashort Hirschsprung’s

The surgical treatment of the ultrashort-segment aganglionosis is as controversial as the existence of this condition.

Normal individuals have an area of aganglionosis above the pectinate line. The length of this aganglionic area has not been accurately or scientifically determined. This is the reason why the diagnosis of ultrashort Hirschsprung is so controversial. Some surgeons propose an operation called myectomy, consisting of the resection of a strip of smooth muscle from the anal verge up to the area where ganglion cells are found. The results of this procedure, again, are highly controversial and there is no scientific basis to explain why this may improve the condition. More scientifically con- ducted studies are required to clarify this issue.

Most cases of Hirschsprung’s disease are diagnosed early in life, but a few patients reach their late teens and some are in adulthood before a diagnosis is made. Hirschsprung’s disease in adults must be distinguished from other causes of megacolon such as Chagas’ disease, volvulus, colonic inertia, Ogilvie’s syndrome, and other disorders of central nervous system.

Typically, the disease in adults is of the ultrashort segment vari- ety. An internal sphincterectomy may yield a satisfactory result as performed after a failed pullthrough procedure.

This operation involves removing a thin strip of the internal sphincter muscle in the posterior midline starting 1 cm above the dentate line. The strip should extend as far proximal as exposure allows, possibly up to 15 cm. Lynn describes a transanal approach, but we prefer a posterior sagittal approach to enable a high myectomy.^21,22Anal manometry may aid in assessment of the adequacy of the myectomy, because the resting tone pressure should be less than 30 mm Hg.

Neuronal Intestinal Dysplasia

Neuronal intestinal dysplasia (NID) refers to a histologic condition that includes hypertrophy of ganglion cells, immature ganglia, hypoganglionosis, hyperplasia of the submucosal and myenteric plexus, giant ganglion cells, as well as hypoplasia or aplasia of the sympathetic innervations of the myenteric plexus. These histologic abnormalities have been described as occurring in a localized or disseminated manner.²³

The histologic diagnosis of NID requires a high index of suspicion as well as the availability of special histologic techniques and expertise. Not all pathologists agree as to the existence of this condition.

NID has become popular because most surgeons expect to find histologic abnormalities in patients who have undergone a technically correct operation for Hirschsprung’s disease and still have symptoms of enterocolitis or constipation. It was also expected that these histologic abnormalities would explain the pathophysiology of other colonic motility disorders.

Unfortunately, a precise correlation between histology and clinical manifestations is lacking. The histologic diagnostic criteria have not been standardized among different pathologists and different countries. In addition, the precise options for therapy have not been clearly established.²⁴

Anorectal Malformations (Imperforate Anus)

Anorectal malformations represent a spectrum of defects characterized by the absence of an external anal orifice. The overwhelming majority of the patients have an abnormal communication between the rectum and the perineum (perineal fistula), the vestibule (vestibular fistula), or the vagina (vaginal fistula) in the female. In some female patients, rectum, vagina, and urethra are fused together forming a common channel (cloacal malformation) and open into a single external orifice. In the male, the communication is with the urethra (rectourethral fistula), or the bladder (rectobladder neck fistula). Only 5% of the entire spectrum of patients are born with no fistula. Anorectal malformations occur in about one in every 5000 newborns. Males seem to have this condition slightly more frequently than females. The most common type of defects seen in boys is a rectourethral fistula and the most common type in girls is vestibular fistula. Table 51-1 shows our proposed classification of anorectal malformations.

Associated Anomalies

Urogenital abnormalities occur in about 50% of all patients with anorectal malformations.²⁵The higher and more complex the anorectal malformations, the higher the incidence of

TABLE51-1. Current classification of anorectal malformations Male

Perineal fistula Rectourethral fistula

Bulbar Prostatic

Rectobladder neck fistula Imperforate anus without fistula Rectal atresia

Female Perineal fistula Vestibular fistula

Imperforate anus without fistula Rectal atresia

Cloaca

Complex malformations

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urologic associated defects. Urologic malformations are a common source of morbidity in these patients. About 90%

of patients with a rectobladder neck fistula in males as well as in cases of cloacas with a common channel longer than 3 cm, have an associated urologic problem. Unilateral renal agene- sis is the most common urologic anomaly encountered in children with these defects. Vesicoureteral reflux is the second most common abnormality. Other important abnormalities include cryptorchidism, hypospadias, renal ectopia, and hydronephrosis.

