Preoperative Evaluation And Preparation

The etiology of the portal hypertension should be determined because this has a direct impact on outcome. Patients with nonalcoholic cirrhosis (e.g., postnecrotic cirrhosis, primary biliary cirrhosis) and those with extrahepatic portal vein thrombosis or primary hepatic fibrosis do better, and have an improved survival after the DSRS than alcoholic cirrhotics (17,18). Because prognosis is directly related to liver functional reserve, the Child-Pugh class status should be assessed. Ideally, the nutritional status should be good, there should be no encephalopathy, the serum total bilirubin should be less than 2 mg/dL, the serum albumin greater than 3 g/dL, there should be no ascites and the prothrombin time should be no longer than 2 sec from the control. Ultrasound assessment of liver volume (between 1000 and 2500 mL) and a functional measurement of the liver reserve by means of the galactose elimination capacity (greater than 250 mg/min) will further aid the selection of good-risk patients for surgery. Careful evaluation of the patient's cardiopulmonary reserve and fitness to tolerate general anesthesia and a major abdominal operation is crucial.

Cirrhotic patients are at risk for the development of hepatocellular carcinoma. Screening involves an abdominal ultrasound or computed tomography (CT) scan and serum a-fetoprotein determination.

Evaluation of the vascular anatomy is performed prior to consideration for shunt surgery. Duplex ultrasound can determine the patency of the extrahepatic portal vein but visualization of the other vessels is limited. Magnetic resonance angiography (MRA)

with gadolinium enhancement is a relatively new, noninvasive study that can provide information on the status of the superior mesenteric, portal, splenic, and the left renal veins. However, contrast angiography is still preferred by many surgeons for a definitive assessment of the vascular anatomy. Visualization of the inferior vena cava and left renal vein to ensure adequate patency, and measurement of the hepatic wedge pressure is performed. Selective injection of contrast is then made into the splenic and superior mesenteric arteries and images are taken during the venous phase of the study.

Optimal anatomic prerequisites for the DSRS include a patent, nontortuous splenic vein with a diameter of at least 10 mm, a short distance between the splenic and left renal veins (less than one vertebral body), and adequate drainage from the left renal vein into the inferior vena cava. If the patient had a splenectomy previously, or the splenic vein is small or thrombosed but a sizable superior mesenteric or portal vein is present, a small-diameter MCS or PCS may be performed. If the whole portal system is thrombosed, then a devascularization procedure (Sugiura operation) is considered.

Preparation of patients for elective surgery involves improving their nutritional status, optimizing cardiopulmonary function, and medical control of ascites when this is present. Electrolyte abnormalities should be corrected and abstinence from alcohol is encouraged. Patients with active liver disease, e.g., alcoholic hepatitis, and chronic active hepatitis have an increased mortality (16), and should not undergo surgery until this has been stabilized. A liver biopsy may be necessary to assess for disease activity. Perioperative antibiotics are given to reduce the risk of infection and prophylactic H2 blocker therapy is recommended for 4-6 wk. Significant coagulopathy is corrected with fresh frozen plasma and vitamin K before surgery.


Distal Splenorenal Shunt (DSRS or Warren Shunt)

There are two essential components to this operation. First, the pancreas is fully mobilized from the superior mesenteric vessels to the splenic hilum. This allows rotation of the gland and adequate visualization of the splenic vein. The vein is dissected out of the pancreatic groove, carefully ligating all the small pancreatic perforating tributaries. It is then divided flush with the portal vein and anastomosed end-to-side to the left renal vein without any tension or twist.

The second part is equally important and involves ligation of the left gastric or coronary vein, right gastric vein and the right gastroepiploic vein. This critical step preserves prograde flow in the portal vein, and confers selectivity to the shunt. Despite this, there is evidence that loss of hepatopetal flow occurs over time in alcoholic cirrhotics, and survival in this group is no better than that achieved by total portasystemic shunting (17,18). Collateral veins develop in the pancreas, which siphon blood away from the high-pressure portal vein to the low-pressure splenorenal anastomosis (Fig. 1). The additional maneuver of total spleno-pancreatic disconnection improves the selectivity of the DSRS, and maintains hepatopetal flow in the longterm (19,20). This is achieved by dividing the splenocolic ligament, and ensuring total mobilization of the splenic vein from the pancreas. The procedure is depicted in Fig. 2.

Mesocaval Shunt (MCS)

The superior mesenteric vein is exposed via a transverse incision at the base of the transverse mesocolon as the vein enters the root of the mesentery of the small bowel. The

Coronary vein Adrenal

Coronary vein Adrenal

Mesenteric Caval Shunt

cava Superior vejn mesenteric vein

Fig. 1. The pancreatic siphon after distal splenorenal shunt.

Coronary Vein Pancreas
Fig. 2. Distal splenorenal shunt with spleno-pancreatic disconnection.

Portal vein

Portal vein

Mesocaval Shunt

Fig. 3. Small-diameter meso-caval shunt.

inferior vena cava is exposed directly through the right transverse mesocolon. An 8-mm ringed PTFE graft is sewn on the anterior surface of the vena cava, tunneled through the mesocolon, and then sewn to the antero-lateral aspect of the superior mesenteric vein. An important maneuver is to completely mobilize the third and fourth portions of the duodenum including the ligament of Treitz to allow the duodenum to ride up and avoid potential compression by the interposed graft. Collateral veins are not ligated. This is illustrated in Fig. 3.

Exposure of the inferior vena cava and portal vein is initially achieved by wide mobilization of the C-loop of the duodenum, and head of the pancreas medially (an extended Kocher maneuver). Sufficient dissection of the anterior surface of the vena cava and lateral aspect of the portal vein is performed to facilitate the performance of the anastomoses. An 8-mm ringed PTFE graft is used as the conduit to join the two structures (Fig. 4). The use of supported grafts prevents kinking, and compression by adjacent viscera. Some authors feel that the ligation of portal collateral veins is important to divert more blood flow toward the liver, and the small diameter shunt, increasing the likelihood of preserving prograde portal flow (21). There is no universal agreement on this. If this is chosen, the umbilical vein is divided at the liver edge. The gastroepiploic, periesophageal, coronary and inferior mesenteric veins are also ligated.

Was this article helpful?

0 0
Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

Get My Free Ebook

Post a comment