Characterization of iron status in young dogs with portosystemic shunt

Susan E. Bunch From the Departments of Companion Animal and Special Species Medicine (Bunch) and Microbiology, Parasitology, and Pathology (Jordan, Sellon, Cullen), College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, and the Department of Pathology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506 (Smith).

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Holly L. Jordan From the Departments of Companion Animal and Special Species Medicine (Bunch) and Microbiology, Parasitology, and Pathology (Jordan, Sellon, Cullen), College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, and the Department of Pathology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506 (Smith).

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Rance K. Sellon From the Departments of Companion Animal and Special Species Medicine (Bunch) and Microbiology, Parasitology, and Pathology (Jordan, Sellon, Cullen), College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, and the Department of Pathology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506 (Smith).

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John M. Cullen From the Departments of Companion Animal and Special Species Medicine (Bunch) and Microbiology, Parasitology, and Pathology (Jordan, Sellon, Cullen), College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, and the Department of Pathology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506 (Smith).

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Joseph E. Smith From the Departments of Companion Animal and Special Species Medicine (Bunch) and Microbiology, Parasitology, and Pathology (Jordan, Sellon, Cullen), College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27606, and the Department of Pathology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506 (Smith).

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SUMMARY

Microcytosis is a common laboratory finding in dogs with congenital portosystemic shunt (pss), although its pathogenesis is not yet understood. Because the most common cause of microcytosis in dogs is absolute or relative iron deficiency, iron status was evaluated in 12 young dogs with pss. Complete blood counting was done before surgical correction in all dogs, and in 5 dogs after surgery, by use of an automated hematology analyzer. Serum iron concentration and total iron-binding capacity (tibc) were determined coulometrically, and percentage of transferrin saturation was calculated. Erythrocyte protoporphyrin content was quantified by use of front-face fluorometry. Serum ferritin concentration was measured by use of elisa. Serum ceruloplasmin content was determined colorimetrically (with p-phenylene-diamine dihydrochloride as substrate) as an indirect indicator of subclinical inflammation, which may result in impaired iron utilization. Special stains were applied to liver (10 dogs; Gomori's) and bone marrow aspiration biopsy (7 dogs; Prussian blue) specimens for qualitative assessment of tissue iron content. Nonpaired Student's t-tests were used to compare serum iron concentration, tibc, percentage of transferrin saturation, and erythrocyte protoporphyrin, ferritin, and ceruloplasmin concentrations in dogs with pss with those in clinically normal dogs. All dogs had microcytosis before surgery; microcytosis resolved in 3 dogs after surgical correction. Serum iron concentration and tibc were significantly lower in pss-affected dogs than in clinically normal dogs. Erythrocyte protoporphyrin, ferritin, and ceruloplasmin concentrations in pss-affected dogs were not significantly different from those in healthy dogs. Excess iron was not detected consistently in liver or bone marrow samples. These results suggest that relative iron deficiency, perhaps associated with altered iron transport and not absolute iron deficiency, is related to microcytosis in dogs with pss.

SUMMARY

Microcytosis is a common laboratory finding in dogs with congenital portosystemic shunt (pss), although its pathogenesis is not yet understood. Because the most common cause of microcytosis in dogs is absolute or relative iron deficiency, iron status was evaluated in 12 young dogs with pss. Complete blood counting was done before surgical correction in all dogs, and in 5 dogs after surgery, by use of an automated hematology analyzer. Serum iron concentration and total iron-binding capacity (tibc) were determined coulometrically, and percentage of transferrin saturation was calculated. Erythrocyte protoporphyrin content was quantified by use of front-face fluorometry. Serum ferritin concentration was measured by use of elisa. Serum ceruloplasmin content was determined colorimetrically (with p-phenylene-diamine dihydrochloride as substrate) as an indirect indicator of subclinical inflammation, which may result in impaired iron utilization. Special stains were applied to liver (10 dogs; Gomori's) and bone marrow aspiration biopsy (7 dogs; Prussian blue) specimens for qualitative assessment of tissue iron content. Nonpaired Student's t-tests were used to compare serum iron concentration, tibc, percentage of transferrin saturation, and erythrocyte protoporphyrin, ferritin, and ceruloplasmin concentrations in dogs with pss with those in clinically normal dogs. All dogs had microcytosis before surgery; microcytosis resolved in 3 dogs after surgical correction. Serum iron concentration and tibc were significantly lower in pss-affected dogs than in clinically normal dogs. Erythrocyte protoporphyrin, ferritin, and ceruloplasmin concentrations in pss-affected dogs were not significantly different from those in healthy dogs. Excess iron was not detected consistently in liver or bone marrow samples. These results suggest that relative iron deficiency, perhaps associated with altered iron transport and not absolute iron deficiency, is related to microcytosis in dogs with pss.

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