Postoperative course of C-reactive protein level after liver surgery-when to worry?

Background: C-reactive protein (CRP) level is an established marker to detect inflammation and infectious complications after surgical procedures, but its use after liver surgery has not been well investigated. This study aimed to elucidate the role of CRP level after elective liver resection and to determine baseline values for a normal postoperative course, as well as the role of CRP level as a predictor of postoperative complications. Methods: All liver resections performed between January 2008 and December 2023 were identified. Patients' characteristics, intraoperative data and postoperative outcomes were analyzed. Postoperative surgical complications within 90 days were graded using the Clavien-Dindo classification system. The postoperative CRP values from postoperative day (POD) 1 to 10 were included. Results: In total, 3,177 liver resections were identified during the study period, of which 85.1% (2,705) were performed for malignant liver disease. In 1,647 (51.8%) cases, there were no postoperative complications. The median CRP level in cases without complication (baseline) was 55 mg/L on POD 1, 130 mg/L on POD 2, 128 mg/L on POD 3, 101 mg/L on POD 4, 80 mg/L on POD 5, 70 mg/L on POD 7 and 120 mg/L on POD 10. The percentage of cases who suffered complications (highest grade) was 7.3% (n=232) with grade I, 14.5% (n=462) grade II, 14.5% (n=461) grade IIIa, 4.2% (n=132) grade IIIb, 3.7% (n=117) grade IVa, 0.4% (14) grade IVb, and 3.5% (n=112) with grade V complications. Infectious complications occurred in 28.9% (n=919) and severe infectious complications (≥ grade IIIa) in 20.4% (n=648) of the cases. The median CRP values in cases with infectious complication were significantly higher on POD 1 (59 mg/L; P=0.01), POD 2 (143 mg/L; P<0.001), POD 3 (164 mg/L; P<0.001), POD 4 (149 mg/L; P<0.001), POD 5 (134 mg/L; P<0.001) and POD 7 (114 mg/L; P=0.043). In multivariate analysis, only elevated CRP values on POD 5 (P=0.003) were predictors for infectious complications. The AUC for POD 5 was the highest at 0.72 and presented the highest predictive accuracy. The optimal cut-off value for CRP level POD 5 was 93 mg/L. The positive and negative predictive values (PPV/NPV) for the cut-off value POD 5 were 79.6% and 87.6%, respectively. Conclusions: Postoperative elevated CRP level on POD 5 is a valuable predictive tool for early detection of infectious complications after liver surgery and can help in decision making for further diagnostic measurements.