EXPERIMENTAL AND CLINICAL TRANSPLANTATION

Objectives: Our aim was to describe a standardized laparoscopic kidney transplant procedure in a pig model.

Materials and Methods: Ten pigs underwent laparoscopic kidney autotransplant. A right-hand assisted nephrectomy was performed through a Pfannenstiel incision. After the graft was washed with Ringer lactate, it was transplanted into the right iliac vessels by pure laparoscopy. To maintain cold ischemia, a gauze-wrapped ice slush was placed below the allograft. The ureteroneocystostomy was performed through the Pfannenstiel incision. The contralateral ureter was ligated at the end of the procedure. After 24 hours, pigs were killed, and the allograft’s perfusion function and presence of urine in the bladder were evaluated.

Results: Procedures for 2 animals (20%) could not be completed because of technical problems in the vascular anastomosis; the other 8 procedures (80%) were completed successfully. Seven allografts (87.5%) were functioning 24 hours after surgery, with urine in the bladder and good perfusion of the allograft. The other kidney presented with a venous thrombosis that was detected after death. Mean surgical times were 56.2 ± 11.7 minutes for vein anastomosis and 44.7 ± 23.1 minutes for artery anastomosis. Mean ischemia time was 193 minutes. Total duration of the procedure was clearly decreased in the last 4 animals undergoing transplant.

Conclusions: Laparoscopic transplant is a difficult procedure that requires experience in kidney laparoscopy and laparoscopic vascular sutures. The experimental model presented is a good training option and can be used to evaluate different methods to maintain cold ischemia and to compare with the traditional open approach.

Key words : Experimental model, Surgical technique, Kidney transplant

One of the most relevant advances in surgery in the past decades has been the introduction of laparoscopy. Compared with the traditional open approach, it reduces wound complications, improves earlier ambulation, reduces hospital stay, improves cosmesis, and reduces pain and need for analgesics. However, the 2-dimensional view and reduced freedom of movement makes it technically more demanding for the surgeon.

In the field of kidney transplant, laparoscopy for nephrectomy in the living donor has become the standard of care in most transplant centers since its introduction in 1995, with similar functional outcomes after transplant compared with open living-donor nephrectomy.¹ Although laparoscopic vessel anastomoses are feasible and reliable,^2-4organ transplant anastomoses are limited by time. The suture skills required to complete the anastomosis within the limited period make this technique highly demanding and may be the reason why the benefits of laparoscopy have not been as widely transferred to kidney transplant recipients compared with living donors. There are few case reports of laparoscopic kidney transplant in the literature,⁵ with 1 series of 72 patients.⁶ The reports have described good functional short-term results of these grafts; however, the lack of standardization in cold ischemia preservation and surgical technique limit the conclusions that can be derived. In addition, the complication rates are not negligible.

Herein, we developed an animal model of laparoscopic kidney transplant that could be useful for standardization of the surgical procedure, therefore allowing for better training and further studies on cold ischemia preservation techniques and comparison between the traditional open and laparoscopic approaches.

Materials and Methods

After approval was obtained from our Experimental Animal Ethics Committee (Universitat de Barcelona), 10 pigs underwent laparoscopic kidney autotransplant. Two surgeons experienced in advanced laparoscopic surgery performed the surgeries. All protocols were in conformity with the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health (86-23, revised in 1985).

Anesthesia
Food was withheld for 8 hours before surgery. Water was supplied ad libitum. Anesthesia was induced with a combination of ketamine (5 mg/kg) and sodium thiopental (10 mg/kg) through peripheral intravenous injection in the auricular pavilion. An experienced anesthetist assessed adequate depth of anesthesia for endotracheal intubation using a cuffed endotracheal tube. Cisatracurium (0.3 mg/kg) was used for neuromuscular blockade. Anesthesia was maintained with the use of desflurane (3%-4%) delivered in 100% oxygen. Mechanical ventilation was initiated immediately after intubation. An internal jugular vein catheter was placed for intravenous fluid therapy and blood collection during the postoperative period.

