Poor lad!
are his poos ok? His weight looks ok, doesn't it.
Has he just been vaccinated?
My springer had the same problem a few years ago, but also did 'cowpats'. X rays showed excessive abdominal fluid. I was told to measure how much she drank (fill some bottles). The vet regarded the diabetes insipidus as part of a complete metabolic confusion (vaccine reaction?). She was losing weight in front of our eyes and as well as steroids he prescribed Panzyme and low fat diet. This worked like magic , proper poos and reduced thirst, death narrowly averted. Her diagnosis was exocrine pancreatic insuffiency. Insulin balance is regulated by the endocrine pancreatic system, and as everyone says can severely affect thirst.
She still drinks more than normal, and I snatch it away to avoid 'accidents'. She doesn't know when to stop, but its not obsessive .
Good luck with the vet. It would be interesting to know the German approach!
