What is adrenal vein sampling (AVS)?

Adrenal vein sampling (AVS) is a procedure used to determine whether one or both adrenal glands are overproducing aldosterone in patients with primary aldosteronism. Blood is sampled from each adrenal vein and the inferior vena cava (IVC) to calculate the selectivity index (SI), lateralization index (LI), and contralateral suppression index (CSI). The results guide the decision between surgical adrenalectomy and medical management.

How is the Selectivity Index (SI) calculated?

The Selectivity Index (SI) confirms adequate adrenal vein catheterization. It is calculated as adrenal vein cortisol divided by IVC cortisol. Thresholds are ≥2.0 for unstimulated protocols and ≥5.0 for cosyntropin-stimulated protocols per the 2025 Endocrine Society guideline. An SI below the cutoff means the catheter was not correctly seated and lateralization cannot be interpreted.

What does the Lateralization Index (LI) mean?

The Lateralization Index (LI) compares the cortisol-corrected aldosterone (A/C ratio) between the dominant and non-dominant adrenal veins. An LI >4.0 indicates lateralized aldosterone production (unilateral disease). A borderline LI falls between 3.0 and 4.0. An LI below 3.0 suggests bilateral disease. The LI guides whether a patient should be referred for adrenalectomy or managed medically.

What is the Contralateral Suppression Index (CSI)?

The Contralateral Suppression Index (CSI) measures whether the non-dominant adrenal gland's aldosterone production is suppressed relative to the IVC. A CSI less than 1.0 indicates contralateral suppression, supporting unilateral disease. It is used alongside the LI, particularly to support lateralization in borderline cases.

Is this AVS calculator free to use?

Yes. The AVS Calculator is completely free. It runs in your browser with no login, no account, and no subscription required. All calculations are performed locally — no patient data is ever transmitted or stored — making it PHI-safe for clinical use.

Which AVS guidelines does this calculator follow?

The calculator follows the 2025 Endocrine Society Clinical Practice Guideline (Adler et al., J Clin Endocrinol Metab, 2025) for threshold values. Selectivity index cutoffs are ≥2.0 (unstimulated) and ≥5.0 (cosyntropin-stimulated). Lateralization threshold is LI >4.0.

Adrenal Vein Sampling Calculator | Free AVS Interpretation Tool

Please review before using the AVS Calculator

This tool is for use by healthcare professionals only.

It does not provide medical advice, diagnosis, or treatment recommendations.
Calculator outputs must be interpreted by a qualified clinician in the full clinical context — including imaging, biochemistry, patient presentation, and surgical candidacy.
You are responsible for selecting threshold values appropriate to your institutional protocol and clinical context. Different frameworks may yield different classifications.
This calculator should not be used as the sole basis for any clinical decision.
All calculations run locally in your browser. No patient data is transmitted, logged, or stored.

By continuing, you confirm that you are a healthcare professional, you have read and understood the above, and you accept full responsibility for any clinical use of the outputs generated by this calculator.

I am a healthcare professional and I agree to the terms above.

Protocol — choose one to continue

Units

Aldosterone

Cortisol

Data Entry

Inferior Vena Cava (IVC) / Peripheral Peripheral Reference · 0 samples

Sample	Aldo (ng/dL)	Cortisol (µg/dL)	A/C Ratio	Incl.

A/C Ratio Used in Calculation (included samples) ⬌ Toggle any sample off to exclude it. All included samples are averaged per AVS guidelines.

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Right Adrenal Vein Samples · 0 included

Sample	Aldo (ng/dL)	Cortisol (µg/dL)	A/C Ratio	Incl.

A/C Ratio Used in Calculation (included samples) ⬌ Toggle any sample off to exclude it. All included samples are averaged per AVS guidelines.

—

Left Adrenal Vein Samples · 0 included

Sample	Aldo (ng/dL)	Cortisol (µg/dL)	A/C Ratio	Incl.

A/C Ratio Used in Calculation (included samples) ⬌ Toggle any sample off to exclude it. All included samples are averaged per AVS guidelines.

—

Disclaimer: This tool is intended to support — not replace — clinical judgment. It does not provide medical advice, diagnosis, or treatment recommendations, and is not a substitute for consultation with a qualified healthcare provider. Threshold values may vary by institution and protocol. This calculator applies the most widely cited published guideline thresholds, and users may adjust thresholds to match institutional protocol. Results must always be interpreted by a qualified clinician in the context of the patient's full clinical picture, including imaging, biochemistry, comorbidities, and surgical candidacy. This calculator should not be used as the sole basis for clinical decision-making.

