The anhepatic phase begins with the clamping of the portal and arterial inflow to the native liver. In cases that allow caval preservation, once inflow is occluded, the hepatic veins are sequentially clamped at the level of the cava and are divided as far into the liver as possible. The portal vein is then clamped close to the confluence and divided above the native bifurcation. A common cuff of all three hepatic veins is then created after a clamp is placed above the level of their entrance into the cava (Fig. 10.2).

When the native cava cannot be preserved, meticulous dissection of the plane behind the intrahepatic cava should be performed prior to inflow occlusion. This exploration should include the entire retrohepatic cava from the diaphragm to the level of the left adrenal vein, with careful attention to the posteriorly lying azygous vein at the level of the diaphragm. Once this dissection is completed, a test occlusion of the portal vein and cava is performed (Fig. 10.3). If hemodynamic instability is encountered, the clamps can be removed and the patient can be resuscitated further. If the patient is hemodynamically stable during the test occlusion, the portal vein is clamped and divided and the cava is divided. The liver and cava are then removed and the vasculature is prepared for anastomosis.

Vascular reconstruction begins with an end-to-end anastomosis of the suprahepatic cava to either the common cuff of the hepatic veins (piggyback) (Fig. 10.4a) or to the native suprahepatic cava (Fig. 10.4b).

If the native cava was preserved, caval flow can be returned once this anastomosis is completed. This is accomplished by careful repositioning of a vascular clamp onto the allograft cava, above the anastomosis. The donor infrahepatic vena cava should be controlled in these cases and can either be used for warm blood flushing at reperfusion, or simply can be ligated prior to reperfusion. In cases requiring caval replacement, an end-to-end anastomosis is then fashioned between the native and allograft vena cavae.

An end-to-end anastomosis between the allograft and native portal veins is then fashioned. Careful consideration of the position of the liver once the abdomen is closed (with placement of cold laparotomy pads above and behind the liver) often leads to considerable shortening of the allograft portal vein. The portal vein should be carefully flushed prior to completion of the anastomosis by temporarily releasing the clamp and filling the allograft with heparinized saline. This technique avoids distal embolization of clot if any is present in the occluded native portal and mesenteric systems. If performed in a running fashion, the portal anastomosis should be completed with a ‘growth factor’ approximating the diameter of the portal vein.

Reperfusion of the allograft occurs with the release of the portal vein. The allograft should be aggressively warmed during this phase, prior to stepwise release of the lower caval clamp (if present) and then the suprahepatic clamp. Once the patient is resuscitated and surgical hemostasis is obtained, attention can be turned to the hepatic arterial anastomosis. In children, arterialization should be performed with optimal inflow, utilizing any potential arterial branch orifices for creation of branch patches. In most cases, end-to-end anastomoses are achieved between a branch patch created by opening the splenic artery at the level of the donor common hepatic artery and splenic arteries and a branch patch of the recipient common hepatic artery at the origin of the GDA. This is generally done with interrupted 7-0 or 8-0 monofilament suture. If the size of the vessels permits a running anastomosis, controlled release of the inflow should be performed to allow maximal expansion of the anastomosis, and the sutures are tied with an additional small growth factor. Doppler interrogation of the artery should be performed in all cases, and any issues should be immediately addressed. In cases of apparently patent anastomoses, arterial inflow can be augmented by occluding the previously dissected splenic artery. If this is unsuccessful or if there is any concern regarding the anastomosis, revision should be performed. If inflow seems inadequate, a deceased donor arterial conduit can be anastomosed in an end-to-side fashion to the infrarenal abdominal aorta and brought through the transverse mesocolon into the lesser sac. A standard end-to-end anastomosis can then be recreated between this conduit and the allograft hepatic artery.

After an allograft cholecystectomy is completed, the biliary reconstruction is then performed to either a retrocolic Roux limb (Fig. 10.5a) or to the native common hepatic/bile duct (Fig. 10.5b). An end-to-side hepaticojejunostomy is completed over a small indwelling biliary stent using 6-0 absorbable monofilament sutures in an interrupted fashion with the sutures tied externally. In general, no more than 10 sutures should be employed for this anastomosis, regardless of the size of the duct. A similar technique is utilized in duct-to-duct anastomoses. The distal ends of the bile duct should be carefully trimmed prior to reconstruction, to ensure adequate vascularity.

