PROGNOSTIC SIGNIFICANCE OF CT PLANIMETRIC CHARACTERISTICS OF THE PANCREAS IN THE DEVELOPMENT OF PANCREATIC FISTULA AFTER PANCREATICODUODENECTOMY

Abstract

The aim of the work: to investigate the prognostic significance of CT planimetric characteristics of the pancreas, such as parenchymal density and ductal diameter to parenchymal thickness ratio (D/P ratio), for the development of clinically significant postoperative panc­reatic fistula (POPF) after pancreaticoduodenectomy (PD).

Materials and Methods. The prospective study included 234 patients who underwent PD between January 2022 and November 2023 at the National Scientific Center of Surgery and Transplantation named after O.O. Shalimov. The main indications for surgery were: pancreatic cancer (n=119; 50.9 %), distal cholangiocarcinoma (n=30; 12.8 %), Fater's ampulla cancer (n=26; 11.1 %), intraductal papillary mucinous neoplasia (n=17; 7.3 %), duodenal cancer (n=12; 5.1 %) and chronic pancreatitis (n=30; 12.8 %).

On preoperative CT images in the axial plane at the level of the expected resection line above the superior mesenteric vein, the density of the pancreatic parenchyma in Hounsfield units (HU) was measured. To determine the D/P ratio, the maximum diameter of the main pancreatic duct and pancreatic thickness were measured in two perpendicular directions: ventrodorsal and craniocaudal. Parenchymal thickness was defined as the distance from the outer edge of the gland to the duct wall. The PAP was determined according to the ISGPS criteria. Logistic regression and ROC analysis were used to evaluate the prognostic significance of CT criteria.

Results. The incidence of clinically significant POPF (type B/C) was 18.8 % (n=44). The median parenchymal density was significantly lower in the POPF group compared with the non-POPF group (22 vs. 39.65 HU, p<0.001). Median D/P ratios were also lower in the POPF group in both the ventrodorsal (0.14 vs. 0.33, p<0.001) and craniocaudal planes (0.12 vs. 0.255, p<0.001).

The multivariate model with the inclusion of parenchymal density and D/P ratio had the highest predictive accuracy (AUC 0.92; 95 % CI 0.87-0.96). The thresholds of ≤26.6 HU for density and ≤0.2 for D/P ratio provided a sensitivity of 81.8 %, a specificity of 91.7 %, a positive predictive value of 62.5 % and a negative predictive value of 98.2 % for POPF. A moderate positive correlation was found between parenchyma density and D/P ratio (r=0.29, p<0.001). An increase in the D/P ratio in the ventrodorsal and craniocaudal planes by 0.1 was accompanied by a decrease in the odds ratio of POPF by 86.4 % (OR 0.136; 95 % CI 0.058-0.318; p<0.001) and 72.6 % (OR 0.274; 95 % CI 0.117-0.639; p=0.003), respectively.

Conclusions. Low pancreatic parenchymal density (≤26.6 HU) and D/P ratio ≤0.2, determined by CT planimetry of the resection plane, are independent predictors of clinically significant POPF after PD. A prognostic model based on these criteria allows to accurately stratify patients by the risk of POPF before surgery. The revealed correlation between parenchymal density and D/P ratio indicates common pathophysiological mechanisms that determine the integrity of the pancreaticoduodenal anastomosis. The results of the study open up prospects for the implementation of personalized preventive strategies for PD based on preoperative CT planimetry.