Introduced several decades ago, kidney transplantation today represents the most effective treatment for end-stage chronic kidney failure, restoring normal kidney function and patient autonomy. It provides better long-term survival and quality of life than hemodialysis or peritoneal dialysis [1] . Despite significant progress in surgical techniques, several post-operative complications may arise, notably vascular complications, with the most frequent being graft artery stenosis [2] . RTAS affects 1% to 23% of kidney recipients [3] - [5] and accountsfor approximately 75% of vascular complications post-transplant. It typically occurs early, usually between 3 months and 2 years after kidney transplantation, with a higher frequency in the first 6 months post-transplant [6] - [9] . RTAS can be completely asymptomatic or responsible for 1% to 5% of post-transplant hypertension [5] [10] [11] . It can lead to graft dysfunction and loss, hence the widespread use of echo-Doppler in routine renal graft surveillance. This examination allows for the detection of asymptomatic stenosis or stenosis causing hypertension, thereby avoiding serious complications. The aim of this study is to determine the prevalence, clinico-radiological characteristics, and to evaluate the outcomes of luminal angioplasty as the first-line treatment for RTAS, through the analysis of record from 27 kidney transplant patients.

Among the 181 renal transplant patients during this period, 27 patients had graft artery stenosis, representing 14.9%, after a median delay of 3.6 ± 3.4 months post-transplant. Twenty-two patients were male and 5 were female with a male-to-female ratio of 4.4. The mean age of recipients was 39 ± 16 years. The mean body mass index was 24 +/− 2 kg/m² with extremes of 19 to 27.5 kg/m². The mean total cholesterol level was 1.98 +/− 0.32 g/l and the mean LDL cholesterol level was 1.5 +/− 0.33 g/l. The mean triglyceride level was 1.85 +/− 0.66 g/l. Six patients had hypertriglyceridemia and 7 patients had pure hypercholesterolemia. The mean age of donors was 48.66 ± 13.55 years, with a predominance of females (65%). The donor was deceased in 15% of cases. Initial nephropathy was mainly represented by undetermined nephropathy (48%), vascular (15%), glomerular (12%), and diabetic (4%). Seven patients had hypertension before transplantation, accounting for 26% of patients. All patients were on calcineurin inhibitors, 85% (23) were on cyclosporin. The residual rate was within target for all patients (see Table 1 ).

N = number; GFR = Glomerular Filtration Rate; LDL: low-density lipoprotein.

The diagnosis was early, within the first 3 months post-renal transplantation in 92.6% of cases (25 patients) and late at 12 and 18 months respectively in 2 patients. The main clinical signs included worsening of pre-existing hypertension in 6 patients, de novo hypertension in 10 cases, acute renal failure in 4 cases with an average creatinine level of 18.5 ± 3.2 mg/l, and the presence of vascular murmur in 1 patient, while 6 patients remained asymptomatic and the stenosis was discovered during routine screening.

Stenosis was diagnosed by renal echo Doppler in all patients. It was primarily located ostially (88.9%) (n = 24), trunk (7.4%) and ostial-trunk (3.7%). The stenosis was significant in 17 cases (63%) with clinical repercussions and a degree of stenosis greater than 70%. The maximum systolic velocity was greater than 300 cm/s in 13 cases (48%). Stenosis was confirmed by angio-MRI in 3 cases and by arteriography in 1 case.

Endovascular treatment indications were selected for six patients with severe hypertension (n = 5), four of whom were on ≥ 3 antihypertensive medications, and/or for graft involvement (n = 4) with an average creatinine level of 18.5 mg/ l, and for severe stenosis > 80% (n = 1) and its intraparenchymal repercussions on the graft. Only one patient underwent angioplasty with stent placement. Endovascular management resulted in stabilization of graft function at a nadir of 15 mg/l creatinine level with controlled hypertension on dual therapy in 5 patients. These patients achieved controlled blood pressure 3 to 6 months after endovascular treatment with only 2 antihypertensive medications, including a calcium channel blocker. Systolic blood pressure decreased from an average of 170 mm Hg to 126 mm Hg and diastolic blood pressure from 90 mm Hg to an average of 72 mm Hg (see Table 2 ). No cases of graft loss were noted among our patients.

