Urine is easily collected by placing a formed section of aluminum foil underneath the section of her cage typically used for urination. This is a very serious condition and should be considered life threatening. Take your rabbit to your veterinarian immediately. Some serious gastrointestinal infections that result in diarrhea can be fatal in less than 24 hours. Heat Stroke Summer is probably the most dangerous time of the year for rabbits.
Bunnies can develop heat stroke with very little warning.
Once symptoms appear, you have to cool down the bunny VERY quickly or she will die. In the early stages of heat stroke, the bunny will stretch out and breathe rapidly. Look for panting, weakness, redness of the ears, and slobbering. As heat stroke progresses, the bunny will become lazy and unresponsive and start sweating around the nose. When the bunny starts throwing back her head and breathing rapidly, she is very close to dying.