With liver diseases it is usually advised to not give the cat any ‘extras’, to spare the liver as much as possible.
The liver is a metabolic organ that regulates the metabolism of proteins, fats, carbohydrates, vitamins and minerals. With liver diseases problems arise with the uptake of substances and their degradation. Because of this, not all harmful substances can be detoxified. Thus, for example, ammonia (waste product of protein) is not transformed into urea, which can result in the accumulation of ammonia in the body.
Giving a kibble of hepatic food from a different brand, as a treat, could be an option. Always consult your veterinarian for suited dietary advice.