Hi....so, I am no vet, but a friend had some similar issues with her dog, and the dog had portosystemic shunt. This is a lucky guess, you need to listen to your vet or get a second vetenerian opinion.
But I agree with you, you have to be careful not to put her under some treatment that is uncomfortable to her, or more aggresive than the disease.
I hope you will come to the bottom of this, and If She is ok and functional, try some natural remedies too (it can’t hurt).
Sending you get well wishes 
How was she when she did not take the appetite suppressant? I would remove every Med that is not life-threatening if it is removed. Too many Meds can interact badly with one another. Does she like Carrots or Broccoli? They make great snacks and my dog loved them Raw or Cooked. Raw is better because they get to crunch it and part of the appeal of a snack is the Crunch!
I would also get a second opinion before considering a Biopsy. If she starts to seize that is a sign that she has some type of Cancer. No seizures is great! My girl started having Seizures when she was 12 and she had a Carcinoma in her small intestine. I had that removed and she lived until she was 16 and I had to let her go because the Cancer had relapsed.
Good luck with your girl but I do not think the combination of Meds is a good one.
Run this suggestion past your vet -
My Keeper has liver problems. Shortly after Marvin died, he became disorientated and refused to eat. My vet (new, senior partner in the Practice) scanned him, did blood works and wanted him hospitalised on a drip for days and a biopsy performed. Otherwise he would die.
I refused and in floods of tears, went to the outgoing senior Vet, a lovely old fashioned hands-on Vet, who looked at the scans and suggested a milk thistle preparation (obtainable on line).
She also spotted a a piece of possibly atrophied bile blocking his gall-bladder and we agreed better a happy dog for a month than a sick one for 6 and if subjected to days in hospital, he would have died - of boredom. . .
She prescribed Destolit 150 mg to disperse the bile and Denamarin Hepatic Nutritional Liver Support to be given one hour before food. He takes the Denamarin in the mornings in low fat super-market pate (!) and the Destolit wrapped in his meal in the evenings. He didn't look or behave like a very sick dog. After a couple of days he was eating voraciously, eager for treats and agile and fleet of foot in the woods.
Within a relatively short space of time, his blood works were back within a much more normal range and they have continued to improve.
That was 22 months ago. Keeper is 2 months short of 13 years of age now. He is still taking both medical preparations and nobody we meet in the woods will believe he is an old man !
Don't do anything without consulting a vet but before any biopsy, maybe a scan would show up something ?
Good luck
also she needs to loose more weight, around 9kg (around 18 lb) is about right, and see if the lost weight helps, it did to my older girl.
Len aka Redial
Queensland, Australia
@antigone Hi, she is no different after a week off the Ursodiol, so I guess that is not the problem. She is a very picky eater, so we tend to be careful with food but she has always been between 24 and 28lbs. Now we are more worried about the low blood sugar, so are trying to get her to eat more. The problem may not be so much about how much she eats, she eats fine at dinner time but won’t eat hardly anything in the morning / afternoon, which is when her sugar was low.
@zande Hi, we are giving her the Denamarin, which is SamE and the Marin plus which is milk thistle. Interesting though that you had a similarly weird disorientation problems. The vet thinks the low sugar is because she is not eating except at night. He is getting and appetite stimulant for her called Entice, don’t know if it will work or not.
@janja Interesting reading on the portosystemic liver shunt, I will mention that to the vet and see what he says. She has had several ultrasounds and they looked over her liver, kidneys, pancreas etc but say everything looks great. It seems a bit baffling to them as she appears to be in great shape and was getting along fine until recently with the dissorientation.
@redial Would love to bring her down, now we have the blood sugar problem we can’t really do much about it.
I think Redial has the right of it. Overweight can cause all kinds of problems, including putting a strain on organs. Can you try to cut the evening meal so she is hungry enough to eat in the mornings too ? I have always fed two (identical) meals a day as a convenient way to control weight.
Often a dog won't eat because the food simply tastes horrible. This could come from a number of internal problems, giving a bad taste in the mouth. And frankly I would try to solve that before giving any more medication to stimulate the appetite which in turn could stimulate weight gain and so on.
@zande At this point it is a challenge to get her to eat at all and if her sugar drops too low I am afraid of seizures. Frankly at this stage she is not eating much at all, around a quarter of a cup of kibble and a quarter of a can of wet food per day.
2 thoughts, just things I thought of while reading this:
What you described (I think) as disorientation, that was what my Gretchen did for a couple of years before she started having real, can't deny it, seizures. When she did have them the first thing I thought of was how she just stood and stared for a few seconds before. I concluded they were related. Nothing like that has happened since she started taking the seizure medicine.
My husband was frying eggs 20 years ago, and I saw him just stand real still, shake for a minute, then fall. It looked like a seizure to me. The EMTs took him to the hospital, the doctors did whatever drs do, and said he had low blood sugar, and nothing like that has happened again.
(totally not basenji related, but gives us a laugh when we think of it now - my son Nick was about 6, was right there and saw it too, and while I was down on the floor said "You think maybe we should turn off the stove?" I had always thought he was born a little adult)
@rugosa When she did it, it certainly could be low blood sugar. The first time she just sat on the couch when I called her to go out and stared at me as though she didn’t know what I was saying, never happened before that. The other time we went to bed (dogs sleep with us...or rather, me and my wife sleep in the bit of the bed the dogs don’t want lol) and she kept going to the door, so we let her downstairs again and she just looked around like she had forgotten something. Almost as though she thought one of us was downstairs but we were not. It was very strange. We took her to the vet and had her ears checked as we thought the first time she might be going deaf. He said her ears looked fine with a little water on them so we cleaned her ears for a few days. Looking back, I think it was the blood sugar.
