*Fetal Surgery Program, Hospital Italiano, Buenos Aires

Definition: Atresia of the pylorus.

Frequency: Gastrointestinal atresias occur approximately in 1:10,000 births but pyloric atresia represents less than 1% of these cases^[1],^[2]. Crooks reported the first congenital gastric luminal obstruction in 1828 and a complete prepyloric mem­brane was reported by Bennet in 1937^[3]. In an extensive review reported by Cook and Rickham in 1989, only 125 cases of congenital gastric outlet obstructions were encountered in a period of 25 years among the patients with a neonatal gastrointestinal obstruction seen at the Liverpool Regional Neonatal Center. The estimated incidence resulted 0.3:10,000².

Etiology: Strong evidences support an autosomal recessive mode for both the isolated pyloric atresia and the pyloric atresia associated to Epider­molysis Bullosa (pyloric atresia + Epidermolysis Bullosa syndrome) which was first reported by Korber and Glasson in 1977².

Pathology: Unlike small bowel, colonic or esophageal atresias, atresias of the antrum-pyloric region do not have a clear etiology^[4]. Vascular ischemia from volvulus is unlikely in a well vascula­rized organ as the stomach which is extensively fixated (unless located in an abnormal position as in a congenital diaphragmatic hernia). An incomplete reso­lution of an endodermal "solid state†(the period when the lumen of the viscera is filled), as it is currently accepted as the most likely mechanism to explain duodenal atresia, is not considered in gastric pyloric atresia.

In the present case, the vascular explanation for a pyloric atresia could certainly be entertained, considering the abnormal and volvulated position of the stomach in the thorax.

Classification: Five types of congenital gastric outlet obstructions have been described:

1. membranous complete atresia of the antrum or pylorus,

An ultrafast MRI was then performed:

Differential diagnosis: Only rarely, pancreatic ectopic tissue protrudes eccentrically from the submu­cosa of the pyloric channel obstructing the lumen³,⁴. This entity is a mucosal heterotopia of pancreatic glandular tissue with or without a duct system within the stomach wall.

Associated anomalies: Among the patients with a congenital gastric outlet obstructions, 18 had a pyloric atresia associated with Epidermolysis Bullosa and 3 cases had an asso­ciated esophageal atresia². Unlike esophageal and duodenal atresias, pyloric atresia is not associated with Down's syndrome³.

Epidermolysis Bullosa is a rare bullous disorder that involves a bullosa se­paration between the basal cell junction and the epithelial basement membrane. Epidermolysis Bullosa fre­quently affects the skin but oral, esophageal, genitourinary and respiratory tract mucosa, can also be affected¹. Familial occurrence of pyloric atresia with or without Epidermolysis Bullosa has been reported in the literature¹,²,⁴,^[7],^[8],^[9].

The Herlitz syndrome includes pyloric atresia and junction type of Epidermolysis Bullosa. This syndrome may present a hemidesmosome deficiency of gastrointestinal mucosa causing esophageal, laryngeal, pyloric and anal atresias⁴,⁹,^[10]. It is not sure that pyloric atresia —Junction type Epidermolysis Bullosa syndrome should be differentiated from the Herlitz syndrome^[11]. Normal basement membrane zone expression of laminin₅ and mutations in the b₄ integrin gene, have been observed in one patient with pyloric atresia - Junction type Epidermolysis Bullosa syndrome.

In pyloric atresia -Epidermolysis Bullosa an inflammatory reaction takes place and proceeds with massive fibrosis penetrating the deep layers and causing damage of skin and obstruc­tion of the intestinal lumen. In view of the recent findings regarding the mole­cular basis of pyloric atresia -Epidermolysis Bullosa, this entity may result from a mutation in one of the integrin genes²,³,^[12],^[13].

Epidermolysis Bullosa could be prenatally diagnosed by electronmicroscopy in fetal skin biopsies taken as early as 18 weeks of gestation. A positive biopsy for Epidermolysis Bullosa in a family with known pyloric atresia -Epidermolysis Bullosa syndrome may facilitate appropriate counseling. The decision making process should take into account the almost fatal outcome of this association^1,2.

Pyloric atresia -Epidermolysis Bullosa has 25% risk of recurrence in future siblings¹. The absence of detectable a₆ integrin, but not b₄ integrin, in these ca­ses raises the possibility that a₆ integrin or its ligands are responsible for the pyloric atresia-junctional epidermolysis bullosa association¹³.

Aplasia Cutis Congenita has also been described with pyloric atresia¹².

