An Approach to Anorectal Malformations in Children

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An Approach to Anorectal Malformations in Children

• D. Hurter
• Diagnostic Radiology
• Bloemfontein
• 28 March 2007

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ANOMALIES OF THE COLON AND ANORECTAL AREA

• Obstruction of the colon in the newborn
• anatomic or
• Functional
• Anatomic obstruction includes
• atresia of the colon
• anorectal atresia
• aganglionosis (Hirschsprung's disease)
• Functional lesions include
• meconium plug-neonatal small left colon spectrum
  and
• intestinal neuronal dysplasia (IND)

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Anorectal malformations

• comprise a spectrum of disease affecting boys
  and girls
• involve malformations of the distal anus and
  rectum, as well as the urinary and genital tracts
• range from minor easily treated defects that
  have an excellent functional prognosis to complex
  defects that are difficult to manage
• are often associated with other anomalies

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• To know where we are going, we must know where
  we have been.

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History

• Throughout the centuries, doctors have seen and
  have tried to treat babies with imperforate anus
• most patients are assumed to have died
• Paulus Aegineta (many many moons ago) suggested
  rupturing an obstructing membrane with the finger
  or point of a knife and then dilating the tract
  until healing was complete. This approach was
  used for many years
• Almost 1000 years later, in 1660, Scultet
  treated an infant with anal stenosis with
  dilatation
• 1676, Cooke used incision and dilatation and
  advised care of the sphincter muscles

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History

• 1710, Littre's suggested performing an inguinal
  colostomy for imperforate anus
• 1783, Dubois acted and other surgeons followed
  suit, but almost all infants died, so colostomy
  remained unpopular and only a procedure of last
  resort
• In 1787, Bell suggested using a midline perineal
  incision to find the bowel
• 1826 Dieffenbach described anal transposition
• 1835 Amussat did mobilization of the bowel
  through a perineal incision with suturing of it
  to the skin and this technique gained rapid
  acceptance. Strictures were less common than was
  observed with earlier procedures

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History

• 1856 Chassaignac used a probe through a stoma to
  guide the perineal dissection
• 1872 Leisrink, McLeod (1880), and Hadra (1884)
  recommended opening the peritoneum if the bowel
  was not encountered from below
• 1930 Imaging to delineate the abnormality was
  first advocated by Wangensteen and Rice
• 1948-1949 Single-stage abdominoperineal
  procedures became widely used
• 1953 Stephens emphasized preservation of the
  puborectalis muscle (remember Cook from 1676?)
• This surgery and its modifications were the
  standard approach until 1980

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History
In 1980 ( De Vries and Pena), the surgical
approach to repairing anorectal malformations
changed dramatically with the introduction of the
posterior sagittal approach (PSARP) This approach
allowed pediatric surgeons to view the anatomy of
anorectal malformations clearly and to repair
them under direct vision
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Anorectal malformations

• Pathophysiology
• The embryology is complicated and involves
  abnormal separation of the genito-urinary and the
  intestinal portions of the hindgut.
• Understanding the anatomy is helpful to prevent
  damage to important structures during surgical
  repair and to preserve the best potential for
  bowel control.
• Bowel control is the main concern for the
  surgeon correcting these anomalies. Urinary
  control and sexual function must also be
  considered.
• Some patients experience fecal and occasional
  urinary incontinence despite excellent anatomic
  repair
• Associated problems, such as a poorly developed
  sacrum, nerve supply, and spinal cord likely
  contribute to an inability to achieve continence

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• Incidence 1 in 5000 live births.
• most common in females is a rectovestibular
  fistula
• 50 of all patients with anorectal malformations
  have an associated urogenital anomaly
• A list of anorectal defects and the percentages
  of patients with associated urogenital anomalies
  is as follows (Rich, 1988)
• Cloaca - 81
• Rectovesical defect - 52
• Recto-prostatic - 40
• Rectovestibular - 9
• Recto-bulbar - 4
• Rectoperineal - 0

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• most common the anus is either ectopic or
  imperforate
• the relationship of the distal rectum to the
  puborectalis muscle divides the imperforate anus
  malformations into high (supralevator) and low
  (infralevator) malformations
• If the atresia occurs below the levator muscle,
  it is termed a low lesion
• treatment consists of an anoplasty rather than
  abdominal surgery.
• If the atresia lies above the levator sling it is
  termed a high lesion.
• high lesions require complex reconstructive
  surgery via both abdominal and perineal approaches

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High Anorectal Malformations (Supralevator)

