The lidocaine/monoethylglycinexylidide test is a valuable alternative to protein C activity to determine shunt closure after surgical attenuation of extrahepatic portosystemic shunts in dogs.

The lidocaine/monoethylglycinexylidide (MEGX) test and protein C activity have both been proposed as promising blood tests to determine closure of extrahepatic portosystemic shunts (EHPSS) in dogs. The aim of this study was to compare test performances of both blood tests preoperatively and after gradual surgical attenuation of EHPSS. Firstly, MEGX and glycinexylidide (GX) were determined 15 min after intravenous administration of 1 mg/kg lidocaine in 40 healthy dogs. The 95 % left-sided reference values of MEGX and GX were 16.8 ng/mL (90 % confidence interval (CI): 11.4-22.6) and 8.3 ng/mL (90 % CI: 2.3-14.2), respectively. Subsequently, protein C activity, MEGX and GX concentrations were determined in dogs with EHPSS before surgery, one month (short-term) and minimally three months postoperatively (long-term) at which time also trans-splenic portal scintigraphy was performed to determine EHPSS closure. A total of 41 dogs with EHPSS were included; 31 dogs had closed EHPSS and ten had persisting shunting long-term. Based on the obtained reference values, dogs with persistent shunting could not be differentiated from those with a closed EHPSS with the lidocaine/MEGX test. However, after defining optimal, disease-specific, cut-off values (39.5 ng/mL for MEGX and 29.0 ng/mL for GX), sensitivity to detect persisting shunting was 88.2 % for both MEGX and GX and specificity was 67.7 % for MEGX and 100.0 % for GX. Sensitivity and specificity of protein C activity to detect persistent shunting with a cut-off of < 70 % was 62.0 % and 100.0 %, respectively. Accuracy of GX outperformed accuracy of protein C activity and MEGX to detect persistent shunting in dogs.