As bodily fluids go, urine is pretty inoffensive. It’s mostly water and doesn’t usually contain any harmful pathogens. It irritates the eyes and prolonged skin contact can cause “diaper rash,” but drinking it is a low risk activity, especially if certain measures are taken. The urinary tract is much more sensitive to bacterial infection than the digestive tract. Unless the person has a urinary tract infection (UTI), drinking urine isn’t going to cause problems with infection (and even then might not be a problem). The concern would be putting excess strain on your kidneys. But if the person urinating and the person consuming are both well-hydrated, healthy kidneys should have no trouble processing the extra salts.
But what about the vagina? Similarly, bacteria that aren’t causing problems in the urinary tract aren’t going to cause them in the vagina. The concern would be disrupting the normal bacterial colonies and pH balance of the vagina, similar to a water douche. Normal urine tends towards acidic (pH ranging from 4.6 to 8.0), but this is more basic than a healthy vagina (pH ranging from 3.8 to 4.5). Frequent urination into a vagina can leave her vulnerable to infection. But as an occasional indulgence, it shouldn’t be problematic unless she has a sensitive bacterial ecosystem. Large quantities of semen (pH ranging from 7.2 to 7.8) would be more problematic.
Feces, on the other hand, have a much higher bacterial concentration and is a common vector for disease. But this is only a problem when contacting an unhealthy person’s feces. If the bacteria weren’t problematic in the digestive system the first time, reintroducing them won’t change that. Feces from healthy people can actually be used to treat people whose natural bacteria have been disrupted. It isn’t dangerous, especially if it’s your own. You certainly can’t give yourself a disease.
Frequently eating large amounts isn’t advisable (and frankly not something I can imagine anyone wanting to do). But anal sex doesn’t cause nearly that much contamination. It’s a lot less messy than people seem to think, even if you don’t do any cleansing. The rectum is more like the urethra than the bladder. It doesn’t store feces; it just provides a path to the exit. There usually is very little if any feces in the rectum unless you are evacuating. Especially given the small amount of contamination, anal to oral sex and rimming are perfectly safe.
But just because bacteria is perfectly safe in your digestive system doesn’t mean you should introduce it to the vagina. The most common culprit in UTIs is E. coli, which is commonly found and usually completely harmless in the digestive tract (though some nasty potentially lethal strains do exist). E. coli also causes Bacterial Vaginosis (BV). Direct anal to vaginal sex is clearly a bad idea, especially in women who are prone to these types of infections.
If you want to switch from anal to vaginal sex without scrubbing up between, you should use a condom. Enemas may reduce the risk of infection but alone are not sufficient to prevent it. They remove the feces but do not kill the bacteria that would cause problems in the vagina (and you wouldn’t want it to since this would also kill the beneficial bacteria in your lower digestive tract).
Urinating after sex is recommended to help prevent UTIs. You should also avoid (if possible) anything that can disrupt the “good bacteria” colonies in your vagina e.g. spermicides, antibiotics, and douching.
Have fun and be safe.