Imaging Studies
In newborn period
Diagnostic imaging of a newborn with imperforate anus includes abdominal ultrasonography (US) to evaluate for urologic anomalies, which should be performed after 72 hours of life (see the image below). An early sonogram may miss abnormalities as a result of physiologic oliguria at birth. [12] In patients with a cloacal malformation, a distended vagina (hydrocolpos) may be identified.
Plain radiography of the spine may reveal spinal anomalies, such as spina bifida and spinal hemivertebrae.
Plain radiography of the sacrum in the anterior-posterior and lateral projections may demonstrate sacral anomalies, such as a hemisacrum and sacral hemivertebrae. In addition, the degree of sacral hypodevelopment may be assessed, and a sacral ratio can be calculated by measuring the distances between key bony structures (see the image below). The sacral assessment should not be done until after the ossification of the coccyx has taken place (>3 months of age).
Spinal US in the newborn period and up to age 3 months (the point at which the sacrum ossifies) may be performed to find evidence of a tethered spinal cord and other spinal anomalies and to rule out a presacral mass.
Crossfire radiography may help demonstrate the air column in the distal rectum in the small percentage of patients in whom clinical evidence does not delineate the likely anorectal anomaly within 16-24 hours.
After newborn period
High-pressure distal colostography is performed on an outpatient basis, after the colostomy has been created. (See the image below.) Hydrosoluble contrast material is injected into the distal stoma to demonstrate the precise location of the distal rectum and its likely urinary communication.
Distal colostography in patient with imperforate anus and rectourethral fistula, in this case at prostatic level.
Hydrostatic pressure under fluoroscopic control is required. A Foley catheter is placed in the mucous fistula, and the 3-mL balloon is inflated and pulled back to occlude the stoma during contrast injection. The hydrostatic pressure must be high enough (manual syringe injection) to overcome the muscle tone of the striated muscle mechanism that surrounds the rectum and keeps it collapsed. This is the best way to demonstrate a rectourinary communication and determine the rectum's true location in the pelvis and perineum.
The contrast material usually fills the proximal urethra and bladder through the fistula. The injection is continued until the child voids, and pictures are taken during micturition to reveal, in a single picture, the sacrum, the location of the rectum, the perineum, the fistula location, the bladder, vesicoureteral reflux (if present), and the urethra.
Colostography is vital in determining the anatomy so that a definitive repair can be planned. [13] In 10% of patients, the fistula is at the level of the bladder neck; in these instances, during the main repair, the surgeon knows that the rectum can be found only through the abdomen, and a combined posterior sagittal and abdominal or laparoscopic approach is used.
The anorectal defect of imperforate anus without fistula may also be demonstrated with this radiologic evaluation. Occurring in approximately 5% of patients, imperforate anus without fistula has a good functional prognosis and is common in individuals with Down syndrome.
In most newborn girls with anorectal malformations (ARMs), except for those with a cloaca and rectovaginal fistula (very rare), distal colostography is not necessary, because the fistula is clinically evident.
If the spine was not evaluated with US in the newborn period, magnetic resonance imaging (MRI) is necessary after age 6-12 months to exclude the presence of tethered cord and other spinal anomalies.
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Newborn boy with imperforate anus.
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Newborn girl with imperforate anus.
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Cross-fire radiograph in which air column in distal rectum can be observed close to perineal skin.
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Perineum of newborn with cloaca. Note single perineal orifice.
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Hemisacrum with presacral mass.
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Absent lumbosacral vertebrae (severe vertebral anomaly).
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Tethered cord.
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Calculation of sacral ratio.
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Ultrasonography demonstrating hydronephrosis in newborn with imperforate anus.
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Cystography of neurogenic bladder.
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Multicystic kidney.
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Mercaptotriglycylglycine (MAG-3) renal scan in patient with multicystic kidney and imperforate anus.
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Vesicoureteral reflux.
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Distal colostography in patient with imperforate anus and rectourethral fistula, in this case at prostatic level.
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Newborn with imperforate anus and rectoperineal fistula.
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Newborn with imperforate anus and bucket-handle malformation (usually associated with rectoperineal fistula).
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Diagram of imperforate anus and rectourethral fistula.
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Augmented-pressure distal colostography demonstrating rectourethral fistula only when adequate pressure is used. Note flat rectum on left, which represents compression of distal rectum in funnel-like sphincteric mechanism.
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Diagram of imperforate anus and rectovestibular fistula.
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Imperforate anus and rectovestibular fistula in newborn.
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Recommended colostomy with divided stomas, with proximal stoma in descending colon.
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Operative view of posterior sagittal anoplasty in newborn with rectoperineal fistula.
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Positioning for posterior sagittal approach.
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Posterior sagittal incision.
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Electrical stimulator used to show sphincteric contractions.
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Electrical stimulator probe used to show sphincteric contractions. Used with electrical stimulator shown in Image 25.
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Posterior sagittal incision showing parasagittal fibers.
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Schematic diagram of anatomy and repair of rectourethral anorectal malformation.
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Posterior sagittal repair of rectovestibular fistula.
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Closure of posterior sagittal incision.
Tables
| Major Clinical Groups | Rare/Regional Variants |
|---|---|
| Perineal (cutaneous) fistula | Pouch colon |
Rectourethral fistula
|
Rectal atresia/stenosis |
| Rectovesical fistula | Rectovaginal fistula |
| Vestibular fistula | H fistula |
| Cloaca | Others |
| No fistula | |
| Anal stenosis |
| Major Clinical Groups | Rare/Regional Variants |
|---|---|
| Perineal (cutaneous) fistula | Pouch colon |
Rectourethral fistula
|
Rectal atresia/stenosis |
| Rectovesical fistula | Rectovaginal fistula |
| Vestibular fistula | H fistula |
| Cloaca | Others |
| No fistula | |
| Anal stenosis |
| Type of ARM | Score |
| Perineal fistula | 1 |
| Anal stenosis | 1 |
| Rectal atresia | 1 |
| Rectovestibular fistula | 1 |
| Rectobulbar fistula | 1 |
| ARM without fistula | 1 |
| Cloaca < 3 cm common channel | 2 |
| Rectoprostatic fistula | 2 |
| Rectovaginal fistula | 2 |
| Rectobladderneck fistula | 3 |
| Cloaca ≥3 cm common channel | 3 |
| Cloacal exstrophy | 3 |
| Spine | Score |
| Normal termination of conus (L1-2) | 1 |
| Normal filum appearance | 1 |
| Abnormally low termination of conus (below L3) | 2 |
| Abnormal fatty thickening of filum | 2 |
| Myelomeningocele | 3 |
| Sacrum | Score |
| Sacral ratio ≥0.7 | 1 |
| Sacral ratio ≥0.4, ≤ 0.69 | 2 |
| Hemisacrum | 2 |
| Sacral hemivertebrae | 2 |
| Presacral mass | 2 |
| Sacral ratio < 4 | 3 |
ARM = anorectal malformation. Individual scores for ARM type, spine, and sacrum are added together. Total scores are interpreted as follows:
|
