What is an APOLT ?

Auxiliary partial orthotopic liver transplantation (APOLT) is a surgical procedure performed for selective cases of acute liver failure in the paediatric age group. The nomenclature is self-explanatory and helps elucidate the steps involved in this unique surgical technique.

Auxiliary :  defined as additional/ supplementary.

• Current ex-vivo liver support devices fail remarkably in their attempt to replicate many of this organs’ diverse physiological functions following acute liver failure [1].
• This role is however adequately taken up by the transplanted graft which “supplements” the failing native liver left behind in the recipient.

Partial & Orthotopic :

• A partial recipient hepatectomy (usually left extended in pediatric group ) is performed followed by implantation of a whole left lobe or left lateral segment graft from an adult donor in an orthotopic i.e. its natural location within the recipient [2].

Who can undergo APOLT ?

• A careful selection process is key for a successful surgical outcome in most clinical scenarios and it is based on a few established guidelines- King's college and clichy criteria [2].

Salient points to consider :

1. Chronicity and cause of liver failure :

APOLT is best suited for acute cases (less than 8 weeks of symptoms) with a one time insult- typically due to drugs (eg. : acetaminophen); toxins (like mushroom poisoning) or viruses (Hepatitis B,E) [2].

2. Age :

In older children APOLT may not be favoured since a larger graft volume will be required which might not be obtained from the standard left lobe technique [4].

3. Absence of cirrhosis in the remnant :

Pre-existing cirrhosis in the native liver is a contraindication for APOLT since these patients would then require lifelong graft support. In addition there is fear of delayed onset malignancy within the remnant [5].

Why an APOLT ?

• Patients who undergo total hepatectomy followed by routine liver transplantation require lifelong immunosuppression. Indeed, in most of these patients with chronic liver disease there is no other viable option.
• However, in acute liver failure (ALF) the liver is morphologically normal and fully functional before the disease process. Given temporary support measures during and for a variable period post-crisis (determined by etiology of insult); the native liver on account of its intrinsic regenerative potential obtains a fighting chance at restoration to full functional capacity [3].
• Hence a “partial liver transplantation” or APOLT is an attractive option in ALF cases; particularly in the paediatric population for a life without immunosuppression in view of their longer life expectancy.

What is the role of the radiologist ?

• With progressive native liver regeneration, graft utility diminishes and its support can be withdrawn. This is brought about by the tailored reduction of immunosuppression which promotes spontaneous graft involution.
• Process of withdrawal should be gradual and it is guided by CT volumetry and HIDA scans which monitor relative percentage of size and function of the native liver remnant and graft parenchyma [5].