Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.
I am sorry to hear that he didn't vomit that rubber band back up and save you the worry.
Now you are correct to be concerned and keeping a close eye on him. Cats who eat rubber bands can obstruct but we can also see those bands loiter in the stomach and cause problems later down the line. In regards XXXXX XXXXX to monitor for, the main red flags for us would be lethargy, anorexia, vomiting, diarrhea, restlessness or any belly discomfort/tenseness or pain. So, at the moment, he is giving no clues of overt trouble with this lurking rubber band and hopefully he stays this way.
That all said, this lack of feces is also concerning. In this case, because he is otherwise bright and well in himself, you can try some constipation relieving tricks at home to see if you can get things moving. If you do these and don't see feces in the next 12-24 hours or see any of the other signs, then we'd want him revisiting the vet so they can reassess him via abdominal palpation +/- x-ray.
In regards XXXXX XXXXX fecal movement, you can start by offering 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). 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, you can administer a small volume of lactulose (LINK) or pharmacy grade liquid paraffin/mineral oil orally (though take care to avoid aspiration, since that would cause problems we'd best avoid) as a GI lubricant.
Furthermore, if he is eating you can mix in some tinned pumpkin or a 1/4 teaspoon of unflavored Metamucil/Benefiber to his food. Just like people, these can restore fecal output regularity. I would offer these with wet food to ease his eating of it, while making sure we are getting water into him (as canned food is 35% water). I would also encourage him to drink to keep his feces appropriately hydrated and avoid any secondary constipation that might slow fecal passage more for Darcy. Make sure he have fresh water and you can even offer low sodium chicken broth if he won’t drink.
So, I would try these tricks to encourage feces (and the offending rubber band) to keep moving through the gut. Again if you try these and don't see feces in the next 12-24 hours or he shows any of those other signs, then we need to see his vet again to make sure they cannot appreciate any obstruction developing and potentially take an xray to see the state of affairs in his gut.
And just to note in case he starts to show any of those worrying signs and needs to be seen to urgently, I wanted to mention that most veterinary practices here do have contingency plans for emergency care for their patients. This means that if you ring the practice, they will likely have a message to direct you on how to contact their emergency service. And if you don't have a vet you can find one local to you, you can check you can check the RCVS Register (HERE) to find your local Vets Now (LINK) who are open all nights/weekends.
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! : )