Results

Copies a brief summary suitable for pasting into a clinical note

Selectivity Index (SI)

Right SI

○ No data

Left SI

○ No data

Lateralization Index (LI)

LI (Higher A/C ÷ Lower A/C)

○ No data

Contralateral Suppression (CSI)

CSI (Contralateral A/C ÷ IVC A/C)

○ No data

INTERPRETATION LOCKED

Indices (SI, LI, CSI) above are calculated independently of any threshold set. To view a classification verdict, interpretation cards, and generate reports, select a threshold framework and acknowledge responsibility for the choice.

Framework:

Reference Thresholds

SI (unstimulated) ≥ 2.0

SI (cosyntropin-stimulated) ≥ 5.0

LI lateralized > 4.0

LI borderline ≥ 3.0

LI bilateral (derived from borderline) < 3.0

CSI suppression < 1.0

ES Guidelines 2025

References

Adler GK, Stowasser M, Correa RR, et al. Primary Aldosteronism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2025;110(9):2453–2495. doi:10.1210/clinem/dgaf284
Most recent Endocrine Society clinical practice guideline. Primary source for SI, LI, and CSI thresholds used in this calculator (SI ≥2.0/5.0, LI >4.0, borderline 3.0–4.0, CSI <1.0).
Rossi GP, Auchus RJ, Brown M, et al. An Expert Consensus Statement on the Use of Adrenal Vein Sampling for the Subtyping of Primary Aldosteronism. Hypertension. 2014;63(1):151–160. doi:10.1161/HYPERTENSIONAHA.113.02097
Expert consensus on adrenal vein sampling methodology and interpretation criteria.
Vonend O, Ockenfels N, Gao X, et al. Clinical impact of strict criteria for selectivity and lateralization in adrenal vein sampling. Eur J Endocrinol. PMID: 27376419
Retrospective review of 73 AVS procedures validating strict SI and LI cutoffs.

🔒 Privacy & Data

Clinical Report

Select sections to include

For clinician use. This tool supports — but does not replace — clinical judgment. Not medical advice.

Calculations Only

Measured values and derived indices (SI, LI, CSI) — no classification, verdict, or interpretation. No guideline attribution.

Clinical Summary

Measured values, calculated indices, and clinical interpretation

Calculation Worksheet

Full A/C ratio workup and step-by-step index derivation

Patient-Friendly Summary

Plain-language explanation of results for the patient

Selected sections print as a single document with page breaks between them.

Changelog

AVS Calculator — Version History

v1.9 October 2026

Sample include/exclude guidance made more visible — the yellow "Toggle any sample off to exclude it" callout now appears prominently next to each site's averaged A/C result (previously small italic text that was easy to miss)
IVC sample variation now flagged with a prominent red warning when included IVC samples differ by >50% in A/C ratio or cortisol. IVC is the reference denominator for both SI and CSI, so variation flows into every index. The warning suggests which sample to re-examine or toggle off.
Method 2 (Highest Value) methodology corrected — SI calculation now uses cortisol from the same sample whose A/C ratio was selected (previously used max cortisol across all samples, which could flip the cannulation verdict). Derivation table label updated to "Right Cortisol (highest-A/C sample) ÷ Avg IVC Cortisol" to match the new logic.
Index Derivation tables now show intermediate values to 4 decimal places so the shown math reconciles with the shown result (previously 2 decimals meant hand-math wouldn't match due to rounding)
Advanced Report print area corners blanked (@page @bottom-left/right) so the browser's auto URL footer no longer prints at the bottom-left (Clinical Report already had this; Advanced now matches)
Reviewer sign-off placeholder planned for a future release (checkbox + initials on each printed page)
Data-entry Cortisol column header unit label fix — "µg/dL" was rendering as "MG/DL" in the uppercase table headers because CSS text-transform:uppercase converts the micro sign (µ) to Greek capital Mu (Μ), which is visually indistinguishable from Latin M. Clinically dangerous (mg/dL is 1000× µg/dL). Unit text now opts out of the uppercase transform. (The report generators were already safe — they use literal "CORTISOL" strings without CSS uppercase, so µ passed through unchanged.)