Sacral and spinal abnormalities are also very common in patients with anorectal malformations. The sacrum is frequently abnormal. The sacral abnormalities also represent a spectrum that varies from a completely absent sacrum to a completely normal one, including different degrees of hypodevelopment. There seems to be a direct relationship between the degree of sacral abnormality and the final functional prognosis. These patients also have hemivertebrae and as a consequence different degrees of scoliosis. The presence of hemivertebrae also seems to be related to a poorer functional prognosis.

Twenty-five percent of patients with anorectal malformations have a defect called tethered cord.²⁶ The majority of patients with tethered cord have a bad functional prognosis. In this condition, the cord is abnormally attached (tethered) to the spine. During the natural growth of the baby, it is believed that the spine grows faster than the cord, producing traction on the nerve fibers that may produce functional disturbances in the motion of the lower extremities and may contribute to sphincter problems.

Hemisacrum is sometimes associated with an anorectal malformation and there is always a mass located in the area of the sacral defect. An anorectal malformation with hemisacrum and a presacral mass is known as the Currarino triad.

The most common sacral masses in these patients are a der- moid, teratoma, lipoma, anterior meningocele, or a combination of all these. These patients also have a poor functional prognosis.

Approximately 8% of all patients with anorectal malformations have esophageal atresia. These patients usually have a very high anorectal defect and other associated anomalies, especially urologic.

About 30% of patients with anorectal malformations also have some sort of cardiovascular congenital anomaly. Most frequently seen are patent ductus arteriosus, atrial septal defect, ventricular septal defect, tetralogy of Fallot, as well as other more complex malformations. Fortunately, only 10% of patients have a cardiovascular malformation with significant hemodynamic repercussions that requires surgical treatment.

The main concern in a patient with anorectal malformation is whether or not the patient will have bowel control, urinary control, and sexual function in the future. The higher the malformation, the worse the functional prognosis will be.

The higher the anorectal defect, the more likely the child will have fecal incontinence, but the lesser the chance of

having constipation. Conversely, the lower the malformation the higher the incidence of constipation and the lower the incidence of fecal incontinence will be.

Description of Specific Defects Males

Perineal Fistula

This is the simplest of all defects. The rectum opens anterior to the center of the external sphincter in the area known as the perineum. The rectal orifice is usually incompetent, meaning that it is too narrow to allow normal passage of stool.

Sometimes, the end of the rectum lies immediately below a very thin layer of epithelium with an external opening located at the base of the scrotum or sometimes at the base of the penis. The meconium sometimes can be seen below that very thin layer of epithelium giving an impression of a black rib- bon. The overwhelming majority of these patients have a normal sacrum, and less than 10% of them have associated defects. The final functional prognosis is excellent,²⁷provided these patients receive adequate treatment. These patients can be operated on during the newborn period. The ideal operation consists of moving the orifice back to the center of the sphincter creating a normal-sized anus.

Rectourethral Fistula

In this group of malformations, the rectum connects to the urethra. In the most common subtype, the rectum opens into the lower part of the posterior urethra known as bulbar urethra and, therefore, the defect is called rectourethral bulbar fistula.

The rectum passes through a funnel-like striated sphincter mechanism to reach the lowest part of the posterior urethra.

