Key words : Children’s hospital, Damascus, Kidney failure, Renal transplant, Syria

Introduction
End-stage kidney disease (ESKD) is rare in children. About 9 children per million age-related population start kidney replacement therapy each year worldwide.¹ A successful kidney transplant (KT) is the optimal method for management of ESKD. Compared with dialysis, children with a well-functioning graft have better survival, better quality of life, near normal growth, and improved cognitive development, particularly for younger children.^2-5
Kidney transplant for children had been inaccessible until recently because of limits in surgery techniques and inefficiency of immunosuppressive drug therapy. Over the past few decades, improvements in surgical techniques and better understanding of the immune system have allowed improvements in pediatric KT outcomes.⁶ Despite advances in surgical techniques, improved immunosuppressive regimens and infection prevention, and improved treatment over the past decade,^7,8 KT remains a challenging procedure in small children.
Kidney transplant differs between children and adults in multiple aspects, including the causes of ESKD, problems associated with growth and psychomotor development, donor-recipient size mismatch, comorbidities associated with the lower urinary tract, nonadherence to medication regimens, the child’s transition to adulthood, and the need for many decades of graft function.^9,10
Although large databases are obligatory to the performance of adequately powered studies, single-center studies may provide more accurate and detailed information about pediatric KT. From Syria, there is little published work and limited data on the status of pediatric KT. Thus, this study was conducted and aimed to present the experience and results of pediatric KT program at our center in Syria.

Materials and Methods
A single-center observational study was conducted at the Children’s University Hospital in Damascus, Syria. The Children’s University Hospital is a public institution under the Syrian Ministry of Higher Education and Scientific Research and affiliated with the Faculty of Medicine at Damascus University. Medical records of all consecutive KTs performed between April 2018 and December 2022 (33 pediatric KTs) were reviewed. All patients were under 14 years old when they underwent KT.
We reviewed sex, age, and weight of the recipient; underlying kidney diseases; sex and age of donor, HLA (A, B, DR) mismatches between the recipient and donor, duration of surgical operation, cold and warm ischemic time, therapeutic regimens, early and late complications, and patient and graft survival.
Anti-cytomegalovirus (CMV) immunoglobulin G (IgG) and IgM antibodies, anti-Epstein-Barr virus IgG and IgM antibodies, HIV antibodies, hepatitis B surface antigen, anti-hepatitis C virus antibodies, complete blood cells count, electrolysis, calcium, phosphorous, coagulation screening, fasting glucose level, kidney function, tuberculin test, urinalysis with urine culture, protein in 24-hour urine, panel reactive antibodies, HLA (class I [A and B foci] and class II [DR foci]), matching and mismatching between the recipient and the donor, cross-matching tests (cytotoxic method) between the recipient and the donor, abdomen ultrasonography and micturating cystourethrogram, multislice computed tomography (CT) scan of pelvic vessels, and multidisciplinary consultations were routinely done for all recipients.
For donor preparation, laboratory investigations of blood and urine (same as for the recipients except panel reactive antibodies), abdomen ultrasonography, multislice CT scan of renal vessels, renogram, and multidisciplinary consultations were routinely done for all donors.
Our present policy is to perform KT only for ABO blood group compatible pairs with negative cross-match test (based on complement-dependent cytotoxicity), having at least 2 HLA matches (A, B, or DR) and with no ongoing viral hepatitis C or B, HIV, or malignancy.
All our donors were living donors, as there is currently no effective deceased donor program in Syria.

Ethical considerations
The Medical Research Ethics Committee of Damascus University approval was obtained before the start of the study without the need for informed written consent from patient caregivers as the study was retrospective with data collection from patients’ medical records, provided that all patient data were treated according to the ethical guidelines with complete respect to patient privacy and anonymity.

Definitions
Cold ischemia time was defined as the period from the start of perfusion with cold preservation fluid after cessation of circulation until the start of the first vascular anastomosis at implantation. Warm ischemia time was defined as the period that begins at the time of removal of the donor’s kidney from storage ice and until the initiation of graft reperfusion, depending on the anastomosis time of renal vessels. Delayed graft function was defined as requiring dialysis within 7 days of transplant. Graft dysfunction was defined as an increase in serum creatinine of 15% or more above baseline.¹¹ Graft failure was defined as a return to dialysis, retransplant, or death.

Surgical technique
The extraperitoneal approach (which avoids the risk of bowel complications, such as postoperative bowel atony and adhesions, and without risk of peritonitis) was achieved via a curved paramedian skin incision. The right side was preferred, because of the direct venous drainage to the distal caval vein. Distal aorta and distal inferior caval vein were sparingly freed. The donor’s renal artery was anastomosed, using an end-to-side technique, to the recipient’s common iliac artery (31 cases), and to the distal aorta (2 cases). The donor’s renal vein was anastomosed to the recipient’s common iliac vein (31 cases), and to the distal caval vein in the same technique (2 cases). The donor’s ureter was anastomosed to the recipient’s bladder using a uretero-cystostomy with an anti-reflux technique and a stent (double J catheter).