Clinical presentation of congenital outlet obstruction: Neonates with pyloric atresia may experience gastric vomitus, apneas, aspiration and res­piratory distress⁹. Symptoms depend on the degree of gastric outlet obs­truction but usually appear soon after birth with non-bilious vomiting. Gastric perforation has also been reported as early as 12 hours of life. If the congenital gastric outlet obstructions obstruction is complete, a plain AP abdominal X-ray will show a large gastric air-bubble and a gas-less non-distended abdomen. A non-distended but air-filled intestine will be apparent if fenes­trated antral or pyloric membrane permits some passage of air. Clinically, an infant with antral web may resemble those babies with hypertrophic pyloric stenosis but both ultrasound and contrast upper gastrointestinal studies, will not show the typical signs of hypertrophic pyloric stenosis.

Surgical Treatment of pyloric atresia: Complete pyloric atresia with anatomic disconnection (gap) are better managed by gastro-duodenal end-to-end anastomosis¹⁰,^[14] since gastrojejunostomies are not well tolerated in neonates and anastomotic ulcers have occurred.

Antral webs and wind-sock types of membranes (perforated or not), require a longitudinal aperture of the gastric lumen, resection of the membrane and a transverse closure of the gastric wall to prevent stenosis⁴. Postoperative outcome is usually uneventful⁹.

If Epidermolysis Bullosa is associated with pyloric atresia, it has been proposed that the surgical treatment of the pyloric atresia should be withheld until Epidermolysis Bullosa demonstrates not to be lethal¹. According to other authors, withholding of operative treatment of pyloric atresia appears inappropriate in stable neonates with Epidermolysis Bullosa, because survival has been observed⁹ and new treatments of Epidermolysis Bullosa are being developed

References

^[1] Rosenbloom MS, Ratner M Congenital Pyloric Atresia and Epidermolysis Bullosa Letalis in Premature Siblings J Pediatr Surg 22:374-376,1987

^[2] Moore CCM. Congenital Gastric Outlet Obstruction J Pediatr Surg 24:1241-1246,1989

^[3] Embryology for Surgeons Gray SW, Skandalakis JE, WB Suanders Co. Phi­ladelphia, 1972. Chap 4, The stomach by Atkin JT, page 101

^[4] Surgery of Infants and Children. Scientific Principles and Practice., edited by Keith T. Oldham, Paul M Colombani and Robert P. Foglia. Lippincot-Raven Publishers, Philadelphia, 1997. Stomach and Duodenum, Chapter 68, by Magnuson DK, Schwartz MZ

^[5] Gerber BC, Aberdeen SD. Prepyloric diaphragm, an unusual abnormality. Arch Surg 90:472-475,1965

^[6] Rizzo G, Capponi A, Arduini D, Romanini C . Prenatal diagnosis of gastroesophageal reflux by color and pulsed Doppler ultrasonography in a case of congenital pyloric atresia. Ultrasound Obstet Gynecol 6(4):290-2, 1995

^[7] Olsen L, Grotte G . Congenital Pyloric Atresia .Report of a familial ocurence. J Pediatr Surg 11:181-184,1982

^[8] Monig PL, Yoder M, Ziegler M: Acquired pyloric obstruction in a patient with epidermolysis bullosa letalis. J Pediatr Surg 102:598-600,1983

^[9] Hayashi AH, Galliani CA, Gillis DA . Congenital Pyloric Atresia and Junctional Epidermolysis Bullosa: A report of a Long Survival and Review of the Literature. J Pediatr Surg 26:1341-1345,1991

^[10] Cetinkursun S, Ozturk H, Celasum B et al . Epidermolysis Bullosa Asso­ciated with Pyloric, Esophageal and Anal Atresia: A case report. J Pediatr Surg 30:1477-1478, 1995.

^[11] Shaw DW, Fine JD, Piacquadio DJ, Greenberg MJ, Wang-Rodri­guez J, Eichenfield LF . Gastric outlet obstruction and epi­dermolysis bullosa. J Am Acad Dermatol 36:304-310,1997.

^[12] Maman E, Maor E, Kachko L, Carmi R . Epidermolysis bullosa, pyloric atre­sia, aplasia cutis congenita:histopathological delineation of an autosomal re­cessive disease. Am J Med Genet 78(2):127-33, 1998

^[13] Shimizu H, Suzumori K, Hatta N, Nishikawa T Absence of detectable alpha 6 integrin in pyloric atresia-junctional epidermolysis bullosa syndrome. Applica­tion for prenatal diagnosis in a family at risk for recurrence. Arch Dermatol 1996 Aug;132(8):919-25

^[14] Weitzel A, G?bel P, Roesner D.Two cases of Pyloric Atresia . Z Kinderchir 9:396-397,1984