imperforate Anus Flashcards
incidence
1 / 5000
types
A. High anomaly (agenesis, atresia) B. Low anomaly (covered, membranous anus)
C/P:
- General: to exclude VACTERL -Abdominaf lO may be present - Local: meconium at tip of penis — high anomaly lmpulse on crying at the anus — low anomaly
lnvest.:
invertogram 24 hrs after birth, lVP, urine analysis
TTT:
a. High anomaly: staged surgery (3 stages) b. Low anomaly: Only perineal surgery
1- High anomalies (More Common) is characterized by
- Failure of the rectum to pass through the pelvic floor (proximal to the pelvic floor).
- Usually associated with fistulous communication with posterior urethra in males or vagina in females.
- ln high anomalies ( M: F =2:1)
Types if High anomalies
a- Anorectal Aqenesis:
- Rectum:
- Forms a blind pouch above the pelvic floor with fistulous communication with UB, urethra or vagina.
- Anal canal:
- ls absent
b- RectalAtresia: - Rectum
- Forms a blind pouch above the pelvic floor.
- Anal canal:
- Forms a blind pouch below the pelvic floor.
low Anomalies is characterized by
- Distal to the pelvic floor. ,
- ln lowanomalies ( M: F =1:2)
- Not associated with other anomalies
- No defect in anal sphincter
Types of Low Anomalies
a-covered Anus:
The anal canal is covered by skin bar and usually opens into an ectopic site anterior to normal position.
b-Membranous Anus:
There is a membrane at the dentate line –> retained meconium –> bulging of this membrane
associated anomalies
VACTERL, more common in high than low anomalies.
Clinical Picture
a-General examination
To exclude associated congenital anomalies.
b-Abdominal examination
There may be evidence of intestinal obstruction.
c-Examination of the perineum
1. Presence of anus, its size and site
2. Presence of an anal dimple
3. lf there is an impulse on crying at the site of the anus + low anomaly.
4. Subcutaneous fistulous track full of meconium -+ ectopic anus
5. Meconium at the tip of the penis + fistula to the bladder or urethra.
6. lf the thermometer can be introduced into the anus for > 1 cm, this excludes rectal
atresia.
DD
Of neonatal intestinal obstructiong) :
1. Duodenal atresia:
–) Vomiting (bile stained or not) –) Double bubble sign on x-ray.
Volvulus neonatorum:
–) Abdominal colic, bile stained vomiting & bleeding per rectum.
–) Doppler shows affected bowel blood flow.
Meconium ileus:
–) Thick meconium
–) Gastrografin is diagnostic & therapeutic.
Hirschsprung disease (long segment) :
–) Barium enema shows stenotic colon. –) Biopsy is diagnostic.
Investigations
- Radiological:
- Plain chest X-ray (Invertogram) :
*24 hours after birthM (enough time for gas to
travel along the colon to reach the distal end
the bowel), the infant is held upside down for
few minutes with radio-opaque marker (e.9.
coin) on the possible site of the anus.
*We can differentiate between high and low anomalies by:
1.Measuring the distance between coin and distal gas shadow:
- if < 1cm —> low anomaly
- if > 1cm —> high anomaly
2. Determining the site of termination of bowel: - proximal to the pubo sacral line –> high anomaly
- Distal to pubo sacral line –> low anomary
- IVP: (ln high anomalies)
- For urinary anomalies
- lf bladder gases are present —> high with fistula.
2. laboratory
-Urine analvsis:
lf meconium is present –> fistulous communication with UB
Treatment
1-High anomalies:
-Treated with staged surgery:
- First staqe: Temporary colostomy
- Second staoe: Anorectal pull-through (abdominal approach)
- Third staqe: closure of colostomy.
Results are not satisfactory because continence may be weak.
2.Low anomalies
- Only perineal surgery.
3. ttt of associated anomalies if found
