{"uid":"cap_fhslXtNBxYAhNpgvD2rin","slug":"fena-calculator-fractional-excretion-of-sodium-60af7850","name":"FENa Calculator (Fractional Excretion of Sodium)","description":"Fractional excretion of sodium (FENa) from plasma and urine sodium and creatinine. Espinel 1976 oliguric ARF strata. Deterministic published formula with citation; not a diagnosis.","url":"https://api.magentlab.com/api/calc/fena","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET","HEAD","DELETE"],"type":"string"},"headers":{"type":"object","additionalProperties":{"type":"string"}},"queryParams":{"type":"object","required":["sodium_mmol_l","urine_sodium_mmol_l"],"properties":{"sodium_mmol_l":{"type":"number","description":"Plasma or serum sodium in mmol/L (110-160)."},"creatinine_mg_dl":{"type":"number","description":"Plasma creatinine in mg/dL (0.1-20). Provide this or creatinine_umol_l."},"creatinine_umol_l":{"type":"number","description":"Plasma creatinine in µmol/L (9-1768). Converted as mg/dL = µmol/L / 88.42."},"urine_sodium_mmol_l":{"type":"number","description":"Urine sodium in mmol/L (1-300)."},"urine_creatinine_mg_dl":{"type":"number","description":"Urine creatinine in mg/dL (1-500). Provide this or urine_creatinine_umol_l."},"urine_creatinine_umol_l":{"type":"number","description":"Urine creatinine in µmol/L (88-44210). Converted as mg/dL = µmol/L / 88.42."}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object"}}}}},"responseSchema":{"type":"json","example":{"path":"/api/calc/fena","count":2,"items":[{"formula":"fena","citation":{"id":"espinel-1976","doi":"10.1001/jama.1976.03270060029022","title":"The FENa test. Use in the differential diagnosis of acute renal failure","source":"JAMA. 1976;236(6):579-581","authors":"Espinel CH"},"disclaimer":"Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.","fena_percent":0.29,"sodium_mmol_l":140,"espinel_stratum":"prerenal","creatinine_mg_dl":2,"formula_expression":"FENa_percent = 100 * (urine_sodium_mmol_l * plasma_creatinine_mg_dl) / (plasma_sodium_mmol_l * urine_creatinine_mg_dl)","urine_sodium_mmol_l":20,"urine_creatinine_mg_dl":100},{"formula":"fena","citation":{"id":"espinel-1976","doi":"10.1001/jama.1976.03270060029022","title":"The FENa test. Use in the differential diagnosis of acute renal failure","source":"JAMA. 1976;236(6):579-581","authors":"Espinel CH"},"disclaimer":"Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.","fena_percent":0.29,"sodium_mmol_l":140,"espinel_stratum":"prerenal","creatinine_mg_dl":2,"formula_expression":"FENa_percent = 100 * (urine_sodium_mmol_l * plasma_creatinine_mg_dl) / (plasma_sodium_mmol_l * urine_creatinine_mg_dl)","urine_sodium_mmol_l":20,"urine_creatinine_mg_dl":100}]}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_FWT5fDTRzC8GIXOijBMD2","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes fractional excretion of sodium (FENa%) from plasma sodium, urine sodium, plasma creatinine, and urine creatinine using the Espinel 1976 formula for oliguric acute renal failure stratification.","exampleAgentPrompt":"Calculate FENa for my patient with oliguria: plasma sodium is 138 mmol/L, urine sodium is 18 mmol/L, serum creatinine is 2.4 mg/dL, and urine creatinine is 120 mg/dL — what does the Espinel 1976 stratification say?","exampleUseCases":[{"title":"Prerenal vs intrinsic AKI triage","prompt":"My ICU patient has new oliguria — serum sodium 141 mmol/L, urine sodium 12 mmol/L, serum creatinine 3.1 mg/dL, urine creatinine 85 mg/dL. Calculate the FENa and tell me if it's consistent with prerenal AKI by Espinel criteria."},{"title":"Nephrology consult documentation","prompt":"I need the FENa value for my consult note: plasma Na 136 mmol/L, urine Na 45 mmol/L, plasma creatinine 310 µmol/L, urine creatinine 6200 µmol/L. Please compute it with the 1976 formula."},{"title":"Automated renal panel interpretation","prompt":"Run the FENa calculation on these labs — serum sodium 139 mmol/L, spot urine sodium 8 mmol/L, serum creatinine 1.8 mg/dL, urine creatinine 200 mg/dL — and flag whether this suggests low or high fractional excretion."}],"resultDescription":"Returns the computed FENa percentage along with the Espinel 1976 oliguric ARF stratum (e.g., prerenal vs. intrinsic renal failure classification), based on the deterministic published formula. Not a clinical diagnosis.","failureModes":["Missing required parameter sodium_mmol_l or urine_sodium_mmol_l returns 400 error","No creatinine value provided (neither mg/dL nor µmol/L for plasma or urine) returns validation error","Values outside physiologic ranges (e.g. sodium < 110 or > 160 mmol/L) may be rejected","Both creatinine unit variants provided simultaneously may cause ambiguity"],"whenToPreferThis":"Use this endpoint when you need a deterministic, citation-backed FENa calculation (Espinel 1976) for oliguric ARF stratification and want automatic unit conversion between mg/dL and µmol/L for creatinine inputs. Prefer over manual calculation or LLM-estimated values when reproducibility and published-formula fidelity matter.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T13:15:30.978Z","isFirstParty":false}