Let's end with a case.
We have a 42-year old woman, with a history
of pulmonary sarcoidosis and she's seen in clinic
and follow up after her second diagnosis of a kidney
stone at the urgent care center by plain radiographs.
She was told she had a radio-opaque stone in
the left kidney following an episode of left flank pain
that's since resolved with aggressive hydration.
Blood pressure is normal at 128/80,
or a little bit high.
Her cardiopulmonary exam is normal. and
she has no CVA tenderness to percussion.
Her electrolytes, serum creatinine are normal.
Calcium though is marginally elevated 10.6 (mg/dL).
Her phosphorous is normal.
Her urine studies show a high specific gravity, a low pH and
she's got about 3-10 red blood cells per high power field,
and interestingly, you can see crystals
present on your microscopic exam.
And let's note the shape of these, they
almost look like an envelope, don't they?
So before moving on, let's look at things
in this history that are going to be helpful
where we're already kind of thinking or
suspecting a diagnosis in this particular patient.
She has a history of sarcoid, along
with an elevated serum calcium,
suspect for maybe hypercalciuria
and a calcium-based stone.
Her stone is radio-opaque on
an abdominal plain radiograph.
We know it's not uric acid - those are radiolucent.
That low urinary pH along with an envelope-shaped
crystal really favors calcium oxalate stones.
So our next question is, what kind of
additional labs do we want in this patient?
So remember, we're thinking
about calcium oxalate stones.
So a PTH we obtained, it's normal but interestingly,
she had a 1,25 D or calcitriol level that was elevated.
So what next steps should we go to at this point?
We want to do a complete
metabolic evaluation of the urine
given the fact that this patient has recurrent
stones in addition to her thorough dietary history.
So we get a complete metabolic evaluation and
we find that that urine calcium is in fact elevated.
Her urine volume is less than
1.5 liters and her urine pH is low.
Her urine oxalate is normal.
So our question now is what
recommendations can we make for treatment.
So we’d want to talk to her about
generalized treatment for stones.
Remember her urine volume is less than 2 liters, it will
be critical for this patient to increase her fluid intake
so that she can void at least 2 to 2 1/2 liters per day.
We want her to avoid sugary drinks that
can precipitate worsening hypercalciuria.
We want to ensure that she is taking a low
sodium diet - less than 2300 milligrams per day.
Remember that's going to help with hypercalciuria.
And finally, we want to load a
moderate animal protein diet as well.
For specific treatment, we can actually have her take
a thiazide diuretic like chlorthalidone to reduce calciuria.
Remember, her 24-hours urine evaluation showed
that she in particular had high urine calcium levels.
We can have her take potassium
citrate in order to alkalinize her urine
and increase urinary citrate that
will help to chelate or bind calcium.
And finally, we want close monitoring of her
electrolytes and her symptoms through this process.
So, what predispose this patient to forming stones?
Let's think about that and take everything in context
and figure out how we arrived at this particular point.
The patient most likely has calcium
oxalate stones due to the hypercalciuria
from her excessive 1,25-dihydroxyvitamin
D production or calcitriol.
Remember she has sarcoid and sarcoidosis
is a granulomatous disease that can lead to
extrarenal production of calcitriol
by activated macrophages.
So this can lead to abnormal calcium metabolism
including an increase in intestinal absorption,
hypercalcemia and in this case, hypercalciuria.
So excellent job at solving this case,
you've been able to assimilate the information
to arrive at the correct diagnosis and treatment.
In conclusion, remember to be a diligent historian
to conduct a thorough physical exam in your patients
and don't forget to drink water.
With that, we conclude our nephrolithiasis lecture.