Chapter 76D Mesocaval shunt

History of the Mesocaval Shunt

Eck first described decompression of the portal system via the portacaval shunt in 1877. The first mesocaval shunt was developed primarily for children with portal vein thrombosis by Marion in 1953 (Marion et al, 1965) and Clatworthy in 1955. In the Marion-Clatworthy J-shunt, the inferior vena cava (IVC) is divided just proximal to the confluence of the iliac veins, and the proximal end is anastomosed to the lateral aspect of the superior mesenteric vein (Clatworthy, 1955). In 1954, Valdoni also described this procedure in a discussion regarding treatment options for portal hypertension. Because of the complications of venous stasis, including intractable lower extremity edema, this shunt never gained popularity in adults.

In 1970, Read and colleagues described the use of homologous vein graft as a conduit for the mesocaval shunt. In 1972, Drapanas reported good success with prosthetic mesocaval shunts by showing efficacy in 25 patients with acute exsanguinating variceal hemorrhage and popularized the procedure. Throughout the 1970s, several authors reported success with autologous, homologous, heterologous, and synthetic mesocaval shunts for the treatment of bleeding varices.

Indications for Mesocaval Shunts

With remarkable advances in endoscopic therapy, interventional radiology, and liver transplantation, the role of surgical shunts in the treatment of complications related to portal hypertension has been revised (see Chapter 76A). Although alternatives exist, surgical shunts remain an important intervention in some patients. The use of transjugular intrahepatic portosystemic shunts (TIPS; see Chapter 76E) has decreased the need for surgical shunts dramatically. TIPS provides only short-term treatment, however; it requires constant monitoring and frequent intervention, and such shunts are appropriate only in patients with advanced liver disease, as a “bridge” to transplantation, or in severely ill patients with a short life expectancy. In contrast, surgical shunt are best performed in patients who have bleeding varices refractory to endoscopic intervention with good hepatic reserve (i.e., Child-Turcotte-Pugh [CTP] classes A and B). Indications for surgical shunt procedures include variceal hemorrhage with good hepatic reserve, failed TIPS, portal vein thrombosis, Budd-Chiari syndrome, refractory ascites, portal hypertensive biliopathy, and small-for-size syndrome in liver transplantation; although more recently, portal decompression has emerged for the treatment of small-for-size syndrome in liver transplantation.

The most common indication for surgical shunt is bleeding varices refractory to medical and endoscopic therapy in patients who have good hepatic reserve and do not need liver transplantation in the near future. Henderson and colleagues (2000) showed excellent outcomes in CTP class A and B cirrhotic patients with refractory bleeding who received surgical shunts. In their series, the overall survival and rebleeding rates were 86% and 6.3%, respectively, with a median follow-up of 36 months. The choice between TIPS and surgical shunts depends on the patient’s hepatic reserve and timing to possible transplantation. If transplantation is expected within 1 to 2 years, TIPS is likely to bridge the patient to transplantation without the need for surgical intervention. However, if transplantation is unlikely to occur within 1 to 2 years, surgical shunting is warranted; more than 50% of TIPS patients require intervention within this time period.

Orloff and coworkers (2002) reported the use of portosystemic shunts in the treatment of 200 children and adults with extrahepatic portal hypertension secondary to portal vein thrombosis. In contrast to patients with intrahepatic portal hypertension secondary to cirrhosis, this patient population is often younger and healthier and often has preserved liver function, making them excellent surgical candidates. In this large series by Orloff and colleagues (2002), 100% of patients had normal liver biopsies with normal liver function, and 66 patients (33%) underwent Marion-Clatworthy–type cavomesenteric shunts with no immediate postoperative mortality. Of note, six adult patients experienced postoperative lower extremity edema. The 15-year actuarial survival was noted to be 95% for all shunt types, with shunt patency at 97.5%. Liver function remained normal for 99% of these patients at 5 years. The authors concluded that portosystemic shunting is the most effective treatment for these patients and that these procedures should be performed early in the course of variceal bleeding episodes.

Although Budd-Chiari syndrome (see Chapter 77) with obstruction of the hepatic venous outflow was traditionally treated with portosystemic shunt procedures, other treatment options—including hepatic vein angioplasty, catheter-directed thrombolysis, TIPS, and liver transplantation—have been successfully introduced. After reviewing 54 Budd-Chiari syndrome patients treated at Johns Hopkins Hospital over 20 years, Slakey and colleagues (2001) concluded that shunting and transplantation result in 5-year survival rates of at least 75% in these patients. Fisher and associates (1999) advocated the use of hepatic vein angioplasty for Budd-Chiari syndrome patients with short-length hepatic vein stenosis or occlusion and surgical shunting for patients with diffuse hepatic vein occlusion or failed angioplasty; others recommend TIPS. However, recanalization of the hepatic veins is not always successful and may require a shunt procedure.

A study using the porcine transplant model suggested that mesocaval shunts may provide protective effects for small-for-size liver grafts by protecting them from portal flow–related injuries (Smyrniotis et al, 2003). Case reports are emerging that demonstrate successful use of this technique to alleviate portal hypertension associated with small-for-size syndrome after living-donor liver transplantation (Boillot et al, 2002; Kokai et al, 2008). A porcine model has demonstrated retention of liver regenerative capabilities despite reduction of venous inflow after left hepatectomy with mesocaval shunt (Pouyet et al, 2007). Given the critical organ shortage and increasing use of segmental grafts, this approach may prove clinically useful in the future.

