• Sign Up

Portacaval Shunt


Portacaval Shunt

Article Author:
Kaitlyn Crossan
Article Editor:
Mark Jones
Updated:
10/11/2020 4:40:03 PM
For CME on this topic:
Portacaval Shunt CME
PubMed Link:
Portacaval Shunt

Introduction

Surgical shunts usage has become less common over the years as advancements in endoscopic therapy, TIPS (transjugular intrahepatic portosystemic shunt) procedure, and liver transplantation has depressed its use.  The surgical shunts can still be an option in patients with refractory variceal bleeding with preserved liver function as well as in patients with portal hypertension. Shunts can be categorized as selective, partial, or total.  The purpose of a shunt is to allow for decompression of gastroesophageal varices and portal system, but the various categories differ in the maintenance of portal flow that is provided to the liver. 

The choice of the shunt is largely dependent on the surgeon's familiarity with the procedure, along with the patient's portal venous anatomy. Total portosystemic shunts are large-caliber connections between the systemic circulation and the portal circulation with either an end-to-side or a side-to-side portacaval shunt.  A mesocaval shunt can also be utilized with an interposed graft. Total portosystemic shunts, including portacaval shunt, prevent variceal bleeding and help to control ascites in an advantageous matter as the construction of such as easy and durable. A disadvantage though is the allowance of portal blood to bypass the liver, which has metabolic functions. This leads to a predisposition for the patient to develop hepatic encephalopathy as well as acute liver failure.

Of note, portocaval shunts are discouraged in a patient who has potential for a liver transplant as scarring from dissection in the porta hepatis, and the dismantling of the shunt increases the complex nature of the overall transplant operation.  An association with portocaval shunts is the development of a sclerotic portal vein, which increases the difficulty to use for vascular anastomoses when performing a transplant.[1][2]

Indications

A primary indication for a portacaval shunt is in relation to upper gastrointestinal hemorrhage. The portacaval shunt is utilized to control massive upper gastrointestinal hemorrhage due to varices that cannot be trolled with endoscopic ablation and transjugular intrahepatic portosystemic shunt, TIPS, the procedure is not available. Oftentimes, a portacaval shunt is the preferred surgical option when a patient has undergone a prior splenectomy, splenic vein thrombosis, throughout post splenorenal shunt, ascites, the reversal of flow in the portal vein, or hepatic vein thrombosis. To select for patients for a direct portacaval shunt procedure, demonstration of a patent portal vein whether preoperatively or via laparotomy should be done.

Shunting procedures are also performed for portal hypertension. Indications for such include portal decompression in patients who have had portal hypertension that is complicated by hemorrhage due to esophageal varices uncontrolled with sclerotherapy. Procedures cannot completely interrupt the portal venous flow provided to the liver such as an end-to-side portacaval shunt, while selective decompression of the portal system using a collateral shunt like a side-to-side portacaval shunt.

Shunting plays a role in the management of a patient with portal hypertension. Portal venous pressure greater than 5 to 10 mmHg defines portal hypertension. A wide variety of etiologies can contribute to the development of portal hypertension and it can be classified as pre-hepatic, intrahepatic, or post hepatic. About 90% of cases within the USA are related to cirrhosis. Some pre-hepatic etiologies include portal vein thrombosis, arteriovenous fistulas, and splenic vein thrombosis. Intrahepatic causes include primary biliary cirrhosis, cirrhosis, infiltrative liver diseases, polycystic liver disease, venous-occlusive disease. Post-hepatic causes include, but are not limited to Budd-Chiari syndrome, inferior vena cava webs or thromboses, congestive heart failure, constrictive pericarditis.

A clinically significant manifestation of portal hypertension is variceal hemorrhage, which has substantial morbidity and mortality. Portal hypertension causes vascular channel dilatation in collateral portosystemic channels which arise where the systemic veins and portal veins meet. A common site of varices includes gastroesophageal with portal inflow coming from the left gastric vein and short gastric veins and systemic outflow from the intercostal, diaphragmatic, and esophageal veins. Collateral sites also include hemorrhoids via the superior hemorrhoidal vein and middle and inferior hemorrhoidal veins, caput medusa a where the left portal vein and umbilical and abdominal wall veins meet. In patients with cirrhosis, 50% have the presence of gastroesophageal varices. An annual rate of variceal hemorrhage is estimated to be between 5% to 15%, with size being the dominant predicting factor of hemorrhage.

