Anorectal malformations

1. Anorectal Malformations
By: Dr Shrikant Nagare

2. Introduction
• Anorectal malformations comprise a wide spectrum
of diseases, which involve the distal anus and
rectum as well as the urinary and genital tracts.
• Defects range from the very minor and easily
treated with an excellent functional prognosis, to
those that are complex, difficult to manage, are
often associated with other anomalies, and have a
poor functional prognosis.

3. Epidemiology
• Anorectal malformations occur in
approximately 1 newborn per 5000 live
births.
• The etiology of such malformations
remains unclear and is likely
multifactorial.
• There are however reasons to believe
there is a genetic component.
Etiology

4. Race
• No known racial predilection has been
reported.
Sex
• No known sex predilection has been
reported.

5. EMBRYOLOGY
• The epithelial lining of various GI tract
is endodermal in origin.
• In the region of anal canal some
epithelium is derived from ectoderm of
proctodaeum.

6. • Parts of the cavity of the yolk sac are enclosed within
embryo to form the primitive gut.
• Primitive gut is in free communication with the rest of the
yolk sac
• Part of the gut cranial to this communication is the foregut,
caudal is hindgut and in-between is the midgut.

7. • Cranially foregut is separated from the
stomatodaeum by the buccopharyngeal membrane.
• Caudally the hindgut is separated from the
proctadaeum by the cloacal membrane.
• At later stage of development these membranes
disappear and the gut opens to the exterior at its
two ends.

8. • The part of the hindgut caudal to attachment of
allantoic diverticulum is called cloaca.
• The cloaca soon divides into the broad ventral part
and narrow dorsal part separated by the urorectal
septum.
• The ventral part is called the primitive urogenital
sinus and dorsal part is called the primitive rectum.

9. • The uro-rectal septum grows towards the the
cloacal membrane and eventually fuses with it.
• The cloacal membrane is divided into the ventral
urogenital membrane and dorsal anal membrane.
• The mesoderm around the anal membrane beomes
heaped up with the result that anal membrane
comes to lie at the bottom of pit called anal pit, or
proctodaeum.
• Anal pit contributes to formation of the anal canal.

10. Derivatives of hindgut
• Left one third of transverse colon.
• Descending and pelvic colon.
• Rectum.
• Upper part of anal canal.
• Parts of the urogenital system derived
from the primitive urogenital sinus.

11. DEVELOPMENTAL ANOMALIES OF GUT
I. CONGENITAL OBSTRUCTION
II. ABNORMAL COMMUNICATIONS OR
FISTULAE
III. DUPLICATION
IV. DIVERTICULA
V. ERRORS OF ROTATION
VI. ERRORS OF FIXATION
VII. SITUS

12. CONGENITAL OBSTRUCTION
• Atresia: missing gut, segment replaced by fibrous
tissue, septum may block lumen.
• Stenosis:
• Non-development of nerve fibres in in the wall
of a part of the intestinal tract: Megacolon,
Hirshprung’s disease.
• Abnormal thickening of muscular wall: CHPS
• External pressure: Annular pancreas.
• Imperforate anus:

13. TYPES OF IMPERFORATE ANUS

14. VARIOUS TYPES OF FISTULAE
1. TRACHEO-ESOPHAGEAL FISTULA:
2. INCOMPLETE SEPTATION OF THE CLOACA: Rectum
may communicate with the urinary bladder, urethra or vagina
or may open onto the perineum at an abnormal site.

15. MALES

16. FEMALES

17. ARM

18. ARM

19. ARM

22. Clinical
• Prenatal ultrasonography examination findings
are often normal, although the polyhydramnios or
intraabdominal cysts may suggest imperforate
anus with associated hydrocolpos or
hydronephrosis.
• Newborns with imperforate anus are usually
identified upon the first physical examination.
• Malformations in newborns that are missed upon
initial examination are often discovered within 24
hours when the newborn is observed to have
distention and has failed to pass meconium and a
more thorough examination is performed.

23. Physical
• During a thorough physical examination, attention
should be focused on the abdomen, genitals,
rectum, and lower spine.
• In females, a perineal fistula can be directly
identified as a small opening on the perineum.
• If none is present, the labia are separated to search
for a vestibular fistula.
• If no fistula is visible and only one opening between
shortened labia is observed, the child has a cloaca.