Eighty-five percent of these patients achieve bowel control when treated properly.²⁷ Approximately 30% of them have other associated defects.²⁷

In the second subtype, the rectum opens into the upper part of the posterior urethra (prostatic) and therefore it is called rectoprostatic fistula. Only 60% of these patients achieve bowel control later in life. Sixty percent of them have important associated defects.²⁷

Most of these patients (rectourethral fistula) require a colostomy at birth and subsequently (usually 1 month later) they receive the final repair of the malformation. Lately, some of the patients with rectourethral bulbar fistula have been repaired primarily during the newborn period without a protective colostomy.

The perineum of patients with anorectal malformations have characteristic features that must be recognized by the clinician. The higher the malformation, the more tendency to have a flat perineum (flat bottom), meaning that the natural midline groove is absent and there is no distinguishable anal dimple. The lower the malformation, the more prominent the midline groove and the anal dimple. In patients with

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rectourethral bulbar fistula, there is a recognizable midline groove as well as an anal dimple and in patients with rectoprostatic fistula, there is conspicuous tendency for the perineum to be flat. Also, the anal dimple tends to be closer to the scrotum, the higher the malformation. One can also frequently see a bifid scrotum in cases of prostatic fistula.

Rectobladder Neck Fistula

This is the highest of all defects in male patients. The rectum is connected to the bladder neck. Ninety percent of these patients have important associated defects. The perineum is frequently flat. The rectum is located above the funnel-like sphincter mechanism (levator). These patients are the only ones that require a laparotomy or laparoscopy in addition to the posterior sagittal approach to be repaired. Only 15% of these patients achieve bowel control later in life.²⁷

Imperforate Anus Without Fistula

This is a rather unusual anomaly that occurs in 5% of all children with anorectal malformations. Half of them also have Down’s syndrome. More than 90% of all patients with Down’s syndrome, who have an anorectal malformation, have this specific type of defect. Eighty percent of the babies with Down’s syndrome and this malformation will eventually have bowel control when they receive an adequate operation.

Approximately 90% of patients with this defect and without Down’s syndrome also have bowel control.²⁸ Patients with this malformation usually have a good sphincter mechanism and a good sacrum.

Rectal Atresia

This malformation occurs in only 1% of all cases. It consists of a complete or partial interruption of the rectal lumen located between the anal canal and the rectum. The external appearance of the perineum is normal. The malformation is usually discovered when a nurse tries to take the rectal tem- perature in a baby. The sacrum is normal as well as the sphincter mechanism. One hundred percent of these patients will have bowel control after a correctly performed operation.²⁵

Female Defects Perineal Fistula

In these female babies, the rectum opens in what is called the perineal body between the normal location of the anus and the female genitalia. All that was described about this defect in males is true for females. These patients can be repaired at birth without a colostomy. The prognosis is excellent.²⁷ Vestibular Fistula

This is by far the most common defect seen in female patients. The rectum opens in the vestibule of the female

genitalia just outside the hymen. Rectum and vagina share a very thin common wall. About 30% of these babies have associated defects. Ninety-three percent of these babies will have bowel control when properly treated.²⁷The sacrum is usually normal.

Vestibular fistula is frequently misdiagnosed as a rectovaginal fistula.²⁹ Vaginal fistula is an extremely unusual defect. It represents less than 1% of all the female defects. In those unusual cases of vaginal fistula, the rectum opens into the posterior vaginal wall deeper to the hymen.

Most of the vestibular fistula cases are successfully operated on at birth without a colostomy. Unfortunately, many of those patients have dehiscence and retraction when the surgical technique used is not adequate. A secondary operation in these cases does not render the same good result as in cases of a well-done primary procedure.

It is uncommon to see this type of defect in females. All that was mentioned about this defect in males is true about this defect in females.

Rectal Atresia

This condition does not differ from the same defect in males.