• With a rectourinary fistula, there may be gas and
  meconium in the bladder
• BUT the plain films may not show gas in the
  bladder, because of meconium plugging
• A rectovaginal fistula can be large enough to
  allow meconium into the vagina and decompress the
  bowel of gas and stool
• There may be a separate vaginal and urethral
  orifice or a single orifice a urogenital sinus
  abnormality with bowel entering from behind and
  the urethra entering from the front
• the vagina is obstructed and there may be
  hydrometrocolpos
• lumbosacral deformities and genitourinary
  anomalies are common
• some patients have calcifications in the abdomen
  that prove to be meconium enteroliths in the
  lumen of the colon secondary to urine and
  meconium mixing

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Air in bladder
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meconium enteroliths in the lumen of the colon
secondary to urine and meconium mixing
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• Loopograms with water-soluble agents show the
  bowel to beak" as it enters through the levator
  sling
• A rectum that terminates above the levator
  usually does not show this beak

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Low Malformations (Infralevator)

• the bowel passes through the puborectalis muscle
  the levator sling
• There may be a fistula to the lower portion of
  the urethra, vagina, posterior fourchette, or
  perineum
• In the male infant, there may be a thickened
  midline cord of tissue running from the anal
  dimple to the base of the scrotum, and meconium
  may appear at the scrotum within a day of birth
• The decision regarding a colostomy rests
  primarily on physical examination
• Preoperative ultrasound appears useful in
  evaluating the distance, but this again is
  subject to the dynamic interaction between the
  atretic bowel and the pelvic floor

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Diagnosis

• Early treatment for neonates born with an
  anorectal anomaly is crucial.
• During the first 24-48 hours of life, answer the
  following 2 questions
• Are any associated anomalies present that
  threaten the baby's life and need to be addressed
  immediately?
• Should the infant undergo a primary procedure
  with no protective colostomy or a protective
  colostomy with a definitive repair at a later
  date?

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Diagnosis

• babies born with persistent cloaca
• determine whether a dilated vagina is present
  and if it should be drained
• whether urinary diversion is required to prevent
  sepsis or metabolic acidosis
• If none of the clinical signs to determine the
  location of the anorectal anomaly are evident by
  24 hours, perform a radiologic test
• This situation is only necessary in
  approximately 10 of patients.

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Radiology

• Plain radiographs may be normal or they may show
  evidence of a distal bowel obstruction.
• The pubococcygeal line or the M-line popularized
  by Cremm may be utilized to relate the level of
  rectal gas to the puborectalis sling prior to
  surgery.
• The use of this has, however, led to
  misdiagnosis.
• Crosstable lateral radiography with the baby
  prone, with the pelvis elevated, and with a
  radiopaque marker placed on the perineum is
  performed
• Rarely, radiography may show the column of air in
  the distal rectum to be within 1 cm of the
  perineum if this is the case, management can be
  similar to that for rectoperineal fistula, and a
  newborn perineal operation can be performed
• If the air column is more than 1 cm from the
  perineum, a colostomy is indicated

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Crosstable lateral radiograph of a patient in
which the air column in the distal rectum can be
observed close to the perineal skin.
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Radiology

• 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

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Radiology

• Abdominal and spinal ultrasonography must be
  performed to evaluate for the presence of an
  obstructive uropathy, spinal anomalies and the
  presence of a tethered cord.
• Trying to determine the location of the distal
  rectum before 16 hours of life is senseless
  because of the contracted state of the funnellike
  sphincter mechanism.
• Normally, the funnel-shaped muscle structure is
  contracted unless overcome with a distending
  force
• MRI, sonar, CT or injection of contrast through
  the perineum falsely locate the distal rectum as
  high at this point in time.

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Radiology

• Distal colostography (performed usually
• 1 month after colostomy) must have adequate
• pressure to demonstrate a fistula from the
• rectum to the urinary tract or this method also
• falsely locates the distal rectum as high in the
• pelvis

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Clinical examination

• Look at the baby clinically to get an idea of
  what may be the diagnosis
• Perineal inspection may show a normal urethra,
  normal vagina, and another orifice that is the
  rectal fistula
• meconium beneath the membranous covering typical
  of a low lesion
• a flat or rockerbottom perineum indicates poor
  sphincter or levator muscle development typical
  of a high anomaly
• female malformations, 95 are of the low variety
• most male anomalies are high

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Newborn boy with imperforate anus.
Newborn girl with imperforate anus.
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Imperforate anus and rectovestibular fistula in a
newborn.
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Newborn with imperforate anus and a rectoperineal
fistula.
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Newborn with imperforate anus and a bucket-handle
malformation (usually associated with a
rectoperineal fistula).
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• What are the possibilities?

