Omphalocele

Omphalocele is a congenital anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall defect in which the intestines are covered by peritoneum Peritoneum The peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum). Peritoneum and Retroperitoneum and amniotic membranes. The condition results from the failure of the midgut to return to the abdominal cavity by 10 weeks’ gestation. Omphalocele is frequently associated with genetic syndromes and chromosomal abnormalities. Prenatal diagnosis can be made by prenatal ultrasound, maternal blood elevated ⍺-fetoprotein, and fetal chromosomal analysis. Treatment includes immediate hemodynamic stabilization followed by primary or staged surgical repair.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition

  • A congenital defect of the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall located at the base of the umbilicus in which the intestine and other abdominal viscera are only covered by the peritoneum Peritoneum The peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum). Peritoneum and Retroperitoneum and amniotic membranes
  • Giant omphalocele measure ≥ 4 cm, contain the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver, and are associated with small undeveloped abdominal and thoracic cavities.
Omphalocele containing omd cyst

Large omphalocele containing omphalomesenteric duct cyst

Image: “Large omphalocele containing OMD cyst” by Yousuf Aziz Khan, MBBS, FCPS (Paediatric Surgeon), Department of Paediatric Surgery, National Institute of Child Health, Rafiquee Shaheed Road, Karachi – 75510, Sind, Pakistan. License: CC BY 3.0

Embryology

  • Gastrointestinal (GI) system development from 3 germinal layers:
    • Mesoderm: connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue (wall of gut tube, blood vessels, smooth muscle)
    • Endoderm: epithelial lining
    • Ectoderm: epidermis and neural crest (neurons of the GI tract)
  • GI tract divisions:
    • Foregut: oral cavity to 1st part of the duodenum
    • Midgut: mid-duodenum to 1st ⅔ of the transverse colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix
    • Hindgut: last ⅓ of the transverse colon Colon The large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal. Colon, Cecum, and Appendix to upper anus
  • 6th week of gestation:
    • Rapid growth of GI tract
    • Midgut herniates through umbilical ring, developing entirely outside the peritoneal cavity.
  • 10th week of gestation:
    • Abdominal cavity is large enough for developing midgut.
    • Midgut completes rotation and returns to abdominal cavity.
Normal process of herniation during embryologic development

Diagram showing the normal process of intestinal rotation and herniation during embryologic development
A: The midgut (multi-colored loop) before herniation
B1–B3: As it grows rapidly, the midgut herniates through the umbilical ring and begins rotation.
C: The midgut returns to the abdominal cavity.

Image by Lecturio.

Epidemiology

  • Prevalence: 1 in 5,000 births
  • Boys > girls
  • Seen more commonly with younger or older mothers (< 20 or > 40 years old)
  • More prevalent in Black patients
  • 60%70% have associated abnormalities, including cardiac and chromosomal. 
  • May occur as part of syndromes:
    • Beckwith-Weidemann constellation of anomalies (macroglossia, macrosomia, hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, visceromegaly, and omphalocele)
    • Cantrell’s pentalogy (cleft sternum, ectopia cordis, anterior midline diaphragmatic hernia, cardiac anomalies, epigastric omphalocele)
    • Trisomy 13 Trisomy 13 Trisomy 13, or Patau syndrome, is a genetic syndrome caused by the presence of 3 copies of chromosome 13. As the 3rd most common trisomy, Patau syndrome has an incidence of 1 in 10,000 live births. Most cases of Patau syndrome are diagnosed prenatally by maternal screening and ultrasound. More than half of the pregnancies result in spontaneous abortions. Patau Syndrome (Trisomy 13), 18, or 21
    • Cloacal exstrophy (vesicointestinal fissure)
  • May be associated with prematurity, intrauterine growth restriction
  • Often seen in familial clustering

Pathophysiology

Pathophysiology is not definitively understood; 2 main theories:

  • Failure of the midgut to return to the abdominal cavity by 10 weeks’ gestation results in omphalocele
  • Failure of abdominal folds to seal, leaving midline defect and externalized abdominal organs

Diagnosis

Most cases of omphalocele (90%) are diagnosed prenatally:

  • Ultrasound: 
    • Part of routine prenatal screening
    • Can show other associated abnormalities 
  • Maternal serum ⍺-fetoprotein levels: Elevated levels are non-specific signs of omphalocele.
  • If detected prenatally, parents should be offered: 
    • Testing for Beckwith-Wiedemann syndrome
    • Microarray chromosomal analysis to evaluate for aneuploidy and trisomies 
    • Prenatal echocardiogram