When dealing with variceal hemorrhage, rapid and aggressive initial management alongside with prevention of recurrent bleeds is crucial as the mortality rate for each bleeding episode approaches about 20%. When managing an acute variceal hemorrhage, the patient should be admitted to the ICU for monitoring, resuscitation, definitive treatment. Airway protection is often needed with endotracheal intubation, which is useful during endoscopy. Venous access should be obtained with large-bore IVs and rapid initiation of blood products for volume replacement. Any existing coagulopathy can be corrected with transfusing FFP and platelets.

Antibiotic prophylaxis with a third-generation cephalosporin is typically employed as cirrhotic patients are at increased risk for infection due to impairment of post defenses particularly after an episode of large gastrointestinal hemorrhage. Spontaneous bacterial peritonitis but attributes to about 50% of these infections with urinary tract infections as well as pneumonia contributing to the remainder. The somatostatin analog, octreotide, vasoconstrict the splanchnic vessels and inhibits glucagon. It is often used as adjunctive therapy to endoscopic therapy when attempting to control acute variceal bleeding.

Rebleeding is a significant risk for untreated patients after the initial episode of variceal hemorrhage.  It is estimated that the median bleeding risk is 70% within 2 years.  It is therefore recommended that secondary prophylaxis begin once the initial hemorrhage has been controlled.  Medicinal prophylaxis includes nonselective beta-blockers, which includes nadolol and propranolol.  Endoscopic variceal band ligation can also further reduce the risk of a rebleed.  If the patient suffers from refractory variceal hemorrhage despite these prophylactic efforts, surgical shunting as well as TIPS can be appropriate.

An emergent esophagogastroduodenoscopy (EGD) is crucial in the diagnosis and therapy for a suspected acute variceal bleed. Its usefulness is in the identification of the presence of varices as well as an exclusion for other sources of bleeding, for example, gastritis, ulcers, portal hypertensive gastropathy. Endoscopic interventions are effective in controlling hemorrhage and almost 90% of patients including sclerotherapy or variceal band ligation. If this fails, luminal tamponade with Sengstaken-Blakemore or Minnesota tubes can be utilized, both of which have large round gastric balloons that can be used to compress the GE junction and decrease blood flow to esophageal varices when placed on traction with a distal port to allow for the evacuation of luminal contents within the stomach. You wary of aspiration pneumonia as it is the most common complication of luminal tamponade, but elective endotracheal intubation is recommended as it can prevent aspiration especially in patients who have encephalopathy.

In an actively bleeding patient, the acute phase of hemorrhage from the gastro-intestinal tract prompts sclerotherapy or an intraesophageal pressure balloon to control the hemorrhage. A continuous IV infusion of vasopressin at approximately 20 to 40 units/h or a selective intra-arterial infusion via the superior mesenteric artery at 0.1 to 0.4 units/min may be administered. Of note, vasopressin efficiently reduces portal pressure aids in the evacuation of blood and any fecal residue lying in the alimentary tract.

It is essential to remove any old blood even if vasopressin is not administered. This can be accomplished via colonic irrigation. This will allow for simplification during exposure and will reduce the risk of ammonia intoxication in the patient. In the circumstances, nonabsorbable antibacterial agents are used to control the nitrogen splitting bacteria located within the gastrointestinal tract. Restoration of blood volume should be performed preoperatively by the judicious use of blood, albumin, and lactated Ringer solution. Dependent on the results of coagulation studies, fresh whole blood products, vitamin K, and platelet transfusions may be indicated

A transjugular intrahepatic portacaval shunt (TIPS) the procedure is in interventional radiologic one where a tract is created between the portal vein and hepatic vein and is kept patent via the deployment of an expandable metallic stent, covered with polytetrafluoroethylene PTFE. This creates a shunt within the liver and reduces his portal pressure. Interestingly, in adults, the portal vein as well as its tributaries are valveless as the valves that existed during fetal circulation have been resorbed. This means the portal system can be decompressed by the creation of a connection to the systemic venous system. The portal vein provides approximately 75% of hepatic blood flow and about 50% of oxygen delivery as well.