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FEMALE
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cloaca
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Clinical examination (cloaca)

• 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), which is present in 50 of
  patients with persistent cloaca

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Radiology

• Making the correct determination of persistent
  cloaca is vital because 90 of babies with
  persistent cloaca have an associated urologic
  problem
• Missing the diagnosis of persistent cloaca means
  that an obstructive uropathy is overlooked
• subsequently, sepsis, acidosis, and sometimes
  death may occur

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MALE
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Imaging Studies

• in the newborn period
• Crosstable lateral radiography
• Plain radiography ( spina bifida, hemivertebrae,
  hemisacrum )
• Ultrasonography ( urologic anomalies, distended
  vagina, spinal anomalies, tethered cord)

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Imaging studies after the newborn period

• Distal colostography on an outpatient basis
• 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.
• demonstrate the rectourinary communication and
  determine the rectum's true height
• contrast material usually fills the proximal
  urethra and bladder through the fistula
• injection is continued until the child voids
• take pictures during micturition to show, in a
  single picture, the sacrum, height of the rectum,
  perineum, fistula location, bladder,
  vesicoureteral reflux if present, and urethra

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Recommended colostomy with divided stomas, the
proximal stoma in the descending colon.
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Augmented-pressure distal colostography showing
rectourethral Notice the flat rectum on the left,
which represents compression of the distal rectum
in the funnellike sphincteric mechanism.
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Distal colostogram of a patient with imperforate
anus and a rectourethral fistula.
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• The anorectal defect of imperforate anus without
  fistula may also be demonstrated.
• This occurs in approximately 5 of patients, and
  it is common in individuals with Down syndrome.
• In most cases of female anorectal malformations,
  except for persistent cloaca, distal
  colostography is not necessary because the
  fistula is evident clinically

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cloaca
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Associated anomaliescomplex is often called the
syndrome of caudal regression

• VACTERL
• V vertebral
• A Anorectal
• C Cardiac
• T Tracheo-esophageal fistula
• E Esophageal, duodenal atresia
• R Renal
• L radial Limb

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Types of urinary tract malformations

• Renal agenesis
• Vesicoureteral reflux
• Neurogenic bladder
• Renal dysplasia
• Megaureter
• Hydronephrosis
• Ectopic ureter

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Ultrasonogram showing hydronephrosis in a newborn
with imperforate anus.
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Vesicoureteral reflux
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Undescended testicle
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• If the spine was not evaluated with
  ultrasonography in the newborn period, MRI is
  necessary after age 3 months (because
  ossification occurs) to rule out the presence of
  tethered cord and other spinal anomalies

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Tethered cord

• refers to the intravertebral fixation of the
  phylum terminale
• has a 25 association with anorectal malformation
• prevalence increases with increasing height and
  complexity of the anorectal anomaly
• Patients with a hypodeveloped sacrum and
  associated urologic problems have a higher
  likelihood of having tethered cord.
• Motor and sensory disturbances of the lower
  extremities may result.
• Patients with tethered cord have a poorer
  prognosis for bowel and urinary function
• Untethering the cord is indicated in the
  neurosurgical literature to avoid motor and
  sensory problems
• No evidence exists that this has an impact on the
  functional prognosis for patients with anorectal
  malformation.

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Tethered cord
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Sacral and spinal defects

• Traditionally the number of sacral vertebral
  bodies was counted
• Objective assessment of the sacrum obtained by
  calculating a sacral ratio
• The sacrum is measured and its length is compared
  with bony parameters of the pelvis
• The lateral view is more accurate because its
  calculation is not affected by the tilt of the
  pelvis.
• Hypodevelopment of the sacrum correlates with the
  patient's functional prognosis
• Normal sacra have a calculated sacral ratio of
  0.77
• Bowel control has never been observed in patients
  with calculated sacral ratios less than 0.3.
• A hemisacrum is always associated with a
  presacral mass, which commonly includes dermoids,
  teratomas, or anterior meningoceles.
• Hemivertebrae may also affect the lumbar and
  thoracic spine, leading to scoliosis.
• Patients may have syringomyelia and
  myelomeningocele.

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A
B
B A
Normal
gt 0.77
Calculation of the sacral ratio
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Hemisacrum with presacral mass.