Cloaca

A cloaca is defined as a malformation in which the rectum, vagina, and urinary tract are fused together forming a common channel. This single channel opens where the normal urethra is located in females. Externally, these babies have rather small-looking genitalia. Separation of the small labia allows the observer to see a single orifice, which confirms the clinical diagnosis of a cloaca. Cloaca represents another spectrum of defects. The length of the common channel varies from 1–7 or even 10 cm. The length of the common channel is directly related to the final functional prognosis for bowel and urinary control. The turning point seems to be around 3 cm. Patients with a common channel shorter than 3 cm can be repaired posterior sagittally without opening the abdomen and the prognosis for bowel and urinary control is good. However, cloacas with a common channel longer than 3 cm represent a serious technical challenge. The operation frequently requires not only a posterior sagittal approach but also a laparotomy. The repair of those complex defects requires experience and familiarization with pediatric urology. The final functional prognosis is not very good in cases with a long common channel.³⁰

Associated defects occur in about 90% of all patients with a common channel longer than 3 cm.

About 40% of patients with cloaca have hydrocolpos (a very dilated vagina full of fluid). The dilated vagina com- presses the trigone and may produce ureterovesical obstruction, megaureters, and hydronephrosis. Approximately 40%

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of the patients with cloaca also have different degrees of septation of the vagina and the uterus. This has important future implications, impacting menstrual flow,³¹ as well as obstetric potential.

Initial Management Male Babies

Perineal inspection and urinalysis allows determingtion of the likely type of malformation in about 90% of the cases.

The presence of a perineal orifice, by definition makes the diagnosis of a perineal fistula. This is also true when the baby has an external defect called “bucket-handle” malformation that is a skin bridge in the midline in the area of the anal dimple. The presence of a good midline groove and an anal dimple, as well as meconium in the urine, means that the patient has a rectourethral fistula. A flat bottom and bifid scrotum are signs of a very high malformation.

Diagnostic studies should be done after 24 hours of life, but not later than 36 hours. The reason for this is that it is necessary to wait until the most distal part of the rectum is distended in order for it to be seen by any of the diagnostic modalities [magnetic resonance imaging (MRI), ultrasound, CAT scan, or simple X-ray films]. Before 24 hours, the most distal part of the rectum is usually collapsed and it is difficult to see by these diagnostic modalities. Also, in order for meconium to be forced through a tiny distal fistula, it is necessary to wait until the intraluminal pressure is high enough to over- come the tone of the striated muscle that surrounds the distal rectum, which usually happens after 24 hours. During the first 24 hours, the clinician must try to answer two very important questions: Does the baby have an associated defect that threatens his/her life? Does the baby need a primary repair or a colostomy?

These questions should be answered in this order. The baby should be examined to rule out the presence of cardiovascular defects. The patient will remain with nothing by mouth, and insertion of a nasogastric tube is recommended to avoid vomiting and potential risk of aspiration. An ultrasound of the abdomen is indicated to rule out the presence of hydronephrosis. An ultrasound of the spine is also useful to rule out the presence of tethered cord. An X-ray film of the lumbar spine and the sacrum will rule out the presence of hemivertebrae and sacral abnormalities. A very abnormal sacrum is usually associated with a very high defect. If after 24 hours the surgeon is still not sure as to the type of defect that the baby has, a cross-table lateral film with the baby in prone position and the pelvis elevated should be performed.

This will show the location of gas inside a distended rectum.

If the rectum is visualized below the coccyx and the surgeons have experience with the neonatal repair of this malformation, the patient can be approached primarily. However, if the rectum is located higher than the coccyx, or the surgeons have no experience with these neonatal operations, it is better

to perform a diverting colostomy and to postpone the main repair for a later date.

Females

It is also true in females that simple inspection of the perineum will allow the surgeon to make a correct diagnosis during the neonatal period in most cases.

The presence of an anal opening in the perineum makes the diagnosis of perineal fistula.

Sometimes it is difficult to see the opening of the rectum in the vestibule because the female genitalia are swollen at birth because of the effect of the maternal hormones. The presence of a fistula in the vestibule establishes that diagnosis. To make the diagnosis of a rectovaginal fistula (extremely unusual defect) one would have to see meconium coming from inside the vagina, deeper than the hymen. The presence of a single perineal orifice makes the diagnosis of a cloaca.