Immunosuppressive protocol
The immunosuppressive protocol for all patients consisted of anti-human-T-lymphocyte globulin (ATG); ATG was administered preoperatively as induction therapy at a dose of 3 mg/kg/day once daily and during the first 2 to 4 days post-KT.
All patients received intravenous methylprednisolone during the surgical operation and on day 1 and day 2 after surgery. Triple immunosuppression included mycophenolate mofetil (1.2 g/m²/day), tacrolimus (0.3 mg/kg/day), and prednisolone. Mycophenolate mofetil and tacrolimus were started preoperatively (the evening before surgery). Oral prednisolone was started on day 3 after surgery at a dose of 2 mg/kg/day until day 14 post-KT; oral prednisolone was then progressively reduced to 0.12 mg/kg/day after 16 weeks post-KT. The target tacrolimus trough blood level was 10 to 15 ng/mL during the first 21 days after surgery, 8 to 10 ng/mL during 6 months after surgery, 5 to 7 ng/mL between 6 and 12 months after surgery, and 3 to 6 ng/mL thereafter.

Statistical analyses
Results are expressed as median and range for continuous variables and as frequencies and percentages for categorical variables.

Results
From April 2018 to December 2022, our center performed 33 KTs. The number of KTs was the least in 2020 (2 cases/year) and in 2019 (4 cases/year), which was because of the COVID-19 epidemic (Figure 1).

Recipients
Most recipients were boys (n = 24; 72.7%), with 9 recipients (27.3%) who were girls. Median age was 10 years (range, 4.5-14 y), and median body weight at the time of transplant was 23 kg (range, 14-39 kg) (Table 1).
Underlying kidney diseases for kidney failure were renal dysplasia-hypoplasia (42.5%), vesicoureteral reflux with reflux nephropathy (18.2%), neurogenic bladder with posterior urethral valves (12%), neurogenic bladder (9%), other congenital anomalies of kidney and urinary tract (9%), and focal segmental glomerulosclerosis (9%).
In 10 patients, KT was performed preemptively (30.3%). Twenty-three patients (69.7%) were on hemodialysis before KT. The median duration of dialysis was 9 months (range, 2 mo to 4.5 y) (Table 1). Pre-KT hepatitis B surface antigen, hepatitis C antibody, and HIV serology were negative in all recipients and donors. All recipients and donors had anti-CMV IgG antibodies, and none had IgM antibodies.

Donors
All donors were living donors and included 19 male and 14 female donors. In 20 cases, the donor was a parent (14 mothers and 6 fathers); in 13 cases, donors were male distant relatives or friends. The median age of donors was 40 years (range, 30-50 y). The HLA (A, B, DR) mismatch numbers between recipient and donor were 4 in 13 cases and 3 in 20 cases (Table 2). The median cold ischemic time was 25 minutes (range, 20-30 min) for all grafts.
The median warm ischemic time was 30 minutes (range, 20-40 min) for all grafts. The median surgical operation time was 3 hours and 30 minutes (range, 3-4 h).

Initial graft function
Initial graft function was observed in all grafts (100%), and no delayed graft function was observed.

Patient and graft survival
During observation time (5 years), 28 patients (85%) continued to show adequate graft function. Three patients (9%) died during the first 3 months after KT. One patient had severe COVID-19 infection, and death occurred during 3 months after KT. Another patient developed severe hemorrhage directly after surgery; the child had exploratory surgery to assess the cause of bleeding, which showed a large amount of blood in the abdominal cavity but no leaking from vascular anastomosis. Prothrombin time and partial thromboplastin time were prolonged with normal platelet count, which suggested anticoagulant excess (possible heparin overdose during surgery); subsequently, cardiac arrest and death occurred. One patient developed severe sepsis with Pseudomonas species and disseminated intravascular coagulation, and death occurred during 3 months after KT.
Two patients were lost to follow-up 2 years after transplant (during transition into adulthood) (6%). The 1-year graft and patient survival rates in our center were 91%.

Complications after KT
Some complications were encountered after KT (Table 3). Recurrent urinary tract infections occurred in patients with neurologic bladder. Those patients did not undergo a voiding cystourethrogram evaluation to rule out vesicoureteral reflux because we surmised that the recurrent urinary tract infections were as a result of use of clean intermittent catheterization with immunosuppression.
Factors contributing to chronic graft dysfunction included poor adherence to immunosuppression treatment (2 cases), recurrent urinary tract infections with neurogenic bladder (4 cases), and donor-recipient size mismatch (1 case).

