Jun Glink , ,, Crolin Vnett , Jun Pekolj , , Jun Mtter , Edurdo de Sntiñes , ,Mrtín de Sntiñes ,

a Department of General Surgery, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina

b Section of HPB Surgery & Liver Transplantation Unit, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina

TotheEditor:

Liver procurement (LP) from a neurologically deceased donor(NDD) is one of the most important spotlights in liver transplantation (LT) [ 1 , 2 ]. The commonly used approaches include the “rapid”en-blocdissection, theinvivonormothermic dissection, or a combination of both, according to the preferences and/or the experience of the LP/LT team. A correct LP is essential to achieve optimal results. On the counterpart, defective execution of any of its steps can leave the liver graft unusable and/or cause severe complications in the recipient [3] .

Although simplified techniques of LP have been described, theinvivonormothermic dissection or “warm technique” has still numerous advantages. It allows anin-situidentification of vasculobiliary structures, shortens the cold ischemic preservation time (of vital importance with marginal donors), reduces and facilitates the graft preparation in the back table, and favors surgical training. For those reasons, we believe that it is the first choice in the hemodynamically stable donor. We herein describe our standard technique that has been used and taught over many generations of transplant surgeons and trainees in a pioneer and high volume center of South America: the Hospital Italiano of Buenos Aires.

Our first step is to perform an extensive cruciate laparotomy,followed by an exhaustive abdominal inspection to rule out organ abnormalities (primary malignancies, graft nodularity, severe steatosis). Subsequently, the hepatic pedicle is examined to identify possible vascular anatomical variations, such as a replaced right hepatic artery (RHA) branching from superior mesenteric artery(SMA), or a common hepatic artery (CHA) arising directly from SMA that can be usually palpated with the index finger behind the porta hepatis. It is also advisable to inspect the lesser omentum to assess a possible replaced left hepatic artery (LHA) commonly branching from the left gastric artery (LGA) or coronary artery [4] .Then, we proceed with retroperitoneal exposure tactics such as“Cattell-Braasch”. This maneuver begins in the dissection of the coalescence fascia of the right colon, extending to the Treitz ligament, allowing the right colon, part of the transverse, and small bowel to be removed even outside the abdomen after its completion [5] . This maneuver is followed by the Voutrin-Kocher maneuver that mobilizes entirely the pancreatoduodenal block. The final purpose of these maneuvers, when executed correctly, is the comprehensive exposure of the retroperitoneum and the inferior vena cava (IVC), the right renal vein (RRV), the first centimeter of the left renal vein (LRV), the ureters, as well as the abdominal aorta and iliac arteries [6] ( Fig. 1 ).

At this point, the mesentery root is exposed, permitting the identification and dissection of the SMA, which can be encircled.This is the second opportunity to estimate an anatomical arterial variation involving the SMA as RHA or a totally replaced hepatic artery, which if present, might be originated at the first 3-4 cm of the SMA. In addition, the identification of the origin of the SMA further allows to recognize the renal arteries, and protects them during further steps. Just then, the abdominal aorta is encircled distally, at the level of the inferior mesenteric artery (IMA) and above the iliac arteries for future cannulation. The small bowel is then wrapped in a laparotomy pad and gently retracted outwards, to expose the Treitz’s angle. The mesentery root is then released from its avascular retroperitoneal attachments and the inferior mesenteric vein (IMV) is now identified and dissected to the left of the Treitz and encircled for future cannulation, just like the abdominal aorta.

Within the porta hepatis, the common bile duct (CBD) is identified to the right of the hilum. The first step we advise to do is to divide the CBD first, to facilitate dissection of the other vascular elements [particularly the portal vein (PV), which has a deeper location]. The surgeon must ensure a long CBD and its section should be just above the pancreas. Special caution should be taken at this step, as the RHA usually runs behind it. Cholecystectomy can be performed at any time, but we perform it on the back table [7] .Subsequently, we identify the hepatic artery and dissect it to the origin of the gastroduodenal artery (GDA), which is then encircled( Fig. 2 ).

The PV can be identified and dissected down to the superior border of the pancreas. If the pancreas is not procured, a dissection of the fibro-ganglionar structures posterior to the PV can be performed in advance, which will provide greater venous length.

Fig. 1. A: Retroperitoneal exposure once the cattel-brasch and voutrin kocher maneuvers are completed. The blue line indicates the IVC and LRV and the red line the AA and RIA; B: AA dissection: the origin of the renal arteries can be seen at its sides and the origin of the SMA upwards. AA: abominal aorta; IVC: inferior vena cava; LRV: left renal vein; RIA: right iliac artery; SMA: superior mesenteric artery.

