A live liver donor has to be a medically fit family member, preferably of the same blood and aged 18-55 years of age. He should be voluntarily willing to donate a part of his liver solely out of emotional or altruistic reasons. All potential voluntary donors agreeing to liver donation are evaluated for fitness and appropriateness of donation through a structured exhaustive medical evaluation process.
All patient donors are subjected to thorough medical evaluation in various stages or phases. Phase one included a battery of blood tests. The second phase includes radiological evaluation with CT liver angiograms and/or MRCP. Phase three involves cardiac, pulmonary, gynaecological and psychiatric assessment. Some donors might need an extended stage five evaluation in case of some abnormalities arising in any of the above stages
Liver donor surgery usually last 4-6 hours (or more in cases of complexities). It usually goes side by side with the recipient’s surgery. A part of the donor liver (right lobe in case of adult recipient and left lobe or left lateral segment in case of pediatric recipient) is removed surgically from the donor either through a open or minimally invasive technique (Laparoscopic or Robotic). Donor is completely awake after the operation and is shifted and nursed in the Liver intensive care ICU for first 2-3 days after which he can be shifted to the ward. He is monitored after the operation by frequent blood tests, x-rays and ultrasonograms. Normally a donor is allowed to take diet slowly by 2nd to 3rd day and move out of bed freely by 5th day after operation. If all goes well he can be discharged within 6-8 days after the operation. Liver regeneration is completed within 3-4 weeks’ time and he is completely fit to resume his normal job by the end of 1 month however he is advised to avoid strenuous activities for 2-3 months as a safety measure.
Donor Liver grafts
The liver retrieved from the donor for use in the patient (recipient) is referred to as liver graft. Depending upon the donor source the type of liver grafts are:
Deceased Donor Grafts
1. Whole Liver Graft
Mostly a complete liver is harvested (retrieved) from a cadaveric donor for use in a single recipient as a whole, hence the name a whole liver graft. This whole liver serves as a very good replacement in adult patients. However, this liver is usually too big and does not fit in if used in pediatric(children) age group patients. This gave rise to the concept of split liver grafts.
2. Split Liver Grafts
The average weight of liver in normal individual is between 1200-1500gms. This approximates to around 2% of the total body weight of an individual. Although, in liver transplant any graft of size around 0.8% of the body weight of patient is good enough to sustain his biological needs. Hence a whole liver provides for much more than what is essentially required. Hence it makes sense to split the liver into two part wherein the two parts can then be given to two different individuals as split liver grafts. This split can be either done during the time of operation in the cadaver donor (called as in-situ splitting) or after retrieval on a back table (ex-situ splitting). The details of these splitting techniques are discussed in section of Split liver grafts. Irrespective of whether it is an ex-situ or an in-situ splitting, liver can be split in two different ways;
a. A right extended lobe and a left lateral segment: In this the liver is split into a bigger right extended lobe graft and a smaller left lateral segment graft of which the right extended lobe is utilized for an adult and the left lateral segment graft is utilized for a pediatric (child) patient.
b. A right lobe and a left lobe: In this the liver is divided into a right lobe and a left lobe graft. This split is more like what is done for retrieval during a living donor operation. Both of these lobes can be used either for two adult patients, or an adult and a pediatric patient.
Living Donor Grafts
Liver is a very unique organ. It has an immense capacity to regenerate. This is the most importance basis over development of Live Donor Liver Transplant. Based on this a part of liver can be removed from an individual safely without harming him in the long term. The liver removed from the live donor is hence a partial liver and the rest of the remaining liver regenerates to full functional capacity within 3-4 weeks’ time. The partial liver graft removed during liver donor surgery corresponds to a defined anatomical lobe or segment of liver. Based on which part of liver is harvested, partial liver grafts in live donor surgery are either of following types:
1. Right lobe graft
A right lobe graft is the most common type of graft harvested during live donor surgery. This graft is utilized for adult recipients however it can be used for children as well if their body weight>30kg. Normally a right lobe constitutes about 60-70% of total liver weight but it can be safely removed from an individual. The remaining liver which is about 30-40% of the total liver weight regenerates into 3-4 weeks’ time to achieve full functional recovery. Preoperative volume calculation of liver hence forms an integral part of live donor assessment. During this assessment distinctive volumes of right lobe and left lobe of liver are calculated thus giving an estimate of graft volume(weight) and remaining liver volume (weight). Conventionally if the volume of remaining liver is less than 30%, then the donor is presumed unfit for right lobe graft retrieval.
2. Left Lobe graft
Left lobe graft are less commonly used for adults as their size falls short of the required liver weight. The minimum liver weight requirement for an adult individual is at least 0.8% of his body weight, and the weight of left lobe of liver usually falls short of it under most circumstances. Hence it is mostly utilized in children whose body weight falls between 10-30kg. It can however be used for adults too if their body weight is less and the presumed liver weight fulfills the 0.8% criteria.
3. Right Posterior Sector Graft
1. This is very rarely used liver segmental graft. It is utilized under very special circumstances when the right lobe cannot be used because it will result into a very low remaining liver volume and a left lobe cannot be used because of insufficient graft (less than 0.8) volume and there is no other potential donor.
4. Reduced Left Lateral Segment or a monosegment graft
1. In very small babies (or infants) especially those weighing less than 6kg in particular the volume of even the left lateral segment graft is too much to either fit in the babies’ tummy or for proper perfusion (blood circulation through liver i.e. the liver is too big for the blood flow to cater to the liver graft completely technically called as large for size). To overcome such circumstances even a left lateral segment graft is trimmed either within during retrieval (in-situ reduction) or after retrieval (ex-situ reduction) to shed of some extra liver volume. This process of reduction can be done either to just trim some extra liver tissue non anatomically or anatomically to shed of a complete segment (usually segment 3 of liver). Based on partial or complete trimming of segment 3 of liver the graft is called either a reduced lateral segment or a monosegment (Segment2) graft.
Domino Graft (Whole liver graft from Living Donor)
This is a very special type of whole liver graft retrieved from a live individual who is himself also a patient but of some metabolic liver disease and the liver is not cirrhotic like that of patients of end-stage liver disease or cirrhosis. He underwent a transplant and receives either a cadaveric or live donor for himself to treat his metabolic liver disease. The liver removed from his body can in turn be safely used in a patient of end-stage liver disease with limited life expectancy without him developing the metabolic syndrome or disease recurrence. Such liver grafts are called as Domino Liver Grafts.
Department of Liver Transplant, HPB and GI Surgery, Venkateshwar Hospital, Sector 18, Dwarka, New Delhi - 110075