One thing I forgot to mention is that during the time period when she had the episodes, she was drinking about double what she normally does. She is now back to drinking normally, so maybe it was a kidney problem? Who knows, she might have some cognitive problems going on and it could be nothing to do with her liver enzymes.
It just all seems so vague and we have no idea of the actual problem.
@dagodingo My Dog started having Seizures when she was 12. You are describing what could be an 'Aura' which is an early indication that a Seizure will occur. Low Blood Sugar caused me to pass out on the Train to work. I think the best place to start is with what one of the very experienced B owners said about switching her feeding schedule. A small amount of Kibble at night and she should be very hungry in the morning. That is the best advice I have seen here regarding her feeding schedule.
My instinct is to take your now Senior Dog to another Vet for a second opinion. Fresh eyes make a difference. Do not worry about insulting your current Vet, Vets and MDs work for US. They are not Gods and should not be treated as such. Small Animal Vets are some of the worst price gougers I have ever come across! It is less expensive for me to have my 1200 lb Horses Vetted and that includes Vaccines. So please consider getting a second opinion from a new Vet.
Basenjis are more common in the US than they were when I got my girl in 1998. I was lucky because the Vet knew immediately what her Breed was because she had a personal interest in the so-called Ancient Breeds. I would contact the BCOA to find a Vet in your area that works with this Breed all the time. I also would not give her too many snacks like Biscuits etc. The grain causes inflammation in the body and that never helps.
Best of luck to you and I had to get a King Size Bed so my Dog could sleep with me without causing me to fall out of the Bed! When they stretch out sometimes it is laterally and when she did that I would fall out of the Bed!
They are hilarious little beings and as soon as my 14-year-old Death Row Rescue Cat passes I will get a relative of my Dog. Debra found her Breeder and another Breeder who breeds from the same lines. I am totally prepared for a new Pup. I would take a Rescue but because I reside in a Condo I only have the Park for outside time. I was told I needed a back yard with a 6 foot wooden fence! My little homewrecker did just fine without the yard or the Fence!
Best of luck to you!
@antigone thanks to all of you that answered. We have had a couple of weeks of hell and as my girl deteriorated, we concluded that she had either a brain problem or more likely a brain tumor. Many things which we thought were arthritis and dementia were actually a cognitive problem. We put her to sleep today as she was suffering too much. She is in peace now. Very tough and I am sure you all know how it is. Hopefully if someone else reads the thread, it may help them.
You did the right thing entirely, difficult as it may have been. You let her go to save HER further suffering. Letting them go with dignity when it is their time is the last chance we get to show them we love them.
@dagodingo I am so very sorry for your loss. The longer we have them the harder it is to lose them. I have been rescuing animals since I was 10 years old. I found a Kitten by the School and I brought her home. My Parents decided I could keep her because there were not any Infants in the House.
Please keep all of her things because that is very important. I had my 16 year old girl euthanized and I had a private Cremation for her. She is in a little Cedar Box on my Desk. My little Mister Smith who was killed by the older and larger female Cat was also Cremated. I only do that for the animals that made a huge mark on my Heart. I still have the Killer Cat because they both came from the same home and both were abused. I refuse to put a healthy animal to sleep. When she passes I will get another B.
Again, I am so sorry for your loss. It takes time to deal with it and I still miss my dog desperately.
First, I'm so sorry for your loss. It is always heart breaking. I never forget my previous animals no matter how long ago. They bring such love into our lives and truly make it better. My first Basenji, Roxie was a rescue who was starved and abused from the first few months. She will be 6 yrs old Nov 12th. As a result she is only about 14 lbs. She is a very picky eater. I experimented with different foods. I quickly determined to leave her dry food out at all times. She will only eat a few bites at a time. She eats more like a cat than dog at times. She is pad trained so if i can't be available to take her out it's no problem. She loves boneless chicken, vegetables and fruit at any time, especially crunchy apples, strawberries, blueberries, peaches, plums, and watermelon. Of course, I only give her a few bites at a time. This is healthy and will encourage most picky eaters. Dogs with very low or very high blood sugar can have episodes just like a human diabetic who become disoriented, pass out, or have seizures. I'm type II diabetic and eat vegetables and fruits daily anyway so a few extra bites don't cost that much. 
@redial said in Advice / help on mysterious health problems.:
also she needs to loose more weight, around 9kg (around 18 lb) is about right, and see if the lost weight helps, it did to my older girl.
What are you basing the "right" weight on? There is no magic number. My champion Sayblee had great tuck up, no fat, 22 pounds at 2. You tell fat by looking at the dog, not breed average.
I am so sorry, was responding to your post and missed your later one about losing her. You tried everything and I know she felt the love. Releasing her was the most painful part, but that you also did for her.
@debradownsouth Her right weight was around 22lbs, which was perfect with a tucked up stomach and a waist. She had a lot of muscle on her until she became more ill. But as it got harder for her to eat and get her meds down her, we compensated with all kinds of cooked foods and didn’t restrict it much. She often would refuse food for days but if you cooked her steak, then for so longs as it smelled good she would eat. She liked beef steaks, filet mignon, scrambled eggs, chicken, pork loin etc, but only if you cooked it fresh. I guess the smell drove her to eat. In fact, I remember one morning while cooking her scrambled eggs and filet mignon, I then made a bologna sandwich for myself and told my wife there was something seriously wrong with the picture lol. Before she became ill she would eat anything food we put in front of her, just as my other boy does now.
