"Concentrated urine" means that there is less water in your pee, making it more yellow and strong-smelling. It can happen when you are not drinking enough fluids or if you have a medical condition. Full definition
«Cats evolved in the desert; their ancestors developed to produce a very concentrated urine,» she says. (mnn.com)
As a result of low water consumption, cats produce more concentrated urine than dogs, which helps to conserve the little water they do take in. (fox19.com)
We know that these crystals occur more frequently in concentrated urine. (2ndchance.info)