Fractional Excretion of Sodium (FENa)
Differentiates prerenal from intrinsic renal failure
- Highest activation tier
- Recommended
- How it is scored
- Scored in code; a stated value is compared only from the structured summary or a supplied value
- Care settings
- ICU, Inpatient
When it activates
Scribeable activates a calculator from the encounter. The Fractional Excretion of Sodium (FENa) can activate when the transcript or pasted chart context documents any of these:
- AKI evaluation
- Differentiating prerenal vs ATN
- Oliguria workup
- Volume status assessment
A coded diagnosis can also activate it. ICD-10 prefixes carried by the registry: N17.
Note-type scope: it activates on notes whose subject resolves to nephrology, hospital medicine, critical care. A note that resolves to another subject does not carry it even when the clinician's specialty matches; a note with no resolvable subject (a generic consultation) falls back to the specialty match.
Inputs the note needs
4 inputs. Each is resolved from the transcript, the pasted chart context and charted labs; at this calculator’s tier a missing input is never requested, and a missing required input keeps the score out of the draft.
| Input | Type | Unit / options | Guidance |
|---|---|---|---|
| Urine sodium | lab | mEq/L | |
| Plasma sodium | lab | mEq/L | |
| Urine creatinine | lab | mg/dL | |
| Plasma creatinine | lab | mg/dL |
Scoring
FENa = (UNa x PCr) / (PNa x UCr) x 100
FENa = (Urine sodium × Plasma creatinine) / (Plasma sodium × Urine creatinine) × 100
Interpretation
<1%: Prerenal (decreased renal perfusion). >2%: Intrinsic (ATN). 1-2%: Indeterminate. Note: Not reliable on diuretics.
Evidence
Sources carried in Scribeable's citation registry for this calculator.
- Espinel CH. The FENa test: use in the differential diagnosis of acute renal failureEspinel (FENA) 1976 · 1976 · link last verified 2026-03-23
How Scribeable handles it in the note
When an encounter activates the Fractional Excretion of Sodium (FENa) (its highest tier is recommended), Scribeable does not ask you for missing inputs. The score is computed in code from whatever inputs resolve from the transcript, the pasted chart context or charted labs; a computed value is written into the draft only when every required input already resolves.
The score is computed in code from the resolved inputs, not recalled by the language model. A stated Fractional Excretion of Sodium (FENa) value is compared against the computed one when the draft's structured summary carries it; a disagreement found there is flagged to the second drafting pass, which is instructed to correct the score and its interpretation, unless Scribeable has supplied the computed value to that pass, in which case the value the draft writes is checked against the supplied one and a detected difference is shown beside the note for you to adjudicate rather than silently rewritten.
Classified as a deterministic formula: a spare suggestion is easy to ignore, so activation is permissive.
See it activate on your own encounter
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