Hemostasis should be meticulously maintained throughout the procedure, and minimal correction of coagulopathy should be needed in the post-anhepatic phase. The use of anticoagulation varies between centers; we routinely use low-dose heparin after reperfusion if a thromboelastogram reveals normal indices.

Abdominal closure is often difficult in children receiving allografts more than twice the size of the native liver. Children with metabolic disorders are particularly prone to the development of venous engorgement and edema while the portal vein is occluded for anastomosis. After closure, transabdominal ultrasound and Doppler interrogation of the allograft should be performed in all cases, and the abdomen should be immediately reopened if there are any changes in vessel waveforms when compared to the ultrasound obtained after arterialization. Changes in ventilatory parameters during attempted abdominal closure also should force the surgeon to consider delayed abdominal closure and immediate placement of a temporary Silastic silo, with planned reexploration several days later, after resolution of the immediate perioperative edema. Daily evaluation of the abdominal laxity allows the surgeon to determine the optimal day of closure. Some patients require immediate closure of only full-thickness skin flaps. In these cases, we delay formal abdominal wall reconstruction for at least 6 months to ensure stability of the allograft, and we often employ muscle-splitting incision and use of bioprosthesis to achieve a tension-free closure.

We have also encountered several cases in which even the skin flaps cannot be primarily closed at the time of LT. These patients are partially closed, and we use negative-pressure wound devices to assist in healing by secondary intention (Fig. 10.6). These patients are generally those with larger graft-to-recipient weight ratios and those who have had multiple abdominal surgeries that limit the elasticity of the abdominal wall. In general, we attempt to close at least skin over the majority of the intestine and colon, in favor of leaving the liver capsule in the base of the open, granulating wound.

Extrahepatic portal vein obstruction (EHPVO) is a rare cause of portal hypertension in children. EHPVO can be acquired (umbilical catheterization, omphalitis, neonatal sepsis) or congenital (anatomic abnormalities, congenital thrombophilias). It often occurs in the absence of underlying liver disease. Although it may take years to manifest clinically, patients with EHPVO generally manifest with gastrointestinal hemorrhage, hypersplenism, and subtle neuropsychiatric disorders associated with mild encephalopathy. Although the long-term natural history of children with EHPVO is not well documented and the timing of surgical intervention is somewhat controversial, a recent consensus group on the treatment of portal hypertension in children has suggested that patients with EHPVO would benefit from creation of a meso-Rex bypass (MRB) at the time of diagnosis.

Since its description in 1992, the MRB has offered a more physiologic solution to patients with EHPVO. An MRB bypasses mesenteric blood flow from the superior mesenteric vein to the intrahepatic left portal vein with an autologous vein graft. Creation of an MRB significantly improves hypersplenism, liver dysfunction (as measured by prothrombin time), encephalopathy (ammonia levels), and growth retardation (weight Z scores). In experienced centers, MRB can be performed with minimal perioperative morbidity and excellent long-term patency rates (91 % at 7 years in one large, single-center study).

Technical variant pediatric liver transplantation (TVPLT) has significantly reduced pediatric transplant waitlist mortality. Variant techniques include deceased donor split liver transplants and live donor liver transplantation (LDLT). Although studies vary in their findings, in centers adept at the procedures, technical variant allografts can be used safely with minimal or no increase in morbidity and mortality. Assessment of the proper graft choice is based on size, the anatomy of the recipient, and an understanding of the pathophysiology of the underlying disease. Normal liver volume is approximately 2 % of recipient body weight, and clinical transplantation aims to replace at least 1 % of recipient body weight with functioning liver mass. In most children weighing less than 20 kg, the left lateral segment from a deceased donor or a healthy adult live donor is often satisfactory. The target ratio of graft weight to recipient weight is 0.8–4 %. For a larger child, sometimes the left lobe is used. Factors that influence the optimal graft mass include the degree of underlying portal hypertension and the recipient’s abdominal domain.