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Protein-losing enteropathy is due to leakage of serum proteins
through the mucosal lining into the lumen of the intestine. This
may result from disruption of the mucosal surface by inflammation
or erosion, rupture of lacteals from high pressure in the thoracic
duct, or damage to the mucosal surface with disruption of the mucosal
barrier.
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Protein-losing enteropathy is a process with an extensive differential diagnosis.
Symptoms of the underlying illness, including diarrhea, abdominal
pain, and allergic phenomena, may be elicited in the history. Weight-for-age,
height-for-age, and weight-for-height can rule out malnutrition
as a cause of hypoalbuminemia. Edema is a frequent finding, and
asymmetric lymphedema may suggest an underlying malformation of
lymphatic channels such as primary intestinal lymphangiectasia.
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Conditions associated with protein-losing enteropathy are listed
in Table 390-1 and are discussed in other
sections of this chapter. Fifty percent to 60% of children
with Crohn disease have mild to pronounced hypoalbuminemia. Protein-losing
enteropathy and finger clubbing have been reported as complications
of gastroesophageal reflux. Protein-losing enteropathy with hypoalbuminemia occurs
in 25% of patients after bone marrow transplantation as
a result of graft-versus-host disease of the intestine. Intestinal
lymphangiectasia causes protein loss, including immunoglobulins,
lymphocytes, hypogammaglobulinemia, and steatorrhea. The intestine
may be the only site of lymphatic obstruction, or it may coexist
with multifocal lymphatic dysplasia (eg, Noonan syndrome). Cardiac
disorders or surgical procedures in which elevated right atrial
pressure is transmitted to the superior vena cava and thoracic duct,
including the Fontan procedure and clinically silent constrictive
pericarditis, can cause intestinal lymphangiectasia and protein-losing
enteropathy. Ménétrier disease is characterized
by hypoalbuminemia due to protein losses from hypertrophic gastric
folds (see Chapter 409). Newly described entities
in which protein-losing enteropathy is prominent include the carbohydrate-deficient
glycoprotein syndrome 1b and congenital heparan sulfate deficiency.
Intestinal lymphangiectasia has been found in intestinal biopsy
specimens of some children with idiopathic nephritic syndrome and
protein-losing enteropathy.
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Other causes of hypoalbuminemia, such as renal disease, liver
disease, and malnutrition, should be excluded by urinalysis and
liver function studies. A reliable estimate of hepatic synthetic
function is provided by the prothrombin time. Vitamin K deficiency
resulting from intestinal malabsorption can lead to an abnormal
result, but this should correct promptly after a parenteral dose
of vitamin ...