• Currarinos triad
• Anorectal anomaly
• Sacral bone abnormality
• Presacral mass

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• Currarinos triad
• sagittal T1-weighted
• image shows
• a (pre)sacral multicystic fatty mass
• sacral agenesis
• tethered spinal cord (arrow)
• anterior displacement of the anorectum

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Absent lumbosacral vertebrae, a severe vertebral
anomaly.
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• Sagittal T1-weighted
• image in a girl, with a
• cloacal exstrophy
• tethered spinal cord (black arrow)
• sacral fibrolipoma (asterisk)
• syringohydromyelia at the caudal end of the
  spinal cord
• an ectopic (pelvic) kidney distal to the
  vertebral column (curved white arrow)

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associated congenital hip dislocation at the
right side (arrow)
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Rectal atresia

• A very rare malformation, occurs in 1 of cases
• The anal canal is normal and externally, the anus
  appears normal
• The anus is open but a variable segment of rectum
  is atretic with no fistula
• A blockage exists 1-2 cm from the anal skin
• Rectal or anal stenosis refers to cases of
  incomplete anal / rectal atresia

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MRI

• Benefits Superior soft-tissue characterization,
  multiplanar imaging, lack of ionizing radiation
• Define the relationship of the rectum to the
  muscles of the perineal floor, especially the
  puberectalis muscle
• for the surgical reconstruction of anorectal
  malformations
• predicting long-term outcomes
• planning postsurgical management
• In addition, MRI used to evaluate the spinal cord
  for tethering
• slice thickness is kept as thin as possible (35
  mm) with small interslice gap (usually 1.25 mm)

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MRI Transvers

• two transverse images are important
• the PC plane through the symphysis pubis and
  coccyx
• rectum lies immediately posterior to the prostate
  or cervix and is surrounded by the triangular
  shaped muscles of the puborectalis muscle with
  its apex directed posteriorly
• The I plane through the ischial rami
• approximates the junction between the rectum and
  the anal canal in healthy subjects and includes
  the bulb of the penis and the external anal
  sphincter. The external anal sphincter is oval
  shaped with the longer axis directed
  anteroposteriorly

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Axial T2-weighted images demonstrating the normal
MR anatomy of the pelvic floor musculature
The level of the ischial rami. The anal canal is
surrounded by the external anal sphincter
(arrows) and situated behind the superficial
transverse perineal muscle (arrowheads)
The level of the pubic symphysis and coccyx shows
the puborectalis muscle (arrows) surrounding the
anal canal and prostate
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Axial T1-weighted image shows the ectopic
anterior location of the anal canal (arrow),
ventral of the superficial transverse perineal
muscle (arrowheads), and outside the normally
developed external anal sphincter (curved arrow)
Normal anatomy
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MRI Coronal

• plane of the posterior pelvis (a), the levator
  ani supports the pelvic floor and the rectum
  rests upon the levator hammock
• midpelvic plane (b), the rectum and anal canal
  penetrate the external anal sphincter. The
  inferior portion of the pubonectalis muscle and
  superior portion of the external anal sphincter
  are contiguous and inseparable.
• anterior pelvic plane (c), the urogenital
  diaphragm, prostate, and penile bulb are
  visualized.

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Coronal image normal MR anatomy
Shown at the level of the sphincter muscle
complex just dorsal of the anal canal the levator
ani muscle (arrowheads) and its interrelationship
with the puborectalis muscle (long arrow) and
external anal sphincter (short arrow). The rectum
is situated above the levator ani muscle.
Shown at the level of the anal canal. The anal
canal passes through the sphincter muscle
complex. Arrow indicates puborectalis muscle,
arrowhead indicates external anal sphincter
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MRI Sagittal

• midsagittal plane (a), the sphincteric muscle
  appears as a curved band-like structure posterior
  to the prostate or vagina. Margins of the
  sphinctcnic muscle are not distinct because of
  its tapering edges.The tip of the coccyx should
  reach the level of the symphysis pubis.
• parasagittal plane (b), the combined
  iliococcygeal and pubococcygeal portion of the
  levator ani is seen as a curved linear structure
  on which the rectal ampulla rests.

