Percutaneous transluminal interventions of transplant renal artery stenosis: A case series study

Introduction and importance: Transplant renal artery stenosis (TRAS) is a well-recognized vascular complication after kidney transplant that can lead to graft loss, when it is diagnosed early and treated appropriately it may prevent kidney damage and related systemic squeals. Case presentation This case-series represents our center experience in managing TRAS using percutaneous transluminal angioplasty [either balloon angioplasty (PTA) or stent placement (PTAS)] in 11 patients. Clinical discussion All treated patients experienced immediate total recovery of renal function and normalization of arterial blood pressure without any drug or reducing the number of drugs used; no complications related to the intervention were reported. Conclusion PTA or PTAS of TRAS can be considered safe and effective when it diagnosed and treated early.


Introduction
Kidney transplant is considered the treatment of choice for end-stage renal disease (ESRD) giving patients a good quality of life [1]. Transplant renal artery stenosis (TRAS) represents one of the major causes of graft failure with reported incidence between (1%-23%) representing about (85%) of vascular complications [2]. It usually occurs between three months and two years after renal transplantation, peaking in the first 6 months post-transplant with a higher incidence in elderly transplanted patients [3]. TRAS presents with many clinical manifestations like; refractory hypertension, oedema and allograft dysfunction in the absence of rejection [3]. Etiologically, TRAS is timely fashioned classified: early and late. The early one may occur due to anastomotic technical defects which need immediate correction or because of prolonged cold ischemia time during surgery which cause vascular wall damage and consequently late fibrosis (acute tubular necrosis), while late TRAS may occur due to trauma of the donor or recipient artery during surgery [4,5].
This retrospective case series represents 11 patients suffering from TRAS treated successfully with percutaneous transluminal angioplasty [either balloon angioplasty (PTA) or stent placement (PTAS)]. The study has been approved by the ethical committee of Damascus University.

Presentation of case
We present a retrospective case series of eleven male patients with an average age of 33.5 years old (table. 1), diagnosed as TRAS. The average time from transplantation to TRAS diagnosis was 21.2 months. This Study was conducted in Al Assad University Hospital, Damascus, Syria. All procedures were done by the professor and chair of department of vascular and endovascular surgery. The study was carried out in accordance with the Declaration of Helsinki.
The study has been reported in line with the PROCESS 2020 criteria. Our strategy aimed to confirm the clinical diagnosis of TRAS by color Doppler ultrasonography (CDU) followed by a selective digital subtraction angiography (DSA) with intention to treat stenotic lesions in the same session.
All patients had hypertension in their clinical complaints upon presentation while chronic kidney disease was observed in 6 patients (No. 1,2,3,5,7,9). Hemodynamic study focused on measuring systolic peak velocity (>200 cm/s), acceleration time in the transplant renal and intra-renal arteries (>0.15 s), ratio peak systolic velocity in the transplant renal artery -to -iliac donor artery (>1.8), documenting tardusparvus wave in all transplanted kidneys.
The systolic peak velocity (SPV) was: (240-300 cm/s) at the anastomosis in eight patients, post anastomotic in two patients (No. 8,9) while in patient (No. 1) no peak systolic velocity augmentation was noticed because of total occlusion of the right common iliac artery (RCIA) (donor axis), this patient was suffering also from critical limb ischemia (CLI) in his right lower limb. The internal iliac artery (end to end anastomosis) represented the donor artery in five patients (No. 1,2,5,7,8), the common iliac artery (end to side anastomosis) in four patients (No. 6,9,10,11) while the external iliac artery (end to side anastomosis) was the donor in patients (No. 3,4). A Well-controlled arterial pressure and an appropriate kidney preparation were obtained previously in all patients. Under local anesthesia, using an appropriate angiographic projection to reveal the lesion site, we documented a total right common iliac artery occlusion (preanastomotic) in one patient (No. 1) (Fig. 1) where the renal insufficiency was associated with (CLI) in his right lower limb, in patients (No. 8,9) a sever stenotic lesion was documented at the origin of the upper renal lobe artery and mid renal artery trunk respectively (post-anastomotic), while in the remaining eight patients the lesions were anastomotic.
The total common iliac occlusion patient (No.1) was crossed, through ipsilateral common femoral artery, by a hydrophilic 0,035 wire and 6F vert catheter and then stented, patients (No. 2,5,7,8) were approached through a contralateral femoral access, introducing an 8F guiding catheter engaging selectively the internal iliac artery (Fig. 2). The remaining patients were treated through an ipsilateral common femoral access using 7F sheath, no guiding catheter was used in this group of patients but a 6F vert catheter employed to engage the lesion. A 0.014 wire used to cross all the above lesions which were treated as mentioned in table (Fig. 3).
contrast injected was less than 75 ml in all procedures. In patient (No. 1) a bare metal stent was deployed directly after recanalization of the common iliac artery. While in the remaining cases a balloon angioplasty was done first then a bare metal stent was deployed in case of residual stenosis over 30% (table. 1).
All patients were given (300 mg) clopidogrel and (81 mg) aspirin the day before the procedure and (50 IU/kg) of heparin sodium was administered immediately before the procedure. (75 mg) clopidogrel, (81 mg) aspirin and (10 mg) atorvastatin once daily were continued lifelong after discharge.
All patients were followed by clinical and lab evaluation including blood pressure measurement and serum creatinine monitoring, in addition to CDU which was done immediately after the procedure, before hospital discharge, at 1, 3, 6, 12 months in the first year, then twice yearly. SPV measurement and SC showed normal values. Blood pressure values became normal in six patients (No. 1,2,3,5,7,11). A single antihypertensive drug was used in the other five patients, the CDU study showed no complications related to the vascular procedures. After 60 months, the patient (No. 1) developed graft loss because of chronic rejection without any evidence of vascular complications documented by a new DSA, the patient was still free of lower limb ischemia with good pedal pulses.

