Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
Now constipation in older cats often has an underlying reason, which can be health based (ie conditions causing dehydration or GI obstruction) or even old aged based (ie arthritis as your vet noted). Therefore, if your lad is struggling to pass feces and vomiting (which is going to limit your ability to treat him at home), then you do want to consider having him examined by his vet to see if any underlying issue is now appreciable.
Now if Bertie isn't vomiting much and can keep food and water down, then you can try settling his stomach to see if you can then help with his constipation. To do so, you can consider trying him with an antacid. There are a number of antacids that are available over the counter and pet friendly. I would advise only treating with one, but the two I tend to use are Pepcid (More Info/Dose) or Zantac (More Info/Dose) These are usually given 20 minutes before food (to allow absorption) and of course you want to double check with your vet if he has a pre-existing condition or is on any medications you haven't noted before.
As long as you can settle his vomiting you can consider trying to get things moving for Bertie. To do so, you can help relieve mild constipation at home with a number of wee tricks. First, you can offer some cow milk. Kitties are like little lactose intolerant people, and while the love milk it can move things down the gut a bit quicker (ie. Cause mild diarrhea in an unconstipated cat). If he is mildly constipated, this might just get things moving in the right direction.
You can also treat them with hairball medication (ie. Catalax). This is available from the vet or the pet shop. It works to lubricate the gut and can facilitate the movement of hard feces out of the rectum. Alternatively, (and again ONLY if he isn't vomiting once you try the antacid), you can administer a small volume of a GI lubricant like Miralax (1 tsp per 24 hours), lactulose (More Info/Dose) or mineral oil orally in food. Since he has been vomiting, we'd not want to give these directly by mouth since vomiting of these substances could lead to the material being aspirated into his lungs (which is best avoided).
Furthermore, if he is eating you can mix in some canned pumpkin or a 1/4 teaspoon of unflavored Metamucil/Benefiver. Just like people, these can restore fecal output regularity. I would offer these with wet food to ease him eating of it, while making sure we are getting water into him (as canned food is 35% water). As well, you also want to encourage your cat to drink as constipation can be complicated by dehydration. Make sure he have fresh water and you can even offer low sodium chicken broth if he won’t drink.
Finally, in regards ***** ***** arthritis (which could be a chronic underlying issue at his age), I would suggest that you consider trying him with glucosamine/chondroitin supplementation. This is a nutrient supplement that is available at your vets, pet shops, and health food stores (as capsules, liquids, and even treats). It works by aiding joint suppleness by helping cartilage replenish itself and blocking enzyme destruction of cartilage in the joint. Often we can find this helpful in cats with mild arthritis and can sometimes be just enough to keep him comfortable and avoid issues like this. Normally we give kitties 50mg glucosamine + 15mg chondroitin a day per 10 pounds of body weight.
While you are doing this, I would advise that you monitor fecal output. I would advise trying the above measures, but if you aren't seeing feces in the next 24 hours, or your cat vomits any further, then they should be evaluated by a vet. Severe impactions of feces are usually secondary to more serious diseases, so if he doesn't respond to our gentle colon cleaning treatments, then he may require more aggressive treatment (ie enemas under sedation).
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and hope to see you again soon! : )