Anorectal Anomalies
A perinium without an anal opening is traditionally described as
imperforated anus .This is inappropriate terminology because most of
anorectal malformations communicate by afistulous track with either the
urinary or genital system or actually open to the skin of the perineum .
Classification:
Development of the distal bowel is arrested at one of two levels ,each
with it’s subtypes .The principle of distinction is in the relation of the end
of the bowel to the chief muscle of continence the puborectalis component
of levator ani.
Arrested development at or above this sling (supralevator lesion)
produces rectal deformities .
Arrested development below the sling (translevator lesion) produce anal
deformities .
In each group the bowel may end blindly or communicate by a fistula with
neighboring viscus or the perineal skin.
Generally :Anorectal anomalies classified into 2 types :
1. Low type (Anal deformities),this is subdivided into :
• Stenosed anus
•
-Covered anus
•
-Ectopic anus
•
-Cutanous fistula ,extending to the perineum or to the scrotum or
ventral skin of penis in male.
• -Ano vestibular fistula in females There are some variations between
male and females .
2. High type (Rectal deformities),in this group the colon or rectum
terminates above the levator ani muscles ,there may be a fistulous
communication to the urinary tract in males(Recto-urethral fistula) or to
the genital tract in females(recto-vaginal fistula) ,some times there is no
connections .
There is a higher rate of associated anomalies in the urinary tract ,vertebral
column ,alimentary canal and heart ,for this reason the mortality is higher
than low type lesions in addition to technical difficulties (i.e. pull through
surgery).
Clinical features :
Any newborn baby should be examined for the presence of congenital
abnormalities .
Examination of the perineum is part of this routine examination, which
may reveal the absence or abnormal anal opening .
Some times the parents are unaware of the baby problem and they bring
him with abdominal distention , vomiting and the passage of meconium
through the urethra or vagina .
Infants with anal stenosis may present weeks or months later with
excessive screaming on defecation with the passage of toothpaste like
stool due to narrow anus.
Examination:
we may be able to differentiate low from high lesions :
Low type there is anal dimple with:
• Stenosed anus :you can’t admit you little finger .
• Covered anus with skin covering the anus with meconium under
the skin .
• Anterior ectopic anus .
Cutanous fistula filled with meconium.or vestibular fistula.
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93BU
High type:
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flat perineum(no anal dimple)
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Meconium may be passed from the urethra or vagina indicating the
presence of fistula .
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TYPES OF DEFECTS ( classification )
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MALE DEFECTS
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1. Low Defects : Perineal fistula
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Median raphe fistula
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Bucket handle malformation
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Anal stenosis
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Anal membrane
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2. Rectourethral bulbar fistula
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3. Rectourethral prostatic fistula
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4. Rectovesical ( bladder neck ) fistula
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5. Imperforate anus without fistula
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6. Rectal atresia and stenosis
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FEMALE DEFECTS
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1. Low defect : Perineal fistula
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2. Vestibular fistula
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3. Vaginal fistula
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4. Imperforate anus without fistula
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5. Rectal atresia and stenosis
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6. Persistent cloaca
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MALE DEFECTS
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1. Low Defects : Perineal fistula
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Median raphe fistula
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Bucket handle malformation
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Anal stenosis
Anal membrane
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2.Rectourethral bulbar fistula
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3.Rectourethral prostatic fistula
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4. Rectovesical (bladder neck ) fistula
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5. Imperforate anus without fistula
6. Rectal atresia and stenosis
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( as in female )
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Female Defects
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1. Low Defect : Perineal Fistula
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2. Vestibular fistula : 3 orifices
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3.
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Vaginal Fistula : 2 orifices
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4. Imperforate anus without fistula
( as in male )
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5. Rectal atresia and stenosis
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6. Persistent cloaca : 1 orifice
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N.B. Anteriorly displaced anus
is a normal anus
situated anteriorly
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ASSOCIATED DEFECTS
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Urogenital
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- Most common
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- 20 – 45 %
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- The higher the malformation the higher the incidence
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Sacrum and Spine
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- Sacrum frequently abnormal
•
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deformed
•
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reduced in number
•
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hemisacrum
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- Spine frequently shows hemivertebrae
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Investigations:
•
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Examination(GUE).the presence of meconium indicate the
presence of fistula to the bowel.
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Invertogram
•
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X-ray taken 12-18 hours after birth ,inverted position ,lateral view,
after putting a mark to see the distal bowel end and it’s relation to
pubococcygeal line and the distance to the mark.
•
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X-ray of the spine for vertebral anomaly (e.x.sacral agenesis).
•
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Very rarely :we may need to do micturating cysto-
urethrogram(MCU)for fistulas or other urological anomalies e.x.
neurogenic bladder or vesico-ureteric reflux .
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Management of Anorectal Malformations:
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Low type lesions have good prognosis .Surgical reconstruction is much simpler
and continence is usually normal .Colostomy is not required and the fistulas
don’t involve other viscera and the coexisting anomalies are less common and
less severe.
•
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Anal stenosis :repeated anal dilatation with dilators.
•
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Imperforated anal membrane (covered anus)need incision and dilatation .
•
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Anterior ectopic anus :mild form need nothing or only dilatation .Severe
form need cut back surgery or transposition .
•
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Anovestibular fistula(low type):transposition surgery with or without
colostomy.
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COLOSTOMY
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Type :
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sigmoid defunctioning with separate stomas
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Site :
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junction of descending with sigmoid
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Incision :
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left iliac , muscle cutting
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N.B. Distal loop should be cleared of meconium during operation
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DISTAL COLOSTOGRAM
-
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Most valuable test
-
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Water soluble contrast into distal stoma
-
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Significant pressure needed
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Under fluoroscopic control
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Contrast usually fills proximal urethra &bladder
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Injection must continue till a voiding episode
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Pictures taken during micturition
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It shows in a single picture :
-
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sacrum
-
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height of rectum
-
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perineum
-
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fistula location
-
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bladder
-
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vesicoureteral reflux
-
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urethra
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No need for voiding cystourethrography or cystoscopy
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Rectourethral bulbar fistula
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Rectourethral prostatic fistula
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Rectovesical (bladder neck ) fistula
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High types:
The prognosis is not good especially in those with multiple congenital
anomalies .Continence is usually affected .
Surgery include:
Colostomy done at the neonatal period .
The definitive surgery done at 9-12months by penna technique or posterior
sagital anorectoplasty (PSARP),through posterior midline incision exploring the
end of the rectum & separating the fistula connected to the urethra in males or
the vagina in females .Then the rectum is pulled through the puborectalis muscle
,closing the muscle around the rectum &fixing the new opening in the perineum
.
Colostomy closure 4-6 weeks later .