I have wondered many times how a human would fare if the kidneys dumped urine into the start of the large intestines somewhere about the appendix instead of into a bladder to be sprayed out. I’m assuming water would be reabsorbed and slower to process out, primarily through sweat and evaporation from the lungs, and maybe diarrhea, though it may be that other waste products, such as salts or ureas may be absorbed into the large intestines instead of being ejected, though I have no idea if it would, or if it would be ejected as intended. Do we have any biologists here that could give insight on if combining both waste paths into one would be advisable?
Then you’ll basically have a cloaca, and perhaps you’ll ended up like bird and reptile which can’t seem to hold their shit and also have watery shit. One of the great things about mammals is they’re able to hold their (relatively) dry shit until they found a safe place to dump it.
That might be a trainability issue rather than a physical capability issue, the more intelligent parrot species are able to be trained to defecate either on command or in specific spots.