Causes and associated conditions
Formation of the anorectal region occurs in the first trimester. During this period, the urorectal septum descends and divides the cloaca into ventral (urogenital) and dorsal (rectal) parts. If this process is disrupted, atresia or stenosis of the anus and rectum occurs. The severity of the malformation depends on the stage at which development arrested.
The pathology is rarely isolated. Up to 70% of patients have associated anomalies:
- VACTERL association: detected in almost half of the patients.
- Currarino triad (Currarino triad): includes the malformation itself, sacral defects, and a presacral mass.
- Down syndrome: diagnosed in 2–8% (usually presenting as an imperforate anus without fistula formation).
Classification
To systematize the malformations, the Wingspread or Krickenbeck classifications are used. Both take the child's sex into account.
The Wingspread system assesses the height of the blind-ending rectum relative to the levator ani muscle. Low, intermediate, and high variants are distinguished.
In modern practice, surgeons prefer the Krickenbeck classification because it details the presence and location of fistulas, which is critical for surgery:
- In males: fistulas may open into the bladder neck, prostatic urethra, or bulbar urethra.
- In females: fistulas usually open into the vaginal vestibule.
- In both sexes: perineal fistulas occur, as well as fistula-free variants (isolated atresia or stenosis).
Cloacal malformations
This is the most complex variant of the malformation, occurring only in females.
Instead of three separate openings on the perineum, a single common channel (common channel) is formed, into which the rectum, vagina, and urethra all open.
The anatomy of these structures is extremely difficult to visualize. The exact length of the common channel is best determined by endoscopy (cystoscopy), as radiological methods often fail to provide adequate detail due to the small size of the structures.
Diagnosis and management
ARMs can be clinically suspected immediately after birth during a perineal examination. The newborn is urgently transferred to pediatric surgeons.
Features of diagnostic imaging in newborns:
- The primary goal in the first days of life is to screen for associated anomalies rather than to perform a detailed assessment of the rectum itself.
- Abdominal ultrasound (with special attention to the kidneys), chest X-ray, and echocardiography are mandatory.
- Spinal ultrasound is indicated to rule out tethered cord syndrome (found in 50% of patients). Precise subsequent evaluation requires an MRI.
- Routine invertography (lateral cross-table radiograph with the infant prone) is not recommended as a standard because it yields a high error rate.
Surgical tactics:
- If a perineal fistula is present, primary repair (posterior sagittal anorectoplasty) is performed within the first two days of life.
- For other forms, a diverting colostomy is created to prevent stool from entering the urogenital tract.
- Radical surgery is postponed for several months.
Prior to definitive surgery, high-pressure colostography is performed. A Foley catheter is introduced through the stoma, the balloon is inflated, and contrast is injected. This allows complete filling of the distal bowel and clear visualization of the fistulous tract.
Briefly: answers to topical questions
What components are included in the VACTERL association?
The VACTERL association includes the following associated congenital developmental anomalies.
- Vertebral anomalies (vertebrae) — V component.
- Anal atresia (imperforate anus/atresia) — A component.
- Cardiac anomalies (cardiac anomalies) — C component.
- Tracheoesophageal fistula (tracheoesophageal fistula) — TE component.
- Renal anomalies (renal anomalies) — R component.
- Limb anomalies (limb anomalies) — L component.
What is the difference between the Wingspread and Krickenbeck classifications?
The difference between the classifications lies in the primary criterion used to evaluate anorectal malformations.
| Characteristic | Wingspread classification | Krickenbeck classification |
|---|---|---|
| Classification criterion | Position of the blind-ending rectum relative to the levator sling (levator sling) | Presence or absence of a fistula and its location; defines 5 types of fistulas based on location |
| Categories | Low, intermediate, and high malformations | Fistula types based on location; also provides information on the location of the atretic segment |
| Significance | Used to classify ARMs | Preferred in modern practice; information on the location of the atretic segment is critical for surgical planning |
Which spinal and vertebral malformations are associated with anorectal malformations?
Anorectal malformations may be accompanied by spinal and vertebral anomalies.
- Spinal cord pathology is found in up to 50% of children with ARMs; most commonly tethered cord syndrome (tethered cord).
- Sacral bone anomalies are part of the Currarino triad, along with anorectal malformation and a presacral mass.
- Vertebral anomalies are a component of the VACTERL association, which frequently accompanies anorectal malformations.
Class and exam questions
Why is immediate radical surgery not performed for ARM?
In most cases (except for simple perineal fistulas), a detailed study of the anatomy of the malformation is required. A stoma is created first to divert fecal flow, and surgery is performed several months later following a complete radiological workup.
What is a cloacal malformation?
This is a severe malformation in females where the urethra, vagina, and rectum merge into a single channel opening onto the perineum via a single orifice.
Why is a spinal ultrasound performed in children with ARM?
Up to 50% of such patients have occult spinal cord pathologies, most commonly tethered cord syndrome (tethered cord).
What is the best way to visualize a fistula before surgery?
The gold standard is high-pressure colostography, in which contrast is injected into the distal bowel segment through the stoma.
What else to study on this topic
- Methodology for performing high-pressure colostography
- Visualization of cloacal structures: cloacography and MRI
- Ultrasound diagnosis of acute appendicitis in children
- Causes of abdominal pain in older children and the role of imaging modalities
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