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An Approach to Anorectal Malformations in Children

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Title: An Approach to Anorectal Malformations in Children


1
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)

10
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.

13
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

14
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

15
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

16
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

21
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

25
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

29
Crosstable lateral radiograph of a patient in
which the air column in the distal rectum can be
observed close to the perineal skin.
30
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

31
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

33
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.
35
Imperforate anus and rectovestibular fistula in a
newborn.
36
Newborn with imperforate anus and a rectoperineal
fistula.
37
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

49
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)

59
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.
61
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.
62
Distal colostogram of a patient with imperforate
anus and a rectourethral fistula.
63
  • 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
65
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

68
Ultrasonogram showing hydronephrosis in a newborn
with imperforate anus.
69
Vesicoureteral reflux
70
Undescended testicle
71
  • 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
74
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.

75
A
B
B A
Normal
gt 0.77
Calculation of the sacral ratio
76
Hemisacrum with presacral mass.
  • Currarinos triad
  • Anorectal anomaly
  • Sacral bone abnormality
  • Presacral mass

77
  • Currarinos triad
  • sagittal T1-weighted
  • image shows
  • a (pre)sacral multicystic fatty mass
  • sacral agenesis
  • tethered spinal cord (arrow)
  • anterior displacement of the anorectum

78
Absent lumbosacral vertebrae, a severe vertebral
anomaly.
79
  • 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)

80
associated congenital hip dislocation at the
right side (arrow)
81
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

82
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

86
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
89
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.

90
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
91
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)
94
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

95
PR-sling
Successful post-repair
External sphincture
96
PR-sling incomplete
Unsuccessful repair
97
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

98
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.
99
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)
100
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
101
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.
104
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

105
Transverse infracoccygeal sonogram shows the
distal rectal pouch (R). The puborectalis muscle
cannot be identified
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107
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
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