- VPS advice to practices re liver biopsies in cats and dogs: pre-op considerations and post-op care
VPS advice to practices re liver biopsies in cats and dogs: pre-op considerations and post-op care
The decision-making process for liver biopsy is quite complicated: many factors are patient-specific. We’re always happy to discuss individual cases.
If we need histopathology or assessment of copper levels then it’s important to consider risk factors for post-op bleeding. It’s not always a black or white decision. In many cases, there’s a grey area where risk has to be weighed against the potential benefits of going ahead.
Specific considerations include…
Specifically Hct <30 in dogs
The threshold for a degree of thrombocytopaenia that represents a serious risk of haemorrhage is in the region of 50-80 x 10^9/l
Coagulation parameters (APTT, PT):
The correlation between prolonged clotting times and actual risk of bleeding after biopsy is very weak. There’s little evidence that any particular level of coagulopathy represents an absolute contraindication for biopsy but we’d generally start thinking seriously about whether to go ahead if APTT or PT are >1.5 x top end of normal.
Animals suspected of having bleeding tendencies should be treated with vitamin K1 (1–5 mg/kg, PO or SC, at 0, 12, 24, and 36 hr, and recheck coagulation at 2 days) before tissue sampling.
Buccal mucosal bleeding time:
A BMBT is also useful. The result is more relevant when performed immediately before the procedure.
If buccal mucosal bleeding time is >5 min, a fresh frozen plasma transfusion is indicated, as is administration of desmopressin acetate (DDAVP, 0.3–1 mcg/kg diluted in saline, slow IV, over 15–30 min), which increases plasma vWF 2-fold over baseline within 1 hr as well as plasma activity of Factor VIII. In many people with liver disease, DDAVP has improved coagulation ability, although the exact mechanisms remain incompletely clarified.
Technical options are:
1) Percutaneous ultrasound-guided core biopsies. This is reasonably convenient in that it’s something we routinely offer and it’s minimally-invasive. We wouldn’t want to deter you from this option since it’s something we’ve been doing for years, mostly without any problems, but it’s important for all concerned to be fully informed.
The biggest issue is that ideally we want samples from at least two different lobes with 14-16 gauge biopsy needles and from both peripheral and central areas to ensure that we get representative and accurate results. Plus two full 2cm long 14G cores for copper estimation (if sending to Colorado for flame atomic absorption spectrometry). So, ideally at least 6 cores. You can sometimes get away with fewer: confidence in results may be lower however.
That’s not always straightforward with percutaneous sampling. It depends somewhat on liver size, patient size/shape and the presence of ascites. Percutaneous liver biopsy carries a not insignificant risk of serious (life-threatening) haemorrhage: about 5% of cases in some published case series. In an ideal world it’s nice to have the option of transfusion in such an event. The presence of pre-existing risk factors increases the need to plan for this.
2) Exploratory laparotomy and wedge biopsies of at least 2 (ideally 3) lobes: ex lap is likely to achieve optimal accuracy in diagnosis, better assessment of copper levels and allows better control of haemostasis. Obviously it’s a lot more invasive, takes longer and has other potential complications such as wound breakdown or anaesthetic considerations. It’s usually more expensive.
The need to assess copper levels is somewhat dependent on breed and presentation. In a Labrador, Bedlington or Westie it’ll be important. In a Springer, arguably less so. It’s suggested that the best copper quantification protocol is to by dry weight atomic absorption spectrometry. Apparently there isn’t anywhere in the UK who will do that: samples (in sterile pot, without formalin) can be sent to Colorado.
The alternative is semi-quantitative copper estimation on formalin fixed samples in UK labs. This may be less reliable.
3) laparoscopic wedge biopsies: same advantages; less invasive; got to find someone to do it…and cost will depend on their pricing. If you know someone locally who routinely does this with a high degree of confidence we’d be grateful to know!
Monitoring after ultrasound-guided core liver biopsies:
Unless there are specific factors in an individual case, we recommend that you keep the patient in clinic, under observation for at least 3 hours. Obviously, that may affect how we schedule our visit.
Please monitor general demeanour, mucous membrane colour, pulse rate and, ideally, blood pressure hourly during that period. It’s highly desirable that you check with in house ultrasound for abdominal effusion shortly before discharging the patient. Please advise owners that delayed bleeding can occur (thankfully this is rare) and if they are concerned that their pet is weak or subnormally-responsive then they should seek urgent veterinary advice.