Discussion
Pediatric KT in Syria started in 2002. In 2003, a new national Syrian legislation, known as Law Number 30, was enacted, which authorized the utilization of organs from brain dead donors. To prevent transplant tourism and organ trafficking, organ donation is limited to Syrian citizens only.
In practice, the Ministry of Health initiates a neutral national committee tasked to ensure that donation and transplantation are conducted in accordance with the applicable laws, assuring the absence of coercion. This committee also ensures that the donor is medically, psychologically, and mentally fit to proceed.
In 2008, the Syrian government limited KT to hospitals in the public sector. Financial support of transplantation and immunosuppression is entirely covered by the government. Since the start of the war in March 2011, access to health care services, including organ transplantation, has been limited. The Syrian war has affected all aspects of organ transplantation. Between 2011 and 2013, the number of KT centers has declined from 8, distributed over 3 cities, to only 4 centers, all located in Damascus. Currently, there are 6 active KT centers in Damascus.
At our center, the pediatric KT program was reactivated in 2018, after having been on halt during the war. The number of KTs was small in 2019 and 2020 because of the COVID-19 epidemic; however, numbers increased in 2021 and 2022 to approximately one KT per month (Figure 1).
A recent study (2021) on pediatric KT in the Middle East revealed an average annual rate per million children population of 2.7, ranging from 0.1 in Pakistan to 9.1 in Syria, which had the highest annual pediatric KT rate per million children population in the Middle East.¹² In 2021, pediatric KT (recipients <14 years of age) accounted for 12% of all KTs, and the pediatric KT (recipients <18 years of age) share was 16.5% of total KTs in Syria.¹²
In Europe, rates of pediatric KTs range from 0 to 13.5 per million children population.¹³ Median age of the recipients in our study was 10 years, with median body weight of 23 kg, which is in line with the medical literature.⁶
According to the North American Pediatric Renal Trials and Collaborative Studies database, approximately 80% of transplants are performed in pediatric recipients who are older than 6 years old, with teenagers representing the largest group of pediatric KT recipients.¹⁴ Most transplant programs require infants to reach at least 10 kg before transplant is considered. Most pediatric transplant recipients are adolescents, but an important fraction is under 5 years old.¹⁰
The youngest child in our series was 4.5 years old and weighted 14 kg, and 2 patients were under 5 years old and weighted less than 15 kg. With a male predominance of diseases leading to kidney failure, the greatest proportion of pediatric transplant recipients continue to be males.¹⁰ This is consistent with our study, where 72.7% were male recipients.
Most of our patients (91%) had congenital anomalies of the kidney and the urinary tract as their underlying disease, which is in line with the medical literature.¹⁰ Anomalies of the lower urinary tract are a major difficulty encountered in pediatric KT. Treatment of urological disorders may necessitate additional procedures such as open vesicostomy and bladder augmentation.¹⁵
Focal segmental glomerulosclerosis, the cause of kidney failure in 10% to 14% of pediatric recipients, has a high risk of recurrence in its idiopathic form; recurrence commonly leads to graft failure, with little hope for successful repeat transplant.¹⁶ In our study, 3 patients (9%) had focal segmental glomerulosclerosis as a cause of ESKD; fortunately, none developed recurrence after KT during more than 2 years of observation.
Ten patients (30.3%) in our study were transplanted preemptively, which is in line with reports by others.^14,17 Twenty-three patients (69.7%) were on dialysis before transplant. All were on hemodialysis, with peritoneal dialysis in our country still facing many challenges, particularly infectious complications.
We believe that a median duration of 9 months on hemodialysis before KT is reasonably short. Research has highlighted the importance of adequate pretransplant preparation and shorter duration on dialysis.¹⁸ Severe CMV infections did not occur; all recipients and donors had anti-CMV IgG antibodies (seropositive); thus, one can realize that the prevalence of CMV in our country is high. We considered all of our cases as moderate-risk patients for development of CMV infection after transplant, and none received CMV prophylaxis. We use CMV prophylaxis (valganciclovir) in high-risk patients with seropositive donors and seronegative recipients.

All of our donors were living donors as there is currently no effective deceased donor program in Syria.
Twenty donors (60.6%) were parents (14 mothers and 6 fathers); this may be because we work diligently to convince parents to donate. However, in 13 cases (39.4%) where the parents were medically not appropriate for donation, and in the absence of an effective deceased donor program, the only solution was to accept other donors (distant relatives or friends), which is legally allowed in Syria. It is worth mentioning that, although nonrelated kidney donors are genetically unrelated, they are in fact emotionally related and linked to the sick child’s family by friendship and affection, which prompted them to donate the kidney. Likewise, when they meet with the National Committee for Organ Transplantation, the potential donors must sign and acknowledge that they have not received any money or anything in return for the kidney donation act. The median age of all donors was 40 years. We insisted, whenever possible, to choose the donor with the best match.

