Any vets around? I could use some advice

[InTropicalTrumpsLand]

Warning: long, and I'm not from the UK (see username).

Ddog's health hasn't been great since she was 9, but it really worsened in the last few weeks. She's a 13 1/2 year old Lhasa Apso who first had problems in her knees, then skin, and now pretty much everything.

On the 30th of July I took her to the vet due to incessant biting and scratching. It isn't new - gets better with corticosteroids. Vet also identified an infection due to repetitive biting and gave her a shot of ABs. Blood was drawn to determine it wasn't hormonal. I mentioned she was acting strangely regarding peeing, but I was assured that since there was no blood, it wasn't to be worried about.

That same week she returned four times for more antibiotics, with no visible improvement. Again I mentioned the weird peeing; Ddog complained upon being examined, something she never does. Urine was drawn and sent to analysis. Was also given immunosupressors to see if that helped with itchness.

The results from the urine sample was what worried us: proteinuria and creatinuria were sky high. The next day (results came late at night) she was hooked to an IV bag, believed to have kidney failure, and had blood drawn to confirm it.

Bloods were inconclusive. There was apparently too much fat in her blood.

Today, new bloods were drawn after she fasted for 12 hours. The results just came up: creatinine and urea within normal range, Alt-TGP in the 250s. Told it's a liver problem, not kidneys.

Tomorrow she's booked for an ultrasound to check the damage, but I can't help but feel the vet is lost - sure it was something, now it's something else. Ddog is also at the vet at least monthly due to allergies, so is this something that can really just appear with no sign beforehand, or did the vets miss something?

Am I expecting too much of the vets, or should I look for a second opinion (difficult, because I don't know anyone else)?

[Funf]

Having had two Lhasas, one lived until 14 but the other was 17 so yours is old but not that old. The younger one was itchy and the vet advised a Royal Cannine dry food, I was very sceptical but it worked a treat.
It may well just be old age, but I fully understand how difficult it is, good vets are almost impossible to find