My toddler seems very disinterested in taking any type of milk or juice. He spits the milk out when I give it to him (in a cup, I've tried several different types of cups for him) and he drinks just little bits of juice each day. Other than him not having wet diapers when he should, he shows no other signs of dehydration. With him not drinking, will this cause long-term problems with his kidneys? If so, what should I do to get him to drink?
There are several thoughts that come to mind when I hear about young toddlers not interested in drinking. The first, and one of the most common factors involves the transition from bottle to cup (or sippy cup). Usually at about your son's age, most people have weaned or are in the process of weaning their children off the bottle. At about the same time, most toddlers have recently (at 1 year) made the switch from drinking breast milk and/or formula to regular vitamin D cow's milk. With this switch comes a decrease in the amount of milk children need to consume—often going from 20 to 32 ounces down to somewhere between 16 and 20 ounces. This expected decrease in intake can sometimes be mistakenly perceived as decreased interest.
For some toddlers, a disinterest in drinking may also relate to the change from bottle to cup. In most cases, cup refusal is relatively short-lived but requires that parents pay closer attention to just how much their children are getting to drink until they become more accepting (and in some cases, more skilled) in cup drinking. It may help to consider a different type of cup—perhaps a sippy cup without a valve or a toddler cup with a straw to make it easier for your toddler to drink more effectively from the cup. It's also worth considering whether your toddler is turning a cold shoulder to milk in a cup simply because it's cold, as many new cup-drinkers have previously only been given warm milk to drink from the breast and/or bottle. If this is the case, it's fine to warm up your toddler's drinks to take the chill off until he adjusts to drinking cold liquids.
The other common reason I see for toddlers to drink a lot less than normal is because food takes over. With a greater interest in and exposure to a wide range of table foods, some toddlers end up consuming a bulk of their daily caloric needs from food. If this is the case, simply offering milk before meals, for example, may help restore a better balance between food and drink.
And lastly, I want to be sure to address the question of dehydration, as inadequate liquid intake and a subsequent lack of urine output can definitely be a cause for concern. Signs of dehydration can include a dry mouth, few (or no) tears, eyes that look sunken, the soft spot on the top of a baby's head may look sunken, lethargy, and as you mentioned, a lack of urine/wet diapers. For infants, this typically means no wet diapers for six to eight hours, while for an older child it means a lack of urine for 12 hours (or only very small amounts of darker yellow, concentrated urine). Whenever these signs of dehydration appear—especially if the problem continues—it is important to discuss the situation with your child's doctor to figure out how best to correct the dehydration.