Definition

An obstructive disorder of the lymphatic system of the gastrointestinal tract resulting in lymphatic hypertension and protein-losing enteropathy.

Pathophysiology

• Lymphatic obstruction results in dilation and rupture of intestinal lacteals with subsequent loss of lymphatic contents (plasma proteins, lymphocytes, and chylomicrons) into the intestinal lumen.
• Although some of the proteins may be digested and reabsorbed, excessive enteric loss of plasma proteins will ultimately result in panhypoproteinemia.
• Hypoproteinemia causes a decrease in plasma oncotic pressure, which, if severe, will lead to edema, ascites, and/or pleural effusion.

Systems Affected

• Gastrointestinal-diarrhea
• Respiratory-pleural effusion
• Skin-subcutaneous edema
• Systemic-ascites
• Vascular-thromboembolic disease

Genetics

A familial tendency for protein-losing enteropathy has been reported for soft-coated Wheaten terriers, basenjis, Yorkshire terriers, and Norwegian Lundehunds, but the actual genetic cause has not been identified for any of these breeds.

Incidence/Prevalence

Uncommon

Geographic Distribution

N/A

Signalment

Signs

• Clinical signs are variable.
• Diarrhea-chronic, intermittent, or continuous, watery to semisolid consistency (typically small bowel type diarrhea); however, not all animals have diarrhea.
• Ascites.
• Subcutaneous edema.
• Dyspnea from pleural effusion.
• Weight loss.
• Flatulence.
• Vomiting.

Causes

Risk Factors

N/A

Differential Diagnosis

• Lymphangiectasia must be differentiated from other causes of protein-losing enteropathy.
• PLE must be differentiated from other causes of hypoalbuminemia.

CBC/Biochemistry/Urinalysis

• Hypoalbuminemia and hypoglobulinemia (panhypoproteinemia)
• Hypocholesterolemia
• Hypocalcemia
• Hypomagnesemia
• Lymphopenia

Other Laboratory Tests

Imaging

• Survey thoracic radiographs to rule out cardiac disease and neoplasia.
• Abdominal radiographs to rule out mechanical intestinal disease (obstruction or partial obstruction) and other causes of PLE.
• Abdominal ultrasound to rule-out mechanical intestinal disease and other causes of PLE.
• Cardiac ultrasound to rule out right-sided congestive heart failure.
• Abdominal ultrasonography can show hyperechoic mucosal striations extending from the lumen to the submucosal layer of the bowel. One study suggested that corn-oil given orally 60–90 minutes before abdominal ultrasonography improves the diagnostic yield.

Diagnostic Procedures

• Endoscopy allows intestinal mucosal visualization and biopsy. Ileal biopsies should be procured in animals that have hypocobalaminemia.
• Laparotomy allows visualization of dilated intestinal lymphatics and biopsies of intestines (full thickness) and lymph nodes, but may be contraindicated in patients with severe hypoproteinemia.
• An ECG can aid in evaluating the heart in animals suspected of having right-sided congestive heart failure.

Pathologic Findings

• Gross findings at laparotomy may include dilated lymphatics that are visible as a web-like network throughout the mesentery and serosal surface.
• May see small yellow-white nodules and foamy granular deposits adjacent to lymphatics.
• Histopathology findings include ballooning distortion of villi, caused by markedly dilated lacteals.
• Villi can be edematous; some have a blunted appearance.
• Usually associated with mucosal edema or diffuse or multifocal accumulations of lymphocytes and plasma cells in the lamina propria.

Appropriate Health Care

May need hospitalization if complications due to hypoalbuminemia develop.

Nursing Care

N/A

Activity

Normal

Diet

• Low-fat diet with high-quality protein. Avoid diets that are excessively high in fiber.
• Dogs with concurrent lymphangiectasia and IBD may benefit from a commercial hypoallergenic hydrolyzed protein diet that is moderately restricted in dietary fat.
• Long-chain triglycerides stimulate intestinal lymph flow and may lead to increased intestinal protein loss.
• Diets fortified with medium-chain triglycerides may be beneficial.
• May feed MCTs to supplement fat and increase caloric intake.
• Commercial sources of MCTs-MCT oil or Portagen (Mead Johnson, Evansville, IN).
• Supplement with fat-soluble vitamins-A, D, E, and K.
• Elemental diets can also be used.

Client Education

Discuss unpredictable disease progression and response to therapy.

Surgical Considerations

• When intestinal lymphangiectasia is secondary to an identifiable lymphatic obstruction, consider surgery to relieve the obstruction.
• Pericardiectomy may be indicated in cases of constrictive pericarditis.
• Patients that benefit from surgical intervention are rare.

Drug(s) Of Choice

• Try corticosteroids if dietary therapy alone is unsuccessful (however, such therapy is not intended to treat lymphangiectasia but rather concurrent gastrointestinal inflammation). Oral prednisone or prednisolone at a dose of 1–2 mg/kg q12h for 5–7 days, followed by 1 mg/kg q12h for at least 6 weeks. In large-breed dogs the starting dose should be more conservative than in small-breed dogs. After remission of the disease, dosage can be slowly tapered to the lowest dose effective at controlling the disease. Alternatively, may consider the use of a locally-effective corticosteroid (e.g., budesonide), or other immunomodulators such as azathioprine or cyclosporine.
• If the patient is cobalamin deficient, cobalamin must be supplemented to achieve therapeutic response: 250–1,500 µg/dog SC once a week for 6 weeks, then one dose 1 month later. Follow with a recheck a month after the last dose to determine the need for continued supplementation.
• If secondary small intestinal dysbiosis is suspected the patient should be treated with tylosin at 10–20 mg/kg q12h for 6 weeks.
• Magnesium sulfate should be supplemented parenterally (IV) at 1 mEq/kg/day in dogs that are hypomagnesemic before oral supplementation with magnesium oxide, magnesium citrate, or magnesium carbonate.
• Diuretics such as furosemide (1 mg/kg q12h) and spironolactone (1 mg/kg q12h) in animals with severe ascites to improve patient comfort.

Contraindications

N/A

Precautions

N/A

Possible Interactions

N/A

Alternative Drug(s)

N/A

Patient Monitoring

• Body weight, serum total protein, albumin, and globulin concentrations, and evidence of recurrent clinical signs (pleural effusion, ascites, and/or edema).
• Patients need to be reevaluated depending on the severity of the disease process.

Prevention/Avoidance

N/A

Possible Complications

• Respiratory difficulty from pleural effusion
• Severe protein-calorie depletion
• Intractable diarrhea

Expected Course and Prognosis

• Prognosis is guarded.
• Some animals fail to respond to treatment.
• Remissions of several months to more than 2 years can be achieved in some patients.

Associated Conditions

Soft-coated Wheaten terriers may have concurrent protein-losing nephropathy.

Age-Related Factors

N/A

Zoonotic Potential

N/A

Pregnancy/Fertility/Breeding

N/A

See Also

Protein-Losing Enteropathy

Abbreviations

• ECG = electrocardiogram
• MCT = medium chain triglycerides
• PLE = protein-losing enteropathy

Client Education Handout Available Online