Vascular Anatomy and Classification Schema of Gastric Varices Relevant to Balloon-Occluded Retrograde Transvenous Obliteration

Chapter 28: Vascular Anatomy and Classification Schema of Gastric Varices Relevant to Balloon-Occluded Retrograde Transvenous Obliteration

Minhaj S. Khaja, Shozo Hirota, Kaoru Kobayashi, Satoshi Yamamoto, and Wael E.A. Saad

Introduction

The complex, highly variable anatomy and hemodynamics of the portal circulation associated with gastric varices (GVs) are challenging. However, it is essential for interventional radiologists to understand the pathological anatomy and hemodynamics of GVs in these patients when making clinical management decisions. Additionally, a thorough understanding is necessary for describing the technical details of the balloon-occluded retrograde transvenous obliteration (BRTO) and balloon-occluded antegrade transvenous obliteration (BATO) procedures. Given the considerable variability in anatomy, pathology, and hemodynamics, numerous descriptive and categorical classifications have been described in the past two decades by Japanese physicians. This chapter reviews the descriptive anatomy as well as the classification schema that have been described that are relevant to the BRTO procedure.

Descriptive Anatomy

The anatomy of the gastric variceal system (GVS), the entity that is sclerosed by the BRTO procedure, is summarized in Table 28.1. This section delineates the descriptive and radiographic anatomy of the GVS relevant to GVs and the BRTO procedure. Additional multimodality detailed radiographic anatomy has previously been published by one of the authors.

The GVS can be divided into three main components: (1) an afferent (portal venous inflow) part, (2) a central variceal part, and (3) an efferent (systemic venous outflow) part ( Fig. 28.1a–28.1d).

Afferent (Portal Venous Inflow) Feeder(s)

The afferent feeders of the GVS are portal venous branches that arise from the splenic vein and supply the GVs ( Fig. 28.1a). These portal venous inflow vessels do not communicate directly with the true (intragastric, submucosal) GVs but rather communicate with the GVS, outside of the stomach, usually in the extragastric or false GVs (described later) ( Fig. 28.2; Fig. 28.3; Fig. 28.4; Fig. 28.5). The portal venous (afferent) feeders include the left gastric vein (LGV), also known as the coronary vein, the posterior gastric vein (PGV), and the short gastric vein(s) (SGV or SGVs). The PGV is usually singular but can be duplicated or have an early bifurcation. There are usually multiple SGVs, but one may predominate amid the other SGVs. On occasion, it may be difficult to differentiate between a lateral-lying PGV or a medial-lying SGV, although neither has any technical implications.

The LGV (coronary vein) travels to the left from its origin in the very distal splenic vein or proximal main portal vein. Commonly, the LGV heads cephalad as it travels leftward as if targeting the gastroesophageal junction just below the medial aspect of the left hemidiaphragm. It terminates near the midline and almost always in the cephalad portion of the GVS. The LGV, strictly speaking, should be a right-sided component of the spontaneous portosystemic shunt because it arises from the portal vein at or near the midline. However, the PGV and SGVs are left-sided components of the greater portosystemic shunt effect of the GVS.¹ This is important to the later discussions of laterality, afferent dominance, and classification systems that determine GVs management.

Fig. 28.1 Sagittal illustrations depicting gastrorenal shunt (GRS) and splenorenal shunt (SRS) anatomic features and hemodynamics. (a) The key labeled sagittal drawing of the basic anatomy of gastric varices (GVs) and their draining GRS. The afferent portal venous feeders originate from the splenic vein (SpV) or portosplenic venous axis. This supplies the GVs, which in turn are drained by the efferent systemic venous system. The most common efferent drainage is the GRS, which commonly empties into the left renal vein (LRV). LPV: intrahepatic left portal vein. (b) Sagittal drawing of the basic anatomy of morphologic or anatomic SRS. The afferent portal venous feeders come off the SpV or portosplenic venous axis. The SRS does not supply any varices and does not run through the wall of the gastrointestinal tract (GIT). The most common efferent drainage is the left renal vein (LRV). The SRS, as depicted, commonly meanders (long and tortuous) and is not a straight, short portosystemic shunt. Sagittal drawing of the basic anatomy and hemodynamics of a GRS without (c) and with (d) a direct SRS component. Please see part A for labeling purposes. Basic GRSs are actually SRSs (or more accurately, spleno-gastro-renal shunts) (c). Occasionally, a direct SRS or connection is seen (d, hollow arrow, SRS component). From Saad WE. Vascular anatomy and the morphologic and hemodynamic classifications of gastric varices and spontaneous portosystemic shunts relevant to the BRTO procedure. Tech Vasc Interv Radiol 2013;16:60–100. With permission from the author and Elsevier.

