Model for End Stage Liver Disease Na Calculator

MELD-Na exists to solve a specific allocation problem: donor livers are scarce, and organ procurement organizations need a single continuous number to rank every candidate on the waiting list by short-term mortality risk, regardless of diagnosis. The three original MELD labs each capture a different organ system in failing cirrhosis — creatinine reflects hepatorenal impairment, INR reflects the liver's clotting-factor synthetic capacity, and bilirubin reflects excretory/cholestatic function — and the logarithmic weighting means each successive point of derangement in any of the three carries increasing marginal risk, which mirrors the accelerating mortality curve actually seen in decompensated cirrhosis. Hyponatremia was added in 2016 because sodium independently predicts death in cirrhosis through a separate mechanism: it reflects the severity of neurohormonal activation (RAAS and ADH) driving ascites and hepatorenal syndrome, information the original three labs do not capture. Adding bounded sodium (125-137 mEq/L) improved 90-day waitlist mortality prediction enough that UNOS replaced plain MELD with MELD-Na as the U.S. liver allocation standard. Scores are capped at 40 because above that level, 90-day mortality without transplant approaches 100% regardless of the exact number, and the score's clinical role shifts from risk-ranking to urgent-listing.

The original model was developed by Malinchoc and colleagues at the Mayo Clinic in 2000, not for transplant allocation at all but to predict survival after elective TIPS (transjugular intrahepatic portosystemic shunt) placement for portal hypertension. Patrick Kamath and the Mayo group validated it the following year as a general short-term mortality predictor across a broad range of liver disease etiologies, and its strong performance prompted the United Network for Organ Sharing (UNOS) to adopt MELD as the U.S. liver allocation standard in February 2002, replacing the older Child-Turcotte-Pugh score and its subjective components (ascites and encephalopathy graded by exam rather than lab values). W. Ray Kim and colleagues demonstrated in a landmark 2008 New England Journal of Medicine study that adding serum sodium meaningfully improved prediction of 90-day waitlist mortality beyond MELD alone, building on earlier work by Scott Biggins in Gastroenterology (2006) that first proposed incorporating sodium. OPTN/UNOS formally implemented MELD-Na as the national liver allocation score in January 2016, and it has since been adapted internationally, with several countries maintaining their own regional variants of the sodium-adjusted formula.