In this talk we're going to discuss diabetes insipidus and SIADH.
This is a problem with too little and too much antidiuretic hormone.
So let?s remember about antidiuretic hormone sometimes called vasopressin.
This is secreted by the posterior pituitary,
it causes an insertion of aquaporin
into the distal collecting duct of the kidney.
Remember that collecting duct, the tissue around it is very concentrated,
so when those aquaporin are placed in
the water will resorbed out of the urine.
Antidiuretics hormone concentrates the urine.
So diabetes insipidus is a problem whether is decreased ADH secretion
from the posterior pituitary.
That is called central DI or central diabetes insipidus.
This can be cause from a damaged hypothalamus or a posterior pituitary.
There's a lots of conditions that can do this,
unusual ones like Wegener?s granulomatosis
which you would see in the patient
who has a coughing up blood and it's urinating blood.
Sometimes it happens in the newborn
who have problems around the birthing period
or gonna happen in patients with sickle cell disease
or with other risk of clots forming inside the brain
or could happen with trauma.
Alternatively, patients could have nephrogenic diabetes insipidus.
In this case they have the ADH being secreted by the posterior pituitary
but the problem is the kidney isn't responding to it.
So either one of these problems
is gonna result in excessive urination
and that excessive urination leads a patient to develop a high sodium,
and it's the high sodium that gets patients in trouble.
So let?s look drill down on causes of central diabetes insipidus.
We see it commonly in children
with significant developmental abnormalities of the brain.
We'll see it in patients with injury to their hypothalamus,
or their pituitary gland, patients with pituitary tumors.
A patient with meningitis or encephalitis
may develop damage to their pituitary gland.
Rarely things like Wegener?s or histiocytosis,
there can be some rare genetic syndromes
where patients develop diabetes insipidus.
This is familial diabetes insipidus and of course after brain surgery.
This is to be compared differently to patients who have nephrogenic DI.
There are genetic receptor or aquaporin mutations that exist in the community.
Patients with chronic renal disease may develop in nephrogenic DI
and certainly renal malformations of the patient
has a bad bilateral vesicoureteral reflux for example
they may develop nephrogenic DI.
Also remember medications
and if it's on your test it's gonna be lithium.
Lithium which is treated usually, use to treat bipolar disease
and other psychiatric conditions
has the consequence of nephrogenic diabetes insipidus.
There's others that do as well though like amphoteracin
which has such bad side effects,
sometimes we just call it amphoterrible.
Clozapine which is an antipsychotic
and foscarnet which is an antiviral for cytomegalovirus.
I've never use foscarnet in my career,
it's very rare to use that in children
but all of these are the medicines
that are accused of causing nephrogenic diabetes insipidus.
So regardless of whether it's central or nephrogenic,
how does diabetes insipidus present?
Well, quite simply they pay a lot.
These patients are gonna have significant polyuria
and if they're cognitively intact will accommodate that by having polydipsia.
They're going to be drinking a lot.
In patients with significant brain disease
who can't mount thirst or lack the ability to drink for themselves.
It's common for them to present with severe dehydration
because they aren't able to regulate their own water level inside their blood.
These patients have a challenge, very challenging to take care of.
So look for signs of systemic diseases as well
that might be resulting in DI.
For example, Wegener?s.
Central DI after surgery or trauma is interesting
and it may come upon a test
that there's a classical triple phase response to trauma and surgery.
We think they're going to have a problem
suddenly we feel like it's all turned out okay
and then we discover they do in fact have a problem.
So after the surgery from maybe one to four days,
patients will have, in a sense a stunned, the posterior pituitary.
It does not want to release antidiuretic hormone,
so these patients will have a polyuric phase they will be peeing frequently.
Then that stored ADH that was there prior to the damaged
to the pituitary or the hypothalamus, suddenly is released
and these patients will have a period
when they are less polyuric or they're peeing normally.
After that as they are now no longer to permanently make ADH
they go back into their polyuric phase
then we call this the antiuretic phase.
So just remember these three phases
in particular for patients who had trauma to the pituitary gland
or if had surgery.
So causes of diabetes insipidus and the symptoms they might be having,
CNS tumors patients may present with morning headaches,
visual changes, or poor school performance.
For Wegener?s disease they'll present with hemoptysis and hematuria.
For vascular injuries especially in sickle cell patients
will know they have sickle cell,
they'll have all the findings of pain crisis
and all the other problems that occur.
Also patients who are hypercoagulable who have a vascular injury,
may have clots and other problems as a result of their hypercoagulability.
In neonates often times there's a story of a bad peripartum experience.
Let's fix [inaudible], whether incapable of breathing well
and that cause the central neuronal injury of the pituitary gland.
Patients with congenital hypopituitarism
typically present with other problems
as well related to their pituitary gland.
They may develop hypoglycemia or micropenis,
as a result of problems with their HPA access.
And then with patients with familial diabetes insipidus
we would expect to hear a family history
that the parent or someone related to them also has that condition.
So in patients with an intact thirst mechanism,
the diagnosis of the disease is largely through a history
because these patients are drinking adequately
to maintain a normal serum sodium and normal labs.
However, if we are going to test for diabetes insipidus
we will typically measure serum and urine osmolality.
In a patient with uncheck diabetes insipidus
we expect high serum osms of more than 300
and low urine osms with the dilute urine.
If we are unclear if they have diabetes insipidus
or some other problems say, psychogenic polydipsia
we may do a water deprivation test.
In patients with DI, a water deprivation test is dangerous
these patients can dehydrate very quickly.
So we need to watch them very carefully in a controlled in-patients setting
when we stop them from drinking
and measure serially their blood levels of sodium
to make sure they're not getting in too much trouble.
In patients where we suspect something might be wrong with pituitary
an MRI of the brain with pituitary cut downs
like you can see in this patient here
with an abnormality of their pituitary gland is indicated.
If a patient has DI we're simply treating it with oral hydration.
Children who can't regulate their own drinking
are in grave danger and we worry about it.
If a patient has central DI they'll be responding to administer DDAVP.
So we can give DDAVP in two different ways,
we can administer it nasally as a spray or we can give it orally.
The nasal medication is rapid onset
chronically it can cause some damage to the oral mucosa
and as a result, it's not a particularly good way
to start off the drug for infants.
Orally, it's a little bit slower onset, there's variable GI absorption
so we have to track these children
and see how they're responding to the drug.
It's a lot easier for parents to administer to infants.
SubQ or IV DDAVP is available but only really use if a patient
is unable for some reason to take it either orally or nasally.