Discussion
TRAS is considered as an important cause of allograft dysfunction and refractory hypertension following transplantation in (1-5%) of patients [6]. It can be diagnosed by computed tomography angiography, magnetic resonance angiography, CDU and DSA which remaines accepted as the golden standard for TRAS diagnosis [7]. Treatments modalities include endoluminal procedures (PTA/PTAS) and open surgery. The latter is considered as a rescue therapy in case of unsuccessful angioplasty or severe stenosis. However, open surgery may lead to many complications such as graft loss, ureteral injury and reoperation [2]. Endovascular intervention is preferred over surgery and may be considered the treatment of choice for TRAS because it is repeatable and has less complication like re-stenosis, renal artery injury or thromboembolism [8]. It is preferred for linear, short and proximal stenosis with success over 80%, higher technical success rates and clinical improvement are reported when PTAS has been used [9][10][11]. Indications for stent placement (PTAS) include: Residual stenosis after PTA of more than (30%), creation of flow limiting flap or presence of pressure gradient of more than (10 mm Hg) after PTA [2]. Clinical success rates following PTA, PTAS or combination were (65.6-94%) and technical success rates higher than (90%) [7]. Willicombe et al. [12] 1 (A,B)Total occlusion of the right common iliac artery, the transplanted kidney anastomosed to the right internal iliac artery. (C)Recanalization and stenting of the right common iliac artery. Specific Antibodies. A systematic review by A. T. Ngo et al. [7] supports PTA/PTAS procedures in TRAS which were done in our cases. The follow-ups in our cases showed good results. However, some needed one antihypertension drug, but they had normal creatinine range. More detailed follow-ups were not possible due to the financial and social hurdles facing Syrians at the moment [13]. These unique circumstances have put additional pressure on hospitals as only few major one remained functional during the war [14].

Conclusion
PTA and PTAS is a safe, effective and repeatable treatment modality in managing TRAS when it is diagnosed early. Many causes of TRAS are explained and they are linked to their time manner. The role of Donor Specific Antibodies in the pathogenesis of TRAS in post-transplant period are goals for further researches.
The case has not been presented at a conference or regional meeting.

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This study has been approved by the ethical committee of Damascus University.

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