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Anorectal Atresia

Anorectal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS) refers to a spectrum of congenital Congenital Chorioretinitis anorectal malformations with an unclear etiology. These anomalies range from a simple imperforate anus in an otherwise normal anorectal region to complex anomalies involving the urogenital system. Anorectal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS) is sometimes seen as an isolated finding, but it may also occur as part of a multi-organ syndrome. Diagnosis is often made during initial newborn Newborn An infant during the first 28 days after birth. Physical Examination of the Newborn examination or after a delay in passage of meconium Meconium The thick green-to-black mucilaginous material found in the intestines of a full-term fetus. It consists of secretions of the intestinal glands; bile pigments; fatty acids; amniotic fluid; and intrauterine debris. It constitutes the first stools passed by a newborn. Prenatal and Postnatal Physiology of the Neonate for over 24 hours after birth. Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas varies based on complexity. Treatment is primarily surgical.

Last updated: 8 Jan, 2021

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Epidemiology

  • 1 in 5,000 births in the United States
  • Boys have a higher incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency than girls.
  • Most cases are sporadic Sporadic Selective IgA Deficiency (no family history Family History Adult Health Maintenance).
  • Parental risk factors:
    • Maternal: obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity and diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus
  • Associated anomalies occur frequently and are easily remembered using the acronym VACTERL:
  • There is an association between anorectal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS) and trisomy 21 Trisomy 21 Down syndrome, or trisomy 21, is the most common chromosomal aberration and the most frequent genetic cause of developmental delay. Both boys and girls are affected and have characteristic craniofacial and musculoskeletal features, as well as multiple medical anomalies involving the cardiac, gastrointestinal, ocular, and auditory systems. Down syndrome (Trisomy 21) and 18.

Etiology

Anorectal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS) arises out of deviations from the normal embryological development of abdominal organs to create the adult rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy and anal canal.

Cloaca of human embryo

Cloaca Cloaca A dilated cavity extended caudally from the hindgut. In adult birds, reptiles, amphibians, and many fishes but few mammals, cloaca is a common chamber into which the digestive, urinary and reproductive tracts discharge their contents. In most mammals, cloaca gives rise to large intestine; urinary bladder; and genitalia. Development of the Abdominal Organs of the human embryo Embryo The entity of a developing mammal, generally from the cleavage of a zygote to the end of embryonic differentiation of basic structures. For the human embryo, this represents the first two months of intrauterine development preceding the stages of the fetus. Fertilization and First Week at 25–27 days

Image by Lecturio.

Classification

Anorectal malformations may be divided into high and low lesions based on the level of the pelvic floor Pelvic floor Soft tissue formed mainly by the pelvic diaphragm, which is composed of the two levator ani and two coccygeus muscles. The pelvic diaphragm lies just below the pelvic aperture (outlet) and separates the pelvic cavity from the perineum. It extends between the pubic bone anteriorly and the coccyx posteriorly. Vagina, Vulva, and Pelvic Floor: Anatomy (levator ani muscle):

  • High/ supralevator Supralevator Perianal and Perirectal Abscess lesions
    • More difficult to correct and prone to fecal incontinence Fecal incontinence Failure of voluntary control of the anal sphincters, with involuntary passage of feces and flatus. Pediatric Constipation
    • Boys:
      • Rectobulbar fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula (most common type)
      • Rectoprostatic fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula
      • Rectovesical fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula
    • Girls: 
      • Rectovestibular fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula
      • Rectovaginal fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula
      • Cloacal malformation has the worst prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas.
  • Low/infralevator lesions
    • Relatively easy to correct, but prone to constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation
      • Rectoperineal fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula in both sexes
      • The rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy communicates with the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions but the canal is not protected by a sphincter. 
    • The anus may also end in a blind pouch.

Diagnosis

Defects are often identified during the newborn Newborn An infant during the first 28 days after birth. Physical Examination of the Newborn physical examination. Missed cases are usually identified within 24 hours following failure to pass meconium Meconium The thick green-to-black mucilaginous material found in the intestines of a full-term fetus. It consists of secretions of the intestinal glands; bile pigments; fatty acids; amniotic fluid; and intrauterine debris. It constitutes the first stools passed by a newborn. Prenatal and Postnatal Physiology of the Neonate and abdominal distension.

