Preoperative assessment

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KYLE J. VAN ARENDONK AND PAUL M. COLOMBANI

31.1 INTRODUCTION

Liver transplantation has become the standard of care for end-stage liver disease in children. As liver transplantation has become increasingly successful, the focus has now shifted to the improvement of long-term outcomes for paediatric liver transplant recipients. The liver transplant operation is no doubt as major an operation as any other performed in children, and thus proper preoperative preparation of both the patient and family is vital to optimise transplant outcomes. The ethics of and specific indications for paediatric liver transplantation are covered elsewhere. This chapter instead focuses on preoperative assessment of the paediatric liver transplant candidate, specifically focusing on medical evaluation, contraindications to transplantation, timing of the transplant procedure and preparation of the child’s family regarding perioperative and postoperative expectations.

31.2 GENERAL PRINCIPLES

Children with chronic liver disease are generally referred for liver transplantation when they develop signs of hepatic dysfunction, portal hypertension or growth failure. Several important principles should guide the initial evaluation of a new transplant candidate. First, the transplant team should confirm the need for liver transplantation by comparing the natural history of the patient’s underlying disease to the expected survival after liver transplantation. One-year and 5-year patient survivals after liver transplantation in the United States were 89.0% and 76.5% for children <1 year old, 85.6% and 76.6% for those 1–5 years old, 90.8% and 85.5% for those 6–10 years old and 92.6% and 80.7% for those 11–17 years old, respectively (for transplants performed in 1997–2004) [1].

For comparison with these average outcomes after transplantation, several tools can be used to assist in determining the prognosis of patients with severe liver disease, most notably the paediatric end-stage liver disease (PELD) model, which is used to prioritise patients for liver allocation in the United States. Similar to the model for end-stage liver disease (MELD) score that is used in adults, the PELD score uses several clinical characteristics – specifically age, serum albumin level, serum bilirubin, international normalised ratio (INR) and growth failure – to predict mortality of children under 12 years of age who are waiting for transplantation (Table 31.1) [2]. In addition to the PELD score, the development of complications from liver disease (ascites, variceal bleeding, hepatic encephalopathy, spontaneous bacterial peritonitis or hepatorenal or hepatopulmonary syndrome) should also be noted given their significant negative impact on prognosis.

Second, the transplant team should confirm that all other effective treatments for the patient’s disease have already been exhausted. While liver transplantation can successfully provide excellent long-term survival and quality of life, the procedure nonetheless is very expensive and has significant risks of morbidity and mortality, and thus should not be undertaken if unnecessary. A number of paediatric liver diseases have other treatments that should be attempted prior to proceeding with liver transplantation. For example, liver disease secondary to tyrosinaemia and glycogen storage diseases often responds well to dietary modifications or medical therapy, preventing or at least delaying the need for liver transplantation. Likewise, some chronic cholestatic disorders, such as Alagille syndrome, can cause growth failure, bone disease, xanthomatosis and severe symptoms such as pruritis, while only rarely resulting in end-stage liver failure. While these symptoms can still merit a valid indication for liver transplantation, all other options for symptomatic therapy should be exhausted first. Partial cutaneous biliary diversion, for example, is an alternative successful treatment for xanthomatosis and pruritus in children with Alagille syndrome [3]. Because the efficacy of these alternative therapies is not guaranteed, however, it is often wise to place the patient on the transplant waiting list while attempting these other interventions.

Table 31.1 Components of the PELD model

PELD model

Age < 1 year

Serum albumin

Serum bilirubin

INR

Growth failure (height or weight Z score of ≤2)

Finally, the assessment should determine the patient’s likelihood of being an appropriate candidate for liver transplantation, specifically the presence of significant comorbidities or acute illnesses that would impact the patient’s likelihood of surviving the operation. This portion of the assessment consists of a complete history and physical examination, cardiopulmonary evaluation and laboratory studies to confirm the severity and aetiology of the patient’s liver disease, as described in greater detail below (Table 31.2). In addition and especially for adolescent patients, the likelihood of adhering to posttransplant medical care should also be assessed.

31.2.1 Preoperative medical evaluation

The paediatric liver transplant candidate should be carefully evaluated with a detailed history and physical examination, with a focus on the patient’s aetiology of liver disease and cardiopulmonary fitness. The evaluation should be guided by the specifics of the patient’s underlying condition. For example, patients requiring liver transplantation for Alagille syndrome should undergo careful examination for congenital heart disease, which is common among these patients and associated with increased mortality [4]. Likewise, patients requiring liver transplantation for cystic fibrosis or α-1-antitrypsin disease should undergo careful evaluation for lung disease [5]. Physical examination should include a careful oral examination for dental caries or abscess that would require dental intervention prior to transplantation.

Potential adjuncts to the cardiopulmonary evaluation include electrocardiography, cardiac echocardiography and pulmonary functions tests. Even in the absence of hypoxia or respiratory symptoms, significant pulmonary alterations are often identified [6]. Hepatopulmonary syndrome can be confirmed with echocardiogram, and the degree of intra-pulmonary shunting can be assessed using ^99mtechnetiummacroaggregated albumin (MAA) perfusion lung scan [7]. Cardiac catheterisation may be necessary when portopulmonary hypertension is suspected in order to rule out other causes of pulmonary hypertension.

Laboratory evaluation should assess the patient’s severity and aetiology of liver disease, as well as renal function and nutritional status. Patients should also be tested for current or previous hepatitis B virus, hepatitis C virus, Epstein–Barr virus, cytomegalovirus and human immunodeficiency virus infections. While laboratory values are important, perhaps the best assessment of the adequacy of liver function is a careful assessment of the patient’s growth and development. The adequacy of nutrition is best monitored with serial triceps skinfold and midarm circumference measurements, rather than weight alone. The absence of continued growth despite maximal nutritional support is a key sign that transplantation should be performed expeditiously.

Abdominal imaging should be performed to rule out the presence of hepatic malignancy and to determine hepatic artery and portal vein anatomy to plan the operative approach. Magnetic resonance (MR) angiography and computed tomography (CT) angiography are excellent tools to evaluate the vascular anatomy, making conventional angiography only rarely necessary [8,9]. A detailed Doppler ultrasound scan may also provide sufficient vascular assessment for many children [10]. In cases of biliary atresia treated initially with a Kasai porto-enterostomy, abdominal imaging can also be helpful to evaluate the type of portoenterostomy performed, which helps in planning the approach to choledochoenterostomy during the transplantation. Abdominal imaging for preoperative vascular assessment of the donor should also be performed prior to living donor liver transplantation.

Table 31.2 Key components of the paediatric liver transplant candidate evaluation

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