Indications for side to side portocaval shunts: Bleeding gastric or esophageal varices caused by portal hypertension due to a cirrhotic liver or by hepatic diseases like schistosomiasis, bleeding due to portal hypertensive gastropathy that is unresponsive to pharmacological therapies, occluded hepatic veins, and patent inferior vena cava with Budd-Chiari syndrome, intractable ascites that is unresponsive to nonsurgical interventions/therapies, or a failed transjugular intrahepatic portosystemic shunt.

No surgical decompressive procedure performed on the portal system has a beneficial effect on liver function. Thus, the end results of such an operation depend largely on the progress of liver disease. In patients who have had a prior splenectomy, thrombosis of a splenorenal shunt, splenic vein thrombosis, or those who have reversed flow in the portal vein, and end-to-side portacaval shunt is the procedure of choice. An end-to-side anastomosis procedure involves the portal vein being ligated into the hilum of the liver and the distal portion of the portal vein anastomosis to the IVC.

Indications for the shunt are when there is no evidence of ascites and when the portal blood flow is reversed into the hepatoportal direction. This can be determined due to rising pressure in the hepatic end of the temporarily occluded portal vein. In an end-to-side portocaval anastomosis, portal venous blood flow is shunted away from the liver, but hepatic artery flow is preserved.[3][4][5]

Contraindications

Tolerability of a portacaval shunt procedure, the patient depends upon liver function time of operation. A good rule of thumb is attempted to improve a patient's nutrition as well as hepatic state prior to surgery. This can include several weeks of medical management consisting of diet, activity, and diuretics. After a thorough history and physical examination, hepatic function studies, as well as hepatosplenic hemodynamic determinations, are then obtained. The selection of procedure is dependent upon the patency of the portal and splenic veins, the result of liver function lab work and studies, the amount of portal venous blood that is being shunted, and if the patient is bleeding acutely. Evaluation of liver function is performed, which includes a combination of clinical factors and laboratory studies.  

Patient selection for portocaval shunting is based on clinical status, the result of liver function tests, and the interpretation of hepatic hemodynamics that are determined via radiological studies. Ideally, the patient's considered for shunting should be less than 60 years old, have no evidence of encephalopathy, ascites, jaundice, or muscle mass wasting. A patient who has a history of ascites or jaundice is at an increased surgical risk. Platelet counts, as well as PTT, should also be within normal limits. Any deviation from these values should be attempted to be corrected through parenteral administration of whole blood, fresh frozen plasma, or albumin as well as through vitamin K. In a patient who suffers from ascites, and diuretic therapy may be indicated. Electrolyte and acid-base imbalances should be controlled, especially if a patient has hypokalemic alkalosis. Any coagulation deficits other than those associated with prothrombin can be corrected with fresh frozen plasma and platelet concentrate. The patient should be typed and screened prior to their operation. At the time of surgical intervention, 10 to 12 units of whole blood should be readily available to the surgeon.

The serum albumin levels should be greater than 3 g/dL when assessing nutritional status. Prothrombin time should be less than 1.5 times normal. Sodium sulfobromophthalein, phenolphthalein used as a diagnostic aid to determine hepatic function, should be below 30% at 30 minutes time. Whilst deviation from these listed criteria is not absolute contraindications for surgery, and it does place the patient at surgical risk as these measurements are directly proportional to the degree of the patient's hepatic decompensation. A liver transplant can also be considered in these patients. If a shunting procedure is desired for portal hypertension, it can be divided into 3 types, which include portocaval, splenorenal, and mesocaval.

When evaluating the patient, esophagoscopy and gastroscopy should routinely be obtained as well as barium studies both the esophagus and stomach. Determination of hepato-splanchnic hemodynamics can be performed from an estimation of total hepatic blood flow, hepatic vein catheterization, splenoportography, indirect portography, liver scan, and visceral angiography. Radionucleotide scanning can be utilized to estimate the total hepatic blood flow. The degree of portal hypertension and the amount of hepato-pedal portal blood flow can be determined with the utilization of hepatic vein catheterization.