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Sagittal FSE T2-weighted image in a boy, 1 year
of age, with a high anorectal malformation. The
rectourethral fistula can be easily depicted,
curving arround the prostate (arrow)
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MRI

• Absence of the rectal pouch at the PC plane is
  considered a high anomaly (5)
• presence of the rectal pouch at the PC plane but
  not at the I plane is considered an intermediate
  anomaly
• presence of the rectal pouch in both the PC and I
  planes considered a low anomaly

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PR-sling
Successful post-repair
External sphincture
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PR-sling incomplete
Unsuccessful repair
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MRI

• Placement of the rectum through the puborectalis
  sling and within the external sphincter muscle
  mass is necessary for an adequate functional
  outcome following surgery
• The puborectalis muscle and external sphincter
  muscle mass can be exquisitely demonstrated with
  MR imaging in multiple planes
• Inappropriate placement of the neorectum may
  yield an inadequate functional outcome

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15-year-old boy with a high lesion and
rectourethral fistula, underwent pull-through at
the age of 6 months with subsequent rectal
incontinence. Transaxial MR images at the PC
level (a) and I level (b) show a markedly
hypoplastic puborectalis muscle (arrowheads, a)
and external anal sphincter (arrowheads, b). The
neorectum marked by a rectal tube is in a
satisfactory position in the puborectalis muscle
(curved arrow, a), but is anteriorly misplaced
within the external anal sphincter (open arrow,
b). Adjacent to the neorectum, an abnormal
accumulation of fat is seen. Mesentenic fat
inadvertently pulled-through during initial
surgery.
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Axial SE T1-weighted image in a boy,
after reconstructive surgery for a high anorectal
malformation. The neorectum (black arrow) is
positioned outside and to the right of a normally
developed external anal sphincter (white arrow)
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110 degrees, Incontinence, low malformation
post-repair
136 degrees, Incontinence, high malformation
post-repair
measurement of the anorectal angle on a sagittal
MRI image. The anorectal angle is
approximately 96 degrees in this patient
without anorectal disease
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US Determination of the Type with Infracoccygeal
Approach

• Transverse images of the anorectal area are
  obtained
• puborectalis muscle must be identified, and the
  relationship between the puborectalis muscle and
  the distal rectal pouch should be evaluated
• puborectalis muscle is seen as a hypoechoic
  U-shaped band
• 7-MHz linear-array transducer
• Neonate placed in the supine position with both
  legs drawn up to the chest.
• The approach site is just inferior to the coccyx
  and posterior to the anus
• thick layer of gel should be applied between the
  transducer and the perineum to prevent artifacts
  from intervening air
• midline sagittal scanning to measure the distance
  from the end of the distal rectal pouch to the
  perineum

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Transverse infracoccygeal sonogram shows the
distal rectal pouch (R), which passes through the
puborectalis muscle (arrows), indicating low-type
imperforate anus. U urethra.
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US

• In high-type imperforate anus, the puborectalis
  muscle is small and tightly applied to the
  urethra or vagina
• the puborectalis muscle usually not identified on
  an infracoccygeal US image of high-type
  imperforate anus

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Transverse infracoccygeal sonogram shows the
distal rectal pouch (R). The puborectalis muscle
cannot be identified
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References

• Caffeys Pediatric Diagnostic Imaging, Tenth
  edition, volume 1 J.P. Kuhn, T.L. Slovis, J. O.
  Haller Mosby 2004
• www.eMedicine - Imperforate Anus Surgical
  Perspective Article by Marc A Levitt, MD.htm
  (2006)
• www.Imperforate Anus US Determination of the Type
  with Infracoccygeal Approach -- Han et al_ 228
  (1) 226 -- Radiology.htm (2003)
• www.Imperforate Anus - University of Michigan
  Pediatric Surgery, Ann Arbor.mht
• www.Neonatal Surgical Emergencies.mht
• Congenital Anorectal Anomalies MR Imaging Y.
  Sato, K.C. Pningle, R.A. Bergman,W.T.C. Yuh,
  S.W.L.Smith, R.T. Soper, E.A. Franken Radiology
  1988 168157-162
• The Cloacal Malformation Radiologic Findings and
  Imaging Recommendations D. Jaramillo, R.L.
  Lebowitz, W. Hardy Hendren, Radiology 1990
  177441-448
• MR imaging of anorectal malformations and
  associated anomalies R.A.J.Nievelstein, A.Vos,
  J.Valk Eur. Radiol. 8, 573581 (1998)
• Grainger Allisons Diagnostic Imaging, A
  Textbook of Medical Imaging R.G. Grainger, D.J.
  Allison Third edition
• Primer of Diagnostic Imaging Third edition R.
  Weissleder, J. Witteberg, M.G. Harisinghani 2003
• Postoperative MRI evaluation of anorectal
  malformations with clinical correlation T.
  Fukuya, H. Honda, M. Kubota, T. Hayashi, A.
  Kawashima, Y. Tateshi, Shono, S. Suita, K.
  Masuda Pediatr Radiol (1993) 23583-586