1.7 Urorectal/Anorectal Malformations         

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Anorectal Malformations:

Anorectal malformations (ARM) are rare congenital anomalies. The incidence of ARM varies between 1:3500 to 1:5000 live births. The estimated risk for a couple having a second child with an anorectal malformation is approximately 1%. They represent a broad spectrum of malformations, in which the rectum and anal canal have not reached their normal position, but end further ventrally (to the front), or even up in the pelvis.  The rectum can even be blind ending (imperforate anus without a fistula) but this is a rather unusual defect, occurring in about 5% of patients, and is associated with Down Syndrome.

If the rectum reaches the outer surface, it might open to the perineum in both boys and girls, or to the vestibulum in girls (“perineal or vestibular fistula”). In the forms positioned in the pelvis, it connects to the urethra or bladder in males (“rectourethral fistula and bladder neck fistula”). In girls, the rectum and urethra form, together with the vagina, a so-called common channel leading to the perineum (“cloacal form”). The spectrum of ARM is currently best described in the Krickenbeck classification.

Initial treatment of anorectal malformations is mostly surgical. This can either be a direct reconstruction of the rectum and anal opening or a temporary stoma. Patients who are given a stoma, often get a reconstruction of the anal opening and rectum after several months. Boys with a bladder neck fistula, and girls with a cloacal form and long common channel mostly need an additional laparotomy during reconstruction.

After initial surgical care, many patients still need additional care for faecal incontinence, constipation or other issues involving the urogenital tract. Patients need life-long care and during adolescence, a transitional programme is needed to transfer responsibility from parents to the patient and from paediatric caretakers to adult care ones.

Anorectal malformations are often associated with other malformations: urological, vertebral/spinal, tracheo-oesophagal, cardiac, urogenital/renal and limb, and others. In approximately 10% of these cases, there is a proven or suspected common genetic cause (“syndromical ARM”).

Collaboration with Orphanet:

In 2021, ERN eUROGEN clinicians and their ePAG Chair joined forces with the ARM-Net consortium and ERN ERNICA clinicians to update the Orphanet classification system for ARMs. The Krickenbeck classification is reflected in the non-syndromic ARM group, and the high/intermediate/low ARM entities have been made obsolete. As a secondary issue, some subtypes were also included. After these amendments, the group code for “non-syndromic” ARM can be used for non-syndromic cases before the ARM type is known, then when the ARM type is known, the disorder code can be used. For syndromic cases, the syndrome disorder code can be used, and the non-syndromic disorder codes can be used as secondary codes. A summary of the collaboration is available here.

The changes were agreed upon by ERN eUROGEN, ERN ERNICA, the ARM Net consortium and the European Paediatric Surgeon’s Association (EUPSA) in April 2021.  On 12 June 2021, ERN eUROGEN was informed by Orphanet that these had been implemented in the Orphanet database. The new ORPHAcodes and classification structure were included in the July 2021 update of the nomenclature pack, a set of computable files that was developed by Orphanet in the framework of the EU-funded RD-CODE project for the implementation of ORPHAcodes in health information systems.

The importance of this change for patients cannot be underestimated. In many countries, reimbursement for and access to services on the diagnosis of rare diseases is based on the Orphanet system. In the future, the changes will allow patients with ARMs to access specialised healthcare and services based on a more accurate clinical diagnosis of their rare condition.

Additional Resources:


A European consortium called ARM-Net was founded in Europe in 2011, composed of many paediatric surgeons dedicated to the care of patients with anorectal malformations, patient organisations (AIMAR, SoMA, VA), geneticists and epidemiologists. ARM-Net is a Supporting Partner of eUROGEN.

ONE in 5000 Foundation
A worldwide resource for the Imperforate Anus/Anorectal Malformation community. Their vision is to ensure that every child born with IA/ARM around the world is guaranteed the following four outcomes, referred to as the AIMS program: AWARENESS; INFORMATION; MEDICAL; SUPPORT.

The website serves to provide this resource by connecting all within the IA/ARM community, which includes families, adults with lived experience, and a network of medical professionals from both the clinical and mental health perspective, who specialise in the paediatric colorectal field. The site contains many videos on IA/ARM topics.

Click here to open a pdf copy of their leaflet.

CURE-Net (in German)
The aim of the network for congenital uro-rectal malformations (CURE-Net) is to evaluate not only basic research in molecular biology but also the success of postoperative treatment and the various forms of follow-up care through multicentre, clinical and psychosocial research with the help of standardized examination methods.

Relevant Articles/Publications:

Dewberry, L., Alaniz, V., Wilcox, D.T. et al. From Prenatal Diagnosis Through Transition to Adult Care: What Everyone Should Know About Anorectal Malformations. Curr Treat Options Peds (2020). https://doi.org/10.1007/s40746-020-00194-4