A "renal diet" is not one uniform food. Composition can differ markedly, so nutrient intake and treatment of the same renal patient can differ too.
Eating faeces can be more than behaviour: for Labrador Scoop, the daily ration provided too little protein. After switching to a better-suited diet, it stopped within days.
Nutrition is essential, yet often neglected in practice. Good advice is tailor-made: calculating requirements, choosing a suitable diet and following up the patient.