Nephrectomy
Pigs were placed in left lateral recumbent position. A Pfannenstiel incision and placement of a GelPOINT platform (Applied Medical, Rancho Santa Margarita, CA, USA) was made. This device was used as a hand port for the nephrectomy and to provide access to remove and enter the graft. Three additional 10-mm trocars were placed in the abdomen as shown in Figure 1. These were used for both the nephrectomy and the transplant procedures. A right nephrectomy was performed by following the same steps as in a conventional hand-assisted living-donor nephrectomy. After completion of the nephrectomy, the kidney was removed and washed with Ringer lactate at bench surgery until the vein output was clear. Reintroduction of the kidney into the right iliac fossa was performed through the GelPOINT platform.

Laparoscopic transplant
To maintain cold ischemia, gauze-packed ice was placed below the kidney. A silk stitch held the perirenal fat attached to the abdominal wall to hold the graft. An additional trocar was placed within the GelPOINT to assist the vascular sutures. The external iliac vein was cross-clamped using 2 bulldog clamps that entered through the GelPOINT. The renal vein was anastomosed in an end-to-side fashion by using 2 running sutures of Prolene 5/0 (Ethicon Inc., West Somerville, NJ, USA). With a bulldog clamp on the renal vein to avoid retrograde graft perfusion, the iliac bulldog clamps were removed to verify that the suture was watertight. The artery anastomosis was also done end to side with a single running suture of Prolene 5/0 (Figure 2). All vascular anastomoses were performed by exclusively using pure laparoscopy. The ureteroneocystostomy was performed through the Pfannenstiel incision after the GelPOINT platform was removed and the contralateral ureter was ligated. The abdominal wall was closed with a running suture of Vicryl 1 (Ethicon, West Somerville, NJ, USA). After pigs were weaned from anesthesia, they were extubated.

Postoperative period
Food and water was supplied after recovery from anesthesia. Pigs were kept alive for 24 hours. A single dose of sodium thiopental, vecuronium, and potassium chloride was used for humane killing of the animals. The Pfannenstiel incision was reopened to check the allograft perfusion and the presence of urine in the bladder. Urine and blood samples were collected and stored before surgery, after surgery, and just before death for future analyses. The presence of urine in the bladder and the absence of thrombosis in the kidney assessed allograft function.

Descriptive statistical analyses were performed with SPSS software (SPSS: An IBM Company, version 17.0, IBM Corporation, Armonk, NY, USA).

The transplant procedure was completed in 8 of 10 animals. In the first 2 animals, the procedure had to be aborted because of technical problems in the vascular anastomosis, which did not occur in the subsequent surgical procedures. Mean surgical time for the complete kidney transplant (starting with the iliac vessel dissection and finishing after ureteroneocystostomy) was 230 ± 56.6 minutes, with a trend to decrease over time as shown in Figure 3. Table 1 summarizes the required times for each portion of the procedure.

Urine output was shown in 7 of the 8 cases. Case 6 had an empty bladder and a graft thrombosis. No incidence of acute bleeding occurred, and none of the pigs died during surgery or before they were killed.

Laparoscopy can be considered a revolutionary surgery at the end of the 20th century. Since the first nephrectomy published in 1991,⁷ the complexity of laparoscopic procedures has been gradually increased, and there are presently few urologic surgical techniques that cannot be performed by laparoscopy.

During the past 30 years, kidney transplant is one technique that has remained unchanged⁸ and has not adapted to the laparoscopy era. In 2004, a group from Johns Hopkins reported on 4 cases of autotransplant for treatment of proximal ureteral avulsion. In 2 cases, the group attempted a laparoscopic implant, but this was abandoned because of technical reasons.⁹ Our first cases are in line with this report, as we also could not complete the first 2 procedures because of problems related to trocar position (clashing of instruments and difficulties in suture management). To overcome this situation, we changed trocar positions and used a pelvitrainer to improve our skills with vascular suturing. As we gained experience, the time of the surgical procedure decreased progressively from 5 hours to less than 3 hours, and the surgeons felt more comfortable and confident during the procedure. The difficulty of the surgical technique may be the reason why it is not until 2009 that a human laparoscopic kidney transplant was successfully performed (by Rosales and associates⁵). In this case, the graft came from a living donor, surgery took 4 hours, and there was immediate urine output. Since then, publication of other attempts has been scarce. Modi and associates6 described a series of 72 successful consecutive attempts of laparoscopic transplant in living donors, with a mean operative time of 224 minutes. The group compared the functional outcomes with the patients who received transplants with the open approach and reported comparable outcomes in terms of graft and patient survival with a median follow-up of 22 months. They also reported a statistically significant difference in analgesic requirements, which was increased in the latter group. It is noteworthy to document the complication rates described in the laparoscopy group, with 4 patients requiring conversion to open surgery and 2 grafts lost because of torsion.

