[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Conditions](https://durgical.com/en/conditions/) › Anorectal malformations (imperforate anus) [Conditions](https://durgical.com/en/conditions/) · [Pediatrics and neonatology](https://durgical.com/en/conditions/) # Anorectal malformations (imperforate anus) Birth defects in which the anus is missing, blocked or misplaced, often with a fistula to the urinary tract or [vagina](https://durgical.com/en/anatomy/vagina/). Surgery repairs them. Updated 2026-11-01 ## Structures involved Tap one to see what it is and open it in 3D. - [Anal canal](https://durgical.com/en/anatomy/anal-canal/) - [Rectum](https://durgical.com/en/anatomy/rectum/) - [External anal sphincter](https://durgical.com/en/anatomy/external-anal-sphincter/) - [Puborectalis](https://durgical.com/en/anatomy/puborectalis/) - [Perineal body](https://durgical.com/en/anatomy/perineal-body/) - [Sacrum](https://durgical.com/en/anatomy/sacrum/) - [Prostatic urethra](https://durgical.com/en/anatomy/prostatic-urethra-seminal-colliculus/) - [Urinary bladder](https://durgical.com/en/anatomy/urinary-bladder/) ## Why it happens - [Defecation and continence](https://durgical.com/en/physiology/defecation-and-continence/) ## What it is A spectrum of congenital defects of the distal [rectum](https://durgical.com/en/anatomy/rectum/) and anus in which the anal opening is absent, narrowed or displaced, often with an abnormal connection (fistula) to the perineum, urethra, bladder neck, vestibule or vagina. ## Who gets it About 1 in 4,000 to 5,000 live births, slightly more often in boys. Around half of affected children have another anomaly, most often urinary, spinal, cardiac or as part of VACTERL association; it is also more frequent in Down syndrome. In Colombia it is managed by pediatric surgery in referral hospitals. ## Causes - Abnormal division of the cloaca by the urorectal septum in the first weeks of embryonic life - Most cases sporadic; occasional familial or syndromic cases (VACTERL, Down syndrome, Currarino syndrome) ## Risk factors - Other congenital anomalies, especially VACTERL association - Down syndrome - Family history of anorectal malformation ## Pathophysiology If the urorectal septum fails to separate the cloaca properly, the rectum ends blindly or opens at an abnormal site. The level of the rectal pouch relative to the [pelvic floor](https://durgical.com/en/anatomy/levator-ani/) muscles (levator ani and [puborectalis](https://durgical.com/en/anatomy/puborectalis/)) and the external sphincter determines the type of fistula and the chances of later bowel control. Abnormal sacral development and tethered [spinal cord](https://durgical.com/en/anatomy/spinal-cord/), which often coexist, further impair continence. ## Classification - Boys: perineal fistula (low); rectourethral bulbar or prostatic fistula; rectobladder neck fistula (highest) - Girls: perineal fistula; vestibular fistula (most common in girls); cloaca (rectum, vagina and urethra share one channel) - Imperforate anus without fistula (common in Down syndrome) and rectal atresia or stenosis - Older scheme: low versus high lesions ## Symptoms and signs - No anal opening, or an opening in an abnormal position, found on the newborn exam - No passage of meconium in the first 24 to 48 hours - Meconium in the urine (boys) or from the vagina or vestibule (girls) - Progressive abdominal distension and vomiting - Flat bottom with a poorly formed gluteal crease (suggests a high defect and sacral anomaly) ## Red flags - Bilious vomiting and marked distension (bowel obstruction or perforation) - Meconium or air in the urine (rectourinary fistula, risk of urinary infection) - Single perineal opening in a girl (cloaca) - Associated cardiac, esophageal or kidney anomalies with respiratory distress or no urine ## Diagnosis **Clinical** Diagnosed on the newborn physical exam, including careful perineal inspection and checking for a fistula. Wait 16 to 24 hours before deciding the approach, since meconium may then appear through a perineal or urinary fistula. **Tests** Urinalysis for meconium. Screening for associated anomalies: echocardiogram, passage of a nasogastric tube to exclude esophageal atresia, and [kidney](https://durgical.com/en/anatomy/kidney/) assessment. **Imaging** Cross-table