Portal Hypertension: A Pictorial Review of Portosystemic Collateral Pathways and Radiologic Interventions A Mirakhur MD1, MC Ferris MD1, RR Gray MD1, A Aspinall MD2, JK Wong MD1 Divisions of 1Interventional Radiology, Department of Diagnostic Imaging and 2Gastroenterology and Hepatology, Department of Medicine, University of Calgary, Canada ANATOMIC SITES OF PORTOSYSTEMIC CONFLUENCE TIPS OBJECTIVES Collateral channels develop in portal hypertension along pre-existing sites of portosystemic confluence. Intrathoracic manifestations of portosystemic collateral vessels characteristically develop by way of the coronary vein (LGV) into esophageal or paraesophageal and cardiophrenic varices.2-4 Other common pathways of portosystemic shunting involve gastroesophageal, paraumbilical, splenorenal, and inferior mesenteric collateral vessels.2-4 Pleuro-pericardial-peritoneal, pancreaticoduodenal, splenoazygos and mesocaval collaterals are unusual pathways for decompression of portal vein.2-4 To discuss the appearances and prevalence of both common and less common portosystemic collateral channels in the thorax and abdomen. To provide a brief overview of established interventional techniques for treatment of portal hypertension and related complications. Gastric Varices Paraesophageal/Esophageal Varices THE PORTAL VENOUS SYSTEM The portal venous system is a unique circulatory system, which connects two systems of capillary beds; one in the wall of the small intestine and spleen, and the second in the hepatic sinusoids. The main hepatic portal vein is usually formed by the splenic vein and the superior mesenteric vein, posterior to the neck of the pancreas. The inferior mesenteric vein usually drains into the splenic vein and does not directly connect to the main hepatic portal vein. Other tributaries of the portal vein, which make up the portal venous system are the left gastric, right gastric, paraumbilical, and cystic veins.1 Figure 13: Subtraction angiography shows TIPS TIPS or Transjugular Intrahepatic Portosystemic Shunt is a percutaneous imaging-guided procedure in which polytetrafluoroethylene (PTFE)–covered stents are deployed bridging the hepatic parenchyma between the hepatic vein and portal vein.5 TIPS reduces the portosystemic pressure gradient by functioning as a side-to-side portacaval shunt. TIPS is performed to mitigate known complications of portal hypertension such as variceal hemorrhage and congestive gastroenteropathy, refractory ascites, hepatic hydrothorax or hepatorenal syndrome.5 B A A B Figure 4: Axial (A) and Sagittal (B) CT images of gastric varices (arrows). Figure 5: Axial (A) & Coronal (B) CT images show large esophageal & paraesophageal varices (ovals). Cardiophrenic/Pericardiophrenic Varices Paraumbilical and Abdominal Wall Varices BRTO Balloon Retrograde Transvenous Occlusion CT Computed Tomography GBVar Gallbladder Varices IMV Inferior Mesenteric Vein IVC Inferior Vena Cava LGV Left Gastric Vein (or Coronary vein) MPV Main Portal Vein MRI Magnetic Resonance Imaging MRV Main Renal Vein MReV Middle Rectal Vein PEVar Paraesophageal Varices ROV Right Ovarian Vein SMV Superior Mesenteric Vein SRS Splenorenal Shunt SV Splenic Vein TIPS Transjugular Intrahepatic Portosystemic Shunt VIBE Volume Interpolated Breathhold Examination, 3D spoiled turbo gradient echo fat saturation BRTO A A B C B Figure 1: Normal portal venous anatomy and direction of blood flow Table 1: Abbreviations. Figure 7: Coronal CT MIP (A), Axial CT (B) & oblique CT reconstruction (TeraRecon) show large paraumbilical varices (arrows) with caput medusa (wide arrows). Figure 6: Coronal Post Gadolinium VIBE MRI sequence (A) & axial CT image (B) show prominent cardiophrenic and pericardial collateral veins (arrows) communicating with the left hepatic vein. Patient had Budd-Chiari syndrome. PORTAL HYPERTENSION For the past 2 decades, the balloon-occluded retrograde transvenous obliteration (BRTO) procedure has become common practice in Asia for the management of gastric varices. This technique involves advancing a catheter from the femoral vein into the outlet of the gastrorenal shunt.6 Following balloon occlusion of the shunt, sclerosant is injected retrogradely to fill the gastric varices.6 BRTO been shown to be effective in controlling gastric variceal bleeding with low rebleed rates.6 In contrast, TIPS has not shown the same effectiveness in controlling gastric variceal bleeding that it has with esophageal variceal bleeding. BRTO has many advantages over TIPS in that it is less invasive and can be performed on patients with poor hepatic reserve and those with encephalopathy (and may even improve both). However, its by-product is occlusion of a spontaneous hepatofugal (TIPS equivalent) shunt, and thus it can worsen portal hypertension, with potential aggravation of esophageal varices and ascites. Portal hypertension is a pathologic increase in portal venous pressure that is generally a consequence of chronic, more rarely acute diseases, affecting hepatic parenchyma or hepatic veins. Normal portal pressure is 5-10 mmHg. Concomitant portal pressure > 12 mmHg and increased wedged hepatic vein pressure (WHVP) gradient between the pressure in the portal vein and inferior jejunal vein > 2-6 mmHg diagnose portal hypertension1. Mesocaval varices Rectal Varices Pericholecystic Varices MReV Figure 2: Schematic showing the pathophysiology of portal hypertension A B Figure 10: CT MIP (TeraRecon) through the gallbladder shows multiple varices. Figure 8: Coronal (A) & RAO CT Reconstructions (B) (TeraRecon) show large collateral veins shunting blood from the IMV into the IVC via the right ovarian vein. REFERENCES Figure 9: Coronal CT reconstruction (TeraRecon) shows para-esophageal & rectal varices. Cichoz-Lach H, Celinski K, Slomka M, et al. Pathophysiology of portal hypertension. J Physiol Pharmacol 2008;59(2):231-238. Cho KC, Patel YD, Wachsberg RH, Seeff J. Varices in portal hypertension: evaluation with CT. RadioGraphics 1995; 15:609–622. Okuda K, Matsutani S. Portal-systemic collaterals: anatomy and clinical implications. In: Okuda K, Benhamou JP, eds. Portal hypertension: clinical and physiological aspects. Tokyo, Japan: Springer-Verlag 1991;51-62. Kim MJ, Mitchell DG, Ito K. Portosystemic collaterals of the upper abdomen: review of anatomy and demonstration on MR imaging. Abdom Imaging 2000;25:462-470. Fidelman N, Kwan SW, LaBerge Jm, et al. The Transjugular Intrahepatic Portosystemic Shunt: An Update. Am J Roentgenol 2012;199(4):746-755. Saad WEA. Balloon-Occluded Retrograde Transvenous obliteration of Gastric Varices: Concept, Basic Techniques, and Outcomes. Semin intervent Radiol 2012; 29(02):118-128. Splenorenal Shunt Reversal of Portal Vein Blood Flow Direction Ascites Liver Figure 3: Portosystemic collateral pathways and direction of blood flow in portal hypertension A B A B Figures 11: Transverse Doppler ultrasound image (A) shows reversal of normal flow direction in MPV, nodular cirrhotic liver & ascites. Normal hepatopetal MPV flow in (B). Figure 12: Craniocaudal (A) & left anterior oblique (LAO) CT reconstruction (B) (TeraRecon) images show a spontaneous splenorenal shunt