Objective:To explore the diagnostic value of color Doppler ultrasonography for transplanted pancreatic venous thrombosis after simultaneous pancreas-kidney transplantation(SPK).Methods:From June 2019 to September 2022, retrospective analysis was conducted for the relevant clinical data of 181 recipients of SPK.Based upon a presence or absence of clinical high-risk factors, such as a sudden decline of blood/urine amylase, elevated fasting blood glucose and D-dimer, they were assigned into two groups of high-risk(n=48)and non-high-risk(n=133). Color Doppler ultrasonography was performed for evaluating the status of transplanted pancreas and reconstructed blood vessels and diagnosing pancreatic thrombosis post-SPK.Also they were divided into two groups of donor splenic vein thrombosis(n=6)and non-thrombosis(n=39)based upon the presence or absence of splenic vein thrombosis.Various laboratory parameters(fasting blood glucose, blood/urine amylase, fatty acids & D-dimer)and transplanted pancreatic ultrasonic measurements(thickness of transplanted pancreatic head/body/tail, inner diameter & blood flow velocity of donor splenic vein, transplanted pancreatic parenchymal arterial blood flow velocity and resistance index)were recorded.Measurement data were tested for normal distribution and homogeneity of variances.Group comparisons for measurement data fulfilling the criteria of normal distribution and homogeneity of variances were conducted by t-test.For data not fulfilling these criteria, Mann-Whitney U test was utilized.Results:Among 9 cases of pancreatic thrombosis as diagnosed by color Doppler ultrasonography, pancreatic venous thrombosis(n=6)occurred in donor splenic vein.The proportion of transplanted pancreatic thrombosis occurring within Week 2 was 88.9%(8/9)and the proportion of transplanted pancreatic venous thrombosis occurring within Week 2 3.3%(5/6). Fasting blood glucose, blood amylase, urine amylase and D-dimer of high-risk group were(14.7±1.9)U/L, (92.6±15.4)mmol/L, (9.7±1.7)U/L and(6.1±2.2)mg/L.The corresponding values for non-high-risk group were(4.9±0.6)U/L, (209.4±34.4)mmol/L, (168.2±95.7)U/L and(1.3±0.6)mg/L respectively.Statistically significant inter-group differences existed( P=0.021, 0.035, 0.001, 0.017). Pancreatic thrombosis was diagnosed by color Doppler ultrasonography in 9 patients in high-risk group and 8 cases occurred within Week 2 post-SPK.Among 6 cases of pancreatic venous thrombosis, 5 cases occurred in donor splenic veins within Week 2 post-SPK.No significant differences existed in the above parameters between group with donor splenic vein thrombosis and group without donor splenic vein thrombosis( P>0.05). Inner diameters of splenic veins in groups with and without splenic vein thrombosis were(11.7±0.5)and(3.9±0.2)mm.Blood flow velocities in splenic veins were(18.3±8.4)and(40.3±16.6)cm/s respectively.The inter-group differences were statistically significant( P=0.001, 0.006). No significant differences existed in thickness of transplanted pancreatic head/body/tail, as well as blood flow velocity or resistance index in transplant pancreatic artery( P>0.05). Conclusions:Fasting blood glucose, blood amylase, urine amylase, fatty acid and D-dimer are important and yet non-specific biochemical parameters in the diagnosis of pancreatic transplantation thrombosis.Color Doppler ultrasonography may provide valuable imaging diagnostic rationales for making an early diagnosis and providing timely interventions of transplanted pancreatic venous thrombosis post-SPK.It is imperative to enhance dynamic monitoring using color Doppler ultrasound within 1-2 weeks post-SPK.Greater attention should be paid to internal diameter and blood flow velocity of donor splenic vein.