JPC SYSTEMIC PATHOLOGY
Signalment: 9-year-old male Cavalier King Charles spaniel
HISTORY (JPC #3103040): This animal had a history of diarrhea. The ileocecal junction appeared thickened on ultrasound. Thickened segments were surgically resected.
HISTOPATHOLOGIC DESCRIPTION: Small intestine: Villi are multifocally expanded by dilated lacteals, the lamina propria and submucosa are edematous, and lymphatics are dilated transmurally. Multifocally, ectactic lacteals and lymphatics contain a variable amount of flocculent, pale eosinophilic proteinaceous fluid and fibrin admixed with few erythrocytes and degenerate neutrophils. Within the submucosa, tunica muscularis, serosa and mesentery lymphatics exhibit a continuum of changes from simple dilation to formation of lipogranulomas, up to 2mm in diameter, which are characterized by partial to complete obstruction of the lumen and replacement by amorphous amphophilic to pale eosinophilic lipid rich material which often contains cholesterol clefts, and/or basophilic granular material, surrounded by high numbers of lipid-laden macrophages, fewer lymphocytes, plasma cells and foreign-body type multinucleated giant cells which are further surrounded by a variably thick band of fibrosis. In severely affected lymphatics endothelial cells are either shrunken with hypereosinophilic cytoplasm and pyknotic nuclei (necrosis), or lost. Multifocally, there is hemorrhage, edema and fibrin admixed with these inflammatory cells. Moderate numbers of lymphocytes and plasma cells infiltrate the mucosa, submucosa, tunica muscularis, serosa and mesentery.
MORPHOLOGIC DIAGNOSIS: Small intestine: Lymphangiectasia, chronic, diffuse, marked, with lipogranulomatous lymphangitis, Cavalier King Charles spaniel, canine.
- Intestinal lymphangiectasia (IL) is the pathologic dilatation of lymphatic vessels and is the most commonly reported cause of malabsorption/protein-losing enteropathy in the dog
- Part of a syndrome characterized by chronic diarrhea, wasting, hypoproteinemia, lymphopenia, hypocalcemia, hypocholesterolemia
- Norwegian lundehund has inherited IL and is predisposed to gastritis and gastric carcinoma
- May be caused by increased lymphatic pressure secondary to lymphatic obstruction
- Primary – idiopathic or congenital condition in some breeds (lundehund, small terrier breeds (e.g. Yorkies, Maltese), and Rottweilers)
- Secondary – most common; caused by obstructive lesions in the lymphatic system (e.g., IBD, granulomatous inflammation or lymphoma in draining lymph nodes) or venous hypertension (e.g., congestive heart failure or congenital vascular anomalies in the liver such as A-V shunting)
- Etiology of the clinical syndrome may be more complex than simple lymphatic obstruction
TYPICAL CLINICAL FINDINGS:
- Anorexia, weight loss, diarrhea, steatorrhea and lethargy
- Ascites and peripheral edema are often present and due to hypoalbuminemia
- Clinical pathology: Panhypoproteinemia, lymphopenia, hypocalcemia and hypocholesterolemia
- Coagulopathies may result from decreased absorption of vitamin K
TYPICAL GROSS FINDINGS:
- Small intestinal mucosa is thickened and contains white chyle-filled lacteals
- Mesenteric lymphatic vessels are dilated with white, milky fluid
- Generalized edema, hydrothorax and ascites
- Mesenteric lymphadenopathy
- Nodular white masses up to 5-10 mm diameter (lipogranulomas) located on serosa at the mesenteric border of the small intestine (rarely on liver, diaphragm, abdominal organs, pleura)
TYPICAL LIGHT MICROSCOPIC FINDINGS: Multifocal to diffuse lesions
- There is dilation of the lacteals and lymphatics of the submucosa, muscularis and mesentery; lipid-laden macrophages may be present
- Blunt villi; crypts hypertrophy (+/-)
- Lipogranulomas: Collar of lipid-laden macrophages that surround centrally located amorphous lipid material +/- cholesterol clefts
- Edema in lamina propria, submucosa
- Crypt abscesses
- Normal to increased inflammatory cell population (lymphocytes, plasma cells, eosinophils) in lamina propria
ADDITIONAL DIAGNOSTIC TESTS:
- Special stains to detect possible initiating fungal or bacterial infection
For chronic diarrhea associated with panhypoproteinemia:
- Alimentary Lymphoma
General causes of hypoproteinemia:
- Loss of proteins can be secondary to: Hemorrhage, protein-losing nephropathy, protein-losing enteropathy, severe exudative skin disease, burns, intestinal parasitism, high-protein effusions
- Decreased production of proteins: Chronic liver disease, exocrine pancreatic insufficiency, cachexia secondary to neoplasia, malnutrition, intestinal malabsorption, lactation, pregnancy
- Secondary or acquired intestinal lymphangiectasia occurs in many animals such as nonhuman primates, cats, cattle, horses, and swine
- Secondary intestinal lymphangiectasia due to Johne’s disease (granulomatous serosal lymphangitis due to lymphatic obstruction)
- Soft coated Wheaten terriers have a familial predisposition for protein-losing nephropathy, protein-losing enteropathy, or both; intestinal lesions include inflammatory bowel disease, lymphangiectasia and lipogranulomatous lymphangitis; renal lesions include chronic glomerulonephritis/glomerulosclerosis
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