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Anal atresia, or imperforate anus, refers to a spectrum of anorectal abnormalities ranging from a membranous separation to complete absence of the anus.
The estimated incidence is 1 in 5000 live births.
There are frequent associations with other congenital abnormalities.
Currarino's triad: anorectal malformations with sacral anomalies and presacral mass lesion 6
Clinically there is no anal opening and failure to pass meconium.
Subtypes can be classified into two broad categories: high (supralevator) or low (infralevator), depending on the location of the atretic portion.
Most cases are sporadic, with occasional familial forms.
can be variable depending on the site of atresia (i.e. high or low), level of meconium impaction and physiological effects such as straining
may show multiple dilated bowel loops with an absence of rectal gas
air within urinary bladder suggests high type 6
calcified meconium in the bowel loops would suggest high type (meconium calcifies due to urine exposure) 6
A coin/metal piece is placed over the expected anus and the baby is turned upside down (for a minimum of 3 minutes).
The distance of the gas bubble in the rectum from the metal piece is noted:
>2 cm denotes high type
<2 cm denotes low type
False-positives may occur if the image is taken in the first 24 hours of life or if there is impacted meconium within the distal rectum 6.
Fluoroscopy (contrast study)
The fistula is considered low (below the levator ani plane) if it is below the pubococcygeal line and high if above it
the anus may be seen as an echogenic spot at the level of the perineum and in anal atresia, this echogenic spot may be absent 4
may show bowel dilatation
an infracoccygeal or transperineal approach may allow differentiation between high and low subtypes 4
kidneys should be assessed in such patients 6
spinal US can reveal spinal cord lesions like tethering of cord 6
Can be used pre/post-operatively to study pelvic floor, renal, and spinal abnormalities 6.
Treatment and prognosis
low subtypes are treated with anoplasty
high subtypes are treated with colostomy with subsequent potential repair
- 1. Harris R, Nyberg D, Mack L, Weinberger E. Anorectal Atresia: Prenatal Sonographic Diagnosis. AJR Am J Roentgenol. 1987;149(2):395-400. doi:10.2214/ajr.149.2.395 - Pubmed
- 2. Berrocal T, Lamas M, Gutieérrez J, Torres I, Prieto C, del Hoyo M. Congenital Anomalies of the Small Intestine, Colon, and Rectum. Radiographics. 1999;19(5):1219-36. doi:10.1148/radiographics.19.5.g99se041219 - Pubmed
- 3. Han T, Kim I, Kim W. Imperforate Anus: US Determination of the Type with Infracoccygeal Approach. Radiology. 2003;228(1):226-9. doi:10.1148/radiol.2281011900 - Pubmed
- 4. Michael Entezami, Ursula Knoll, Matthias Albig et al. Ultrasound Diagnosis of Fetal Anomalies. (2004) ISBN: 9781588902122 - Google Books
- 5. Lane F. Donnelly. Diagnostic Imaging. (2005) ISBN: 141602333X - Google Books
- 6. Lee Alexander Grant, Nyree Griffin, Ronald G. Grainger. Grainger & Allison's Diagnostic Radiology Essentials. (2013) ISBN: 9780702034480 - Google Books