The various types of anorectal fistula in male imperforate anus

Ultrasound imaging of the anorectal malformation during the neonatal period: a comprehensive review

Anorectal malformation (ARM) is classified as low, intermediate, or high; accurate diagnosis of the type during the early neonatal period is important to determine the appropriate initial surgical approach. This review assesses the role of ultrasound examination in the classification of ARM during the neonatal period, with a focus on landmarks on the sonogram, the approach used for sonography, and the optimal examination timing. The following three factors on the sonogram are used for the classification: location of the fistula, the distance between the distal rectal pouch and the anal dimple (perineum) (P-P distance), and the relationship between the puborectalis muscle and the distal rectal pouch. Three approaches can be used to evaluate ARM by ultrasonography, namely, suprapubic, perineal, and infracoccygeal approaches. Each approach has its own advantages and disadvantages. Optimal timing of the ultrasound examination is also important with respect to each factor to classify ARM. We have described the pitfalls of ultrasound in diagnosis of cases, namely ARM with Down syndrome (which tends to be without fistula), ARM with low birth weight, ARM with unusual location of fistula, ARM with opened fistula (where the P-P distance is unreliable), and cloacal malformation (variation of the high-type ARM).

Sonography for an Imperforate Anus: Approach, Timing of the Examination, and Evaluation of the Type of Imperforate Anus and Associated Anomalies

This systematic review outlines the role of sonography in an imperforate anus. The diagnostic performance for type of imperforate anus is superior on the day after birth than that on the day of birth by using the pouch-perineum distance. Three approaches can be used (suprapubic, infracoccygeal, and perineal). The pouch-perineum distance, fistula location, and relationship between the puborectalis muscle and distal rectal pouch are useful for classifying the type of imperforate anus. However, the pouch-perineum distance measured has an overlap between the low and high/intermediate types of imperforate anus. Sonography can be useful for some of the associated anomalies and helpful for surgeons in some cases.

Changes in the Distance Between the Distal Rectal Pouch and Perineum From the Birth Day to the Next Day in Neonates With an Imperforate Anus

OBJECTIVES

To evaluate changes in the distance between the distal rectal pouch and the perineum (pouch-perineum distance) from the birth day to the next day and to determine which day is better for diagnosis of a low-type imperforate anus in neonates.

METHODS

We reviewed medical records at our hospital from May 2003 to August 2015 and identified 9 neonates with a radiographically and surgically proven low-type imperforate anus and 9 with high/intermediate types of imperforate anus who had undergone sonography on both the birth day and the next day before the first surgical treatment. The sonograms were reviewed to measure the pouch-perineum distance at both examinations. The Wilcoxon signed rank sum test and a receiver operating characteristic curve analysis were used for the statistical analyses.

RESULTS

The pouch-perineum distance on the next day (mean ± SD, 9.37 ± 4.89 mm; range, 2.1-20.9 mm) was significantly shorter than on the birth day (15.75 ± 6.67 mm; range, 8.1-37.2 mm; P = .001). The receiver operating characteristic analysis showed significantly better diagnostic performance (P < .001) of the pouch-perineum distance on the next day (area under the curve, 0.864) versus the birth day (0.420) for the low-type imperforate anus.

CONCLUSIONS

The pouch-perineum distance was shorter on the next day than on the birth day, and the diagnostic performance of the pouch-perineum distance on the next day was significantly superior to that on the birth day for the diagnosis of a low-type imperforate anus. We recommend sonography on the next day in neonates with an imperforate anus when possible.

Congenital Pouch Colon

Congenital pouch colon (CPC) is an unusual abnormality in which a pouch-like dilatation of a shortened colon is associated with an anorectal malformation. It is categorized into four subtypes (Types I–IV) based on the length of normal colon proximal to the colonic pouch. In males, the pouch usually terminates in a colovesical fistula just proximal to the bladder neck. In girls, the terminal fistula opens either into the urethra or in the vestibule, close to the urethral opening. Girls usually have a double vagina with a wide inter-vaginal bridge, a monocornuate uterus on each side, and urinary incontinence due to a widely open bladder neck. Associated major malformations are uncommon with CPC but sometimes, especially in reports from outside India, major abnormalities are present suggesting an early, severe error in embryogenesis. The more severe Types I/II CPC can usually be diagnosed by a large gas shadow or air-fluid level on X-Ray abdomen. For all subtypes of CPC, it is preferable to preserve a segment of the pouch by fashioning a narrow colonic tube for pull-through, the technique known as coloplasty or tubular colorraphy. Girls need additional management of the genitourinary abnormalities. Postoperatively, fecal continence levels are usually poor, especially with Types I/II CPC.