v1.8 September 2026

Advanced report restructured — Index Comparison at top, Measured Values shared, then Method 1 (Average) and Method 2 (Highest Value) each as self-contained sections (Calculated Indices, Clinical Interpretation, Calculation Worksheet)
Report page breaks — each major section prints on its own page in both the regular Clinical and Advanced reports
Report popup URLs — switched to blob URLs so the print footer shows the domain instead of about:blank
Patient summary — pre-emptive classification text removed from preview box; replaced with "Patient Summary Free Text" (user-controlled, empty by default); printed finding card appears only if text is typed
Patient summary threshold bug fixed — was using hardcoded SI cutoffs (3.0 stimulated / 2.0 unstimulated), now reads from the active guideline preset so clinical and patient reports stay in sync
Patient summary "results are unclear" — when cannulation falls below the selectivity threshold, patient page now shows a single clear "results are unclear" card with doctor-will-interpret language instead of a misleading "technically successful" statement
Copy Results to Clipboard fixed — was silently failing due to a ReferenceError; now writes the real classification (Lateralized → Right/Left, Borderline, Bilateral, Non-selective) matching the on-screen verdict
Footer: "About This Calculator" link added next to Changelog/Validation/Methods; bottom About section is now collapsible (closed by default)
ARR Calculator link removed from footer

v1.7 May 2026

Classification engine — unified classify() function drives all verdicts from a single source of truth
Removed clinical recommendations — tool now reports findings only, leaves interpretation to clinicians
Customizable patient report — editable preview text carries through to printed patient summary
Advanced report parity — averages, index derivation, threshold column, and dual-method workup (average + highest value)
CSI interpretation now context-aware based on actual LI classification
Validation testing — 8 synthetic datasets covering all classification buckets, viewable from footer
Removed average aldosterone from workup summary rows (not used in any calculation)
Updated all patient-facing text across 6 languages to remove management advice

v1.6 April 2026

App logo — vein branch icon added to header and browser tab favicon
IVC Add Sample button — now consistent with adrenal vein sections
Excluded sample flagging — visual notice when samples are toggled off
Reset All button — more prominent with red hover state
Methods modal — explains SI, LI, and CSI formulas with equations
Cite This Tool modal — APA, AMA, and Vancouver formats with one-click copy
Version number badge on every printed report
Date and time auto-populated on clinical reports and patient summaries
Guideline preset badge on printed report
SEO improvements — meta tags, Open Graph, JSON-LD structured data
Report headers: Adrenal Vein Sampling Calculator on left, avsresults.com on right
About:blank suppressed from report footers
Patient summary page breaks and font size optimized

v1.5 March 2026

Multilingual patient summaries — English, Spanish, Mandarin, Korean, Farsi, Russian
Language pill selector in print modal
SI calculation corrected — now uses adrenal cortisol ÷ IVC cortisol
Calculation worksheet with per-sample averages for aldo, cortisol, and A/C ratio
Report restructured — one page per section with patient label strips
Print layout optimized for single-page sections
Cloudflare Web Analytics added (cookieless)
Copyright notice added
"Endocrine Society" replaced with "ES Guidelines" in labels
Unit label bug fixed — µg/dL no longer renders as mg/dL in reports

v1.4 March 2026

Clinical Report modal with section checkboxes (Summary, Worksheet, Patient Summary)
Single print window with page breaks between selected sections
Patient-Friendly Summary merged into Clinical Report dropdown
Calculation worksheet with index derivation table
Report page order restructured

v1.3 March 2026

Patient-Friendly Summary with plain-language interpretation
PHI removed — patient name/MRN fields replaced with label box
Feedback form via Formspree
Session timestamp in results panel
On-screen interpretation cards
Input validation with shake animation
Outlier warning for samples deviating >50% from section average
Clear section button per vein

v1.2 March 2026

Multi-sample support per vein (up to 8 samples)
Toggle to include/exclude individual samples
Unit conversion — aldosterone (pg/mL, ng/dL, pmol/L) and cortisol (µg/dL, nmol/L, ng/mL)
Cosyntropin-stimulated protocol support
Customizable threshold inputs
Guideline presets — ES 2025 (Adler et al.)

v1.0 March 2026

Initial release
SI, LI, and CSI calculation
IVC, right, and left adrenal vein inputs
Clinical report export

Validation Testing

Classification Engine - May 2026

Eight test datasets were used to verify the classification logic across all four outcome categories (lateralized, borderline, bilateral, non-selective), CSI concordance/discordance, and protocol-dependent SI thresholds. All tests used the ES 2025 guideline thresholds.

