Interactions between virus-related factors and post-transplant ascites in patients with hepatitis C and no cirrhosis: role of cryoglobulinemia

Approach to persistent ascites after liver transplantation

Persistent ascites (PA) after liver transplantation (LT), commonly defined as ascites lasting more than 4 wk after LT, can be expected in up to 7% of patients. Despite being relatively rare, it is associated with worse clinical outcomes, including higher 1-year mortality. The cause of PA can be divided into vascular, hepatic, or extrahepatic. Vascular causes of PA include hepatic outflow and inflow obstructions, which are usually successfully treated. Regarding modifiable hepatic causes, recurrent hepatitis C and acute cellular rejection are the leading ones. Considering predictors for PA, the presence of ascites, refractory ascites, hepato-renal syndrome type 1, spontaneous bacterial peritonitis, hepatic encephalopathy, and prolonged ischemic time significantly influence the development of PA after LT. The initial approach to patients with PA should be to diagnose the treatable cause of PA. The stepwise approach in evaluating PA includes diagnostic paracentesis, ultrasound with Doppler, and an echocardiogram when a cardiac cause is suspected. Finally, a percutaneous or transjugular liver biopsy should be performed in cases where the diagnosis is unclear. PA of unknown cause should be treated with diuretics and paracentesis, while transjugular intrahepatic portosystemic shunt and splenic artery embolization are treatment methods in patients with refractory ascites after LT.

Five myths about variable selection

Multivariable regression models are often used in transplantation research to identify or to confirm baseline variables which have an independent association, causally or only evidenced by statistical correlation, with transplantation outcome. Although sound theory is lacking, variable selection is a popular statistical method which seemingly reduces the complexity of such models. However, in fact, variable selection often complicates analysis as it invalidates common tools of statistical inference such as P-values and confidence intervals. This is a particular problem in transplantation research where sample sizes are often only small to moderate. Furthermore, variable selection requires computer-intensive stability investigations and a particularly cautious interpretation of results. We discuss how five common misconceptions often lead to inappropriate application of variable selection. We emphasize that variable selection and all problems related with it can often be avoided by the use of expert knowledge.