The typical single best source of estimating the portal hemodynamics is splenoportography. To undergo this study, prothrombin time must be less than 1.5 times the normal with an operating room readily available, should trouble from hemorrhage subsequently developed. splenoportography can reveal the patient's degree of portal hypertension and the degree of opacification of the portal vein. This provides pertinent information concerning the severity of compromise to portal blood flow to the liver. The information gathered from the listed hemodynamic studies can influence the choice of which shunt is to be performed.[6][7][8]

Preparation

To perform a portacaval shunt, a general anesthetic is required. With regard to anesthesia, major hazards include hypoxia and hypotension. In patients who have impaired liver function, there is the possible danger of using a halogenated compound, so these agents should not be employed during the surgical operation. Other commonly used general anesthetic agents, as well as muscle relaxants, appear to have no to a little adverse effect on liver function. The availability for the administration of fluids and of blood products in adequate amounts in a rapid fashion, if needed, should be made.

In terms of positioning the patient, the be patient should be elevated on the right side to an approximately 30-degree angle to aid in the extension of the right subcostal region into the flank area to accommodate for better exposure for the procedure. The table should be adjusted in order to widen the space between the right iliac crest and the right costal margin in order to perform the operation via a long, right subcostal incision. If the decision between performing a portocaval and splenorenal shunt is not made prior to the operation, the patient should be put in the supine position so either procedure can be carried out by extending the initial central incision to the appropriate direction.

In terms of operative preparation, the skin is cleansed above the nipples and well below to the pubic symphysis. On the chest, particularly, the left side should be prepped as an extension of the incision into the thorax may be required.[2]

Technique

An incision along the right subcostal margin is made, which crosses the left rectus abdominis muscle and extends into the flank. Adequate exposure can also be obtained with a large, midline incision extending to the xiphoid process. This right, subcostal incision extends from the xiphoid to well into the flank region and is typically made 2 fingerbreadths below the costal margin. Once the peritoneal cavity is opened, routine exploration is carried out. The diagnosis of portal hypertension is then confirmed. This is done by catheterization of an omental vein, preferentially towards the stomach. This measurement is useful even if the splenic pulp pressure was measured preoperatively as this will allow for a more valid comparison of the pressure’s pre-shunt versus post shunt. The pressure typically measures 30 cm of saline or greater above the portal vein level. If pressures are considerably lower, this would not indicate the necessity or even desirability of a shunting procedure to be performed. If a prior splenoportogram has identified a suitable portal vein, dissection begins to mobilize the duodenum.

When the presence of a suitable portal vein for a portacaval shunt is in doubt, the portal vein should be first isolated and then surveyed with a portal venogram before exposure of the inferior vena cava is undergone.

Once the entrance is gained into the peritoneal cavity, retractors are then placed, and an incision of the posterior peritoneum overlying the inferior vena cava is incised with electrocautery by an extended Kocher maneuver. Any fibro areolar tissue that covers the anterior surface of the IVC is cleared, and the vessel is isolated circumferentially by both blunt and sharp dissection from the entrance of the left and right renal veins, below, all the way to the point where it disappears posteriorly to the liver above. To accomplish this, tributaries must be ligated with fine silk ligatures and then subsequently divided. Often included tributaries are the right adrenal vein, pairs of lumbar veins, and hepatic veins from the caudate lobe of the liver.

Over the posterior peritoneum, collateral venous networks are typically enlarged considerably and are thus subject to increased pressure. This is important as this normally avascular area may, in fact, be quite the opposite, and while performing dissection during the Kocher maneuver, progress should be made by clamping and ligating peritoneal surfaces instead of a usual simple incision lateral to the descending portion of the duodenum. Precautions like these apply to all dissections performed during the procedure located in the retroperitoneal space as well as in the hepatoduodenal ligament. The inferior vena cava usually is exposed without much difficulty. If additional exposure is required, it may be obtained by resection of a portion of the enlarged caudate lobe of the liver. Through and through mattress sutures of 0-0 silk are placed to control bleeding prior to division of the liver. Next, the caudate lobe of the liver is freed from the IVC and any veins encountered or subsequently ligated. The use of argon beam electrocoagulation may be helpful in this circumstance. Using careful dissection, the portal vein is identified within the hepatoduodenal ligament. During the dissection process, it can be helpful to place tape or rubber tissue drain around the common bile duct. This will facilitate exposure of the portal vein.