If none of these signs are present after 24 hours, the baby should have a cross-table lateral film in prone position. Most likely the baby has an imperforated anus with no fistula (which represents 5% of all cases).

During the first 24 hours of life, the baby should be subjected to the same tests described for the male patient. If the baby has a cloaca, an ultrasound of the abdomen should be performed not only in the upper abdomen to rule out hydronephrosis, but also in the lower abdomen to rule out the presence of hydrocolpos. Most babies with a cloaca need a diverting colostomy. These babies should not be taken to the operating room unless the surgeon has already ruled out the presence of hydrocolpos. The hydrocolpos must be drained at birth, particularly when the baby has hydronephrosis. Before trying other procedures for the treatment of the hydronephrosis and megaureter, the hydrocolpos must be drained, which usually will take care of these problems.

Colostomy

Colostomies in babies with anorectal malformation should be totally diverting. Loop colostomies are contraindicated; they may allow the passing of stool from the proximal into the distal colon, producing direct fecal contamination of the urinary tract. The ideal colostomy should be created in the descending colon, with separated stomas. Both stomas should be separated enough as to allow the placement of a stoma bag over the proximal stoma. Distal to the mucus fistula, the baby should have enough length of colon to allow a comfortable pullthrough at the time of the main repair.

In cases of cloaca, the surgeon must also drain the hydrocolpos through the abdomen. When the vagina is so distended that it reaches the upper abdomen, it can be drained in the form of a vaginotomy, suturing directly the vaginal wall to the abdominal wall. When the vagina is not that large, it can be drained with a tube that is exteriorized through a separate hole in the abdominal wall.

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Two weeks after the colostomy, a high-pressure distal colostogram should be performed.³²This consists of injection of hydrosoluble contrast material through the distal limb of the colostomy to delineate the anatomy of the distal colon and to establish an accurate anatomic diagnosis. This is, by far, the most important diagnostic study in anorectal malformations.

Trying to repair these malformations without a good distal colostogram exposes the babies to serious injuries of the urinary tract, particularly in males.³³

Main Repair Males

Perineal fistulas can be repaired performing a minimal posterior sagittal anoplasty. The baby is placed in prone position with the pelvis elevated. Multiple stitches are placed at the mucocutaneous junction of the fistula orifice. An incision dividing the sphincter mechanism, posterior to the anal orifice, is performed, and the rectum is carefully dissected to be moved back and relocated within the limits of the sphincter.

During the dissection of the anterior rectal wall, special care must be taken to avoid injury to the posterior urethra, which is the most common and feared complication in these operations. The babies must have a Foley catheter in the urethra during this operation. If the surgeon does not have enough experience and the baby has a very narrow fistula orifice, a simple procedure called cutback can be done, consisting of a posterior cut of the fistula to make the orifice wider. Another alternative in a very sick baby or when the surgeon does not have enough experience is simply to subject the patient to dilatations of the fistula.

In cases of rectourethral fistulas, the patients are subjected to a posterior sagittal anorectoplasty. The baby is placed in prone position with the pelvis elevated and with a Foley catheter in place. A posterior sagittal incision is performed between both buttocks running from the middle portion of the sacrum to the base of the scrotum. The entire sphincter mechanism is divided exactly in the midline using an electrical stimulator to be sure to leave an equal amount of sphincter muscle on both sides of the midline.

The posterior rectal wall is identified and is opened in the midline. The fistula is identified and multiple fine silk stitches are placed taking the rectal mucosa immediately above the fistula in order to exert uniform traction to facilitate the dissection and separation of the rectum from the urethra. A submucosal plane is established in the anterior rectal wall to avoid damage to the urinary tract. About 1 cm above the fistula site, the dissection continues full thickness until the rectum is completely separated from the urinary tract. After this, a circumferential dissection with division of extrinsic vessels of the rectum is performed until enough length has been gained to bring the rectum down to the perineum and to anas- tomose it without tension to the skin in the area of the anal sphincter. Occasionally, we find that the rectum is very dilated

and cannot be accommodated within the available space of the sphincter mechanism. Under those circumstances, it is recommended to taper the posterior rectal wall as much as necessary so as to be able to accommodate the rectum within the limits of the sphincter. It must be the posterior rectal wall that is tapered, rather than the anterior wall so that a suture line is not opposed to the urethral fistula that was closed.

