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 did not reach its 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, 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 care takers to adult care ones.
Anorectal malformations often associate with other malformations: urological, vertebral/spinal, tracheo-esophageal, cardiac , urogenital/renal and limb, and others. In approximately 10% of these cases, there is a proven or suspected common genetic cause (“syndromical ARM”).
A European consortium called ARM-Net composed by many paediatric surgeons dedicated to the care of patients with anorectal malformations, patient organisations (AIMAR, SoMA, VA), geneticists and epidemiologists was founded in Europe in 2011.
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