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.
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.