Fig. 28.2 Sagittal illustrations depicting the detailed anatomy of the gastric variceal system (GVS). (a) Labeled sagittal drawing of the detailed anatomy of gastric varices (GVs) and their draining gastrorenal shunt (GRS). For simplified and basic anatomy, see Fig. 28.1a. The GVS is composed of the afferent portal venous feeders, the central variceal part, and the GRS (systemic venous drainer or drainers). The central variceal part has the extragastric or false GVs (F.GV), the intragastric submucosal or true GVs (T.GV) (dashed ellipse) and a perforator vein or varix communicating between the false and true GVs (hollow arrow). The cluster of false GVs is the central part of the GVS where the true GVs, the afferent feeders, and the GRS all communicate. Please see the simplified illustration in Fig. 28.5. The degree of convolutions of the false GVs varies considerably from one GVS system to the other. Notice the difference in convolutions and sacculations between (a) and (b). The GRS is composed of an intraperitoneal convoluted or transitional part and a retroperitoneal part. The transitional or intraperitoneal part is usually more tortuous and drains the false GVs as it transitions from intraperitoneal to retroperitoneal. The retroperitoneal part is usually more straight and is composed of two subparts: the GRS proper and the common venous stump (common stump), which is the common drain of the GRS proper and the left adrenal vein (Adr. V). LGV: left gastric vein; LRV: left renal vein; PCP: pericardiophrenic vein; PGV: posterior gastric vein; St: stomach. From Saad WE. Vascular anatomy and the morphologic and hemodynamic classifications of gastric varices and spontaneous portosystemic shunts relevant to the BRTO procedure. Tech Vasc Interv Radiol 2013;16:60–100. With permission from the author and Elsevier.

Fig. 28.3 Portal venogram through a transjugular intrahepatic shunt (TIPS). showing the gastric varices (GVs) and the gastrorenal shunt (GRS) and its parts. (a,b) Two digitally subtracted angiogram images (portograms) in sequence performed through a TIPS. The TIPS is patent. There is a small diminutive splenic vein (SpV), which most likely represents a recanalized, previously thrombosed splenic vein. There is also reversal of flow in the splenic vein. The GVs (a,b) are supplied by the short gastric vein (SGV); the posterior gastric vein (PGV); and, most dominantly, the left gastric vein (LGV). The GVs empty into the GRS, which then empties into the left renal vein (LRV), which anatomically empties into the inferior vena cava (IVC) and right atrium (RA). MV: mesenteric vein; PV: main portal vein. From Saad WE. Vascular anatomy and the morphologic and hemodynamic classifications of gastric varices and spontaneous portosystemic shunts relevant to the BRTO procedure. Tech Vasc Interv Radiol 2013;16:60–100. With permission from the author and Elsevier.

Fig. 28.4 Detailed anatomy of the gastric varices (GVs) and gastrorenal shunt (GRS) on sagittal and coronal reformats with fluoroscopic correlation. This aids in the preprocedural imaging planning. (a-l) Contrast-enhanced sagittal reformats of a CT image with magnified insets (b,d,f,h). The proximal to distal description is flow based. The proximal GRS is caudal and nearest to the GVs. The distal GRS is retroperitoneal as the GRS merges with the left renal vein (LRV). The proximal GRS is the convoluted portion, which starts intraperitoneal (intraperitoneal convoluted portion) and passes retroperitoneally to merge with the vertically oriented (relatively straight) retroperitoneal distal portion of the GRS. The convoluted portion that passes intra- to retroperitoneally is referred to by the current authors as the “transitional portion” of the GRS (d).