Exposure of the portal vein should extend from the hilum of the liver to the pancreas on the superior surface, where pancreatic tributaries should not only be located but also protected. Once all 3 structures within the hepatoduodenal ligament have clearly been identified, the leftover fatty adipose tissue containing enlarged venous and lymphatic channels can be divided to allow the portal vein to be brought into closer proximity with the inferior vena cava.

Once the inferior vena cava has completely been mobilized, it can be lifted upwards toward the portal vein. If complete isolation of the IVC circumferentially is not accomplished, failure of the procedure can ensue and may not be able to be completed as the separation between the portal vein and IVC is too wide. Next, a superior retractor is positioned medially to retract the liver at the point of the entrance of the portal triad.

In the postero-lateral aspect of the portal triad lies the portal vein, and it is approached posteriorly. Division by blunt and sharp dissection of fibrofatty tissue on the posterior lateral aspect of the triad, which contents include nerves, lymph nodes, and lymphatics, is performed. Importantly, there is no portal venous tributary on this aspect of the triad, so this technique is safe in nature. Once the surface of the portal vein has been exposed, a vein retractor or Gilbernet retractor is inserted to medially retract the common bile duct. Next, the portal vein is circumferentially mobilized at the midportion. An umbilical tape is used to encircle the portal vein. The vein is isolated up to its bifurcation into the hilum of the liver. The portal vein and IVC can then be brought together using traction via the surrounding umbilical tapes. This will elucidate adequate mobilization of the portal vein and the inferior vena cava. This is crucial to show that the vessels can be approximated without excessive tension. The inability to do so provides evidence that the vessels have not been mobilized adequately and necessitates further dissection of such vessels.

It is suggested that to facilitate the approximation of the vessels, resection of part of an enlarged caudate lobe in a cirrhotic liver can be performed, but sources are conflicting. Tributaries located on the medial aspect are ligated in continuity with silk and then divided. The umbilical tape was used to pull the portal vein out of its bed to clear it to the point where it disappears posteriorly to the pancreas. There is a tough, fibrous fatty tissue that connects the portal vein to the pancreas that requires division. Tributaries located on the medial aspect of the portal vein and the posterior lateral aspect are divided. It is typically unnecessary to divide the splenic vein.

In order to perform a side-to-side portocaval anastomosis, wide mobilization of the portal vein is a reason for a difficulty that surgeons may encounter to complete a side-to-side shunt is the failure of mobilization of the portal vein posterior to the pancreas. In certain patients, it may be necessary to divide part of the head of the pancreas in between right-angle clamps to allow for adequate mobilization of the portal vein. Suture ligatures can be used to trolled bleeding from the edges of the pancreas that is divided. Prior to incision of the pancreas, it is imperative that the surgeon inserts his/her index finger in the tunnel between the pancreas and the portal vein in order to palpate to detect the presence of a replaced common hepatic or right hepatic artery off of the superior mesenteric artery and to cross the portal vein. With a portacaval shunt, the portal vein blood flow provided to the liver is diverted. Hence ligation of the hepatic arterial blood supply can be lethal.

Prior to the formation of the portocaval anastomoses, pressures within the portal vein and inferior vena cava are measured via a saline manometer by means of direct needle puncture. If the pressure gradient of the portal vein-inferior vena cava is greater than or equal to 150 mm saline, this is representative of a clinically significant portal hypertension. Typically, patients who have bleeding esophageal varices have a gradient of 200 mm saline or more.

Where the portal vein crosses closest to the IVC is commonly just proximal to the entrance of the renal veins. If a side-to-side portacaval shunt has been decided, 2 non-crushing clamps are applied onto the portal vein for it to be rotated to expose the inferior surface. This step is necessary as it helps prevent twisting or angulation of the portal vein as the anastomosis is being accomplished. In preparing the anastomotic sites, 2 points must be borne in mind. The first point is that the inferior vena cava and portal vein are not parallel in relation to each other. Hence openings in the longitudinal axis of each would lead to twisting of the anastomotic site upon releasing the clamps. It is crucial to incise the portal vein in an oblique fashion to avoid twisting of the site.