The immunosuppression protocol that we adopted in all patients was calcineurin inhibitor (tacrolimus), mycophenolate mofetil, and steroids; ATG was administered before transplant in all patients as induction therapy without important side effects.
We use ATG because we consider children who have active immunity high-risk patients for development of acute rejection episodes.

Outcomes
The results of pediatric KT in our center were encouraging, with initial graft function in 100% of cases; no delayed graft function was observed.
During our observation time of 5 years, 28 patients (85%) showed adequate graft function.
We observed 3 mortalities (9%) during the first 3 months (severe COVID-19 infection, postoperative hemorrhage most likely because of a supratherapeutic anticoagulation, and sepsis). Two patients were lost to follow-up 2 years after KT, during transition into adulthood (6%). The 1-year graft and patient survival rates in our center were 91%.
Harambat and colleagues have reported that patient survival was 97%, 94%, 92%, and 91% at 1, 5, 10, and 15 years post-KT, respectively, and graft survival was 90%, 79%, 67%, and 55% at 1, 5, 10, and 15 years post-KT, respectively.¹⁹ A report of North American Pediatric Renal Trials and Collaborative Studies data (2012-2017) showed graft survival rates at 1, 3, and 5 years of 99.5%, 97.2%, and 94.9%, respectively, for living donor pediatric KT.²⁰ Available data on graft survival after pediatric KT in the Middle East region are usually from single-center experiences, with 1- and 5-year graft survival rates ranging from 90% to 98% and 78% to 92%, respectively.¹²

The neurogenic bladder is still a challenging case in pediatric KT, with risk of recurrent urinary tract infections in all patients with neurogenic bladder after KT.
In our study, 7 patients had neurogenic bladder, and all developed recurrent urinary tract infections after KT. Urinary tract infections may result in an increased risk of graft loss, especially if associated with urinary tract abnormalities. In our study, chronic graft dysfunction occurred in 7 patients (21%) at 1 year after KT, which was linked to recurrent urinary tract infections with neurogenic bladder (4 cases), poor adherence to immunosuppression treatment (2 cases), and donor-recipient size mismatch (1 case: patient was aged 4.5 years and weighed 14 kg and the donor was the father).
Early urological evaluation for posttransplant bladder dysfunction and emphasis on immunization adherence are the mainstays of pediatric pretransplant and posttransplant evaluations.²¹

Nonadherence in pediatric KT is widespread, with rates as high as 75% among adolescents, necessitating effective health education, including behavioral skills, motivational strategies, close follow-up, and close monitoring of calcineurin inhibitor trough levels.^22,23

Obstacles to initiation of deceased donor transplant in Syria
Unfortunately, 21 years after the implementation of a legal framework, a deceased donor transplant program remains inactive in Syria. Lack of public awareness, education, and motivation for organ donation; limited resources; and small numbers of organized teams of transplant surgeons and nephrologists appear to be major limiting factors.
The practice of living nonrelated kidney donation inadvertently obstructed the establishment of deceased donor organ donation by hiding the necessity and reducing the urgent need to initiate a national deceased donor program.
Deceased organ donation has been challenging in many countries of the emerging world, demanding changes in legislation (brain death legislation), community involvement, better infrastructure, and interventions to address educational, social, and religious barriers to organ donation. Only 4 of 54 countries in Africa have brain death legislation (South Africa, Tunisia, Egypt, and Sudan).²⁴

As a consequence, living kidney donation remains the most widely practiced source of transplant in the Middle East.
Progress in deceased donation programs have been reported from Iran, Turkey, Kuwait, the Kingdom of Saudi Arabia, and most recently the United Arab Emirates.¹²
Dialysis centers for pediatric patients do exist in the major cities in Syria, and all children in need have the availability for dialyses. Yet, there is no available data on how many children do not have the opportunity to be transplanted. However, certainly there are some children on dialysis who do not have the opportunity to be transplanted either because of nonavailability of a suitable donor or because they are too small in size or too young. Establishing a deceased donor transplant program, advancing the overall medical and surgical expertise for the transplantation of young children, and having broader international collaborations (eg, through so-called sister kidney programs) may help alleviate those issues in the future.
Moreover, we would like to see a nationwide waiting list for patients with kidney failure to come into effect, even if we are still relying on living donors and not just managing through each hospital independently as we are presently doing. This approach will improve the chances of transplant while enhancing the opportunities for better cooperation between transplant centers nationwide. We hope and insist on continuing and trying to overcome all challenges in the near future.

Conclusions
Syria is still suffering from the consequences of the war, affecting organ transplant in many ways. The commitment of transplant teams despite these huge challenges remains unique and extraordinary.
The good 1-year graft and patient survival rates in our study were encouraging. However, we admit that the number of patients included in our study was small and the follow-up duration was also not long enough; future research is needed to improve long-term outcomes.

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