Fig. 28.4 There are extragastric intraperitoneal “varices” (f,h, solid white arrows) that can be considered the most convoluted portion of the intraperitoneal GRS. However, the “true GVs” are intragastric and submucosal (h-l, hollow arrows). The posterior gastric vein (PGV) (which is the main portal venous feeder in this case) is seen coming off the splenic vein (SpV) in (h-l) and is labeled in (h) as the proximal PGV (Px PGV) as it comes off the SpV and the distal-PGV (Dst PGV) as it merges with the extragastric varices. Gon. V: left gonadal vein; Intra-Perit GRS: intraperitoneal most proximal portion of the GRS; PB: pancreatic body in cross-section; Phr. V: phrenic vein, inferior phrenic vein; Retro-Perit GRS: retro-peritoneal vertically oriented distal portion of the GRS; Sp: spleen; St: stomach; transitional GRS, the convoluted portion that connects the intraperitoneal GRS to the retroperitoneal portion of the GRS. (m-p) Contrast-enhanced coronal reformat of CT image (m) and its fluoroscopic correlates (n-p). The distal retroperitoneal GRS (m, asterisk) has two tandem web narrowings (m,n, hollow arrows). These tandem webs were also appreciated on the sagittal reformats (f). (o) represents balloon-occluded venogram (hollow black arrow at balloon), and (p) represents the balloon-occluded sclerosant administration (hollow black arrow at balloon). During the procedure and under fluoroscopy (n-p), the web narrowings are confirmed (n, hollow arrows), and the main portal venous feeder (in this patient, it is the PGV) is also confirmed (o: between solid and hollow white arrows). Notice that when contrast (heavy liquid contrast) only was used, the PGV was visualized.

Fig. 28.4 (o, between solid and hollow white arrows); however, when the foam sclerosant (lighter foam) is used (p) the PGV is not visualized. The take-home point is that the foam sclerosant acts differently from the heavier liquid nonionic contrast. Occasionally, the opposite may occur. The portal feeder may be seen on the GRS contrast venogram but will be seen during sclerosant administration. From Saad WE. Vascular anatomy and the morphologic and hemodynamic classifications of gastric varices and spontaneous portosystemic shunts relevant to the BRTO procedure. Tech Vasc Interv Radiol 2013;16:60–100. With permission from the author and Elsevier.

The posterior gastric vein travels straight up or slightly to the left of the GVS, arising from the middle or near middle splenic vein. The PGV can be singular or duplicated, and its course may be straight, meandering, or spiral. The SGV arises from the splenic hilum or very proximal splenic vein just beyond the hilum. The SGV then travels medially toward the GVS and enters the GVS, commonly higher than the PGV. It usually enters the GVS slightly higher than the PGV (ventral to the GVS). As previously mentioned, it may be difficult to differentiate a PGV from SGV; however, SGVs are shorter and smaller than the PGV and usually arise from the splenic hilum or just outside of it.1 From a hemodynamic standpoint, however, differentiation of these two veins is not important because they both arise from the proximal half of the splenic vein and are clearly left-sided components of the portosystemic shunt effect of the GVS.

The portal venous feeders of the GVS vary in dominance. Whereas the LGV is the dominant inflow vessel in some patients, the PGV/SGVs are dominant in others. In some patients, all three vessels (LGV, PGV, and SGVs) are codominant. This combination of codominant afferent feeders signifies a complex GVS. The SGV is rarely, if ever, the sole dominant portal venous feeder in a patient with a patent splenic vein in the authors’ experience. However, in the setting of splenic and/or portal venous thrombosis, the SGV becomes the main and only portal venous feeder because the only splenic outflow is through the SGVs and gastric wall varices. In this specific situation, the gastric wall varices are not only confined to the proximal stomach (fundus and cardia) but also involve the distal stomach (body, antrum, and gastric outlet).¹

Fig. 28.5 Illustrations depicting the anatomic relationships of the different components of the gastric variceal system (GVS). The GVS is composed of the afferent portal venous feeders (hollow arrows), the central variceal part, and the gastrorenal shunt (GRS; systemic venous drainer or drainers). The central variceal part has the extragastric or false gastric varices (F.GV), the intragastric submucosal or true gastric varices (T.GV), and a perforator vein or varix communicating between the false and true GVs (black arrow). The GRS is the efferent (curved arrow) systemic venous drainage. The cluster of false GVs is the central part of the GVS where the true GVs, the afferent feeders (A), and the GRS all communicate. From Saad WE. Vascular anatomy and the morphologic and hemodynamic classifications of gastric varices and spontaneous portosystemic shunts relevant to the BRTO procedure. Tech Vasc Interv Radiol 2013;16:60–100. With permission from the author and Elsevier.