A second point to keep in mind is that a simple longitudinal window either in the IVC or portal vein will not be adequate for a satisfactory shunt due to the low pressures within the venous system. In this manner, a simple slit opening will tend to close as it will behave more like a valve, thus resulting in a high incidence of portacaval shunt failure. A definite portion of the veins should be excised in an elliptical fashion to create an anastomosis between windows. It is not commonly necessary cross clamped the IVC completely.

To perform a side-to-side portocaval anastomosis, a Satinsky clamp is placed in an oblique fashion across and approximately 5 cm segment of the IVC on the anterior medial wall parallel to the overlying portal vein. The clamp is placed in order to exclude a portion of the lumen, which is satisfactory for this purpose. In general, the anastomosis should be created, so it is at least as large as the diameter of the patient's portal vein. Continuous suture of fine, nonabsorbable suture material on atraumatic needles helps accomplish the anastomosis itself. The IVC is then lifted towards the direction of the portal vein. An approximately 5 cm segment of the portal vein is then isolated in between 2 angled vascular clamps, and then the portal vein is depressed forwards inferior vena cava. This allows for the vessels to be in apposition with one another. An approximate 2 to 2.5 cm strip of the inferior vena cava, as well as a 2 to 2.5 cm in length strip of the portal vein, is excised using scissors. The excision is performed in a longitudinal segment of the walls of each of the vessels. 5/0 silk is used as a retraction suture, placed in the IVC on the lateral wall opening, and a hemostat is used as a weighted attachment to keep the orifice open.

Clamps over the portal vein are released briefly to facilitate flushing out of any clots. Both vessel’s openings are next irrigated with saline. To begin the anastomosis, a posterior continuous over and over suture of 5/0 vascular suture material is used. This is tied at each end of the anastomosis site. Beginning at each end of the anastomosis site, an anterior row of sutures, which consists of everting continuous horizontal mattress stitch of 5/0 vascular suture material, is performed. This suture is started at the most the site and is stopped after about 3 to 4 throws and left in a loose fashion so that the anterior surface of each vessel be the completion of the anastomosis is being performed. This helps prevent inadvertent inclusion of the posterior wall into the anterior row of sutures. This suture is begun at the superior end of the anastomosis site and is with a continuous level of tension until the inferior suture is encountered. Once this meeting occurs, her suture is drawn tight. Subsequently, prior to neatly drying the inferior suture, released momentarily to again flush out irrigated using saline. Once the anastomosis is completed, a single interrupted tension suture placed just distal to each of the ends of the anastomosis. Remember that the IVC and the portal vein are both very fragile. This necessitates caution during suturing to avoid trauma to the venous walls. This precaution applies to the surgeon as they are suturing as well as to the assistant who is holding the clamps.

Even a small slight shearing force that is created by shifting the vascular clamps patient to one another can disrupt a partly completed anastomosis. Notably, leaks from the anastomotic site, especially the left side, can be rather difficult to expose for any subsequent re-suturing. Once the anastomosis is finished, one at a time is the occluding clamps released to check the suture line for adequacy. Even though the portal vein represents a higher-pressure system in the anastomosis, it can be convenient to release one of the portal clamps first as they tend to be easier to reapply if there is unsatisfactory hemostasis. Once all clamps are released, it is often possible to detect the proper function of the shunt just by visible turbulence in the inferior vena cava. Help to aid the opening that lies between the two veins via invaginating the portal vein on the anterior wall can be used to make certain of the patency of the anastomotic site. If a repeat measurement of pressure within the portal system is taken, this tends to show that there has been a reduction to about half of the preoperative measured level.

