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ANORECTAL
MALFORMATION
(ARM)
CONTENTS
vIntroduction
vEmbryology
vGenetics and associations
vIncidence
vClassification
vApproach to a patient
ANORECTAL MALFORMATION
Complex group of
congenital anomalies
involving the anus
and rectum, as well
as the urinary and
genital tracts in a
significant number of
cases.
EMBRYOLOGY
Abnormal development of the urorectal
septum in early fetal life.
At 3 weeks
EMBRYOLOGY
At 5,7,8 weeks
GENETICS
ARM
SYNDROMIC
NON-SYNDROMIC
SPORADIC
FAMILIAL
LADD AND GROSS CLASSIFICATION- 1934
WINGSPREAD
CONFERENCE
CLASSIFICATION- 1984
High (Supra-levator)- Male
High (Supra-levator)- Female
Intermediate- Male
Intermediate- Female
Low (Trans-levator)- Male
Low (Trans-levator)- Female
Miscellaneous- Female
Miscellaneous- Male
INCIDENCE & FREQUENCY
2-2.5 per 10,000 live births
M:F ratio= 1.5:1
Supra-levator lesions more in males
Associated anomalies more in males
Commonest-
- recto-urethral fistula
- ano-vestibular fistula (female)
RISK FACTORS
Mothers >35 years old
Maternal recreational drug use
Parental consanguinity
Maternal residence at high altitude
Paternal occupation in vehicle manufacture
Consumption of raw vegetables (pesticides)
Geographical (pouch colon)
ANATOMY
NORMAL -VS -ARM
APPROACH TO A PATIENT
OF ARM
Prenatal Diagnosis- USG
(Low sensitivity and specificity)
Dilated colon
Oligohydramnios and a highly distended vagina (in
females)
Absence of circular rim of hypoechogenicity (Anus).
Enterolithiasis
Polyhydramnios if associated with UGI obstruction.
Associated anomalies.
GOALS OF INITIAL ASSESSMENT
1. To determine the level of the malformation
in relation to the muscular sphincters and the
site of any fistulous communications.
2. To determine the integrity of sphincters and
their nerve supply.
3. To document any associated anomalies that
may affect survival.
ALGORITHM FOR MALE ARM
I. LEVEL OF MALFORMATION
Neonatal examination
1. Good perineal examination under a good light
2. Position of the anus or its absence; fistula.
3. Perineal shape (midline raphe)- parasagittal
fibers and gluteal development.
4. Passage of a soft catheter greater >2 cm into the
rectum and the presence of meconium passage
rules out atresia
vNormal size of the anus- 1.3 + (3 ? birth wt in kg) in
mm
HIGH ARM-FLAT GLUTEUS
EVIDENCE OF FISTULA
H/O meconuria
Meconium at the tip of
meatus
Meconium/squamous
epithelium in urine
microscopy
ANTERIOR ECTOPIC ANUS
Anal index of < 0.34 in girls
and < 0.46 in case of boys
Anal index-
- Ratio of scrotal-anal distance
to
the
scrotal-coccygeal
distance in males and
- fourchette-anal distance to
fourchette-coccygeal distance
in females.
LOW ARM WITH FISTULA IN SCROTUM,
MECONIUM TRACT IN PERINEUM
PERINEAL FISTULA WITH PROBE IN SITU
ALGORITHM FOR MALE ARM
AXR
INVERTOGRAM
* Narsimharao KL et al. Am J Roentgenol 1983; 140: 227-229
Cross-table Prone lateral x-ray (CTPL)
12?24 hrs after birth
Prone position, hips- slightly flexed-3 mins
Centering on the greater trochanter
LOW
HIGH
ALGORITHM FOR MALE ARM
COLOSTOMY
HIGH DIVIDED SIGMOID COLOSTOMY (HDSC)
Bowel decompression and protection for the final
repair
Facilitates the distal colostogram
Relatively short segment of defunctionalized distal
colon- less chances of microcolon
Mechanical cleansing
Large rectourethral fistula- Less metabolic acidosis
Doesn't permit stool distally
Easy pull through
ANOPLASTY
Computed Tomography
Demonstrate the level of the terminal colon
Increased detail - osseous structures
musculature.
