2. Development of anal canal
Cloaca: Early in embryonic life allantois(urinary) and
hindgut(rectum and upper part of anus) open into a
common chamber called cloaca
The cloaca becomes separated into the bladder and
postallantoic gut(rectum) by the downgrowth of
urogenital septum.
At this time an epiblastic bud , the proctodaeum, grows in
towards the rectum
The proctodaeum fuses with rectum in 3rd month of
intrauterine life and forms the anal canal
5. Surgical anatomy-Anal canal
Anal canal starts where rectum passes through the pelvic
diaphragm and ends at the anal verge
The muscular junction between the rectum and anal canal
is felt as a anorectal bundle or ring
The internal sphincter is a thickened continuation of
circular muscle coat of rectum. It is pearly white in colour
and involuntary muscle
The longitudinal muscle is a continuation of longitudinal
muscle coat of rectum
The external sphincter is pink in colour and composed of
voluntary muscle
6. Surgical anatomy-Anal canal
Intersphincteric space exists between external and
internal sphincter
The puborectalis maintains the anorectal angle and is
essential for preservation of continence
7. Surgical anatomy-Anal canal
Pink columnar epithelium rectal mucosa changes into red
cubical epithelium in anal canal
Mucosa is thrown into 8- 12 anal columns of Morgagni
which are joined at their lower ends by anal valves. This
wavy junction is called dentate line
The dentate line separates
Above Below
• Cubical epithelium from squamous epithelium
• Autonomic nerve supply from somatic nerve supply
• Portal venous system from systemic venous system
8. Surgical anatomy-Anal canal
Anal valves of Ball are series of transversely placed
semilunar folds linking the columns of Morgagni
The crypts of Morgagni are small pockets between lower
ends of columns of Morgagni. Anal glands open into these
anal crypts by a narrow ducts
The anorectal ring marks the junction between the rectum
and the anal canal. It is formed by the joining of
puborectalis muscle
deep external sphincter
conjoined longitudinal muscle
highest part of the internal sphincter
9. Surgical anatomy-Anal canal
Arterial supply by branches of superior, middle and
inferior haemorrhoidal arteries
Venous drainage : the superior and middle haemorrhoidal
veins drain via the inferior mesenteric vein into portal
system. The inferior haemorrhoidal veins drain the lower
half of the anal canal to the external iliac vein
Lymphatic drainage: upper half of anal canal drain into
postrectal lymph nodes. Lower half drains to superficial
and deep inguinal nodes
10. Imperforate anus
One in 4500 are born with an imperforate anus
The VATER or VACTERL syndrome (vertebral, anal,
cardiac, tracheoesophageal, renal, and radial limb
anomalies) occurs in approximately 15% of patients.
A tethered cord and other types of spinal cord
abnormalities are observed in half of patients
Approximately 60% of patients with high or intermediate
forms of imperforate anus have some form of associated
genitourinary (GU) malformation or vesicoureteral reflux
11. Imperforate anus
Two main types: Low and High depending on whether
termination of bowel is below or above the pelvic floor
Low abnormalities
Covered anus: anal canal is covered by a bar of skin with a
track running forward to the perineal raphe
Ectopic anus: anus is situated anteriorly and may open in
the perineum in boys or more commonly in the vulva in
girls
Stenosed anus: the anus is microscopic
Membranous stenosis: anus is covered with a thin bulging
membrane
20. Initial Management of the Newborn
It is best to wait 24 hours prior to any surgery to allow
progression of gas or meconium through the bowel
To decide whether temporary colostomy is needed
21. Initial assessment
Imperforate Anus in Boys
Features of low anomaly are:
If an external opening is visible in the perineum
Presence of meconium just below the skin of the perineum.
A skin formation called a “bucket handle”
An apparently well-formed anal dimple and gluteal crease
Features of high anomaly needing colostomy are:
Associated cleft scrotum or significant hypospadias
Complete absence of the gluteal fold (the crease between the
buttocks)
Absence of anal dimple
Presence of abnormalities of the sacrum .
24. Imperforate anus in girls
If only two openings are seen in the perineum, including
the urethra and vagina, and meconium is seen coming
from the vagina, an anomaly called a rectovaginal fistula
or cloacal variant is present.
If neither a fistula nor meconium is noted on or just
beneath the perineum, ultrasound or an x-
ray(Invertogram) may be done to see if the rectum is near
the skin where the anus was supposed to be. If it appears
to be less than 1 cm away from the skin it is a low variety
If only one opening is seen, it must be assumed that there
is a problem called a cloaca
26. Treatment of low anomalies
Initially by dilatations
After 3-4 weeks
V-Y anoplasty for stenosed anus
Anal transposition for ectopic stenosed anus
Cutback procedure for ectopic stenosed anus
Regular dilatation of anoplasty by the parents after 3
weeks to prevent stenosis
29. Treatment of high anomalies
Initial sigmoid colostomy
Distal colostogram to define the lower limit of rectum and
fistula
Currently the posterior sagittal anorectoplasty (PSARP)
procedure described by de Vries and Pena is the preferred
technique
Laparotomy /laparoscopic rectal pull through operation
after division of abnormal fistula into urinary tract
Regular dilatation of new anus after 3 weeks
Colostomy closure after 3 months
40. Conclusions
Clinical results are different for each type of the
malformations.
Faecal continence is good in low anomalies
Constipation is a common sequelae seen after the repair of
an anorectal malformation.
Urinary control can be expected in the overwhelming
majority of male patients after repair of imperforate anus
provided a good surgical technique was performed