Thresholds Used

SI cutoff: ≥ 5.0 (stimulated) / ≥ 2.0 (unstimulated)
LI: > 4.0 lateralized / 3.0–4.0 borderline / < 3.0 bilateral
CSI: < 1.0 = contralateral suppression present

Test	Category	Expected	Actual	Result
1	Lateralized LEFT, CSI concordant	Lateralized LEFT	Lateralized LEFT	PASS
2	Lateralized RIGHT, CSI discordant	Lateralized RIGHT	Lateralized RIGHT	PASS
3	LI boundary — just under 3.0 bilateral cutoff, CSI suppressed	Bilateral	Bilateral	PASS
4	Borderline, CSI not suppressed	Borderline	Borderline	PASS
5	Bilateral	Bilateral	Bilateral	PASS
6	Non-selective (right side fails)	Non-selective	Non-selective	PASS
7	Non-selective (both sides fail)	Non-selective	Non-selective	PASS
8	Protocol toggle (same data)	Stim: Non-sel Unstim: Borderline	Stim: Non-sel Unstim: Borderline	PASS

8 / 8 tests passed

Test Dataset Details

Test 1 — Lateralized LEFT, CSI concordant

Protocol: Cosyntropin-stimulated

Location	Sample	Aldo	Cortisol
IVC	1	60	20
IVC	2	60	22
Right	1	250	250
Right	2	280	270
Right	3	230	230
Left	1	9000	400
Left	2	8500	380
Left	3	9500	420

              IVC avg A/C: 2.86 | Right avg A/C: 1.01 | Left avg A/C: 22.50

              SI Right: 11.90 ✓ | SI Left: 19.05 ✓

              LI: 22.22 | CSI: 0.35 (suppressed)

              Classification: Lateralized LEFT

Test 2 — Lateralized RIGHT, CSI discordant

Protocol: Cosyntropin-stimulated

Location	Sample	Aldo	Cortisol
IVC	1	100	25
IVC	2	95	25
Right	1	8000	300
Right	2	8500	325
Right	3	7800	290
Left	1	1200	250
Left	2	1100	230
Left	3	1300	270

              IVC avg A/C: 3.90 | Right avg A/C: 26.57 | Left avg A/C: 4.80

              SI Right: 12.20 ✓ | SI Left: 10.00 ✓

              LI: 5.54 | CSI: 1.23 (not suppressed)

              Classification: Lateralized RIGHT

Test 3 — LI just below 3.0 bilateral cutoff, CSI suppressed

Protocol: Cosyntropin-stimulated

Location	Sample	Aldo	Cortisol
IVC	1	100	20
IVC	2	100	20
Right	1	750	250
Right	2	780	260
Right	3	720	240
Left	1	3600	400
Left	2	3700	410
Left	3	3500	390

              IVC avg A/C: 5.00 | Right avg A/C: 3.00 | Left avg A/C: 9.00

              SI Right: 12.50 ✓ | SI Left: 20.00 ✓

              LI: 2.9999 (just below the 3.0 borderline cutoff) | CSI: 0.60 (suppressed)

              Classification: Bilateral — confirms strict operator semantics at the LI = 3.0 boundary

Test 4 — Borderline, CSI not suppressed

Protocol: Cosyntropin-stimulated

Location	Sample	Aldo	Cortisol
IVC	1	50	20
IVC	2	55	22
Right	1	1500	450
Right	2	1600	480
Right	3	1400	420
Left	1	4400	400
Left	2	4200	380
Left	3	4600	420

              IVC avg A/C: 2.50 | Right avg A/C: 3.33 | Left avg A/C: 11.00

              SI Right: 21.43 ✓ | SI Left: 19.05 ✓

              LI: 3.30 | CSI: 1.33 (not suppressed)

              Classification: Borderline

Test 5 — Bilateral

Protocol: Cosyntropin-stimulated

Location	Sample	Aldo	Cortisol
IVC	1	80	18
IVC	2	75	20
Right	1	5000	350
Right	2	5200	380
Right	3	4800	320
Left	1	5500	360
Left	2	6000	400
Left	3	5800	380

              IVC avg A/C: 4.10 | Right avg A/C: 14.32 | Left avg A/C: 15.18

              SI Right: 18.42 ✓ | SI Left: 20.00 ✓

              LI: 1.06 | CSI: 3.49 (not suppressed)

