Should we be checking coagulation before ultrasound-guided biopsies?
This is a common and important issue. Contrary to what one might think, the evidence from human medicine is that coagulation screening tests are unnecessary prior to general surgery unless there is a history of coagulopathy or other predisposition.
http://www.ncbi.nlm.nih.gov/pubmed/3190281
http://www.ncbi.nlm.nih.gov/pubmed/?term=eika+havig
To quote the latter: ‘The study demonstrated complete lack of correlation between the preoperative evaluation of bleeding risk and the observed surgical bleeding’. So there!
he most extensive and best-documented veterinary case series looking at the issue is that of Bigge et al.
http://www.ncbi.nlm.nih.gov/pubmed/?term=correlation+bleeding+(1993-1996)
….although I suspect that it’s not much read in full because JAAHA is not at the easy end of the accessibility spectrum. So it may be worth reviewing the main findings here. They also have important implications for advice given to owners pre-operatively when seeking informed consent.
The authors reviewed 434 cases which underwent core biopsies of abdominal and thoracic organs in a University clinic. Major complications (defined as requiring transfusion or fluids due to haemodynamic compromise or death) occurred in 10% of cats and in 4% of dogs. All major complications were observed within 10 hours. Kidney biopsies accounted for 9/13 major complications in dogs and 6/13 in cats.
Minor complications (decrease in haematocrit >10% but no intervention required) occurred in 30% cats and 19% dogs.
Platelet counts <80 x 10^12/L were significantly associated with likelihood of complications in both species (22% risk of major complications in thrombocytopenic dogs, 50% in cats). If thrombocytopenic animals are excluded from the overall figures then risk of major complications falls to 2% and 8% in cats and dogs respectively.
Coagulation testing was more complex: in cats an APTT > 1.5 x normal was associated with increased risk. The same was not true in dogs. However, dogs with OSPT > upper end of reference range were more at risk. Reasons for this difference are unclear.
Take home messages:
Major complications occurred in about 10% of cats even when thrombocytopenic animals were excluded and despite the fact that procedures were performed by experienced and specialised technicians. Owners need to know that US-guided biopsies in this species are not without significant risk.
In dogs, biopsies of most organs in non-thrombocytopenic individuals were relatively safe but kidney biopsies are significantly more risky.
Platelet counts <80 x 10^12/L should prompt serious consideration of whether biopsy is warranted.
High OSPT in dogs and APTT >1.5 x upper end reference range in cats are also a concern. However, the association is less strong than with thrombocytopenia and reasons for species difference are not yet elucidated.
