Hi zack,
I think the enemas would help heal and clean the colon. Also many components of urine are better assimilated, such as enzymes, larger hormones, antibodies, antigens, proteins in general. By retaining these get more time to enter.
I agree it can make it more difficult without a diagnose. I've not been to the doc, or taken a pill.more or less, for 30 yrs. The only thing that would get me there is extreme pain etc. But don't think I'm doing too well with the self-diagnosing, maybe that won't matter with the uropathy.
I reckon my skinniness is at least partly genetic - parents skinny, when young anyway. I've stayed as skinny (+10kg) to mid-fifties so am not exactly a success story from your pov maybe:-) Anyway, do you have any symptoms, even small? For example under-active thyroids can cause skinnines, even though it's usually the opposite, here.
Nutrients have to generally go from intestine to cell which I should imagine could be distrupted by physical artifacts or bodily functions.
Tap water is full of crap and is a lot more toxic than in Armstrong's time - I scoop handfuls of nasty looking grit out of mine every couple of months. It's basically inorganic minerals coupled with toxic substances. The cells can't use them so they get deposited everywhere, and this might also hinder digestion. Distilled water acts like a solvent, its negative charge attracts positive toxins for elimination. Clay does the same thing, but cannot effect all of the body like DW. A distilled water fast is recommended by many for cleaning the body internally, esp. the blood - they drink about 4-5 litre a day, eat as usual, and dial back on the UT probably.
Personally I would not increase calories, rather more organic if pos. veg/fruit/nuts + juices, making sure no salt. Then start with a series of small urine fasts, say in the weekend. This will get your body ready for the long one, and maybe also increase your weight.
But you maybe should closly monitor the weight until it gets back into a normal range, but build muscle, not fat - ha, a doc once told me I had anorexia and would be dead soon due to lack of eating.
Whatever you do, take it slow and good luck.