 To relieve tension off of the anastomotic suture line. The overlying clamp on the inferior vena cava is first removed, followed by the hepatic side of the portal vein, and then the last clamp removed is that on the intestinal side. Bleeding around the anastomosis does not frequently occur, but it can be controlled to well-placed interrupted sutures of the same 5/0 vascular suture material used. As the pressures in the inferior vena cava and portal vein are measured prior to the anastomosis, post shunt pressures are measured. The post shunt pressures in the inferior vena cava and the portal vein are usually identical. Of note, a pressure gradient that is greater than 50 mm saline between the vessels, is indicative of an obstruction within the anastomosis even if the obstruction cannot be appreciated on palpation. In these cases, the anastomosis should be opened to remove any existing clots, and if required, the entire anastomoses may have to be taken down and redone. It is critical that there be a saline gradient no greater than 50 mm between these vessels to permanently achieve adequate portal decompression and avoid thrombosis of the portacaval shunt. In terms of closure, the incision is closed in layers. Ordinarily, drainage of the right upper quadrant is not a requirement unless unusual trauma to the liver, biliary system, or pancreas has occurred. The employment of retention suturing can be useful.

 A side-to-side anastomosis and a portacaval shunt have been preferred by some surgeons in the presence of portal hypertension with no evidence of an increase in pressure on the hepatic and of the temporary occluded portal vein. This is suggestive that the arterial supply was going to the liver and that decreasing the portal pressure via this anastomosis with the inferior vena cava will not result in the diversion of arterial supply provided to the liver. An advantage to type of shunt is the fact that it provides decompression to the hepatic sinusoids, which have the potential to be beneficial in treating patients who have intractable ascites coinciding with variceal hemorrhage. Using the portacaval shunt in treatment for refractory ascites is not a universally accepted indication for the procedure, although several studies suggest that it may, in fact, be an effective model for therapy. A side-to-side portacaval shunt is preferred when attempting to control refractory ascites.

If an end-to-side portacaval shunt is desired, this is done by dividing the portal vein and in as close proximity to the liver hilum as possible. A key factor is to ensure that the proximal stump of the portal vein is not left to short, as this is a large vein and under a considerable amount of pressure. Enough room should be left for a double ligature, the second of which being a transfixion suture ligature with several millimeters of vein cuff to assure proper and adequate control of the hepatic side of the portal vein. Note that a longer length stump of the portal vein must be retained if a double end to side shunt is indicated.

The placement of a non-crushing vascular clamp will be as close in proximity to the pancreas as possible on the portal vein to leave the maximal amount of portal vein freed for the anastomotic site. Yet again, the appropriate side on the inferior vena cava is chosen and then excluded by the usage of a partially occluding vascular clamp, and an elliptical excision of the vein wall is performed. As with the side-to-side portocaval anastomosis, a single layer continuous anastomosis of the arterial synthetic suture is performed for an end-to-side portacaval shunt. This anastomosis may be easier to accomplish, but again note the fragility of the vein walls when approaching this. Once the anastomosis has been completed, individually, the clamps are removed. If the hemostasis achieved a satisfactory, the procedure is then concluded as described above.[8][9][2]

Complications

When dealing with postoperative care, in the immediate postoperative phase, it is crucial to prevent hypoxia in the patient. It is recommended that for the first 24 to 48-hour time periods, oxygen is administered routinely. Serial hematocrits, as well as central venous pressure, should be assessed to ensure the maintenance of an adequate blood volume. Portocaval shunts have the highest incidence of hepatic coma, so efforts postoperatively should be continuous to decrease protein catabolism.

During the postoperative period, when the patient is NPO, they should receive a minimum of 200 g of carbs per day. This will aid in the prevention of the undue breakdown of protein. Once p.o. intake is resumed, protein intake should be restricted initially to 30 g/day. If the patient tolerates this well, gradual increments, usually an increase in 10 g every other day, can be instilled until a level of about 50 to 75 g of protein per day is accomplished. Patient tolerance of this nitrogen load can be monitored with a fasting and a 2-hour postprandial blood ammonia level. If any signs of hepatic insufficiency develop, protein intake should be restricted, and the patient should receive intestinal antibiotics. Monitoring of the prothrombin activity and supplemental vitamin K can be given as needed.

