Clinical Significance of Anemia in Dogs with Acute Kidney Injury

Acute kidney injury (AKI) is associated with significant morbidity and mortality in dogs, and clinical outcomes are influenced by several factors, including the severity of renal injury and the presence of systemic complications. Among these, anemia is increasingly recognized as an important hematological abnormality that deserves attention during patient assessment. Beyond identifying its presence, understanding how anemia relates to disease severity, therapeutic intervention, and patient outcome can help veterinarians develop a more comprehensive picture of dogs affected by AKI¹. 

Clinical observations indicate that anemia becomes more frequent as renal injury progresses and is commonly encountered in dogs requiring intensive management. Although its presence alone does not necessarily predict survival, careful interpretation of hematological findings can provide valuable clinical insight throughout the course of hospitalization. 

Anemia Becomes More Common as AKI Severity Increases 

Evaluation of dogs across different IRIS AKI grades demonstrated a clear relationship between disease severity and the frequency of anemia. Anemia was identified in 40% of dogs with IRIS Grade 2, increasing to 64% in Grade 3, 83% in Grade 4, and 70% in Grade 5. Overall, the frequency of anemia increased significantly with progression of the IRIS grade (p < 0.0001)¹. 

Despite this increase in prevalence, the severity of anemia itself did not differ significantly among the different IRIS grades. Similarly, mild-to-moderate anemia remained more common than severe forms across all grades. Non-regenerative anemia consistently predominated irrespective of disease stage (p < 0.0001)¹. 

These findings suggest that advancing renal injury increases the likelihood of developing anemia rather than necessarily producing more severe reductions in hematocrit. 

What Does This Mean During Clinical Management? 

Clinical observations also demonstrated that anemia was encountered more frequently in dogs managed with hemodialysis than in those receiving medical management¹.

This difference is likely related to the fact that hemodialysis is generally reserved for dogs with more severe azotemia, oliguria, hyperkalemia, fluid overload, or failure of initial medical therapy. Consequently, these patients may experience more advanced uremia and inflammation, increasing the likelihood of developing anemia¹.

For the practicing veterinarian, these findings reinforce the importance of monitoring hematological parameters throughout hospitalization, particularly in dogs requiring renal replacement therapy or presenting with advanced AKI. 

Does Anemia Influence Clinical Outcome? 

When survivors and non-survivors were compared, the overall frequency of anemia did not differ significantly, occurring in 74% of survivors and 64% of non-survivors¹.

However, an important distinction emerged when the characteristics of anemia were evaluated. Dogs that did not survive were more likely to present with more severe anemia and poorer regenerative responses than survivors¹.

These observations suggest that while the mere presence of anemia may not predict outcome, careful assessment of its severity and regenerative status can provide additional clinical information during patient monitoring. 

Current Perspective on Erythropoietin 

Reduced erythropoietin production has been proposed as one mechanism contributing to anemia in AKI, particularly as renal injury becomes more severe. Experimental observations indicate that erythropoietin concentrations may initially increase during the early phase of AKI before declining over time^1,2.

At present, however, the clinical benefit of erythropoietin supplementation in AKI remains uncertain. Clinical evaluations have not demonstrated consistent improvements in transfusion requirements, renal recovery, or survival following erythropoietin treatment^3,4.

These findings highlight that management of anemia in dogs with AKI should continue to focus on comprehensive patient assessment while additional evidence becomes available regarding targeted therapeutic interventions. 

Practical Clinical Insights 

• Evaluate hematological parameters alongside IRIS AKI grading during the initial assessment.

• Recognize that the likelihood of anemia increases as AKI progresses, even though its severity may not parallel disease stage.

• Dogs requiring hemodialysis should be monitored closely for hematological changes during hospitalization.

• Assess the regenerative response in addition to hematocrit, as poorer regeneration was more commonly observed in non-surviving dogs.

• Interpret anemia as one component of the overall clinical picture rather than an isolated prognostic indicator.

Key Clinical Takeaway 

Anemia becomes increasingly common as acute kidney injury progresses and is encountered more frequently in dogs requiring hemodialysis. Although its presence alone does not distinguish survivors from non-survivors, greater anemia severity and poorer regenerative responses may accompany less favorable outcomes. Incorporating hematological assessment into routine evaluation and ongoing monitoring can provide valuable clinical information when managing dogs with AKI.

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. Yamashita T, Noiri E, Hamasaki Y, Matsubara T, Ishii T, Yahagi N, Nangaku M, Doi K. Erythropoietin concentration in acute kidney injury is associated with insulin‐like growth factor‐binding protein‐1. Nephrology. 2016 Aug;21(8):693-9. https://doi.org/10.1111/nep.12656 

3. Aoun M, Sleilaty G, Boueri C, Younes E, Gabriel K, Kahwaji RM, Hilal N, Hawi J, Araman R, Chelala D, Beaini C. Erythropoietin in Acute Kidney Injury (EAKI): a pragmatic randomized clinical trial. BMC nephrology. 2022 Mar 13;23(1):100. https://link.springer.com/content/pdf/10.1186/s12882-022-02727-5.pdf 

4. 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