Angiotensin-converting enzyme (ACE) inhibitors; Calcium channel blocker: CCB.

The remaining patients are under systematic clinical, biological and radiological surveillance. It’s worth noting that 9 patients have been put on antiplatelet therapy.

RTAS represents about 75% of vascular complications post-transplantation and accounts for 1% to 5% of post-transplant hypertension [5] [10] [11] . Its incidence varies from 1.3% to 12.5% according to different series [3] [15] - [17] and its prevalence ranges from 1% to 23% of cases [3] - [5] . It typically occurs between 3 months and 2 years after renal transplantation, with a higher frequency in the first 6 months post-transplantation [6] - [9] . In our series, RTAS was observed in 14.9% of cases with an average delay of 3.6 ± 3.4 months.

RTAS was clinically suspected in 21 of our patients either by impact on graft function or hemodynamic repercussion (HBP), consistent with existing literature [3] [5] [15] [18] . It was significant in 17 cases (63%) of our series with clinical repercussion and a stenosis degree exceeding 70%. However, stenoses can be incidentally discovered by Doppler ultrasound, as was the case with 6 of our patients. The widespread use of Doppler ultrasound controls allows the discovery of asymptomatic stenoses [18] - [21] .

RTAS may result from defective surgical technique, curvature or angulation of the renal artery, size discrepancy between donor and recipient renal arteries and atherosclerosis of the donor’s or recipient’s renal arteries [22] - [24] . Several risk factors are associated with the occurrence of SAG including extended criteria donors, advanced age of recipient and donor, hypertensive nephropathy, delayed graft function and prolonged cold ischemia time [8] [25] . Some studies have found a higher prevalence of RTAS in the case of deceased donors [15] - [17] [26] . In our series, donors were living in 85% of cases. End-to-end anastomoses are also associated with a lower incidence of RTAS than end-to-side anastomoses in some studies [27] . It is also noteworthy that calcineurin inhibitor toxicity should be sought due to its preglomerular vasoconstriction mechanism affecting blood pressure and graft function [22] .

Endovascular treatment is indicated if the stenosis is symptomatic, hemodynamically significant or if the risk of thrombosis is high. Stenosis is treated by percutaneous transluminal angioplasty (PTA) with or without stenting. Angioplasty with or without stent has a success rate of approximately 70% to 90% [15] [28] - [30] . It allows control of systolic and diastolic blood pressure, a decrease in the number of anti-hypertensive medications and creatinine. However, the risks are not negligible: Thromboembolic events, pseudoaneurysms, traumatic arteriovenous fistulas, hematomas and nephrotoxicity of iodinated products used. Six of our patients underwent endovascular treatment, with successful results manifested by stabilization of graft function at a nadir of 15 mg/l of creatinine with well-controlled hypertension under dual therapy in 5 of them. Surgery also yields good results but with a high risk of surgical complications that can lead to graft loss and high mortality. It is indicated in case of angioplasty failure and recurrent lesions [31] .

It is important to recognize renal graft artery stenosis in patients with hypertension after transplantation because it is associated with graft loss and high mortality, and most importantly, because it is potentially treatable.

Given the small sample size of our study, we were unable to conduct an analytical study identifying the different risk factors present in our patients. Moreover, some data were missing in our records such as the type of surgical anastomosis.

RTAS is a significant vascular complication of renal transplantation that predicts adverse outcomes for both the patient and the graft. Renal Doppler ultrasound represents a sensitive and non-invasive means to detect it. It should be suspected in the presence of refractory and/or progressive hypertension and/or acute renal failure. Angioplasty is an excellent treatment modality for stenosis in cases of refractory hypertension and allograft dysfunction. However, therapeutic strategies still warrant further investigation through prospective trials. Early diagnosis is therefore crucial to successfully restore graft function and prevent complications.

Reference sheet:

Kidney recipient:

Name:

Sex: *female*Male:

Date of birth:

Medical history before the kidney tranplant:

Initial nephropathy:

*Indeterminate:*Diabetic:*Glomerular: *Vascular:*Other:

Kidney Donor:

Living donor:Donor in a state of brain death:

Date of birth

Body masse index:

Medical history:

Transplantation date:

End-to-end anastomosis:End-to-side anastomosi:

Surgical trauma: *Yes*No

Arterial plication *Yes*No