Vitamin preparations can also serve as a useful adjunct and be administered to the patient postoperatively. A rather dangerous postoperative problem that can also be distressing is ascites. It is critical to monitor the fluid and sodium intake to prevent and/or minimize this complication. If the development of ascites occurs, it can be best managed by severe sodium restriction in combination with diuretic therapy. There is an increased incidence of peptic ulceration following a portacaval shunt procedure. This should be remembered, and appropriate, low-sodium antacid therapy and proton pump inhibitors should be administered.[2][10]

Enhancing Healthcare Team Outcomes

Portacaval Shunt

The management of portal hypertension and variceal hemorrhage is challenging and complex. While once the domain of the general surgeon, today it is realized that the family practitioner, anesthesiologist, and allied healthcare practitioners play a vital role. To derive good outcomes, the goals and objectives of the portacaval shunt have to be defined prior to taking the patient to surgery. A recognition of symptomatology of the patient, typically seen in a primary care setting with a proper referral is of large importance. As with any other complex procedure, the preoperative workup must be thorough and the patient should be seen by a pulmonologist and cardiologist to optimize lung and cardiac function. Because of the potential risk of injury to the vascular system, caution during dissection should be undertaken and if an inadvertent injury occurs to these structures, prompt consultation from a vascular surgeon is warranted.

During the early postoperative period, close interdisciplinary management by the surgical team, anesthesiologists, and nursing staff is warranted for the optimized stabilization of these critical patients and for early identification of appropriate management of complications.

Evidence-based Approach

By utilization of an interprofessional team, thus providing a holistic and integrated approach to postoperative care, the best possible outcomes for the patient can be achieved.

Level 5 evidence-Patients with portal hypertension tend to have a syndrome of multiorgan dysfunction. These patients are thus at an increased risk for perioperative morbidity and mortality. The preoperative assessment should seek to distinguish between a patient who has compensated versus decompensated cirrhosis and identify factors that increase surgical risk, including malnutrition, coagulopathy, and renal dysfunction. 

The Child-Turcotte-Pugh and Model for End-stage Liver Disease scores are some of the most commonly used tools for surgical risk stratification. Perioperative risk in patients with portal hypertension and cirrhosis may be mitigated by referral to the proper specialist providers, nutritional optimization, as well as avoidance of surgery when imprudent. Referral to proper specialists can better identify patients who are candidates for surgery and whom surgery will prove beneficial for. In the circumstance of portacaval shunt procedures, this includes, but is not limited to a nephrologist, gastroenterologist, hematologist, and in severe cases, a transplant surgeon. Nutritionists aid in the optimization of a patient's nutritional status prior to surgical intervention. Medicinal recommendations via the specialist and pharmacist are critical to the positive outcomes for the patient. The approach to the patient is holistic and an integrative process that utilizes an entire team of medical professionals.[11][3][2]


References

[1] Leung KK,James PD,Jaberi A,Hirschfield GM, Esophageal Stenting as Bridge Therapy to Direct Intrahepatic Portocaval Shunt for Refractory Variceal Bleeding. Hepatology (Baltimore, Md.). 2020 Aug 11     [PubMed PMID: 32780882]
[2] Zatevakhin II,Tsitsiashvili MS,Shipovskiy VN,Monakhov DV,Chelyapin AS, [Redo surgery for portacaval shunt dysfunction after TIPS procedure]. Khirurgiia. 2019     [PubMed PMID: 31317936]
[3] Šmíd V, Liver fibrosis. Vnitrni lekarstvi. 2020 Summer     [PubMed PMID: 32972186]
[4]     [PubMed PMID: 32901570]
[5]     [PubMed PMID: 32671331]
[6]     [PubMed PMID: 32965518]
[7] Fejfar T,Vaňásek T,Hůlek P, Bleeding in portal hypertension. Vnitrni lekarstvi. 2020 Summer     [PubMed PMID: 32972182]
[8] Philips CA,Rajesh S,George T,Ahamed R,Mohanan M,Augustine P, Early, late, or no shunt embolization in patients with cirrhosis- and portosystemic shunt-related hepatic encephalopathy. Indian journal of gastroenterology : official journal of the Indian Society of Gastroenterology. 2020 Sep 15     [PubMed PMID: 32929684]
[9] Glowka TR,Kalff JC,Manekeller S, Update on Shunt Surgery. Visceral medicine. 2020 Jun     [PubMed PMID: 32775351]
[10]     [PubMed PMID: 32874401]
[11]     [PubMed PMID: 32976187]