Imperforate Anus with Fistula Exiting at the Penile Skin

We present the case of a male neonate with imperforate anus and a fistula exiting on the penile skin. Anorectal malformations in boys often present themselves with an entero-perineal or entero-urinary tract fistula, the type of which is a key feature for the classification and the treatment plan. A fistula exiting in front of the scrotum, such as described in our case, is very rare and is not incorporated in the current classification and treatment algorithms. Scarce reports on misjudgment concerning the position of the blind rectal pouch in similar cases, led us to perform a colostomy instead of a one-stage correction. A posterior sagittal anorectoplasty was performed eight months later and the rectal pouch was found inside the levator sling, justifying the cautious approach. The colostomy was closed three months later and after six months the distal part of the fistula was excised. We believe that in cases with a rare fistula presentation, the position of the rectal pouch is not predictable and the surgeon should proceed with caution.

Nonfluoroscopic pressure colostography in the evaluation of genitourinary fistula of anorectal malformations: experience in a resource-poor environment

BACKGROUND

Radiological imaging is paramount for defining the genitourinary fistulae commonly associated with anorectal malformations prior to definitive surgery. The imaging options are resource-limited in many parts of the world. Nonfluoroscopic pressure colostography after colostomy is a cheap method for the evaluation of anorectal malformations.

OBJECTIVE

To describe our experience with nonfluoroscopic pressure colostography in the evaluation of anorectal malformations in boys.

MATERIALS AND METHODS

The study included 12 boys with anorectal malformation who had colostomy and nonfluoroscopic pressure-augmented colostography with water-soluble contrast medium between January 2006 and December 2007.

RESULTS

Patient ages ranged from 2 days to 1 year. The types of genitourinary fistula were rectovesical (7.7%) and rectourethral (92.3%). Oblique radiographs were of diagnostic value in all patients. The types of anorectal malformations were high, intermediate and low in 75%, 8.3% and 16.7%, respectively. Short-segment urethral constriction was a common feature of rectourethral fistula (75%, n=9).

CONCLUSION

Our experience has shown that genitourinary fistulae associated with anorectal malformations can be demonstrated reliably by nonfluoroscopic pressure colostography with two oblique radiographs, providing an option in resource-poor settings where fluoroscopic equipment is scarce.

Micturating cystography and "double urethral catheter technique" to define the anatomy of anorectal malformations

Ano-rectal malformations (ARM) in the male patient may be associated with a fistulous communication between the rectum and urethra. Pre-operative radiological assessment is important to delineate (a) the presence and level of the fistula, (b) the anatomy of the posterior urethra and (c) any anomalies in adjacent structures. Bladder catheterisation can be technically difficult when performing an MCUG and distal loopogram in such patients. This can be due to urethral stricture, tortuous or kinked urethra or preferential passage of catheter into a large fistula and leads to an inadequate study. We describe a "double urethral catheter technique" to enable urethral catheterisation when the fistula is large.

Anal and ano-urogenital malformations: a histopathological study of "imperforate anus" with a reconstruction of the pathogenesis

Histopathological information about "anorectal malformations" is scarce and the pathogenesis still controversial. Autopsy specimens of 20 human fetuses and newborns with "main" types of the disorder were studied histologically. Supplemented with surgical-anatomical data from the literature and with information from our own and earlier embryological research in animal models as well as from recent observations on the normal development of the human perineum, the study allowed for a new reconstruction of the pathogenesis of the disorder. The histological analysis of the malformations in human fetuses and newborns showed a ventralward deviation of the anal canal as the principal deformity. Ano-urogenital communications and differently structured ectopic anocutaneous canals issued from anywhere between the bladder and the vestibular/urethral orifice (female urethra excluded) and between the orifice and the usual site of the anus, respectively, or they ended blindly, but with a suggestion of lost communication. They occurred isolated or in association with other primary or secondary regional anomalies. Patho-embryological data from animal models revealed that the deviation was caused by defective development of the dorsal cloaca and not by disturbances in a series of fusion processes inside and outside the cloaca, as is currently believed. This mechanism fits well into recent adjustments of ideas about the normal development of the perineum. The cause of the defect is still obscure, but a malfunctioning of cells ingressing from an end-stage primitive streak that affects the dorsal side of the prospective cloaca appears most likely. The data collected permit a new reconstruction of the pathogenesis of anal and ano-urogenital malformations.

