Uric acid crystals only show up when the urine output is very low, partly
because the crystals are concentrated and partly because the acid milieu
changes their structure so that they are red.

If this baby is not getting much reduced milk, then it is unlikely these are
uric acid crystals. How does the doctor know this is not blood? That would
be my first thought if the baby is otherwise doing well.  We probably have
at least two weights, I hope, since she saw the doctor twice.  If the weight
is also up, the baby cannot be dehydrated.

Jack Newman, MD, FRCPC