24. Associated malformations
• Cardiovascular malformations: Tetralogy of Fallot, ventricular septal
defects, Transposition of the great arteries and hypoplastic left heart
syndrome.
• GI malformations: Tracheoesophageal abnormalities, Duodenal
obstruction due to annular pancreas or duodenal atresia, Malrotation,
Hirschprung disease.
• Vertebral anomalies; Lumbosacral anomalies.
• Spinal anomalies: spinal dysraphism, tethered spinal cord, Cord
lipomas and syringohydromyelia.
• Currarino described a triad of sacral defect, presacral mass, and
imperforate anus.
• Urinary anomalies: Mild hydronephrosis, Vesicoureteric reflux, renal
agenesis and dysplasia.
• Crptorchidism:
• Vaginal and uterine abnormalities: Bicornate uterus and uterus
didelphys, vaginal septum, Vaginal duplication and agenesis.

25. IMAGING STUDIES

26. Inversion Radiography
Invertogram or lateral pelvic radiography at 24 hours:
• Holding the baby upside down and using lateral radiography
to observe the level of gas in the distal rectum.
• A similar, but more humane, approach is cross-table lateral
pelvic radiography with a radio-opaque marker on the anal
dimple with the child in the prone position and the hips slightly
raised.
• If the pouch is observed within 1 cm of the marker, some
surgeons offer primary repair without colostomy.
• For pouches farther than 1 cm, colostomy is performed.

27. If the caudal segments of the sacrum
are deficient, the PC line can be
developed by projection from the pubis
through the same site on the ischium,
which is approximately the junction
between the upper quarter
and the lower three-quarters.

28. • The soft tissues lying at the level of the PC line are the
bladder neck, the verumontanum, the pelvic reflection from
the rectum to the prostate, and the external os of the cervix.
• In assessing the gas bubble in an ARM, its relation to the PC
line defines the essential factor of whether the blind pouch is
above or below the attachment of levator ani to the pelvic
wall.
• I line corresponds to the upper surface of the bulb of the
urethra in the male and the upper limit of perineal body and
the level of the triangular ligament in the female.
• The anal pit is normally 1–2 cm caudal to the ossified ischium.

30. Pressure-Augmented Colostogram
• Beyond the neonatal period, in those who have
undergone a diverting colostomy, the anatomy
of the terminal colon and fistula can be accurately
depicted fluoroscopically by performing a pressure-
augmented colostogram.
• Safe technique that can successfully
demonstrate the presence or absence of a fistula.

31. Pressure-Augmented Colostogram...
• The investigation involves the injection of water-
soluble contrast medium into the distal limb of
the colostomy using a balloon catheter.
• The balloon is inflated and traction applied to
the catheter to occlude the stoma.
• Water-soluble contrast medium is then injected
under constant gentle pressure until a fistula is
filled, and visualized with the aid of fluoroscopy.
• The presence of a fistula is initially indicated by the
appearance of a nipple of contrast arising from the
terminal colon.

33. Micturating Cystourethrography
• Used to assess for the presence of associated
vesicoureteric reflux.
• The antegrade urethrogram component of the study,
together with a retrograde urethrogram performed whilst
removing the catheter, may demonstrate the site of a
recto urinary fistula.
• This is not as reliable at demonstrating a fistula as a
pressure-augmented colostogram

35. ULTRASONOGRAPHY
• Initial reports involved scanning from the anal
dimple and measuring the distance between the
terminal colon and the skin at the anal dimple site.
DISADVANTAGES:
• Application of too much pressure at the anal
dimple distorting the distance to the terminal colon.
• The colon being difficult to visualize if
decompressed by surgery or a large fistula.

36. CT scanning
• CT provides increased detail, particularly of the osseous
structures, as well as being able to demonstrate the pelvic
floor musculature.
• There is difficulty, however, in distinguishing meconium from
the rectal wall and adjacent musculature, due to limitations
in contrast resolution.
• This limits its usefulness in detecting the site of any fistula,
although it has been used to demonstrate the level of the
terminal colon.

37. MRI
• Improved contrast resolution allows easy
differentiation of meconium from the rectal wall and
levator musculature.
• In the neonatal period, meconium is easily
visualized on MRI as hyper intense material on
T1-weighted imaging, due to its lipid content.
• MRI can accurately detect the level of the
terminal bowel, and the state of the pelvic
floor musculature.