Patients with bleeding GVs (13% to 53%) have been shown to have higher rebleeding rates than patients with esophageal varices (11% to 22%) after transjugular intrahepatic portosystemic shunts (TIPS).2 Moreover, TIPS has shown variable results with GVs (wide range of rebleeding, 13% to 53%) and has shown more consistent results with esophageal varices (narrower range of rebleeding, 11% to 20%).² Based on these reported outcomes, there are two theories, based on hemodynamics, as to why TIPS have poorer and less consistent results with GVs than esophageal varices. The first theory is that portosystemic shunting through the gastrorenal shunt (GRS) varies significantly in volume, and therefore large GRSs may not be affected by the TIPS and may even compete with the TIPS. As such, a low portosystemic pressure gradient may reflect a large GRS with high flow. It is commonly believed that TIPS is not effective in managing GVs in the setting of a low (<12 mm Hg) portosystemic gradient presumably because of a large shunt.² The second theory is that the portal venous feeders (PGV or SGV) of GVs are farther away from the TIPS compared with the LGV in patients with EVs. As a result, the TIPS may be effective in decompressing GVs with a dominant LGV and less effective in decompressing GVs with a dominant PGV or SGV.² The Saad GVs management classification is based on the latter theory in which LGV-dominant GVs would likely respond to TIPS and PGV- or SGV-dominant GVs would respond less to TIPS and that BRTO may have a greater and more effective role in managing these patients (see later discussion).

Central Variceal Part of the Gastric Variceal System

The central elements of the GVS are composed of the true submucosal intragastric and false extragastric varices ( Table 28.1; Fig. 28.2; Fig. 28.4; Fig. 28.5). The submucosal intragastric varices are the ones that bleed. There may be thickened folds in the stomach that do not have varices beneath them. These folds may represent mere thickened rugae (gastric folds) or autothrombosed GVs. Between the intra- and extragastric varices is a perforator vein/varix ( Fig. 28.2; Fig. 28.5).

The extragastric varices are saccules or convolutions located outside the gastric wall ( Fig. 28.2; Fig. 28.4; Fig. 28.5). The extragastric varices play a key role in the GVS because the afferent portal feeders empty into them, the perforator vein arises from them and penetrates the gastric wall to the true intragastric varices, and the GRS (efferent venous drainer) arises from them and empties into the left renal vein (LRV). Whereas some patients have elaborate false varices and convolutions, others have a simple network composed of one simple varix or chamber. As such, the degree of extragastric variceal complexity varies considerably among patients.

Efferent Systemic Venous Drainage

The efferent systemic venous drainage of the GVS can vary widely in complexity. Simple efferent drainage may only have a GRS present, but more complex systems may have multiple draining systemic veins such as the inferior phrenic or pericardiophrenic vein, whose hemodynamic significance also varies (see the later discussion of the Kiyosue and Hirota classifications).^3–5 For the purpose of this section, the detailed anatomical description is focused on the GRS and the pericardiophrenic or inferior phrenic vein (IPV).

The Gastrorenal Shunt

The GRS arises from the intraperitoneal extragastric varices or convolutions in the lesser sac. The intraperitoneal portion of the GRS is usually convoluted and transitions from an intra- to a retroperitoneal location as it travels caudally and posteriorly ( Fig. 28.4). As such, the name of this portion of the GRS is the “intraperitoneal transitional (convoluted) portion of the GRS” After the GRS transitions into the retroperitoneum, it usually becomes less convoluted and travels inferiorly in the retroperitoneum, where it reaches the confluence of the common stump of the left adrenal vein and itself (GRS) ( Fig. 28.2; Fig. 28.3; Fig. 28.4).