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title: 星期天值日生：Clinical problem solver episode 194

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# 星期天值日生：Clinical problem solver episode 194
# Polyuria
[Podcast連結](https://clinicalproblemsolving.com/2021/08/18/episode-194-schema-polyuria/?fbclid=IwAR0Bw9MZkY8-IxhLRlX7S5_txKobTnhUABCI7z8n5iOqAVPGKI8WdoPiB60)

32 y/o female presented with 3 days Hx of worsening global headache w/o Nausea or vomiting, visual disturbance, local weakness, also present with polyuria with nocturia every 2 hours, pass 4 L urine/day
PE: BP: 150/79, Pulse: 85, RR:17 on room air, Dry mucosa, other normal
UA: gravity 1.005, w/o blood and protein
Na : 152 mmol/dL,
Urine osmolarity : 175 mOsm/kg H2O, Serum osmolarity : 308 mOsm/kg H2O

# Polyuria
* Definition: > 3 L/days (adult) or 2 L/m2/day (child)
* Etiology:
    * Osomotic diuresis: excess urine solute, Uosm: normal / elevated
        Ex: Glycosuria/mannitol/ increase IV saline (increase Na intake)
    * Water diuresis: excess urine water, Uosm: decreased
        * Ability to concentrate urine? =ADH function? Take water deprivation test
            1. Primary polydipsia: able to concentrate urine (increase Uosm after water deprivation)
            2. Diabetes insipidus: not able to concentrate urine
        * copeptin test, conpeptin stimulation test/ ddAVP response
            1. central: ADH deficiency—decreased copeptin/response to ddAVP
            2. nephrogenic: ADH resistance—elevated copeptin/unresponse to ddAVP
# Hypernatremia
## Normal Pathophysiology: elevated Na->hypothalamus
Increase water consumption (thirst)
Increase water retention (elevated ADH)
## Etiology
1. Decrease free water intake: NPO, desert/ critical ill, dementia/ decrease in thirsty (hypodipsia, adipsia: possible hypothalamus lesion)
2. Increase water loss or have difficulty of water retention
    able to compensate with increase free water intake
    1. Renal:DI
    2. Extra-renal (GI:diarrhea/Skin: sweats)
3. Increase intake of hypertonic fluid: sodium bicarbonate/hypertonic saline/seawater ingesting
# Clinical reasoning in this case
* True polyuria (4L/D), with low Uosm(175) : water diuresis
* Combine with hypernatremia (Na:152)
* Favor diabetes insipidus
* CT: enlarged pituitary gland
* Response to intra-nasal ddAVP : Central DI
# Clinical pearls
* 當病人呈現frequency of urination時，需注意total urine volume。Polyuria output 會增加，urgency, frequency or hesitancy則不會有urine volume的改變。
* Polyuria 病人合併hypernatremia時，未必需要再進行water depredation test。Hypernatremia 已是water depredation的狀態，ADH會上升，但是Uosm卻仍低，表示是DI。
* 反之，Polyuria若Na正常可能是free water intake有compensate。
* Copeptin 是AVP prohormone 的一部分，c/w 循環中的AVP。不過Copeptin相較於AVP較穩定。
* 補充：https://www.nature.com/articles/nrendo.2015.224
* https://medium.com/nephrology/%E9%AB%98%E9%9B%84%E5%A4%9C%E6%9C%AA%E7%9C%A0-da36074f08b7
![](https://i.imgur.com/Ux8EmqW.png)

# 個人心得
聽完這個case覺得以後聽到解尿頻率增加時，要特別去留意尿量的變化，尿量好像要記I/O才能比較掌握，一開始病人好像很難從症狀很客觀的告訴我們尿量的變化?