Because subsequent transplantation often is anticipated in patients receiving portosystemic shunts, the shunt procedure should minimize as much as possible any potential compromise of the technical aspects of the transplant operation. In contrast to portacaval shunts, the distal splenorenal and mesocaval interposition shunts do not alter the porta hepatis anatomy. In a case control study comparing decompressive procedures involving the hepatic hilum with both TIPS and other surgical shunts, Dell’Era and colleagues (2005) noted significantly higher operative times, higher transfusion requirements, increased hospital and intensive care unit (ICU) stays, and higher perioperative mortality in patients with procedures that affected the hepatic hilum. These findings have been reproduced by other authors as well (Menegaux et al, 1994; Mazzaferro et al, 1990; Brems et al, 1989), however, other studies have not found this association (Gonzalez et al, 2005; Abou Jaoude & Almawi, 2001; Boillot et al, 1991). The mesocaval interposition shunt is technically less challenging than the distal splenorenal shunt and requires minimal retroperitoneal dissection. It effectively relieves portal hypertension, and in contrast to the distal splenorenal shunt, it also relieves or prevents secondary ascites.

Shunt Materials and Mesocaval Shunt Size

Multiple variations of the mesocaval shunt procedure have been described in the literature, and significant debate has ensued regarding the ideal graft material and diameter for the mesocaval shunt. In 1970, Read and colleagues presented a series of eight mesocaval shunts with homologous vena cava. Also in 1970, Lord and associates published a report on seven mesocaval H-grafts with polytetrafluoroethylene (PTFE) prostheses, of which six remained patent for 20 months. Despite Lord’s early success, many clinicians remained fearful of using prosthetic grafts in the venous system because of experimental failures in long-term patency. In 1972, Drapanas published data on 25 more mesocaval shunt procedures that used 19- to 22-mm Dacron interposition grafts and showed excellent patency rates. Drapanas cited a superiority of Dacron over PTFE for better incorporation into host tissues and continued to use Dacron in his studies.

Throughout the 1970s, several other groups reported success with large-diameter prosthetic grafts. In 1977, Filtzer and coworkers reviewed their institution’s experience with 20 patients who underwent mesocaval shunt procedures using 18- to 22-mm Dacron grafts for bleeding esophageal varices. The long-term patency rate approached 90%. In 1975, Drapanas and associates published a follow-up study on the hemodynamics of 80 mesocaval shunts using large-diameter (18 to 22 mm) Dacron grafts. In this series, a decrease in mean portacaval pressure by 50% was noted, and 44% maintained hepatopetal portal flow. Only three graft thromboses occurred, and overall patency rate was 95%. One patient developed graft infection, however, with subsequent sepsis and death.

Although recurrent esophageal varices and hemorrhage were rare after these procedures, the large-diameter portacaval and mesocaval grafts (16 to 22 mm) often resulted in total portal shunting and loss of prograde portal flow, which many investigators thought led to progressive liver dysfunction and high rates of encephalopathy. Sarfeh and colleagues (1986) investigated the importance of maintaining hepatic portal perfusion for prevention of encephalopathy by systemically reducing the portacaval H-graft diameters. After reviewing 88 patients treated with portacaval shunting for bleeding esophageal varices, they reported maintenance of hepatopetal flow in 82% of patients with 8-mm PTFE H-grafts, 46% with 10 mm PTFE H-grafts, and only 3% with 14- to 20-mm Dacron grafts. Preserved prograde portal flow correlated with decreased rates of encephalopathy, which was observed in only 9% of patients with 8-mm PTFE H-grafts compared with 39% of those with large-diameter Dacron grafts. Although early graft thrombosis was more common in the small-diameter grafts (16%), the cumulative shunt patency rate was 97% for those grafts. One patient experienced graft infection with subsequent sepsis and death. In another study, Isaksson and colleagues (2005) noted that patients with a 14-mm mesocaval shunt had a steady, worsening performance in postoperative follow-up on several psychometric tests, and the rate of hepatofugal portal flow was 90% at 12 months in these patients.

Throughout the 1980s, most reports of small-diameter grafts focused on their use in the portacaval position as opposed to a mesocaval shunt. All studies showed a slightly increased rate of perioperative shunt thrombosis over the large-diameter shunts; this was mostly managed via angiographic revision (Collins et al, 1994; Rypins et al, 1988), and all small-diameter portacaval shunt procedures were coupled with aggressive portal vein collateral ablation.

More recent studies have shown the efficacy of small-diameter mesocaval shunts. Mercado and associates (2000) reviewed a 10-year experience with 10-mm PTFE mesocaval shunts for the treatment of bleeding esophageal varices in mostly low-risk patients with preserved hepatic function. Thirty-three patients underwent the procedure; 81% maintained long-term patency evaluated by angiography, but 15% developed episodes of rebleeding. Only 11% had encephalopathy, and 12-month survival was 81%. Mercado and colleagues (1996)

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