Fig. 2. Celiac trunk and hepatoduodenal ligament dissection. The branches of the celiac trunk are marked in red (LGA, GDA, CHA). The PA is marked with a red asterisk. The CBD is marked in yellow lines. The PV is marked in blue lines. LGA:left gastric artery; GDA: gastroduodenal artery; CHA: common hepatic artery; PA:pyloric artery; CBD: common bile duct. PV: portal vein.

Once the hepatoduodenal-ligament dissection is concluded, the left lobe is mobilized by dividing the suspensory ligament and the left triangular ligament. The left diaphragmatic crus is dissected and divided, to expose the abdominal aorta above the celiac trunk.Then, supra celiac abdominal aorta is encircled with an umbilical tape for future aortic cross-clamping.

Once the abdominal time is accomplished, we perform the anterior sternotomy (unless intrathoracic organs are procured, in that case, it should have been done before). Gauze protection of the graft is recommended to avoid harming the liver parenchyma during these movements. After placing a sternal retractor, the pericardium is dissected and the right atrium is identified. The IVC will be transected at the junction with the right atrium for exsanguination and to vent the preservation solution.

The next step consists of the full heparinization of the donor administrating intravenously 30 0-50 0 U heparin per kg of donor body weight or 25 0 0 0-30 0 0 0 U of intravenous heparin that is usually enough to prevent vascular thrombosis during cannulation.

After 3-5 min of the heparinization, the distal abdominal aorta is ligated and a 24-Fr aortic cannula is placed and secured with an umbilical tape or a silk 1-0 tie. Special attention must be taken not to introduce the cannula too far, as it can block the flow of renal arteries. For venous cannulation, the IMV is ligated distally and a 14-Fr cannula is introduced up to the origin of the PV trunk. The palpation of the hepatic pedicle must be performed then, to ensure that the cannula is correctly placed in the PV and not introduced in the splenic vein, which would result in poor and slow perfusion.

The supra celiac aorta is cross-clamped to prevent the cold preservation solution from flowing into the upper part of the body and extremities and to favor its concentration into the abdominal organs [ 7 , 8 ]. Once perfusion is initiated, the IVC is concomitantly transected near the right atrium. While cold perfusion is being started through the venous and arterial cannulas, cooling of the abdominal organs with saline at 4 °C in the abdominal cavity is necessary, and slushed ice is placed into the peritoneal and pericardial cavities to complete the cooling process [9] .

There is no current consensus on the total volume of the flushing solution to be used. It depends on whether it is a low or highviscosity solution. Although between 3 and 6 liters are generally necessary to achieve appropriate organ perfusion.

The organs must be keptinsituuntil the perfusion is complete,and if it is not performed in the normothermic stage, the gallbladder is now incised near the fundus and the bile is washed out.

Once perfusion is completed, we firstly approach the hepatic hilum, where the CHA must be widely dissected up to its origin in the celiac trunk, but not yet divided. The GDA is left as long as possible and divided (just in case a further vascular reconstruction is needed). The splenic artery is divided in its origin when the pancreas is procured, if not it may be divided at any level. The LGA is ligated close to the gastric wall, preserving a left hepatic arterial variation if present. The CBD division occurred previously, so the next step is the division of the PV.

If the pancreas is procured, the PV is divided preserving approximately 1.5 cm for the pancreatic graft. Otherwise, a tunnel behind the pancreatic neck can be dissected, just as it is done in Whipple procedure, and the pancreatic parenchyma is divided at that level.As a result, a long vein comprising the SMV and the splenomesenteric trunk is obtained, just in case a complex venous reconstruction is required.

The liver has already been mobilized in previous stages, as well as the suprahepatic IVC, but they are still attached to the diaphragm whose division is completed now with scissors.

The crucial final step is the excision of a large arterial patch from the anterior aortic wall, containing the origin of the celiac axis and SMA. Before obtaining this patch, the arterial supply to both kidneys must be identified and protected. We then complete the retroperitoneal release and extract the graft. The liver is then included in a refrigerated container and perfused again with 1 liter of preservation solution through the venous cannula. This final gesture would not only improve graft preservation but also may reduce ischemic type biliary injury [10] .

In conclusion, even though the LP has diverse technical variations described over the last years, we still believe that the benefits of the warm or “invivonormothermic” dissection technique is of choice since not only decreases the ischemic time but also enhances surgical training in university health institutions.

Acknowledgments

None.

CRediT authorship contribution statement

Juan Glinka : Data curation, Formal analysis, Writing - original draft. Carolina Vanetta : Data curation, Formal analysis, Writing - original draft. Juan Pekolj : Conceptualization, Supervision,Writing - review & editing. Juan Mattera : Conceptualization,Supervision, Writing - review & editing. Eduardo de Santibañes :Conceptualization, Supervision, Writing - review & editing. Martín de Santibañes : Conceptualization, Supervision, Writing - review &editing.

Funding

None.

Ethical approval

This study was approved by the Ethics Committee of the Hospital Italiano de Buenos Aires (No. 27111).

Competing interest

No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.