40. Cloacagram
• In a female child with a clinical cloacal malformation, water-
soluble contrast medium can be instilled into the cloaca to
determine the anatomy and length of the common channel.
• Multiple catheters may be required to outline the genital
and urinary components with contrast medium.
• Alternatively, a balloon catheter can be used, with the
balloon inflated outside the patient and applied to the cloacal
opening to occlude it.
• If contrast does not reflux into the colonic component and a
colostomy is present, then a pressure-augmented
colostogram can be performed, as in a male.

42. Endoscopy
• Endoscopy of the orifices within the
urogenital sinus or common cloacal
channel in particular, may be
helpful.

43. Assessment for Associated
Malformations
• Associated malformations are identified in
approximately 50% of children with ARM.
• Some of these defects may be life threatening or
may have a greater impact than the ARM itself
on the quality of survival of the child.
• It is imperative, therefore, that these are
identified prior to undertaking surgery to treat the
ARM.

45. Persistent Cloaca
• Persistent cloaca represents the most complex
deformity in female anorectal, vaginal, and
urogenital malformations.
• It is defined as a defect in which the rectum, one
or two vaginas and the urinary tract converge into
one common channel.
• It is very rare and occurs in 1:250,000 newborns.

48. Persistent Cloaca
Associated malformations

51. Congenital Pouch Colon
• The condition is defined as an anomaly in which
all or part of the colon is replaced by a pouch-like
dilatation, which communicates distally with the
urogenital tract via a large fistula.
• In this condition, a supralevator anorectal
malformation (ARM) is associated with a colonic
pouch of variable size (5–15 cm in diameter).

52. Congenital Pouch Colon

53. Congenital Pouch Colon

54. Rectal Atresia
• Rectal atresia is a rare type of
anorectal malformation (ARM)
constituting 1–2% of the ARM.
• Male:Female ratio is 7:3

57. Rectal Ectasia
• Rectal ectasia is defined as a state of massive
dilatation of the rectum and sigmoid colon.
• It may be primary (presenting at the time of birth) or
secondary (developing later as a result of distal
obstruction or inadequate evacuation)
• Balloon-like rectum, colonic inertia, megarectum,
terminal fecal reservoir syndrome, pseudo-
Hirschsprung’s disease and rectal inertia

58. Rectal Ectasia

59. Rectal Duplication
• Rectal duplications form only 5% of alimentary tract
duplications, with less than 100 cases reported in
the English literature up to the present date.
• Enterocystoma of the rectum, enterogenous cyst of
the rectum, tail gut cyst, precoccygeal cyst,
rectal cyst, and cystic hamartoma.
• The majority of rectal duplications are located in the
retrorectal space as a cystic mass

60. TYPES

62. Anal Canal Duplication
• Anal canal duplication can be an isolated
anorectal pathology or a part of caudal twinning
syndrome that is characterized by the presence
of twinning of the hindgut derivatives, giving rise
to doubling of its derivatives, namely the colon,
rectum, bladder, urethra, genital organs, and
kidney.

63. Investigation
• Investigations such as fistulogram, contrast
enema, micturating cystourethrography (MCU),
renogram, ultrasonography, and MRI, are
performed to gain information about the location
and communication of the double ani with the
genitourinary and intestinal tracts.

64. Vesicointestinal Fissure
• Vesicointestinal fissure, or cloacal exstrophy, is a severe
congenital abnormality of the infraumbilical body wall, which
exhibits the following features:
1. Exomphalos.
2. Elephant-trunk deformity,
3. The pubic bones are widely separated and in a male the penis is
split, with each pubic bone segment carrying a corpus
cavernosum and hemiglans.
4. In a female the clitoris is similarly split and the vagina is
duplicated.

66. Anomalies Associated
with Cloacal Exstrophy
• Symphysis pubis diastasis
• Anomalies of the posterior elements of the vertebral column and
sacral dysplasias.
• 11 pairs of ribs
• CTEV
• Renal Anomalies
• Undescended testes in males and duplication of the internal
genitalia in females
• Spinal dysraphism, meningocele, meningomyelocele, and spinal
lipoma
• Malrotation, large bowel duplication, appendiceal duplication, and
short bowel
• Omphalocele (exomphalos)

67. Conclusion
• The initial assessment of a newborn with ARM
is aimed at identifying the anatomy of the
malformation, the presence of any associated
anomalies that may impact on immediate survival
or future quality of life, and the state of the
pelvic floor musculature and its innervation, which
will impact on future function.

68. Thank you !