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Microcytosis and iron status in dogs with surgically induced portosystemic shunts
D P Laflamme1, E A Mahaffey, S W Allen
1Department of Physiology, University of Georgia, Athens 30602.
Abstract:
Microcytosis is common in dogs with congenital portosystemic shunts (PSS) and acquired liver disease. The objective of this study was to determine if microcytosis could be induced in normal dogs by surgical creation of PSS, and to characterize the changes in hematology and iron status. Hematocrit, mean cell volume, mean cell hemoglobin, and mean cell hemoglobin concentration decreased linearly from 45.5%, 69.1 fL, 22.8 g/dL and 33.1% to 39.5%, 55.9 fL, 17.8 g/dL and 31.9%, respectively, 18 weeks after creation of PSS. The erythrocyte count did not change, but red cell distribution widths indicated a shift to a heterogenous population with decreased volume. Mean cell volume and mean cell hemoglobin decreased rapidly after induction of PSS and were significantly (P < .05) different from presurgery values within 2 weeks. Serum iron and copper concentrations and total iron binding capacity were decreased in dogs with PSS. Liver iron concentration doubled after creation of PSS, with the majority of stainable iron located in Kupffer cells. The changes in erythrocyte indices and measures of iron status in dogs with surgically induced PSS were similar to those in dogs with congenital PSS. Microcystosis developed rapidly in dogs after induction of PSS. These results indicate that iron deficiency was not the cause of microcytosis in these dogs.
Insights
Surgically creating portosystemic shunts (PSS) in dogs rapidly induced microcytosis, similar to congenital PSS. This study found iron deficiency was not the cause of this condition in dogs.
Area of Science:
- Veterinary Medicine
- Hematology
- Canine Pathophysiology
Background:
- Microcytosis is frequently observed in dogs with portosystemic shunts (PSS) and liver disease.
- The underlying cause of microcytosis in these conditions is not fully understood.
Purpose of the Study:
- To investigate if surgical induction of PSS in healthy dogs causes microcytosis.
- To characterize hematological and iron status changes following PSS creation.
Main Methods:
- Surgical creation of PSS in normal dogs.
- Monitoring hematological parameters (hematocrit, MCV, MCH, MCHC, RDW) over 18 weeks.
- Assessing serum iron, copper, total iron-binding capacity, and liver iron concentration.
Main Results:
- Microcytosis, characterized by decreased MCV and MCH, developed rapidly within 2 weeks post-surgery.
- Erythrocyte count remained unchanged, but RDW indicated increased red blood cell volume heterogeneity.
- Serum iron and copper levels decreased, while liver iron concentration doubled, with iron accumulating in Kupffer cells.
Conclusions:
- Surgically induced PSS in dogs mimics the microcytosis seen in congenital PSS.
- Iron deficiency is not the primary cause of microcytosis in dogs with induced PSS.
- The study provides insights into the pathophysiology of microcytosis associated with portosystemic shunting.