Doppler Ultrasonographic Evaluation of Gastrointestinal Hemodynamics in Food Hypersensitivities: A Canine Model

The Role of the Mesentery in Crohn's Disease: The Contributions of Nerves, Vessels, Lymphatics, and Fat to the Pathogenesis and Disease Course

Crohn's disease (CD) is a complex gastrointestinal disorder involving multiple levels of cross talk between the immunological, neural, vascular, and endocrine systems. The current dominant theory in CD is based on the unidirectional axis of dysbiosis-innate immunity-adaptive immunity-mesentery-body system. Emerging clinical evidence strongly suggests that the axis be bidirectional. The morphologic and/or functional abnormalities in the mesenteric structures likely contribute to the disease progression of CD, to a less extent the disease initiation. In addition to adipocytes, mesentery contains nerves, blood vessels, lymphatics, stromal cells, and fibroblasts. By the secretion of adipokines that have endocrine functions, the mesenteric fat tissue exerts its activity in immunomodulation mainly through response to afferent signals, neuropeptides, and functional cytokines. Mesenteric nerves are involved in the pathogenesis and prognosis of CD mainly through neuropeptides. In addition to angiogenesis observed in CD, lymphatic obstruction, remodeling, and impaired contraction maybe a cause and consequence of CD. Lymphangiogenesis and angiogenesis play a concomitant role in the progress of chronic intestinal inflammation. Finally, the interaction between neuropeptides, adipokines, and vascular and lymphatic endothelia leads to adipose tissue remodeling, which makes the mesentery an active participator, not a bystander, in the disease initiation and precipitation CD. The identification of the role of mesentery, including the structure and function of mesenteric nerves, vessels, lymphatics, and fat, in the intestinal inflammation in CD has important implications in understanding its pathogenesis and clinical management.

Gastrointestinal hemodynamics in dogs with nonfood induced atopic dermatitis

BACKGROUND

Canine atopic dermatitis can be a result of exposure to aeroallergens or trophallergens. Hemodynamic alterations occur in dogs with food hypersensitivity.

HYPOTHESIS/OBJECTIVES

To evaluate if hemodynamic alterations occur in dogs with NFICAD with lowered resistance to diastolic flow at fasting, after feeding, or both.

ANIMALS

Ten healthy dogs and 22 dogs with NFICAD were included from the hospital population.

METHODS

Blinded prospective study. Peak systolic velocity (PSV), end diastolic velocity (EDV), mean velocity (MV), pulsatility index (PI), resistive index (RI) and PSV/EDV ratio were measured at fasting for both arteries (cranial mesenteric artery [CMA], celiac artery [CA]) and at 40 minutes after feeding in CMA and at 60 minutes in CA. The results were analyzed statistically with a mixed model.

RESULTS

There was no difference detected between groups of dogs for any variable except EDV during fasting (P = .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

There is no decrease in resistance in NFICAD to diastolic flow. This observation could be explained by the absence intestinal inflammation in NFICAD.

Two-dimensional grayscale ultrasound and spectral Doppler waveform evaluation of dogs with chronic enteropathies

Sonography is an important diagnostic tool to examine the gastrointestinal tract of dogs with chronic diarrhea. Two-dimensional grayscale ultrasound parameters to assess for various enteropathies primarily focus on wall thickness and layering. Mild, generalized thickening of the intestinal wall with maintenance of the wall layering is common in inflammatory bowel disease. Quantitative and semi-quantitative spectral Doppler arterial waveform analysis can be utilized for various enteropathies, including inflammatory bowel disease and food allergies. Dogs with inflammatory bowel disease have inadequate hemodynamic responses during digestion of food. Dogs with food allergies have prolonged vasodilation and lower resistive and pulsatility indices after eating allergen-inducing foods.

The canine model of dietary hypersensitivity

IgE-mediated dietary hypersensitivity affects approximately 1% of the canine population. There are no breed associations and < or =50% of the patients are aged <1 year at presentation. The most common causative allergens are beef, chicken, milk, eggs, maize, wheat and soyabean. Affected dogs generally display cutaneous disease and 10-15% of the patients may have concurrent alimentary involvement. Diagnosis is currently based on dietary restriction followed by provocation. Procedures for the detection of serum allergen-specific IgE and IgG antibodies are widely available, but these tests correlate poorly with clinical presentation and dietary testing. Recent studies have demonstrated the allergen specificity of IgE antibodies by immunoblotting and have described blood lymphocyte proliferative responses to food allergens. In addition to investigations of spontaneously-arising dietary hypersensitivity, it has also proved possible to study this disorder experimentally. Small colonies of dogs sensitive to particular dietary proteins have been used to study clinical and serological responses to allergen challenge. Hypersensitivity has been experimentally induced in dogs of an atopic phenotype by repeated subcutaneous injection of alum-adjuvanted dietary allergen during neonatal life. These models have been used to trial a range of modified protein or hydrolysate diets. The dog provides a unique large-animal model for investigation of the immunopathogenesis of human dietary hypersensitivity. The dog is closely related genetically to man and shares environmental disease triggers with man. Spontaneously arising canine dietary hypersensitivity is a good clinical mimic of the human disease, and ability to therapeutically manipulate this adverse response in the dog might lead to benefits for human patients.

Evaluation of colonoscopic allergen provocation as a diagnostic tool in dogs with proven food hypersensitivity reactions

OBJECTIVE

To evaluate the colonoscopic allergen provocation (COLAP) test as a new tool for the diagnosis of IgE-mediated food allergy.

METHODS

Oral food challenges as well as COLAP testing were performed in a colony of nine research dogs with proven immediate-type food allergic reactions. In addition, COLAP was performed in five healthy dogs.

RESULTS

When compared with the oral challenge test, COLAP accurately determined 18 of 23 (73 per cent) positive oral challenge reactions (73 per cent) in dogs with food allergies and was negative in the healthy dogs.

CLINICAL SIGNIFICANCE

The accuracy of this new test may be higher than that for gastric sensitivity testing. Therefore, COLAP holds promise as a new test to confirm the diagnosis of suspect IgE-mediated food allergy in dogs.