The limits of the sphincter are electrically determined. The only difference in the surgical treatment between the rectourethral bulbar fistula and the retroprostatic fistula is that the latter requires a more significant dissection to bring the rectum down.

Rectobladder Neck Fistula

Fortunately, this malformation occurs in only 10% of male patients.²⁷This is the only defect that requires a laparotomy or laparoscopic assistance in addition to the posterior sagittal operation.³⁴This is because the rectum is located too high to be reached from below. The posterior sagittal incision is only performed to create the path through which the rectum should be pulled down. A midline laparotomy or laparoscopy is performed. The rectum is dissected above the peritoneal reflexion. The surgeon must create a plane of dissection as close as possible to the bowel wall, but without injuring the rectal wall. One must keep in mind that the ureters and vas deferens run in the same direction toward the bladder neck and, therefore, one must keep those structures under vision during the dissection of the rectum. The bladder neck is located about 2 cm below the peritoneal reflexion and, therefore, it is very easy to find the end of the rectum and to divide and suture the fistula site. The rectum then must be mobilized to be pulled down through the tract that has been previously established through the posterior sagittal incision.

In cases of imperforate anus without fistula, the operation is not necessarily easier than in patients with a fistula because the rectum is still intimately attached to the posterior urethra.

These patients are approached posterior sagittally, the posterior rectal wall is opened in the midline, and multiple stitches are placed in the edge of the rectal wall to exert uniform traction and to facilitate the separation of the rectum from the urinary tract.

Special care must be taken during the dissection of the anterior wall to separate it from the urinary tract. These patients more often require a rectal tapering, because usually they have a more dilated rectum.

Rectal Atresia

These patients also require a posterior sagittal approach. The entire sphincter mechanism is divided posterior sagittally.

Both rectum and anal canal are opened posteriorly. The dilated proximal rectum is anastomosed to the anal canal and

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then the sphincter mechanism is meticulously reconstructed in the midline. These patients have an excellent prognosis.

Female defects Perineal Fistula

The repair of this malformation is the same that was described for male patients, except that the rectum is usually separated from the vagina so there is no risk of vaginal injury.

Vestibular Fistula

The complexity of this malformation should not be underesti- mated. The patient is placed in prone position with the pelvis elevated. Multiple fine silk stitches are placed at the rectal vestibular orifice. A posterior sagittal incision is performed, dividing the sphincter mechanism to find the posterior rectal wall, which is easy to recognize. The main technical challenge in the repair of this defect is represented by the common wall that exists between the rectum and vagina. There is no plane of separation between these two structures. One must make two walls out of one. This is achieved by a meticulous dissection applying uniform traction with multiple silk stitches into the rectal lumen. The dissection must continue until the rectum has been completely separated from the vagina. Usually the rectum of these patients requires very little mobilization because it is located significantly low. The limits of the sphincter are electrically determined, the perineal body is reconstructed, and the rectum is placed within the limits of the sphincter.

Rectovaginal Fistula

This is an extremely unusual defect.²⁹These malformations can be repaired posterior sagittally. The repair is the same as described for vestibular fistula, except that these patients require much more mobilization of the rectum in order to move it down and relocate it in the center of the sphincter.

Cloaca

Cloaca repair represents a significant technical challenge, particularly in patients with a long common channel.³⁰

Repair of Cloaca with a Common Channel Shorter Than 3 cm. These patients are approached posterior sagittally.

