Urine becomes more concentrated as one dehydrates. If one is in a survival situation where one has become dehydrated then the urine produced once dehydrated would be relativley concentrated. The body will produce uric acid at a relatively constant rate as a by-product of cellular respiration. If you are drinking a lot of water the kidneys will be actively removing it to maintain the ideal blood ph level thus producing a rather dilute urine. If you are dehydrated the kidneys will be attempting to conserve water for exactly the same reason. So the concentration of urine, and thus its effect on the body when re-ingested, will depend on the circumstances of its production.
Thus in a survival situation with limited fresh water, where that water is rationed, the body will be in a constant state of dehydration and so producing concentrated urine. If one consumes that concentrated urine the problem is that it may be so concentrated as to set up an osmotic gradient such that water would be drawn from the capillaries in the intestine out of the body, thus making matters worse! I do believe this is the issue when drinking sea water. Also the US navy carried out an experiment to see if sailors cast adrift at sea could survive by giving themselves sea water enemas thus allowing the large colon to absorb water as that is one of its existing functions. The experiments proved that the sailors dehydrated more quickly with the enema than without it and that was ascribed to the osmotic gradient created in the large colon removing water from the subject's body.
So drinking dilute urine would not be a major problem but drinking concentrated urine could/would be. Urine from a healthy person is normally pathogen free.
