Does the Underlying Cause of Acute Kidney Injury Influence Anemia in Dogs?

Acute kidney injury (AKI) in dogs can result from a variety of underlying conditions, including infectious diseases, nephrotoxic insults, ischemic or inflammatory disorders, urinary tract obstruction, and causes that remain undetermined. Although these conditions ultimately impair renal function, they may not influence hematological parameters in exactly the same way. For practicing veterinarians, evaluating anemia alongside the underlying etiology can provide valuable clinical context during the initial assessment and subsequent case management. While anemia is frequently encountered in dogs with AKI, clinical observations suggest that its occurrence may vary depending on the initiating cause, making a complete hematological evaluation an important part of the diagnostic work-up¹. 

How Does Anemia Vary with Different AKI Etiologies? 

Clinical evaluation of dogs with AKI demonstrated that anemia occurred across all etiological groups, although the frequency differed numerically between them. The highest proportion of anemic dogs was observed in infectious AKI, where 82% of affected dogs were anemic at presentation. This was followed by ischemic/inflammatory AKI (71%), AKI of unknown origin (67%), nephrotoxic AKI (63%), and obstructive AKI (50%). Despite these numerical differences, statistical analysis did not identify a significant difference in the frequency of anemia among the various etiologies, indicating that anemia should be anticipated irrespective of the underlying cause of renal injury¹. 

Interestingly, the frequency of anemic dogs was significantly higher than that of non-anemic dogs across all etiological categories except nephrotoxic AKI, highlighting that anemia remains a common clinical finding in most forms of AKI¹.

Why is Anemia More Frequently Encountered in Infectious AKI? 

Among the different causes of AKI, infectious diseases demonstrated the greatest proportion of anemic patients. Several mechanisms may contribute to this observation. 

Inflammatory cytokines released during infection stimulate hepatic production of hepcidin, reducing iron availability despite adequate iron stores and limiting the response of erythropoiesis to endogenous erythropoietin. In addition, certain infectious diseases may contribute to anemia through hemolysis, direct erythrocyte injury, platelet dysfunction, disseminated intravascular coagulation, or clinically significant blood loss^2,3. 

These mechanisms are particularly relevant in infections such as leptospirosis, babesiosis, and leishmaniosis, all of which may present with AKI and have been associated with coagulation disorders or hemolytic processes that can further influence red blood cell parameters^4,5,6,7.

The comparatively lower frequency of anemia observed in nephrotoxic AKI may reflect earlier referral following toxin exposure, particularly in dogs requiring prompt interventions such as hemodialysis, allowing evaluation before anemia becomes clinically apparent¹. 

Clinical Relevance for Everyday Practice 

Although identifying the cause of AKI remains essential for treatment planning, these observations reinforce the importance of interpreting hematological findings within the context of the underlying disease process. 

The absence of anemia should not exclude a particular etiology, nor should its presence be attributed solely to impaired renal function. Instead, anemia should be interpreted alongside the patient's clinical presentation, biochemical abnormalities, and suspected cause of AKI. 

A complete erythrogram performed at admission provides an important baseline for monitoring disease progression and may help identify concurrent processes that contribute to altered red blood cell parameters during hospitalization. 

Practical Clinical Insights 

• Assess hematological parameters in every dog diagnosed with AKI, regardless of the suspected underlying cause. 

• Infectious causes of AKI may warrant particularly careful evaluation of red blood cell parameters because multiple disease mechanisms can contribute to anemia^1,5,6,7. 

• Interpret anemia together with the underlying etiology, biochemical profile, and overall clinical status rather than as an isolated laboratory abnormality. 

• Even when anemia is absent at presentation, continued monitoring remains valuable, particularly in dogs with progressive renal injury or prolonged hospitalization. 

Key Clinical Takeaway 

The underlying cause of AKI can influence how frequently anemia is encountered, with infectious AKI showing the highest proportion of affected dogs in clinical observations. However, because anemia occurred across all etiological groups and was significantly more common than the absence of anemia in most categories, hematological evaluation should remain an integral component of the assessment of every dog with AKI. Careful interpretation of erythrogram findings alongside the underlying disease process can support a more comprehensive clinical evaluation and informed patient management.

References 

1. Rimer D, Chen H, Bar-Nathan M, Segev G. Acute kidney injury in dogs: etiology, clinical and clinicopathologic findings, prognostic markers, and outcome. Journal of Veterinary Internal Medicine. 2022 Mar;36(2):609-18. https://academic.oup.com/jvim/article-pdf/36/2/609/66665591/jvim16375.pdf 

2. Lippi I, Perondi F, Ghiselli G, Santini S, Habermaass V, Marchetti V. Anemia in Dogs with Acute Kidney Injury. Veterinary Sciences. 2024 May 13;11(5):212. https://www.mdpi.com/2306-7381/11/5/212 

3. Nairz M, Weiss G. Iron in infection and immunity. Molecular Aspects of Medicine. 2020 Oct 1;75:100864. https://www.sciencedirect.com/science/article/pii/S0098299720300224 

4. Lippi I, Perondi F, Lubas G, Gori E, Pierini A, D’Addetta A, Marchetti V. Erythrogram patterns in dogs with chronic kidney disease. Veterinary Sciences. 2021 Jun 30;8(7):123. https://www.mdpi.com/2306-7381/8/7/123 

5. Honse CO, Figueiredo FB, Alencar NX, Fátima Madeira MD, Gremião ID, Schubach TM. Disseminated intravascular coagulation in a dog naturally infected by Leishmania (Leishmania) chagasi from Rio de Janeiro–Brazil. BMC veterinary research. 2013 Mar 5;9(1):43. https://link.springer.com/content/pdf/10.1186/1746-6148-9-43.pdf 

6. Rafaj R, Matijatko V, Kiš I, Kučer N, Živičnjak T, Lemo N, Žvorc Z, Brkljačić M, Mrljak V. Alterations in some blood coagulation parameters in naturally occurring cases of canine babesiosis. Acta Veterinaria Hungarica. 2009 Jun 1;57(2):295-304. https://www.researchgate.net/profile/Vladimir-Mrljak/publication/26653538 

7. Sonderegger F, Nentwig A, Schweighauser A, Francey T, Marti E, Mirkovitch J, Schuller S. Association of markers of endothelial activation and dysfunction with occurrence and outcome of pulmonary hemorrhage in dogs with leptospirosis. Journal of veterinary internal medicine. 2021 Jul;35(4):1789-99. https://academic.oup.com/jvim/article-pdf/35/4/1789/66652868/jvim16163.pdf