The entire sphincter mechanism is divided in the midline and the posterior sagittal incision is extended down to the single perineal opening. The common channel is also opened in the midline to expose the anatomy of the defect. The entire defect can be repaired through this incision without opening the abdomen. Once the anatomy has been exposed, the first step is to separate the rectum from the vagina, which is performed in the same manner as was described for a rectovestibular fistula. Once the rectum is separated, it should be mobilized to gain length and to be placed in a normal location. The next step consists of mobilizing both vagina and urethra together,

following a specific technical maneuver called “total urogenital mobilization.”³⁵Multiple 6-0 silk stitches are placed in the edge of the open common channel as well as the edges of the vagina. These stitches allow the surgeon to exert uniform traction on the entire urogenital structure. The urogenital channel is divided full thickness approximately 5 mm proximal to the clitoris, creating a plane of dissection that is very easy to find, between the common channel and the posterior aspect of the pubis. In a matter of a few minutes, one can reach the upper portion of the pubis. Conspicuous fascial attachments exist between the vagina, the genitourinary structures, and the upper part of the pubis. These fascial attachments are avascu- lar and are known as suspensory ligaments of the vagina and urethra. These are divided and the retropubic fat is identified.

By dividing these suspensory ligaments, one can gain approximately 2 cm of mobilization of the urogenital structures.

Some extra dissection of the lateral walls of the vagina as well as its dorsal wall gains another centimeter, and by doing that, one can repair the urethra and the vagina in a very satisfactory manner. More than 50% of the patients with cloacas have a common channel shorter than 3 cm and, therefore, it is possible to repair most of these defects with this reproducible technique. The blood supply after this mobilization is excellent. Urethra and vagina are then sutured to the labia in their new position.

The limits of the sphincter are electrically determined and marked with temporary silk stitches. The perineal body is reconstructed with long-term absorbable sutures, the rectum is placed within the limits of the sphincter, and the anoplasty is performed. The total urogenital mobilization does not change the final functional prognosis. Patients with a common channel of less than 3 cm and a good sacrum have more than an 80% chance of having bowel control and an 80%

chance of having urinary control without bladder intermittent catheterization.²⁸ After the urethra and vagina have been repaired, the urethral meatus is now located 5 mm deeper to the clitoris in a position that makes it perfectly visible which is important if the baby needs catheterization. Twenty percent of these babies will require intermittent catheterization post- operatively in order to empty the bladder.

Surgical Repair of Patients with Cloaca with a Common Channel Longer Than 3 cm. We specifically recommend these patients to be referred to specialized centers dedicated to the treatment of complex malformations. The repair of these defects usually requires not only a posterior sagittal approach, but also a laparotomy and a series of decision- making steps that require experience and special training in urology. The first part of the operation consists of performing a total body preparation so that the patient can be approached through the perineum (posterior sagittally) and through a laparotomy. The posterior sagittal approach and total urogenital mobilization is attempted because occasionally one can achieve a total repair in patients with a common channel up to 4 cm. If this maneuver is not enough to make

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the vagina comfortably reach the skin of the perineum, one has to go into the abdomen and continue the dissection of the vagina as well as its separation from the urinary tract. This is a difficult and tedious maneuver. The bladder must be opened and the ureters must be catheterized because they run through the common wall that separates the bladder and the vagina. Once the vagina has been entirely separated from the urinary tract, then the surgeon evaluates whether or not the vagina reaches the perineum. If that is not possible, then he or she has to make an important decision as to the best way to repair the malformation. In very specific cases, with bilateral hydrocolpos, the surgeon can perform a maneuver called “vaginal switch,” consisting of resecting one of the hemiuteri, resecting the vaginal septum, tubulariz- ing both hemivaginas to create a single one and switching down what used to be the dome of one hemivagina to the perineum, taking advantage of the fact that the distance between both hemiuteri is longer than the vertical length of both hemivaginas. This maneuver is only feasible if the patient has two large hydrocolpos.