Physical examination

  • Clues about the neonate Neonate An infant during the first 28 days after birth. Physical Examination of the Newborn’s type of malformation:
    • Perineal opening: indicates a low defect 
    • Urine Urine Liquid by-product of excretion produced in the kidneys, temporarily stored in the bladder until discharge through the urethra. Bowen Disease and Erythroplasia of Queyrat sampling for meconium Meconium The thick green-to-black mucilaginous material found in the intestines of a full-term fetus. It consists of secretions of the intestinal glands; bile pigments; fatty acids; amniotic fluid; and intrauterine debris. It constitutes the first stools passed by a newborn. Prenatal and Postnatal Physiology of the Neonate:
      • In boys without a perineal opening and girls without a perineal or vestibular opening
      • Positive sample indicates urinary tract Urinary tract The urinary tract is located in the abdomen and pelvis and consists of the kidneys, ureters, urinary bladder, and urethra. The structures permit the excretion of urine from the body. Urine flows from the kidneys through the ureters to the urinary bladder and out through the urethra. Urinary Tract: Anatomy fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula.
    • Palpation Palpation Application of fingers with light pressure to the surface of the body to determine consistency of parts beneath in physical diagnosis; includes palpation for determining the outlines of organs. Dermatologic Examination for abdominal masses: may indicate hydronephrosis Hydronephrosis Hydronephrosis is dilation of the renal collecting system as a result of the obstruction of urine outflow. Hydronephrosis can be unilateral or bilateral. Nephrolithiasis is the most common cause of hydronephrosis in young adults, while prostatic hyperplasia and neoplasm are seen in older patients. Hydronephrosis or hydrocolpos
  • Discovery of anorectal atresia Atresia Hypoplastic Left Heart Syndrome (HLHS) should prompt a close examination for associated congenital Congenital Chorioretinitis anomalies:

Imaging

  • Prenatal ultrasound may identify suggestive features such as
    • Polyhydramnios Polyhydramnios Polyhydramnios is a pathological excess of amniotic fluid. Common causes of polyhydramnios include fetal anomalies, gestational diabetes, multiple gestations, and congenital infections. Patients are often asymptomatic but may present with dyspnea, extremity swelling, or abdominal distention. Polyhydramnios
    • Intra-abdominal cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change
    • Hydrocolpos
    • Hydronephrosis Hydronephrosis Hydronephrosis is dilation of the renal collecting system as a result of the obstruction of urine outflow. Hydronephrosis can be unilateral or bilateral. Nephrolithiasis is the most common cause of hydronephrosis in young adults, while prostatic hyperplasia and neoplasm are seen in older patients. Hydronephrosis  
  • By 24 hours of age, if the infant has not passed stool:
    • Lateral prone radiograph should be obtained.
    • Ultrasound may also identify associated genitourinary and gastrointestinal anomalies.
    • Other radiographic studies such as urethrogram, cologram, and fistulagraphy may be used.
    • Spinal magnetic resonance imaging (MRI) may be indicated in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with abnormal pelvic radiography.

Management

Medical

  • Once defects are identified, the infant should not be fed orally.
  • Individualize intravenous fluids Intravenous Fluids Intravenous fluids are one of the most common interventions administered in medicine to approximate physiologic bodily fluids. Intravenous fluids are divided into 2 categories: crystalloid and colloid solutions. Intravenous fluids have a wide variety of indications, including intravascular volume expansion, electrolyte manipulation, and maintenance fluids. Intravenous Fluids and electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes to meet nutritional needs for the infant.
  • If urinary fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula is suspected: broad-spectrum Broad-Spectrum Fluoroquinolones antibiotics
  • Treatment of life-threatening anomalies should take precedence.

Surgical

  • Primary repair: often performed on rectal pouches
    • < 1 cm identified on imaging
    • With or without perineal/vestibular fistulas
    • Without associated urogenital anomalies
  • Colostomy + staged repair: performed in children who do not qualify for primary repair
    • Within or after 24 hours: early colostomy 
    • Several weeks later: posterior sagittal Sagittal Computed Tomography (CT) anorectoplasty (most common procedure)
    • When wounds have healed: colostomy closure
Imperforate anus with rectopenile fistula surgery

A urethrography (a) showing the urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy and bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess, with a small amount of contrast appearing in the rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy. The location of the fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula entering the urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy is displayed (arrow). Limited posterior sagittal Sagittal Computed Tomography (CT) anorectoplasty (b) with division of the rectum Rectum The rectum and anal canal are the most terminal parts of the lower GI tract/large intestine that form a functional unit and control defecation. Fecal continence is maintained by several important anatomic structures including rectal folds, anal valves, the sling-like puborectalis muscle, and internal and external anal sphincters. Rectum and Anal Canal: Anatomy (upper arrow) and a catheter in the fistula Fistula Abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body. Anal Fistula (lower arrow).

Image: “Urethrography showed the urethra Urethra A tube that transports urine from the urinary bladder to the outside of the body in both the sexes. It also has a reproductive function in the male by providing a passage for sperm. Urinary Tract: Anatomy and the bladder Bladder A musculomembranous sac along the urinary tract. Urine flows from the kidneys into the bladder via the ureters, and is held there until urination. Pyelonephritis and Perinephric Abscess” by Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, 610041, People’s Republic of China. License: CC BY 4.0

References

  1. Rosen NG. (2019). Pediatric Imperforate Anus. Medscape. NewYork NY. WebMD. Retrieved Oct 6, 2020, from https://emedicine.medscape.com/article/929904-overview#a2
  2. Cuschieri A; (2002). EUROCAT Working Group. Anorectal anomalies associated with or as part of other anomalies. Am J Med Genet.
  3. Anorectal malformations in neonates. Afr J Paediatr Surg.  2011; 8(2):151-4 (ISSN: 0974-5998)

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