Fibromuscular dysplasia and living kidney donors: a narrative review

Abstract

To address the shortage of grafts, renal transplant teams actively utilize all available donation options, including those that challenge the conventional criteria for living donors. However, this approach may involve situations requiring careful assessment of specific risks—particularly those that could jeopardize donor safety, expose the recipient or graft to vascular complications associated with certain arterial reconstructions, or threaten graft function in the recipient. Kidney donation in the context of fibromuscular dysplasia represents one such scenario, as this condition encompasses all three of these risks. Transplant centers that do not automatically exclude such donations recommend a selective approach, with decisions to accept these kidneys made on a case-by-case basis through evaluation by multidisciplinary teams comprising nephrologists, angiologists, and transplant surgeons. This narrative review aims to provide an update on (1) the identification and assessment of this arterial lesion during predonation evaluation, (2) the acceptability criteria for kidneys affected by fibromuscular dysplasia, (3) the safety and long-term outcomes for donors following nephrectomy, and (4) technical considerations for transplanting these grafts and their outcomes in recipients.

HIGHLIGHTS

Fibromuscular dysplasia-affected kidneys can be safely transplanted from carefully selected living donors The contralateral kidney must be morphologically intact and functionally optimal No significant extrarenal fibromuscular dysplasia should be present Dysplasia must be proximal or limited to the arterial trunk, allowing reliable vascular reconstruction Informed consent is essential in this ethically sensitive donor context

INTRODUCTION

Fibromuscular dysplasia (FMD) is an idiopathic, nonatherosclerotic, noninflammatory arterial lesion primarily affecting small- and medium-sized arteries, particularly those subject to mobility. This condition leads to segmental stenoses, which are often asymptomatic, and less commonly results in dissections, aneurysmal changes, or arterial tortuosity.

In renal transplantation, previously unrecognized renal artery FMD may be incidentally detected on computed tomography angiography (CTA) during vascular evaluation of potential living donors. This situation necessitates increased caution and further investigation to address specific clinical concerns. This narrative literature review aims to provide evidence-based responses to these clinical issues.

EPIDEMIOLOGICAL SIGNIFICANCE OF FIBROMUSCULAR DYSPLASIA IN DONOR SELECTION

Long considered a rare condition, the prevalence of renal FMD has been revised to range between 2% and 6.6%. This increase is due in part to enhanced screening of potential living kidney donors, in whom systematic evaluation for this lesion is recommended [1,2]. Beyond its often asymptomatic nature, renal FMD exhibits two features that further justify screening during predonation evaluations: a familial prevalence of 7.3% to 11% [3,4] and a marked female predominance, affecting women in more than 80% of cases, predominantly between the ages of 30 and 50 years [5–7]. Notably, kidney donations from living donors are usually intrafamilial, and women donate more frequently than men [8–10].

Additionally, several epidemiological characteristics directly influence the suitability of such donations due to potential safety concerns for donors. Based on the ARCADIA (Assessment of Renal and Cervical Artery Dysplasia) registry, renal FMD manifests as bilateral disease in 49% of cases and frequently exhibits multisite involvement, with extrarenal arterial dysplastic lesions commonly associated with bilateral renal FMD [5]. Moreover, data from the United States Registry for Fibromuscular Dysplasia indicate intracranial aneurysms in approximately 13% of FMD cases [11]. Consequently, these epidemiological aspects must be carefully considered. Undetected renal or extrarenal dysplastic lesions during predonation evaluations can, depending on their location and progression, lead to serious long-term complications for living donors.

HISTOLOGICAL PROGRESSION AND IMPACT OF FIBROMUSCULAR DYSPLASIA ON THE RENAL TRANSPLANT ARTERY

Histologically, renal FMD manifests in several subtypes. Of these, the medial subtype is the most common, occurring in approximately 70% of cases. Other forms include the perimedial variant, found in fewer than 1% of affected adults [4]; the intimal subtype, seen in 5% to 10% of cases; and adventitial involvement, occurring in fewer than 1% [12].

Apart from dissection and aneurysmal dilation, the most common and progressive complication across all histological subtypes is arterial stenosis, potentially leading to renovascular hypertension. These risks can cause significant complications in transplanted kidneys, including those from living donors, as several studies have reported [13–16]. Such complications typically arise within the first few months after transplantation. This issue underscores the importance of anticipating possible histologic progression and addressing it surgically during transplantation when necessary.

Regarding stenosis, although intimal and perimedial lesions are rare, they differ from the other subtypes by demonstrating a more aggressive narrowing process, frequently resulting in complete occlusion of the main renal artery. Such occlusion inevitably leads to renal atrophy and eventual renal failure. However, this histological classification of renal artery FMD [17–19] is no longer applicable in current clinical practice, due to widespread adoption of endovascular treatments, which preclude the acquisition of dysplastic tissue for histopathological analysis [6]. Additionally, this classification cannot influence decision-making regarding kidney donation, as lesion tissue samples can only be retrospectively analyzed after graft harvesting.

IMAGING FINDINGS OF FIBROMUSCULAR DYSPLASIA IN PREDONATION EVALUATION AND DIAGNOSTIC ACCURACY

Identification of Fibromuscular Dysplasia

Renal FMD in living donors is usually identified incidentally via CTA of the abdominal aorta and its branches, which is routinely performed as part of predonation vascular evaluation. Two main patterns are typically observed (Fig. 1).

Fig. 1.