If this maneuver (vaginal switch) is not feasible, then the surgeon must replace the vagina. The alternatives are first to replace it with rectum. The distal part of the rectum can be used to replace the vagina, which can be done in two different manners. If the patient has enough length of rectum, one can use the most distal part (preserving its blood supply), to be separated from the fecal stream, mobilized forward, and replacing the distal part of the vagina.

In other cases, if the rectum is very dilated, one can divide it longitudinally. The anterior portion is tubularized and moved forward to form the neovagina preserving the necessary vessels from the inferior mesenteric branches. The posterior aspect will serve as a rectum. The blood supply of the posterior aspect will be provided intramurally from the branches of the inferior mesenteric vessels. The rectum has an excellent intramural blood supply.

If these maneuvers are not feasible, the next choice could be sigmoid colon. If the colostomy interferes with these maneuvers, then one can use the small bowel.

In cases of extremely high malformations, one may find two little hemivaginas attached to the bladder neck. The rectum also may open in the bladder neck. The separation of these structures is performed through the abdomen. Once the separation has been performed, one may notice that there is no bladder neck left. Under those circumstances, the surgeon must have enough experience to decide whether or not the bladder neck can be reconstructed or whether it is better to per- manently close the whole distal part of the bladder and open a vesicostomy. Those patients will require a continent diversion later in life. Because these patients have the highest incidence of vesicoureteral reflux, this operation through the abdomen represents a good opportunity to reimplant the ureters.

Patients with a common channel shorter than 3 cm are left with a Foley catheter, which stays in place for 2 or 3 weeks.

Patients with a common channel longer than 3 cm require a

suprapubic cystostomy or vesicostomy at the end of the operation. One month after surgery, through the suprapubic tube, a cystogram is performed, the tube is clamped, and the patient is observed to see if she is capable of emptying her bladder spontaneously or if she requires intermittent catheterization.

The most common sequela from the urinary point of view in babies with cloaca is the incapacity to empty the bladder.

These babies do not have the type of neurogenic bladder that is seen in patients with spina bifida and myelomeningocele.

These patients rather have a floppy large bladder that does not empty. Most of the cloaca patients have a competent bladder neck. The combination of a competent bladder neck with a floppy hypotonic bladder makes these patients ideal candi- dates for intermittent catheterization, which allows them to remain completely dry.

When the bladder neck was not present at birth or was destroyed during surgery, these patients will need a continent diversion later in life. This operation usually will consist of a bladder augmentation and creation of a conduit with a one- way valve mechanism that allows the patient to be catheterized intermittently in order to empty the bladder without urine leakage.

Results of Treatment of Anorectal Malformations

About 75% of all patients with anorectal malformations (when subjected to a good operation), have bowel control.²⁷ The bowel control is not perfect. This becomes evident when the patients have severe constipation, which may produce overflow pseudoincontinence, and soiling. Also, a severe episode of diarrhea may show that the bowel control is not normal. Twenty-five percent of all patients have fecal incontinence and require some form of medical management.

Because anorectal malformations cover a wide spectrum of defects, the clinical and functional results vary depending on the specific type of malformation. Patients with a cloaca with a common channel longer than 3 cm usually have fecal incontinence and require intermittent catheterization to empty the bladder. Patients with cloaca with a common channel shorter than 3 cm and a normal sacrum have bowel control 80% of the time and only 20% of them require intermittent catheterization to empty the bladder and remain completely dry. Ninety- four percent of all patients with rectovestibular fistulas have bowel control. Babies with perineal fistulas have bowel control 100% of the time. Rectobladder neck fistula patients only have bowel control 20% of the time, rectoprostatic fistula 60%, and rectourethral bulbar fistula 85%.²⁷ Patients with imperforate anus with no fistula will have bowel control between 80% and 90% depending on whether or not they have Down’s syndrome.²⁹

Constipation is a problem in most patients with anorectal malformations in whom the rectum was preserved during the main repair of the defect. Constipation should not be under- estimated as a problem. When not treated properly, the