A 7y FN DSH presented to the primary care veterinarian after the owner noted specks of blood in the house over the weekend and they suspected sneezing. No vomiting or diarrhoea had been noted, but the cat had stopped eating.
Physical examination was unremarkable and there was no evidence of external haemorrhage, nor petechiation.
Preliminary diagnostics showed a non-regenerative anaemia (PCV 18%), with unremarkable biochemistry and an unremarkable AFAST / TFAST scan. FIV and FeLV testing were negative. The anaemia worsened over the next couple of days decreasing to 10-12%, however the cat remained quite bright and reassessment showed the anaemia to have become regenerative based upon an in-house reticulocyte count. Urinalysis was unremarkable. More complete abdominal ultrasound showed a small volume of free fluid that was too small to sample, but was otherwise unremarkable. Thoracic radiography was also unremarkable. Some melaena was suspected during the second day of hospitalisation.
Pending further diagnostic results, dexamethasone was administered for possible IMHA.
- A blood smear is above for you to evaluate. What comments would you make about this smear?
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- What differential diagnoses would you consider at this time to guide any treatments?
The smear evaluation demonstrated erythrocyte anisocytosis, with 4 polychromatophils (larger erythrocytes, staining blue - yellow arrow). These findings indicate bone marrow regeneration compatible with the regenerative anaemia documented. Manual platelet count was normal. An in-saline agglutination test (pre-dexamethasone administration) was also performed and was negative.
Although spherocytosis was not suspected, given the difficulty in assessing for spherocytes in feline blood smears, a Coombs Test was performed (pre-dexamethasone) and was pending at the time of initial consultation with the VetCT Telemedicine Team.
An Internal Medicine Specialist discussed this case, in which finances were also limited. Supportive care with omeprazole was recommended given some potential for GI bleeding, and doxycycline was also commenced in case of infectious haemolytic anaemia. Dexamethasone was continued given that GI bleeding could not be verified, and therefore an immune mediated IMHA was still considered possible.
The PCV continued to decrease, the cat deteriorated clinically and repeat haematology showed the anaemia was no longer regenerative with a low reticulocyte count. Blood typing showed the cat to be Type B, so a search for a compatible donor commenced.
Unfortunately this search was unsuccessful… An Internal Medicine Specialist therefore discussed the option of a xenotransfusion using dog blood. Xenotransfusion progressed well, with no acute reactions, however lysis of the transfused cells was seen within days and the post-transfusion PCV reduced to a worrying 12%. However, at this time the anaemia was noted to demonstrate some regenerative capacity and the cat's PCV subsequently improved to 20% with ongoing management as outlined above and the cat was able to be discharged home.
No further episodes of suspected melaena were noted in this case and the final diagnosis remained open with IMHA considered most likely, but with GI blood loss not entirely excluded. Ongoing monitoring together with tapering of glucocorticoids was recommended as per standard protocols.
This case demonstrates the potential benefit of xenotransfusion where a more compatible donor is not available. This is never a first choice for transfusing cats, but can be useful to stabilise patients until such time that prescribed treatments have sufficient time to work, or to potentially allow additional diagnostic workup where possible. Repeated xenotransfusion is not possible.
In a case series, 49 cats underwent xenotransfusion given the lack of a compatible donor, and as a result of a variety of underlying causes. Delayed lysis within 1-6 days post-transfusion was common. When considering non-neoplastic causes, xenotransfusion allowed stabilisation and survival of severely anaemic cats in 18/35 (51.4%) cats long-term, with 15/18 cats (83% still alive more than 5 months later).
More information from the abstract on this case series can be found here. If you have a case where you are considering using a xenotransfusion and wish to discuss this option, please do not hesitate to contact our Internal Medicine Specialists at the VetCT.