Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 15 years of experience. I look forward to working with you.
What you report on Murphy does concern me that he is having pain from somewhere so severe he doesn't want to move. Our top locations for this type of pain is either the spine (neck/back) or abdomen. You can gently probe these areas and if he cries out during this, then you found the problem. Either way, he really must be seen today, if you suspect pain this severe. This is not something that should wait until Monday, especially if we think this could be back pain. With back pain it could have started by something he did yesterday and now it hurts a lot today. Another possible indication of back pain is if you get him up (be careful not to get hurt doing this if he is very painful) and he stands or walks with his spine arched or tail tucked or he cannot control his limbs or support himself, then spinal pain becomes more of a concern.
Now, this may not be due to pain. With profound weakness there are other problems we do have to think about such as internal bleeding (check his gums and if they are white/pale then this is a critical emergency and he must be seen now) or anemia for another reason, or even an electrolyte problem or low blood sugar issue or even profound infection. Some dogs during the season changes can get vestibular disease which causes profound vertigo and nausea so a dog may not want to move but usually we will also see his head being tilted and he may have some rapid back-and-forth eye movement.
If he progresses to become back to normal over the next hour or two, then have him rest the weekend (no long walks or rough play and avoid stairs) with normal food/water.
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