Chapter 87. Congenital Malformations of The Digestive System: Foregut Malformations - Review of Medical Embryology Book

ESOPHAGEAL ATRESIA AND STENOSIS: esophageal atresia often occurs with tracheoesophageal fistula but may occur independently (rare)

Atresia or stenosis is due to unequal division of the foregut into respiratory and digestive parts or failure of esophageal recanalization
In esophageal atresia, amniotic fluid cannot enter the intestine for absorption and transfer to the placenta for removal, resulting in polyhydramnios (excess amniotic fluid)

PYLORIC STENOSIS: reduced lumen of the pyloris due to hypertrophy of the sphincter muscle layers. Its cause is unknown but may be genetic

It is the most common abnormality of the stomach in infants, develops in fetal life, and occurs in about 1/200 males and 1/1000 females
Extreme narrowing of the pyloric lumen obstructs the passage of food, resulting in severe progressive vomiting

ATRESIA OF THE GALLBLADDER AND BILE DUCTS is the most serious malformation of extrahepatic biliary system and is seen in 1/20,000 births

Results from persistence of the solid stage of the duct and gallbladder development. The bladder remains atretic, and the ducts appear as narrow, fibrous cords
Atresia may be limited to only a small part of the common bile duct leading to distention of the bladder and the hepatic duct, resulting in a severe, steadily increasing jaundice after birth
Duplication, partial subdivision, and diverticula of the gallbladder are also seen

LIVER MALFORMATIONS: variations in lobulation are common, but gross malformations are rare. Variations of the hepatic ducts, common bile ducts, and cystic ducts are common
PANCREATIC MALFORMATIONS

Accessory pancreatic tissue (heterotopic pancreatic tissue) may be found anywhere from the distal esophagus to the tip of the primary intestinal loop. It is seen most frequently in the wall of the stomach or duodenum or in a Meckel's diverticulum
Pancreatic bladder: a part of the ventral pancreatic bud grows out with the liver bud and forms a pancreatic nodule
Annular pancreas is a rare malformation consisting of a thin flat band of pancreatic tissue surrounding the second portion of the duodenum

It may be symptomless but may also constrict the duodenum and result in an obstruction
Probably caused by the growth of a bifid ventral pancreatic bud around the duodenum which fuses with the dorsal bud to form a ring