Protein-losing enteropathy

What is protein-losing enteropathy?

Protein-losing enteropathy (PLE) is a rare condition characterised by a loss of serum protein into the gastrointestinal (GI) tract, resulting in hypoproteinaemia which can be complicated by oedema, ascites, pleural and pericardial effusions and malnutrition¹ .

Protein-losing enteropathy occurs in a number of GI conditions that cause excessive loss of serum proteins into the GI tract. Three main mechanisms are involved, as below.

Mucosal disease with ulceration with protein loss across disrupted mucosal surface

• Chronic gastric ulcer.

• Gastric carcinoma.

• Lymphoma.

• Inflammatory bowel disease.

• Idiopathic ulcerative jejunoileitis.

Lymphatic obstruction causing loss of protein-rich chyle

• Primary intestinal lymphangectasia² .

• Secondary obstruction due to:

  • Heart disease³

  • Infection

  • Neoplasm

  • Retroperitoneal fibrosis

  • Sarcoidosis

Idiopathic alterations in mucous capillary permeability

• Ménétrier's disease.

• Zollinger-Ellison syndrome.

• Acute viral or eosinophilic gastroenteritis.

• Coeliac disease.

• Allergic protein-losing enteropathy.

• Giardiasis and hookworm infections.

• Amyloidosis.

• Common variable immunodeficiency.

• Systemic lupus erythematosus (SLE).

Protein-losing enteropathy epidemiology

Because the condition is so multifactorial, the prevalence rate is not known.

Protein-losing enteropathy is a common complication of Fontan's operation¹ . This is a procedure carried out in children with severe congenital heart disease, in which venous blood is diverted from the right atrium to the pulmonary arteries without passing through the right ventricle.

Protein-losing enteropathy symptoms

The clinical presentation is very variable, depending on the underlying cause but mainly consists of oedema due to hypoproteinaemia¹ . Consider protein-losing enteropathy in any patient presenting with oedema, especially if this is against a background of GI disease⁴ .

History

• A dietary history should be taken to exclude malnutrition as a cause of reduced albumin synthesis.

• Check the patient's medical history for information about renal disease (increased protein loss) or hepatic disease (reduced albumin synthesis).

• Ask about GI symptoms, in particular any symptoms suggestive of enteritis (eg, diarrhoea, abdominal pain).

• Ask about alcohol intake.

• Check for a history of congenital heart disease, episodes of pericarditis, serious streptococcal infection, or prior heart surgery (increased interstitial pressure can be a cause).

Examination

• Check the general nutritional status of the patient - eg, height, weight, head circumference in children.

• Look for signs of acute liver disease (eg, enlarged liver, tenderness in the right upper quadrant).

• Look for signs of chronic liver disease (eg, jaundice, splenomegaly, prominent veins on the abdomen).

• Check for signs of right heart failure - eg, ascites and jugular vein distension.

• The finding of high blood pressure may suggest renal or cardiac disease.

• Look for signs of GI pathology - eg, abdominal tenderness, macroscopic or microscopic blood and mucus in the stool.

Differential diagnosis of protein-losing enteropathy

• Collagenous and lymphocytic colitis.

• Hypoalbuminaemia.

• Hypogammaglobulinaemia.

• Inflammatory bowel disease.

• Malabsorption.

• Mycoplasma infections.

• Pericarditis.

• Restrictive cardiomyopathy.

• Salmonellosis.

• Yersinia enterocolitica.

Investigating protein-losing enteropathy¹

The initial step in the evaluation of any patient with hypoproteinaemia and/or low albumin levels is to exclude other, more common causes, such as malnutrition, liver and renal diseases.

• Serum proteins - by definition low albumin levels will be present.

• Liver and renal disease should be excluded by the appropriate function tests.

• Evidence of protein loss via the GI tract should be investigated in patients with oedema, hypoalbuminaemia and normal renal and liver function tests.

• Alpha-1-antitrypsin (A1AT):

  • A1AT is a protein synthesised in the liver that is neither actively secreted nor absorbed.

  • Raised A1AT levels in stools is a marker for protein loss but is not very specific as this is also seen in liver disease.

  • However, the most commonly used and reliable method to determine enteric protein loss is to determine the clearance of A1AT from plasma.

  • The measurement of A1AT clearance requires both a blood sample to determine plasma A1AT level and a 24-hour stool collection to determine stool volume and stool A1AT level.

• Viral serologies may be useful.

• Scintigraphy is a more accurate test. It involves the use of radio-labelled substances which are administered intravenously and then detected by the use of serial abdominal X-rays. The two common agents used are technetium Tc ^99m labelled dextran or human serum albumin⁵ . This test is expensive and time-consuming and is usually reserved for patients who have a negative A1AT test⁶ .

• Upper and/or lower endoscopy and mucosal biopsies may be needed to elucidate underlying causes.

Protein-losing enteropathy treatment and management

There is no specific treatment for protein-losing enteropathy and so management is directed at the underlying cause and treatment for malnutrition and micronutrient deficiencies¹ .

Non-drug

A low-fat diet associated with medium-chain triglyceride supplementation is the cornerstone of primary intestinal lymphangiectasia medical management⁷ .

Drugs

• The importance of treating the underlying cause cannot be overestimated. One study reported the resolution of protein-losing enteropathy by the simple measure of treating the patient's chronic diarrhoea with loperamide. The use of diuretics for congestive heart failure is another example⁸ .

• Octreotide has been shown to be useful in some patients. It is a potent inhibitor of many hormones affecting the gut and has a marked effect on reducing blood flow to the intestines.

• Supplementation with fat-soluble vitamins may be helpful.

• PLE is a common complication of Fontan's operation¹ . Heparin produces benefits independent of its anticoagulant effect⁹ . Steroids can be an effective therapy but must be continued long-term at a low dose¹⁰ . Enteral steroid therapy has also been used, but there is still the possibility of systemic absorption¹¹ .

Surgery for protein-losing enteropathy patients

• In patients who have undergone Fontan's procedure, making a window in the baffle that separates the systemic venous pathway from the pulmonary venous atrium has helped to resolve PLE, presumably due to a reduction in systemic venous pressure.

• In patients whose PLE is secondary to a cardiac cause (eg, restrictive cardiomyopathy, constrictive pericarditis, tricuspid valvar stenosis and insufficiency), restoration of the unobstructed flow of blood in the superior or inferior caval vein may be curative. Post-Fontan patients may benefit but are unlikely to be cured¹² .

• Cardiac transplant is occasionally used to treat intractable PLE in patients who have had previous heart surgery.

• PLE after Fontan's operation associated with lymphangiectasia (blockage of the intestinal lymphatics) has been successfully treated by resection of the affected area of bowel¹³ .

Protein-losing enteropathy prognosis

This depends on the underlying disease but improved management techniques are reducing mortality and morbidity of many causes¹ .