Anorectal Malformations: Spectrum of Defects and Treatments
The Colorectal Center at Cincinnati Children's Hospital Medical Center provides information on the spectrum of defects and treatments for anorectal malformations. You may view a presentation by Dr. Marc Levitt on Anorectal Malformations to learn more.
With anorectal malformations, we are dealing with a spectrum of defects; therefore, each malformation has different anatomical characteristics.
Rectourethral Fistula Coronal View The normal descent of the rectum has been halted. Therefore, the parasagittal fibers get closer together in the midline. |
Below the lowest part of the rectum, all the striated muscle fibers meet together forming a solid mass of muscle which is very thin in its lateral aspect.
The length of the solid mass of muscle depends upon the height of the defect. The lower the defect, the shorter that solid mass and the wider the funnel-like muscle structure.
Rectourethral Fistula Coronal View | 
Rectourethral Fistula Sagittal View |
The images above show a view of a detailed anatomy of a male with a rectourethral fistula. Consistent with the idea of a spectrum of defects, the degree of muscle development varies from case to case.
Perineal Fistula | 
Rectourethral Bulbar Fistula |
Rectorurethral Prostatic Fistula | 
Rectobladder Neck Fistula
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In one extreme of the spectrum, low defects can be seen which are associated with almost normal muscles. At the opposite extreme of the spectrum, there are very high defects with severe degrees of muscle underdevelopment.
Very high defects are more frequently associated with abnormal sacrums and poor muscle development.
Rectourethral Fistula Coronal View |
Rectourethral Fistula Sagittal View |
There is some evidence that the internal sphincter is present in patients with anorectal malformations regardless of the height of the defect. That involuntary sphincter seems to be located in the most distal part of the rectum.
Very little is known about the blood supply of the rectum and pelvis in cases of anorectal malformations. Observations made during the surgical procedures confirm the impression that we are dealing with a spectrum of abnormalities; thus, very low types of defects are seen to have good muscles, blood supply, and innveration, indistinguishable from normal individuals.
At the other end of the spectrum, extremely high defects (rectobladder neck or high cloacas) can be seen where hemorrhoidal vessels cannot be identified because the bowel is located very high above the pelvis.
Something similar must occur with the innervation of the rectum in cases of anorectal malformations, although this has not been documented.
Bladder innervation as well as nervi erigenti in cases of high anorectal malformations seem to run closer to the midline than normal, becoming more susceptible to surgical damage when violating the basic principle of staying in the midline.
There seems to be a direct correlation between the degree of sacral abnormality and the neurologic deficit of the pelvic organs, and the degree of muscle atrophy.
Very high defects are more frequently associated with an abnormal sacrum and poor innervation.
Detailed anatomic dissections in postmortem specimens of cases with anorectal malformations are scanty.
No information related to sensory innervation in cases of anorectal malformations is obtained before these patients are operated on.
Clinical and functional evaluations are carried out after the repair of the defect; thus, we are evaluating instead the anatomical changes provoked by the surgical technique.
Very low defects are rarely evaluated, mainly because these patients usually behave like normal individuals postoperatively.
Patients operated on with high defects show intrarectal sensation to rectal distension, but the exquisite sensation described by Duthie and Gairns is absent.
Information concerning sympathetic and parasympathetic innervation can be extrapolated from postop manometric studies; however, no valid conclusions can be drawn from the available information due to lack of uniformity in the selected groups of patients and techniques employed.
Associated Defects
Urogenital Defects
The genitourinary tract is the most serious and frequent site of associated defects in anorectal malformations. The frequency of this association varies from 20 to 54 percent depending on the source of reference.
Those centers that follow a more strict protocol of urologic evaluation in patients with anorectal malformations usually detect a higher incidence of these defects.
It is also true that the higher the malformation, the more frequently it is associated with a severe urologic problem. Forty-eight percent of our patients had associated genitourinary anomalies.
It is important to mention our series is not representative of what happens in most places because we receive many referrals of the more complex malformations which have more chances of being associated with a urologic defect.
Patients with a high cloaca or a rectovesical fistula demonstrated almost a 90 percent incidence of associated genitourinary abnormalities; whereas, low defects had a frequency of association of less than 14 percent.
Sacrum and Spine Defects
The sacrum is frequently abnormal. Sacral vertebrae may be deformed or reduced in number. It is well known that the absence of more than three sacral vertebrae is associated with a severe neurogenic deficit, including neurogenic bladder and lack of bowel control.
Other defects such as hemisacrum, may also lead to important neurogenic deficits. The upper spine frequently shows hemivertebra.
For more information or to request an appointment, please contact the Colorectal Center at Cincinnati Children's.
