André Martin Mansoor
André Martin Mansoor

@AndreMansoor

10 Tweets 5 reads Jul 16, 2024
1/10
A 60 y/o woman presents with subacute, progressive, severe hyponatremia (Na 118).
Let’s walk through an approach to this common problem.
2/10
First we confirm we are dealing with hypotonic hyponatremia.
This begins to narrow our differential.
3/10
Next we want to know the status of extracellular fluid volume. Our patient has low JVP, no peripheral edema, and dry mucous membranes, narrowing our differential even further.
4/10
Is the hypovolemia renal or extrarenal? Urine sodium can be helpful here. Usually in the setting of hypovolemia, urine Na should be very low (usually <10) as the kidneys try to hold on to salt/water to preserve volume.
In our case, urine sodium is unexpectedly high at 34.
5/10
There are a few conditions in which hypovolemic hyponatremia is associated with an unexpectedly high urine Na, because the urine IS the source of the Na/fluid loss.
6/10
Our patient is not on diuretics. But she does have a history of RCC with nephrectomy/adrenalectomy, leaving a solitary adrenal gland. An ACTH stim test is in order.
It's positive (meaning that cortisol did not appropriately rise above 18), confirming adrenal insufficiency.
7/10
Plasma ACTH levels drawn prior to the stim test are elevated, indicating that we are dealing with primary (ACTH-independent) adrenal insufficiency.
8/10
The solitary right adrenal gland is full of tumor (metastases from previously known RCC).
9/10
The cause of our patient’s hyponatremia is adrenal insufficiency secondary to malignant infiltration of the adrenal gland.
10/10
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