Polyuria and hyperosmolar hyperglycemic state

Today we discussed an 80 year old many with polyuria and weakness, found to have a hyperglycemic hyperosmolar state, or HHS (previously HONK).

We discussed the differential diagnosis of polyuria:

If urine osmolarity = (# of particles/urine volume), urine vol must = # of particles/urine osm.

Thus, polyuria is a problem of either too many particles or too low urine osmolarity.

Too many particles:

Glucose in DM

NaCl in people on diuretics or post-ATN or with a salt-wasting nephropathy

Urea in people receiving tube feeds

Too low osmolarity:

Primary polydipsia

Diabetes Insipidus

We also discussed the various causes of diabetes insipidus. See here for a review of DI that highlights these causes nicely.

Lastly we discussed HHS and its management. Patients with HHS are often profoundly volume deplete (up to 10L), with sugars much higher than in DKA. Although some advocate for treatment without insulin, in most situations IV insulin is required or helpful. I can't summarize it better than the great algorithm in this article - see here.