Clinical Presentation

  • Newborn Newborn A neonate, or newborn, is defined as a child less than 28 days old. A thorough physical examination should be performed within the first 24 hours of life to identify abnormalities and improve outcomes by offering timely treatment. Physical Examination of the Newborn findings:
    • Full-thickness ventral wall defect
    • Herniation of intestines through umbilical ring, may also contain abdominal organs
    • Covered in clear sac composed of amniotic membrane and peritoneum Peritoneum The peritoneum is a serous membrane lining the abdominopelvic cavity. This lining is formed by connective tissue and originates from the mesoderm. The membrane lines both the abdominal walls (as parietal peritoneum) and all of the visceral organs (as visceral peritoneum). Peritoneum and Retroperitoneum
    • Size usually varies from 4–12 cm 
    • Occur centrally, in epigastrium, or in hypogastrium
  • Delivery can be challenging and requires a specialist.
    • Rupture of omphalocele sac can occur in ⅕ of cases.
    • Umbilical cord clamping must be carefully done to avoid damaging intestinal structures.

Management

Perinatal management

  • Attend to vital signs and evaluate respiratory distress (due to lung hypoplasia).
  • Avoid pressure and manual reduction.
  • Cover omphalocele with non-moist dressing.
  • Screen for hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, associated with Beckwith-Weidemann syndrome.
  • Apply nasogastric tube decompression.
  • Administer prophylactic broad-spectrum antibiotics in case of rupture.
  • Perform echocardiogram prior to any surgical procedure.

Surgery

  • Small-to-medium–sized defects with normal lung: early (within 24 hrs) primary repair (resection of membrane and closure of defect)
  • Giant omphalocele: multi-staged procedure to allow intra-abdominal accommodation and pulmonary maturation 
  • Enteral feeding can be established very early after closure.

Differential Diagnosis

  • Gastroschisis Gastroschisis Gastroschisis is a congenital abdominal wall defect characterized by the complete lack of closure of the abdominal musculature. A portion of intestine does not return to the abdominal cavity, thereby remaining in its early embryonic herniated state but with no coverings. Gastroschisis: a full-thickness defect of the anterior abdominal wall Anterior abdominal wall The anterior abdominal wall is anatomically delineated as a hexagonal area defined superiorly by the xiphoid process, laterally by the midaxillary lines, and inferiorly by the pubic symphysis. Anterior Abdominal Wall through which the intestine and/or other abdominal viscera freely protrude. No membrane or sac covers the bowel/intestine. Diagnosis is via prenatal ultrasound and treatment is surgical after birth. Gastroschisis Gastroschisis Gastroschisis is a congenital abdominal wall defect characterized by the complete lack of closure of the abdominal musculature. A portion of intestine does not return to the abdominal cavity, thereby remaining in its early embryonic herniated state but with no coverings. Gastroschisis is not commonly associated with other birth defects.
  • Pentalogy of Cantrell: a rare syndrome consisting of multiple congenital abnormalities, including a lower sternal defect, anterior diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm defect, pericardial defect, abdominal wall defect, and congenital heart anomalies. Diagnosis is made prenatally by ultrasonography. Treatment requires complex medical and surgical care.
  • Bladder exstrophy-epispadias complex: a spectrum of congenital defects: epispadias (failed closure of urethra), bladder exstrophy, and cloacal exstrophy (most severe defect, which includes anal atresia and omphalocele). Treatment is surgical, with goals to close abdominal wall defect, achieve urinary continence, and reconstruct genito-urinary area.
  • Umbilical hernia: presents as a protrusion in the neonate’s umbilical area. There is incomplete closure of the fascia of the umbilical ring, but with intact 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. Structure and Function of the Skin covering the ring. It is important to determine the reducibility, as incarcerated hernia is a complication. Surgery is indicated for defects > 1.5 cm in those > 2 years of age and for complications such as strangulation, incarceration, or rupture.

References

  1. Stallings EB et al. (2019). Population-based birth defects data in the United States, 20122016: A focus on abdominal wall defects. Birth Defects Res. doi: 10.1002/bdr2.1607
  2. Marshall J et al. (2015). National Birth Defects Prevention Network. Prevalence, Correlates, and Outcomes of Omphalocele in the United States, 1995-2005. doi: 10.1097/AOG.0000000000000920
  3. Bhatia, A., Shatanof, R., Bordoni, B. (2020). Embryology, Gastrointestinal. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK537172/ 
  4. Roux N et al. (2018). Early surgical management for giant omphalocele: Results and prognostic factors. J Pediatr Surg. doi: 10.1016/j.jpedsurg.2018.04.036
  5. Glasser, J., Windle, M., Carter, B. (2019). Pediatric Omphalocele and Gastroschisis (Abdominal wall defects). Medscape. Retrieved 4 Oct 2020, from https://emedicine.medscape.com/article/975583-overview#a5

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