My friends miniature schnauzer has had something similar but more with vomiting Very poorly had to be syringe fed They thought might have been a kidney stone as apparently it’s common to their breed
Morse, my friends dog, is fine now. Yesterday he underwent ultrasound scans under sedation, which showed nothing. They think he possibly had a kidney stone that he has passed. She said he was in so much pain, just shivering and shaking poor little thing