Fractional Excretion of Sodium (FENa)

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

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.

Scoring

FENa = (UNa x PCr) / (PNa x UCr) x 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.

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Can activate in: Internal Medicine, Hospital Medicine, Critical Care / ICU.