The donor terrain around your transplant center.

What is MMAT, and why "topography"?

MMAT — Median MELD at Transplant — is a single number per donor hospital that summarizes the typical acuity of patients who received livers procured from that hospital during a recent cohort window. A donor hospital with MMAT 22 tells you the typical recipient of its organs was at MELD 22 — meaning even patients at relatively lower acuity were reaching transplant from its supply. A donor hospital with MMAT 35 tells you only patients near the top of the MELD ladder were reaching transplant from its supply.

Lay those MMAT values out across every donor hospital inside a transplant center's acuity circles and the result behaves like a topographic map. The valley floors are donor hospitals with low MMAT — where supply was abundant relative to demand, and lower-MELD patients reached transplant. The ridges and peaks are donor hospitals with high MMAT — where supply was scarce relative to demand, and the offer queue cleared only sick-enough candidates. Plains are the middle.

The weather/terrain framing is more than decoration. It mirrors how a glass-cockpit avionics suite (G1000-class) presents flight information: not as a wall of independent gauges (airspeed, attitude, fuel, terrain, weather), but as a single integrated picture you can read in one glance. The same intent applies here. Instead of staring at donor count + median wait + MELD-at-transplant + region as separate instruments, the terrain shows the whole picture.

The five terrain bands

• Deep valley. MMAT in the lowest band. Lower-MELD patients reached transplant from this donor hospital's offers. From a candidate's perspective, donors classified here are the "easy ground" — abundant relative to local demand.
• Valley. Below-average MMAT. Still favorable for lower-MELD candidates, but not as low as the deep valleys.
• Plain. Mid-range MMAT, roughly the national median. The "normal terrain" of U.S. liver transplant.
• Ridge. Above-average MMAT. Donors here were absorbed by sicker candidates; lower-MELD candidates faced a harder climb to reach those offers.
• Peak. Highest MMAT band. Donors classified here cleared only the most acutely ill candidates in the local queue. From a candidate's perspective, donors classified here are the "hardest ground" — scarce relative to demand.

The MMAT topography of the United States

Below is the live MMAT pressure field painted across the full United States — continental, Alaska, Hawaii, and Puerto Rico — as a true synoptic chart. The donor-hospital MMAT values are interpolated across the country (inverse-distance weighted, masked to the land within donor reach) and rendered as isobands (filled bands between the canonical band thresholds: deep_valley ≤ 27, valley 28–29, plain 30, ridge 31–32, peak ≥ 33) plus isolines (integer-MMAT contour lines, bold at multiples of five — the cartographic convention NWS uses for surface pressure). Each band is extruded in 3D, so peaks literally rise above valleys, on top of the USGS digital elevation model published by Mapbox. Drag to rotate; scroll to zoom; use the CONUS · AK · HI · PR buttons on the right to jump between regions. Tap any donor pin to draw its 150 / 250 / 500 nautical-mile acuity rings on the terrain.

For raw donor counts inside each circle (numeric, sortable), see Donor Supply by Center.

Per-state summary

A state-level rollup of the inner (150-NM) circle terrain across that state's adult liver transplant programs. Useful as a quick-read when you don't yet have a specific listing center in mind. Each card shows program count, total donor catchment, and the average median MMAT inside the 150-NM circle across that state's programs.

How to read this map

The base layer is the real geographic terrain of the United States from the USGS digital elevation model. The Rockies rise, the Great Plains stretch flat, the Appalachians ridge along the East. That terrain is just orientation — it tells you where you are, not where the MELD pressure is.

The painted layer on top is the MMAT topography. Each donor hospital is a sample point with one number — its Median MELD at Transplant — and the heatmap renders those samples as a continuous surface. Blue regions are valleys: clusters of donor hospitals where lower-MELD candidates reached transplant. Red regions are peaks: clusters where only the sickest candidates cleared the offer queue. Plains are the national middle. The terrain is not predictive — it is a descriptive cross-section of the most recent SRTR cohort.

Two patients in the same state can sit in very different MMAT terrain. A patient listed at a center inside a blue valley sees a different supply environment than a patient listed at a center on a red ridge — even if the two centers are 200 miles apart. The acuity rings let you visualize that mechanically. Click any donor hospital on the map and the three nested rings (150 / 250 / 500 NM — purple for a donor, green for a center) appear around it — that is the literal geographic catchment used by OPTN's 2020 allocation policy. A donor hospital in eastern Tennessee draws very different circles than one in central Texas.

Important caveat about reading terrain: a peak-heavy region does not mean every patient there will wait a long time. It tells you historically only sicker candidates reached transplant from that supply — which could mean the candidate list at local centers was sicker, the local OPO was generally more conservative, or supply genuinely thinned out for low-MELD offers. Pair what you see on the map with center-level patient-volume data on Compare Centers to decide what the terrain is telling you about your situation specifically.

Limits and methodology notes

• MMAT is published per donor hospital by SRTR for a rolling cohort window. The bands shown here are derived by classifying each donor hospital into one of five MMAT tiers calibrated to the national distribution.
• Topography reflects historical cohort outcomes (March 2025 – February 2026 in the current snapshot). It is descriptive, not predictive. Allocation policy, patient mix, and donor supply can shift the terrain between cohort windows.
• Donor hospitals with very low recent volume contribute to the count but have noisier MMAT estimates. Centers with predominantly small donor hospitals in their inner circle will have terrain bars that should be read with that volume context.
• Status-1 candidates are nationally eligible and not subject to the acuity-circle ordering; their outcomes do not factor into the band a candidate at lower listing acuity would actually face.
• Pediatric allocation rules differ. This page covers adult programs.