Question

what happens to the kidneys when you drink too much water?

Answer 1

The descriptions of the hormone systems are usually referred to in the opposite case ie when the blood osmolality increases - this might be the result of dehydration rather than too much water. However, you could infer that the opposite effects on the kidney might be seen: too much water might lead to less ADH and less aquaporin tranlocation to the membrane of the collecting duct. This would cause more water to leave the kidney and go to the bladder rather than be reabsorbed via the vasa recta blood vessel. There's a good page to start on here: http://en.wikipedia.org/wiki/Kidney

Answer 2

Drinking too much water can lead to a condition known as water intoxication and to a related problem resulting from the dilution of sodium in the body, hyponatremia. Water intoxication is most commonly seen in infants under six months of age and sometimes in athletes. A baby can get water intoxication as a result of drinking several bottles of water a day or from drinking infant formula that has been diluted too much. Athletes can also suffer from water intoxication. Athletes sweat heavily, losing both water and electrolytes. Water intoxication and hyponatremia result when a dehydrated person drinks too much water without the accompanying electrolytes.