💧 Osmolar Clearance (Cosm)
UseWhen to use: renal concentrating/diluting workups with measured osmolalities and urine flow.
StrataCosm is the plasma volume cleared of osmoles per time; CH₂O = V − Cosm.
LimitsWhen not to use: calculated osm instead of measured when gap matters. · Pitfall: flow unit errors. · Teaching adjunct.
SourceStandard osmolar clearance definition
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
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Methodology · worked example, guidelines & full notes
(Uosm×V)/Posm.
When to use
When to use: renal concentrating/diluting workups with measured osmolalities and urine flow.
How it works
Cosm = (Uosm × V) / Posm.
Key points
- (Uosm×V)/Posm.
- Pairs with CH₂O.
- Next: Na/K context.
References
- Standard osmolar clearance definition
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Urine osmolality | 400 mOsm/kg |
|---|---|
| Plasma osmolality | 290 mOsm/kg |
| Urine flow rate | 1.5 mL/min or L/day |
| Flow unit | mL/min |
→Cosm2.07mL/min
- CH₂O：-0.57 mL/min
- V used：1.50 mL/min
- Uosm/Posm：1.38
| Urine osmolality | 400 mOsm/kg |
|---|---|
| Plasma osmolality | 290 mOsm/kg |
| Urine flow rate | 1.5 mL/min or L/day |
| Flow unit | L/day |
→Cosm1.44mL/min
- CH₂O：-0.40 mL/min
- V used：1.04 mL/min (from L/day)
- Uosm/Posm：1.38
Verification & sources · governance
FAQ
Frequently asked questions
- Does Osmolar Clearance (Cosm) upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is Osmolar Clearance (Cosm) calculated in practice? Can you show a worked example?
- Inputs: Urine osmolality 400 mOsm/kg, Plasma osmolality 290 mOsm/kg, Urine flow rate 1.5 mL/min or L/day, Flow unit mL/min → Result: Cosm 2.07 mL/min（CH₂O: -0.57 mL/min, V used: 1.50 mL/min, Uosm/Posm: 1.38） Inputs: Urine osmolality 400 mOsm/kg, Plasma osmolality 290 mOsm/kg, Urine flow rate 1.5 mL/min or L/day, Flow unit L/day → Result: Cosm 1.44 mL/min（CH₂O: -0.40 mL/min, V used: 1.04 mL/min (from L/day), Uosm/Posm: 1.38）