Spiral CT Manifestations Of Collateral Venous Pathways In Pancreaticogenic Splenic Vein Occlusion

Objective To investigate the spiral CT manifestations of collateral circulations owing to pancreaticogenic occlusion of splenic vein concerning the bypassing routes and corresponding collateral vessels and the anatomic correlations.Materials and Methods 33 cases of pancreatic disease were analyzed retrospectively, including 28 cases of pancreatic carcinoma, 3 cases of acute pancreatitis and 2 case of chronic pancreatitis. 9 cases of pancreatic carcinoma and 2 cases of pancreatitis are proven by surgery or pathological findings. 2 cases of pancreatic carcinoma are postoperative recurrent cases. 12 cases of pancreatic carcinoma and 1 case of pancreatitis have clinical, experimental and imaging evidences. The rest 5 cases of pancreatic carcinoma and 2 cases of pancreatitis are proven by typical imaging features and clinical follow-up. None of the 33 cases show any evidence of liver cirrhosis either in histories or in imaging findings. 27 cases were scanned with Siemens Somatom plus 4 VA CT scanner, 6 cases were scanned with Siemens Sensation 4 multi-row-detector CT scanner. Bolus infusion of 80-100 ml of Omnipaque or Ultravist (300mg/ml) was performed at a rate of 2-3 ml/sec. Layer thickness varied from 3.0mm to 10.0mm.The major vessels of upper abdomen were observed, and emphasis was placed on the pathwayand diameter of each vessel. All the 33 cases demonstrated significant narrowing or complete occlusion of the splenic vein accompanied by formation of collateral veins in perigastric and/or omental regions. The cases were divided into 2 subgroups: ISVO group without occlusion of portal vein or superior mesenteric vein, and NISVO group with occlusion of portal vein and/or superior mesenteric vein. The criteria for diagnosis of collateral circulations are: (1) EV: submucosal varicose at lower part of the esophagus. (2) CV: vascular structure can be seen in the hepatogastric ligament with a diameter-≥ 6mm, or varicose located in the same area. (3)SGV: vascular structure can be seen in the gastrosplenic ligament with a diameter≥6mm, or varicose located in the same area. (4)GEV : diameter≥ 5mm. (5)GCT : diameter≥5mm. (6)RSCV : diameter≥ 4mm. (7)MCV: diameter≥ 4mm. (8)PSPDV: diameter≥3mm.Results All 33 cases displayed dilated vessels in the areas between gastric fundus and splenic hilum and/or along the gastric greater curvature. In ISVO cases, it could be shown that SGV(85%), CV(78%), GEV(78%) and GCT(64%) was varicose or dilated. While in NISVO, other collateral veins such as RSCV (37%), MCV (37%) and PDPDV (10%) could also be seen. Conclusion Two predominant collateral pathways of SVO are: ①SGV→fundic veins→CV, and ②GEV →GCT→ SMV. The feature of their distributions and pathways is characteristic on spiral CT and of clinical significance on preoperative staging of pancreatic carcinoma and PSPH evaluation.