Imperforate anus: US determination of the type with infracoccygeal approach

PURPOSE

To assess the usefulness of infracoccygeal transperineal ultrasonography (US) in differentiation between high- and low-type imperforate anus.

MATERIALS AND METHODS

Infracoccygeal US was prospectively performed with a 7-10-MHz linear-array transducer prior to corrective surgery in 14 neonates with imperforate anus. The approach site was just inferior to the coccyx and posterior to the anus. Transverse images of the anorectal area were obtained. The puborectalis muscle was identified, and the relationship between the puborectalis muscle and the distal rectal pouch was evaluated. US findings were compared with surgical findings.

RESULTS

In 10 neonates, a low-type imperforate anus was correctly diagnosed at infracoccygeal US. In those with low-type imperforate anus, the puborectalis muscle was seen as a hypoechoic U-shaped band (n = 10), and the distal rectal pouch passed through the puborectalis muscle (n = 10). In four neonates with high-type imperforate anus, the puborectalis muscle was not identified (n = 4).

CONCLUSION

Infracoccygeal transperineal US enables the determination of the type of imperforate anus.

Urorectal septum malformation sequence: Insights into pathogenesis

We characterize the urorectal septum malformation sequence (URSMS) in discordant fetal lambs and relate it to the human syndromes with which URSMS is associated. We found abnormal external genitalia, imperforate anus, and fistulous connections between the rectum, bladder, and vagina. Discordance among the dizygous twins eliminated teratogens as a likely etiologic factor. We summarize the relevant literature and propose a molecular model for the pathogenesis of the URSMS, in which alterations in sonic hedgehog and homeobox genes lead to caudal mesodermal deficiency during blastogenesis.

Magnetic resonance imaging in children with anorectal malformations: embryologic implications

PURPOSE

The aim of this study was to evaluate the spectrum of developmental anomalies in the caudal region of patients with anorectal malformations (ARM) and relate them to the new insights in the embryogenesis of this region.

METHODS

Forty-nine patients with ARM were investigated with magnetic resonance imaging (MRI); 24 preoperatively (preop) and 25 postoperatively (postop). Of this group, 17 patients had a high (or intermediate) ARM, 28 a low ARM, and 4 a cloacal malformation (CM). The evaluation of the imaging studies included the level and type of ARM (preop); the developmental state of the sphincter muscle complex (SMC); and the associated anomalies of spinal cord, spine, and urogenital system. The anomalies detected were ordered and related to recent embryologic observations in the caudal region.

RESULTS

With MRI, the level of ARM was depicted effectively in 23 of 24 patients (96%) investigated preop, including 5 of 9 clinically proven fistulae in those with high ARM and CM (56%). Maldevelopment of the SMC was observed in 14 of 49 patients (29%). Associated anomalies of spinal cord and spine were found in 51% of patients, more frequently in those with high ARM, low ARM with fistulae, and cloacal malformations. Associated anomalies of the urogenital system were found in 37% of patients.

CONCLUSIONS

As illustrated by the current study, MRI has become indispensable for the visualization of the nature of congenital ARM and associated anomalies. Moreover, MRI aids in understanding the morphology and pathogenesis of these complex congenital malformations. Based on the MRI and recent embryologic observations, a new and simplified classification of ARM is introduced, including a more appropriate nomenclature.

The role of radiology in children with anorectal anomalies; with particular emphasis on MRI

Anorectal anomalies have a reported incidence of between 1 per 1000 and 1 per 9630 live births. The international classification subdivides anorectal malformations into high, intermediate, low and miscellaneous deformities with emphasis on the sex of the child. The classification is based on where the rectum terminates in relation to the levator ani muscles above the levator is termed a high (supralevator) lesion, at the level of the levator intermediate, and below is a low or translevator anomaly. A modified classification has recently been proposed by Pena based on his anatomic observations during posterior sagittal anorectoplasty-the terms high, intermediate and low lesions continue to be used but with slightly different connotations. Approximately 50% of all patients with anorectal anomalies have associated other congenital lesions. These lesions necessitate a variety of radiological investigations which will be outlined briefly. The pertinent muscular anatomy of the pelvic floor and recent advances in surgical techniques will be discussed. The particular role of MRI in the evaluation of the pre-operative newborn or infant prior to definitive pull-through repair surgery and the post-operative, older, paediatric patient with continuing problems will be reviewed. Reference to the other radiological options, and their usefulness, in the evaluation of anorectal malformations will be made throughout the text.