              Classification: Bilateral

Test 6 — Non-selective (right side fails)

Protocol: Cosyntropin-stimulated

Location	Sample	Aldo	Cortisol
IVC	1	100	25
IVC	2	90	25
Right	1	110	30
Right	2	105	28
Right	3	95	32
Left	1	4000	300
Left	2	4200	320
Left	3	3800	280

              IVC avg A/C: 3.80 | Right avg A/C: 3.46 | Left avg A/C: 13.34

              SI Right: 1.20 ✗ | SI Left: 12.00 ✓

              Classification: Non-selective (right side)

Test 7 — Non-selective (both sides fail)

Protocol: Cosyntropin-stimulated

Location	Sample	Aldo	Cortisol
IVC	1	80	30
IVC	2	85	28
Right	1	95	40
Right	2	100	38
Right	3	90	42
Left	1	110	50
Left	2	115	48
Left	3	105	52

              IVC avg A/C: 2.85 | Right avg A/C: 2.38 | Left avg A/C: 2.21

              SI Right: 1.38 ✗ | SI Left: 1.72 ✗

              Classification: Non-selective (both sides)

Test 8 — Protocol toggle (same data, different classification)

Location	Sample	Aldo	Cortisol
IVC	1	100	20
IVC	2	100	20
Right	1	300	50
Right	2	320	52
Right	3	280	48
Left	1	5000	250
Left	2	5200	260
Left	3	4800	240

              SI Right: 2.50 | SI Left: 12.50 | LI: 3.34 | CSI: 1.20

              Cosyntropin-stimulated (SI cutoff ≥ 5.0): SI Right fails → Non-selective

              Unstimulated (SI cutoff ≥ 2.0): SI Right passes → Borderline

Test datasets used synthetic values within typical clinical ranges for AVS. Validated against ES 2025 guideline thresholds.

Calculation Methods

All calculations are performed locally in your browser. No data is transmitted or stored.

Selectivity Index (SI)

Confirms adequate adrenal vein catheterization. Calculated as adrenal vein cortisol divided by IVC cortisol:

SI = Adrenal Vein Cortisol ÷ IVC Cortisol

Thresholds: ≥2.0 (unstimulated) or ≥5.0 (cosyntropin-stimulated) per ES Guidelines. If multiple samples are entered, cortisol values are averaged across included samples before division.

Lateralization Index (LI)

Compares cortisol-corrected aldosterone (A/C ratio) between the dominant and non-dominant adrenal veins:

LI = (Dominant Aldo ÷ Dominant Cort) ÷ (Non-Dominant Aldo ÷ Non-Dominant Cort)

A/C ratios are calculated per sample first, then averaged across included samples. The side with the higher average A/C ratio is designated dominant. Threshold: >4.0 per ES Guidelines.

Contralateral Suppression Index (CSI)

Assesses suppression of aldosterone in the non-dominant gland relative to IVC:

CSI = (Non-Dominant Aldo ÷ Non-Dominant Cort) ÷ (IVC Aldo ÷ IVC Cort)

A CSI <1.0 indicates contralateral suppression, supporting unilateral disease. Used in conjunction with LI.

Multi-Sample Averaging (Main Calculation / Clinical Report)

When multiple samples are entered for a vein, A/C ratios are calculated for each sample individually (Aldo ÷ Cort per sample), then averaged across included samples. This preserves per-sample accuracy and is consistent with published multi-sample AVS methodology. Excluded samples are omitted from all averages.

Advanced Report — Method 2: Highest Value

The Advanced Report shows a sensitivity-analysis comparison of two methods side-by-side. Method 1 is the standard averaging approach described above. Method 2 selects the single sample with the highest A/C ratio from each adrenal vein (its cortisol also feeds that side's SI calculation, so both indices use the same sample). IVC cortisol is still averaged across all included IVC samples — as the peripheral reference, IVC lacks a biological "highest A/C" criterion. Comparing the two methods can help identify whether a single outlier sample is driving a lateralization result.

Guideline References

Adler GK et al. J Clin Endocrinol Metab. 2025;110(9):2453–2495.
Rossi GP et al. Hypertension. 2014;63(1):151–160.

Selectivity Index (SI)

Lateralization Index (LI)

Contralateral Suppression Index (CSI)

Multi-Sample Averaging (Main Calculation / Clinical Report)

Advanced Report — Method 2: Highest Value

Guideline References

APA

AMA

Vancouver