The liver has an incredible capacity to recover following an injury. In some patients this can be overwhelmed by autoimmune disease (primary biliary cirrhosis, Wilson’s disease, etc). Others manage to lay waste to their livers through external factors like alcohol consumption, drugs, or a hepatitis virus. Whatever the cause, a number of patients end up with cirrhosis and portal hypertension. To alleviate portal hypertension and bypass the liver, a transjugular intrahepatic portosystemic shunt (TIPS) can be placed. The use of this procedure outside of an emergent setting was controversial in advanced liver disease, and morbidity and mortality benefits over endoscopic or medical management were unknown.
Prior to this study, the Child-Pugh class and scoring system loosely determined when to proceed with a TIPS procedure. While the Child-Pugh system is beneficial for classifying a broader spectrum of liver dysfunction, its shortcomings lie in an inability to distinguish between imminent hepatic failure and cirrhosis that can be managed medically for a few more months. It fails to account for increases in creatinine and kidney failure, which are associated with increased mortality. By using this system, we were performing elective TIPS placement without a proper risk-benefit analysis. This created a scenario in which a perceived improvement in symptoms was traded for increased encephalopathy and worsening liver function.
Malinchoc and colleagues looked at 231 patients who underwent an elective TIPS procedure for recurrent variceal bleeding (75%) or refractory ascites (25%). Of this group, 25 patients were either lost to follow-up or received liver transplants within 3 months and were subsequently excluded from analysis. The authors found that mortality was strongly associated with increases in bilirubin, creatinine, INR and cause of cirrhosis. In fact, in certain situations TIPS had the opposite effect – 3-month mortality increased significantly post-procedure. Using multivariate analysis, the team developed a scoring system and bedside nomogram with these four variables for predicting 3-month mortality post-TIPS placement. Now known as the MELD score, it received praise for a strong concordance (c)-statistic score of 0.87 indicating high clinical accuracy. The basis of this system quickly gave rise to the pediatric liver disease model (PELD), also utilized in a similar fashion. While the scope of the study itself was narrow, the model was found to be generalizable to chronic liver disease and for liver transplant stratification. MELD quickly replaced the 36-year-old Child-Pugh classification for transplant allocation used by the United Network for Organ Sharing (UNOS). This study was a game changer for liver transplant candidates. Patients with the most severe disease, who previously may have been classified as moderate under the Child-Pugh system, moved up in line for a liver transplant. It also provided a means to soundly advise patients and family members on the risks of an elective TIPS, which was no small victory. All together, the MELD study will likely remain the standard for chronic liver disease stratification for years to come.