Congenital abnormalities

See Table 55.2.

Cystic fibrosis

This is inherited as an autosomal recessive condition. The abnormal genes have been defined and diagnosis of the dis­order can now be confirmed by DNA testing. It most frequently occurs amongst Caucasians, in whom it is the most commonly occurring inherited disorder (incidence one in 1800 live births). Heterozygous carriers of the gene are asymptomatic but can be identified by DNA analysis. Recent reports suggest that such patients may develop pancreatitis later in life. Such findings may give insight into mechanisms of pancreatic disease.

The disorder is the result of a generalised dysfunction of exocrine glands. Glandular secretions have abnormal physio­chemical properties resulting in malabsorption caused by pancreatic insufficiency, chronic pulmonary disease arising from plugging of bronchi and bronchioles, and elevated sodium and chloride ion concentrations in sweat. It is the most common cause of chronic lung disease among children in developed countries.

Secretions precipitate in the lumen of the pancreatic duct causing blockage which results in duct ectasia and fatty replacement of exocrine acinar tissue. The islets of Langerhans usually appear normal, but diabetes mellitus can occur in older patients. Steatorrhoea is usually present from birth resulting in stools which are bulky, oily and offensive. At birth the meconium may set in a sticky mass and produce intestinal obstruction (meconium ileus). Although about 15 per cent of patients do not develop clinical steatorrhoea, most show complete exocrine insufficiency.

The earliest clinical signs of cystic fibrosis are poor growth, poor appetite, rancid greasy stools, abdominal distension, persistent cough, emphysematous chest and finger clubbing. Later the liver may become cirrhotic as a result of bile-duct plugging and signs of portal hypertension may appear; corpulmonale may develop and the appearance of secondary sexual char­acteristics may be delayed. The mother may have noticed that the child is salty when kissed — levels of sodium and chloride ions in the sweat above 90 mmol/litre confirm the diagnosis.

Treatment is aimed at control of the secondary conse­quences of the disease. Malabsorption is treated by administration of pancreatic enzyme preparations, and pulmonary function preserved with aggressive physiotherapy and anti­biotics. A suitable diet is low in fat but contains added salt to replace the high losses in the sweat. With optimal treatment 80 pet cent of the patients diagnosed early should survive to beyond their 19th year.

  Annular pancreas

This is the result of failure of complete rotation of the ventral pancreatic bud during development, so that a ring of pan­creatic tissue surrounds the second or third part of the duodenum. It is more prevalent in the Down’s syndrome child, and in infants with other congenital gut abnormalities. It is one of the causes of obstructive vomiting in the neonate. The vomiting can be bile stained if the duodenal obstruction is below the ampulla of Vater. Peristaltic waves and upper abdominal distension may be seen, and plain abdominal radiographs show the ‘double bubble’ sign of the interrupted gastroduodenal shadow produced by the rigid ring of pancreatic tissue. The usual treatment is bypass (duodeno­jejunostomy or duodenoduodenostomy). Attempts at resec­tion of the band may result in a pancreatic fistula. The disease may occur in older life as one of the causes of pancreatitis, in which case resection of the head of the pancreas is preferable to lesser procedures.

Ectopic pancreas

Ectopic pancreas can be found in the submucosa in parts of the stomach, duodenum or small intestine (including Meckel’s diverticulae), the gall bladder, adjoining the pancreas, for example in the hilum of the spleen, or in 2 per cent of carefully conducted necropsies, within the liver. Ectopic pancreas in the wall of the intestine may give rise to symptoms and can be a cause of cysts, but this is extremely rare.

Congenital cystic disease of the pancreas

This sometimes accompanies congenital disease of the kidneys arid liver, and occurs as part of the von Hippel—Lindau syndrome.