Difficulty in distinguishing meconium from the
rectal wall and adjacent musculature- and so
the site of fistula.
Radiation cost to the patient.
MRI
No radiation burden
Easy
differentiation of
meconium from the rectal
wall
and
levator
musculature
Level of the terminal bowel,
and the state of the pelvic
floor musculature
Fistulae
(difficult
in
neonates)
II. Assessment of the Sphincter
complex and Nerve supply
Absent
S4 AND S5-
Normal variant
Absent S3,4,5 - Variable
incontinence
Absent S1 AND S2 -
always incontinent
Hemisacral
defects-
Results unpredictable
Meningomyeloceles.
? The sacral ratio is a valuable prognostic tool
? It quantifies degree of sacral agenesis
? Patient with ratio < 0.5 are universally incontinent
? Ratio that approach 1 usually predict a good prognosis
KRICKENBECK SURGICAL PROCEDURES
Pressure-augmented colostogram
Posterior sagittal Anorectoplasty (PSARP)
Jack knife position (Prone)
PSARP
Electrical stimulator- sphincter location.
Rectourethral fistulas
Rectourethrobulbar fistula Rectourethroprostatic fistula
-Most frequent defect in male patients
-Rectum identified and
opened posteriorly in
between stay sutures
-Fistula visualized
-Rectum separated from
the
urethra,
and
mobilised.
-Rectum passed in front
of levator and within
sphincter.
-Anoplasty done.
Recto-bladder neck fistula
Combined abdomino-perineal approach
Poor prognosis
ANTERIOR SAGITTAL ANORECTOPLASTY(ASARP)
ARM VARIANTS
I.PERSISTENT CLOACA
Defect in which the
rectum, one or two
vaginas and the urinary
tract converge into one
common channel.
Cloacal anomalies
Short common
Long common
Double vagina/uterus
channel
channel
Hydrocolpus
Posterior
High rectal
cloaca
implantation into
vagina
DEFINITIVE MANAGEMENT
Genitogram
Genitoscopy
3D MR Genitography
SURGERY
Posterior sagittal approach
Rectal mobilization (sub
serosally)
Total Uro Genital
mobilization
Vulval & perineal
reconstruction
Abdomino- perineal
approach if long common
channel.
VAGINAL SWITCH
VAGINAL AUGUMENTATION
From rectum
From colon
From small intestine
2. CONGENITAL POUCH COLON
2.5 ? 9 % of ARM in North
India.
All or part of the colon is
replaced
by a pouch-like dilatation,
which communicates
distally with the urogenital
tract via a large fistula.
MODIFIED WAKHLU'S CLASSIFICATION
Depending on length of available colon
? Wakhlu AK, Tandon RK, Kalra R (1982) Short colon with anorectal
malformation. Indian J Surg 44:621?629.
? Narsimha Rao KL, Yadav K, Mitra SK, Pathak IG (1984) . Congenital short colon with
imperforate anus (CPC syndrome). Ann Pediatr Surg 1:159
MANAGEMENT
3. RECTAL ATRESIA
1-2% of ARM
Common in
South India
End to end
anastomosis via
PSARP route.
Postoperative management
Foleys catheter
IV antibiotics and wound care
Anal dilatation (after 2 weeks) till desired size
Colostomy closure
COMPLICATIONS
EVALUATION OF OUTCOMES
FUNCTIONAL OUTCOME DURING CHILDHOOD- LOW ARM
Functional outcome during childhood ? high
malformations: PSARP
TREATMENT OF FECAL INCONTINENCE
Proper bowel
management program
Dietary modifications
Surgical procedures to
improve continence
OTHER OUTCOMES
Urinary function
Sexual function
Long-term growth and development
This post was last modified on 08 April 2022