Sometimes with pancreatitis the liver values and lipids/enzymes might be off but one needs the SNAP/Spec fPL tests (possibly with supporting ultrasound scan) for a positive Dx.
Saoirse had an abdominal ultrasound as part of her workup when she was first Dx'd with diabetes. (The treating vets at the time were absolute pants with cats and, after her physical exam they initially suspected ascites when it was actually Saoirse's bladder being full to the brim from drinking over a litre of water in the previous 24 hours. Long and angry-making story ...) The scan picked up the pancreatic inflammation. Thereafter I monitored her status by getting periodic Spec fPL tests run (after switching to a different veterinary practice).
If the appy stimulant is being dosed every three days then pound to a penny they're treating Ringo with mirtazapine. For general information, an alternative appy stimulant is cyproheptadine. An antihistamine, cyproheptadine's appetite stimulant effect is gentler and of shorter duration than mirt but it can be dosed as frequently as q8 hrs if needed, making it really helpful for 'fine-tuning' appetite stimulation in a somewhat more 'real time' fashion - if appetite is OK, you can skip a dose; if it stalls you don't have to wait very long before giving the next dose. (Note: Cypro is metabolised in the liver so need to check it's OK with the vet.) Cyproheptadine is less likely to adversely interact with buprenorphine and less likely to cause behavioural changes (mirtazapine's a tetracyclic anti-depressant, often dubbed 'miaowzapine' because it can cause unusual vocalisation and agitation). Saoirse had a major adverse reaction to her one and only dose of mirtazapine (pupils dilated to the size of dinner plates, ravening hunger, severe agitation and aggression - mirtazapine can cause serotonin syndrome) but she did great on the cypro; the only side effect was slight drowsiness that wore off about 1 hour after dose administration. Other cats get on famously with mirt. As they often say here, every cat is different (ECID)!
For convenience I'm reposting a couple of links for you below. I found them invaluable in helping me to manage Saoirse's nausea and inappetence issues. In particular, the IDEXX document (a suitably authoritative source!

) is great to wave around the place when discussing/pushing for anti-nausea and appetite stimulant meds from the vets (including a supply for administration during recovery at home!).
IDEXX Labs - Pancreatitis Treatment Guidelines (inc. recommended meds for managing nausea and inappetence)
Nausea & Inappetence - Clinical Signs & Treatments
Mogs
.