lateral (prone) radiograph to estimate the height of the rectal pouch; renal ultrasound; spinal ultrasound or MRI for tethered cord; sacral radiographs; later, a distal colostogram to show the fistula before repair. ## Differential diagnosis - Hirschsprung disease - Meconium plug or meconium ileus - Anal stenosis or anteriorly displaced anus - Low intestinal atresia ## Goal of treatment Relieve obstruction safely, find associated anomalies, place the rectum within the sphincter muscles and achieve the best possible bowel and urinary control. ## Treatment **Acute** Newborn stabilization: nothing by mouth, intravenous fluids, gastric decompression and antibiotics when there is a urinary fistula or sepsis. **Surgical** Surgery by level: anoplasty for low perineal fistulas; diverting colostomy then posterior sagittal anorectoplasty (PSARP) and later colostomy closure for higher defects; complex reconstruction for cloaca. **Rehabilitation** Postoperative anal dilation program and a bowel management program (diet, laxatives or daily enemas) to achieve social continence. **Follow-up** Long-term follow-up of continence, constipation, kidney and urinary function, [spine](https://durgical.com/en/anatomy/region/spine/) and quality of life; nursing teaching of stoma and dilation care to families. ## Complications - Fecal incontinence or soiling - Chronic constipation and megarectum - Anal stricture or mucosal prolapse after repair - Recurrent urinary tract infection and urologic problems - Neurogenic bladder or bowel from tethered cord or sacral defects ## Prognosis Children with low defects and a normal [sacrum](https://durgical.com/en/anatomy/sacrum/) usually achieve good bowel control. Higher defects, cloaca, sacral anomalies and tethered cord reduce continence, but most achieve social continence with a structured bowel management program. ## Prevention - No known prevention; genetic counseling for families with a history of the defect ## Test yourself Think of the answer, then tap the question to see it. ## What is the most common anorectal malformation in girls? Rectovestibular fistula. ## A newborn boy has no anus and meconium in the urine. What does this indicate? A rectourinary (urethral or bladder neck) fistula, a higher-type malformation usually needing a colostomy first. ## Which association should be screened for in every child with imperforate anus? VACTERL: vertebral, anal, cardiac, tracheoesophageal, renal and limb anomalies. ## Why wait about 24 hours before deciding the surgical approach? Rising intraluminal pressure may push meconium through a fistula, showing its site and the height of the defect. ## Which standard operation repairs higher anorectal malformations? Posterior sagittal anorectoplasty (PSARP), usually after a protective colostomy. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/anorectal-malformations/) ## Related conditions - [VACTERL association](https://durgical.com/en/conditions/vacterl-association/) - [Hirschsprung disease](https://durgical.com/en/conditions/hirschsprung-disease/) - [Down syndrome (trisomy 21)](https://durgical.com/en/conditions/down-syndrome/) - [Esophageal atresia and tracheoesophageal fistula](https://durgical.com/en/conditions/esophageal-atresia-and-tracheoesophageal-fistula/) - [Spina bifida (myelomeningocele)](https://durgical.com/en/conditions/spina-bifida/) - [Congenital kidney anomalies (horseshoe kidney, renal agenesis)](https://durgical.com/en/conditions/congenital-kidney-anomalies/) - [Vesicoureteral reflux](https://durgical.com/en/conditions/vesicoureteral-reflux/) - [Functional constipation in children](https://durgical.com/en/conditions/functional-constipation-in-children/) - [Large bowel obstruction](https://durgical.com/en/conditions/large-bowel-obstruction/) Educational information, not medical advice. For any symptom, see a health professional. Sources: [Imperforate anus](https://medlineplus.gov/ency/article/001147.htm) (MedlinePlus (U.S. National Library of Medicine), 2024). [← All conditions](https://durgical.com/en/conditions/) ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/conditions/anorectal-malformations/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/anorectal-malformations/