This is one of my old favorite puzzlers.  (I think it was the name that first
attracted me.  "Brick dust" is such a perfect description!)  I remember
reading about this condition in a pediatric textbook in my early days as a
nurse---that would be around 1975, and the book was NOT a new book then.  The
book said that brick dust urine was a normal finding in a newborn, so that is
what I have been teaching to parents since 1975.

In my days as a nursery and post partum nurse, most of them working 20-28
hours a week in a hospital with about 2000 births a year---you can do the
math to figure out how many diapers I have changed!---I saw brick dust urine
in probably one or two diapers a month.  It was something I saw more commonly
than pseudomenses (well of course that would be just in the female
babies...).  The babies I took care of were almost all under 4 days old, and
I don’t recall seeing brick dust in any brand new babies (first 24 hours).  I
saw brick dust urine from bottle babies as well as breastfed babies.  I have
seen it at least once in a quite wet diaper. And several times I saw it as a
pinkish residue on the baby’s bottom and legs but not in the diaper.

In disposable diapers with a lining, the brick dust may collect on the
lining, while the urine that shows in the absorbent material inside the
diaper has no dust.  Get the picture?  The lining acts like a strainer and
catches the dust as the urine passes through.

I spent awhile reading in the hospital library last week.  Here are some
things I learned.

A text on the kidney said, "Most [crystals of many different types] result
from urine concentration, acidification, and ex vivo cooling of the sample
and have little pathologic significance."  This text went on to describe uric
acid crystals in a list of many kinds of crystals.

So…I wonder whether the crystals form after voiding.  Has anyone on the list
ever actually watched a kid peeing pink?

Reading through lists of the signs of dehydration in babies, I did not find
urate crystals mentioned.  As Jan Barger asked---wouldn’t it be listed if it
were a common finding or a definite indicator of trouble?

Looking in several book indexes for uric acid crystals or urate crystals, I
found no mention that their presence indicates any pathology.

Specifically one neonatology text said that "pink urine [due to] the presence
of…uric acid-urate…may be seen in some normal infants."  The same text said
that high urinary concentration and low urine pH lead to an increased risk of
uric acid precipitation, but did not say specifically that this was a
problem.

Fetal urine is hypotonic re plasma; newborn urine is isotonic or hypertonic.
 The fetus produces the amniotic fluid by voiding, and I remember reading
somewhere that this can be up to 500 mL a day!

So…now to the questions.  Consider a kid who in utero has been getting all
the fluid intake it needs and has been voiding a dilute fluid (I hesitate to
refer to it as urine, since the kid is swimming in it and drinking it).  Now
the baby is born, and it will go through a transitional period as it shifts
from getting its fluids IV (through the cord) to getting its fluids PO (by
mouth).  And the first fluid Mother Nature provides is the mother’s
colostrum, which we know is kinda thick in most women.

I have heard an explanation (maybe it’s been here on Lactnet, but I know I
read it elsewhere first) that the relatively concentrated colostrum helps the
baby coordinate the handling of its body fluids during the transition to
extra-uterine life.  Babies seem to be a little OVER-hydrated when they are
born. It certainly looks that way to me, based on this frequent finding: when
a baby is born in a USA hospital, we put a couple of identification bracelets
on the ankles, and we put them on tight enough so we can JUST slip the tip of
a finger underneath.  This is supposed to assure that they are tight enough
to stay on but loose enough not to impede circulation.  And what happens?  By
the next day the bracelets are falling off.  Now, I know that the BRACELET
hasn’t changed its circumference.  Thus, I must assume that the baby’s ANKLE
has gotten smaller, and that a loss of extracellular fluid is the reason.

I also remember reading (in the bygone days when I didn’t take notes and
reference everything) that the concentrated colostrum in the baby’s gut acts
to attract water from the baby’s circulation into the gut; this helps liquefy
the meconium so the baby can pass it more easily. It probably liquefies mucus
in the stomach too.  And moving fluid out of circulation helps with closing
the baby’s ductus.

So…I infer, if these snatches of remembered reading are correct, that the
baby is not SUPPOSED to take in much fluid for a day or two.  It may start
out with a couple of dilute voids, because it’s getting rid of fluid that was
already on board.  And then it may have more concentrated voids until it’s
getting an ample supply of mother’s milk.

A young baby’s normal urinary output, according to a recent pediatric text,
can be as much as 100 mL per kilo per day.  (For comparison, adults put out
40 mL/kg/d.)  That would be 300 mL per day for a 3 kilo kid (10 ounces for a
6.6 pound kid), or 500 mL for a 5 kilo kid (16+ ounces—a pint!--for an 11
pound kid).  These numbers are consistent with the wet diapers we see after
the milk has come in.

But what’s normal for a baby during the transition????  Who has looked at
this?  And if anyone has, which babies have they been looking at?  A lot of
the babies who do get studied seem to be the sick ones.  (Remember that
pediatrics got its start studying babies who were in hospitals because they
or their mothers were sick.)

An interesting aside from my reading was a literature review which said that
97% of babies studied after 1970 voided in the first 24 hours; virtually all
babies had voided by 48 HOA (hours of age).  Why "after 1970?"  Because
before 1970 it was standard practice to limit the feedings given to new
babies in hospital nurseries, so in pre-1970 studies only about 94% of the
kids had voided in the first 24 hours!

What we NEED is for someone to measure intake and output from normal babies.
 You know…NORMAL: born in supportive circumstances without a lot of
intervention, kept skin-to-skin with their mothers, nursing on cue with good
technique.  Then we’d find out more of what we’d like to know.

So my conclusion is that we need to look at more than the diaper when a baby
is voiding pink dusty urine.  If the baby looks fine and is nursing fine, I
wouldn’t worry but I’d follow up.  If the baby doesn’t look well-hydrated or
the milk supply is low or the baby is not nursing fine, I’d pump and feed or
use Brand X, keep the baby skin-to-skin, and follow up.

Thanks for listening.