A topic of great importance in kidney transplant is the maintenance of cold ischemia. In laparoscopic transplant, it becomes of crucial importance since the time of surgery is longer than in the open approach and the graft is not easily accessible. In their report, Rosales and associates maintained cold ischemia by means of intra-abdominal ice and transcutaneous continuous irrigation with cold saline solution. In their study of laparoscopic orthotopic kidney transplant, Be and associates used a similar method through a 5-mm trocar.¹⁰ However, Modi and associates did not maintain cold ischemia. Recently, a study following the IDEAL (Idea, Development, Exploration, Assessment, Long-term follow-up) model for the assessment of new surgical procedures was published in which robotic kidney transplant with regional hypothermia was studied. They inserted the graft into the abdominal cavity through the GelPOINT access covered with a gauze jacket filled with ice slush and added more ice with modified Toomey syringes.^11,12 In our study, we placed some gauze-wrapped ice slush below the kidney as we do in open kidney transplant. Although Modi and associates performed more than 70 procedures without cooling the kidney during the transplant and describe acceptable functional outcomes, it is well known that cold ischemia is one of the most important factors related to appearance of delayed graft function. We suggest that an evaluation and comparison of different methods of cold ischemia preservation in laparoscopy should be performed to guarantee preservation of kidney temperature as in open surgery.

Regarding the effect of the pneumoperitoneum, initial reluctance of laparoscopy for living-donor nephrectomy was based on the hypothesis that pneumoperitoneum may have an adverse effect on kidney function. Although pneumoperitoneum reduces renal blood flow and may reduce kidney function temporarily during laparoscopy, its clinical effect is insignificant when optimizing surgical and anesthetic techniques.^13-15 Modi and associates lowered the peritoneal pressure from 15 to 8 mm Hg after anastomosis to improve graft perfusion. Applying the same principles as we do in kidney donation, this technique seems to be an adequate measure to minimize the effects of laparoscopy, although further research in this area could offer more evidence.

Finally, a comment on the benefits of laparoscopic transplant versus the open approach has to be made. Decreased wound length from 15 to 20 cm in the open approach to 5 to 6 cm in laparoscopy could be useful to improve the current 3% to 4% incisional hernia and 16% to 21% wound infection rates for this procedure.^16,17 To reduce surgical aggressiveness, Øyen and associates used a minimally invasive technique for kidney autotransplant, where laparoscopy and open surgery were combined to perform a laparoscopic nephrectomy and then a vascular anastomosis using a 7-cm pararectal incision.¹⁸ However, a 7-cm incision is a too short to securely perform a conventional kidney transplant; therefore, the combination with a laparoscopic approach is the natural evolution toward a less invasive technique. Moreover, being placing this incision in a Pfannenstiel position will improve cosmetic results dramatically.¹⁹ However, we are facing a situation that is presently creating strong debates. Similar to all of the recent minimally invasive surgery advances like Natural Orifice Transluminal Endoscopic Surgery (NOTES) and Laparoendoscopic Single Site Surgery (LESS), we still need to elucidate what is the real benefit of decreasing the length of the scars (apart from the obvious cosmetic improvement) and need to answer whether the effort required to perform this technique is of value in terms of economic benefit and patient safety.

Regarding the limitations of our study, we acknowledge that it is a study to evaluate a feasible surgical technique so that a standardized surgical model could be described. This model will allow for future studies to compare different cold ischemia preservation methods and can be useful as a training model for groups who are interested in developing a program of laparoscopic transplant.

In conclusion, laparoscopic transplant is a difficult procedure that requires experience in kidney laparoscopy and in laparoscopic vascular sutures. An experimental pig model is a good option to train surgeons in laparoscopic transplant, allowing standardization of a feasible technique, to evaluate different methods to maintain cold ischemia in the graft, and to compare the technique with the open approach.

Volume: 14 Issue: 1 February 2016

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