Article of the Week

 

We will be posting commentaries on articles relating to internal medicine and endocrinology that we think are of interest.

 

August 11th, 2022

Splenectomy in the management of primary immune-mediated hemolytic anemia and primary immune-mediated thrombocytopenia in dogs

 

In humans with ITP or AIHA, as in dogs, glucocorticoids represent first-line treatment. Splenectomy is performed in chronic, refractory ITP, with two thirds discontinuing medical treatment by 5 years after splenectomy. Despite increased use of rituximab (monoclonal antibody targeting CD20) and thrombopoietin receptor agonists, splenectomy remains an important treatment option for human ITP, and immune-mediated hematological disorders are a common reason for nontraumatic elective splenectomy. In human AIHA, splenectomy might theoretically be more beneficial when Fc-mediated phagocytosis is the predominant mode of erythrocyte destruction (compared to complement-mediated phagocytosis or intravascular hemolysis) but, overall, outcome after splenectomy is variable and unpredictable.

 

Published response and relapse rates for dogs with IMHA, ITP, and CIST (concurrent IMHA and ITP) treated medically are variable. Response rates of 80% are reported with the use of prednisolone alone in IMHA, with relapse rates of 11% to 24%. With ITP, 1 study reported that 89.6% of dogs survived to discharge, with a 41% relapse rate. Little data is available for the long-term follow-up of CIST treated medically: 1 study reported that only 24% of dogs treated medically were alive at 30 days from hospital admission, and another that 75% of dogs survived to discharge.  Splenectomy could be an attractive option in cases poorly responsive to medical treatment, or where sustained medical treatment is cost prohibitive, produces adverse effects or is unavailable.

 

Only small case series about splenectomy as treatment for immune mediated hematological disorders in dogs are published, making drawing conclusions difficult; however, splenectomy appears well tolerated. Our experience is that splenectomy is usually offered either as a “last resort” in cases refractory to immunosuppressants, or where splenic abnormalities are identified. Anecdotally, some of these cases appear to respond favorably, often despite failing multiple prior treatment modalities.

 

The objective of this retrospective study was to describe the clinical outcomes of dogs with IMHA, ITP, and CIST that underwent splenectomy. We hypothesized that splenectomy would be beneficial in allowing for immunosuppressive drug dose reduction or discontinuation.

 

Background: Current reports about the use of splenectomy for the management of immune-mediated hemolytic anemia (IMHA) or immune-mediated thrombocytopenia (ITP) or both in dogs are limited.

 

Objectives: To retrospectively describe the use of splenectomy as part of the management for IMHA, ITP, and concurrent IMHA and severe thrombocytopenia (CIST) in dogs. It was hypothesized that splenectomy would be beneficial in allowing for reduction of dose of immunosuppressive drugs or discontinuation in 1 or more of these groups.

 

Animals: Seventeen client-owned dogs (7with IMHA, 7 with ITP, and 3 with CIST) were identified across 7 UK-based referral hospitals from a study period of 2005 to 2016.

 

Methods: Data were collected retrospectively via questionnaires and included information about diagnosis, management and treatment response before and after splenectomy. Based on clinical outcome, treatment with splenectomy as part of the management protocol was classified as either successful or unsuccessful.

 

Results: Six of 7 dogs with ITP were managed successfully with splenectomy as part of their management protocol (3 complete and 3 partial responses), although 1 subsequently developed suspected IMHA. Of the 7 dogs with IMHA, splenectomy was part of a successful management protocol in 4 dogs (2 complete and 2 partial responses). In the CIST group, 1 case (1/3) responded completely to management with splenectomy as part of the management protocol.

 

Conclusions and Clinical Importance: Splenectomy was considered successful and well tolerated in most cases of isolated ITP. Whether there is a benefit of splenectomy in cases of IMHA and CIST could not be determined in the current study.