Predonation computed tomography angiography. (A) Multifocal renal artery fibromuscular dysplasia (FMD). White arrows indicate the extent of the dysplasia, affecting the distal two-thirds of the main renal artery, with the characteristic “string-of-beads” appearance. (B) Concentric arterial narrowing in a young woman, suggestive of monofocal renal artery FMD. ARG, left renal artery.

Focal FMD: this form is characterized by an isolated, elongated tubular narrowing greater than 1 cm, or shorter than 1 cm with an hourglass-shaped narrowing (Fig. 1B). Focal FMD is less common and typically affects young individuals of both sexes, usually unilaterally. It most frequently occurs postostially or at the mid-trunk level, and histologically often involves the intima [7,20]. Following donation approval, arterial implantation of this graft type rarely requires complex vascular reconstruction, as the lesions tend to be limited in extent.

Multifocal FMD: observed in 80% to 90% of cases, this pattern is frequently bilateral and primarily affects middle-aged women. It consists of a series of stenoses and dilatations [7], creating a characteristic “string-of-beads” appearance (Fig. 1A). Histologically, this presentation most often corresponds to medial fibroplasia (Fig. 2). Implantation of renal grafts affected by this form into the recipient’s iliac arteries can be technically complex due to the typical location and downstream extension of the lesions, which often involve the distal two-thirds of the main renal artery and the proximal portions of its primary branches.

Fig. 2.

Two renal allografts exhibiting multifocal fibromuscular dysplasia of the main renal artery, the most common subtype. White arrows indicate the dysplastic arterial segment following longitudinal arteriotomy performed under cold ischemia on the back table. (A) Overview of a renal graft with the main renal artery (arrow) affected by multifocal fibromuscular dysplasia. (B) Magnified view highlighting the multifocal dysplastic lesions (arrow) affecting the main renal artery of a second allograft.

Differentiation From Non-Dysplastic Arterial Stenosis

The “string-of-beads” appearance on renal artery angiography is considered nearly pathognomonic of multifocal FMD. However, isolated arterial narrowing should raise suspicion and prompt consideration of alternative etiologies, including monofocal dysplasia. Some of these conditions may be clinically significant, especially since the diagnosis of this vascular abnormality relies on excluding inflammatory arteritis and atherosclerotic arteriopathy.

In this context, Takayasu arteritis, which may initially be asymptomatic, should be strongly suspected in young women whose clinical examination reveals absent upper limb pulses, suggesting associated stenosis or occlusion of the subclavian artery. This must be confirmed by imaging of the supra-aortic trunks [21]. Renal artery stenosis of inflammatory origin is frequently associated with concentric, regular thickening of the aortic wall on CTA, which may occasionally enhance after contrast administration. Magnetic resonance angiography can complement computed tomography findings by revealing signs of vascular inflammation such as mural edema, indicating active disease [21]. These highly specific imaging features should prompt evaluation of the patient’s inflammatory biomarkers.

Atherosclerotic plaque is strongly suspected when renal artery stenosis is ostial in location, often representing extension of an adjacent aortic plaque. This typically appears as a focal imprint on the juxtaostial aortic wall on CTA. In contrast, FMD rarely involves the ostial segment of the renal artery [22], and the aortic wall usually appears normal. Beyond this characteristic distribution, calcifications of the aortic wall and/or other arteries are commonly present in these cases, typically involving older patients with multiple cardiovascular risk factors.

DECISION-MAKING IN FIBROMUSCULAR DYSPLASIA DONOR SELECTION

The decision to accept or exclude donor candidates with renal FMD should be made on a case-by-case basis, considering the following factors: (1) the candidate’s renal function; (2) the extent of the dysplastic lesion in the downstream segment of the affected kidney’s renal artery; (3) whether the lesion is unilateral or bilateral; (4) the presence of extrarenal manifestations of FMD; (5) according to some authors, the desire for future pregnancy among younger candidates; and (6) whether the donor has provided fully informed consent and understands the specific risks associated with this systemic disease. These factors are discussed in detail below.

Renal Function Assessment Protocol

The protocol for assessing kidney function in donor candidates with FMD is identical to that used for candidates without renal morphological abnormalities. Completion of this evaluation—and confirmation of normal results—is required before proceeding with predonation CTA, and thus before any incidental discovery of FMD. Therefore, we will not detail the protocol here. However, its primary objectives are threefold: (1) to exclude undiagnosed or early-stage kidney disease or renal insufficiency during the predonation evaluation; (2) to identify and assess genetic risk factors, such as family history of diabetes or hereditary nephropathy, along with metabolic and cardiovascular risk factors that may negatively impact the donor’s long-term renal function, including smoking, hypertension, glucose intolerance, and obesity; and (3) to evaluate the relative function of each kidney through isotopic imaging, ensuring that, in cases of functional asymmetry, the kidney selected for donation is not the dominant one.

Extent of Fibromuscular Dysplasia in the Downstream Renal Artery

CTA performed during predonation vascular evaluation enables the detection and definitive diagnosis of the dysplastic lesion in the affected kidney. Furthermore, it facilitates assessment of the lesion’s extent within the renal arterial tree and determination of its distal limit. This limit should not extend beyond the proximal portion of the first two major branches of the renal artery, a restriction justified by the technical feasibility and safety of subsequent arterial reconstruction in the recipient.

Although catheter-based arteriography has largely been replaced by CTA due to lower invasiveness, it remains the preferred imaging modality in two scenarios: (1) when CTA fails to clearly confirm the diagnosis of dysplasia, and (2) when the downstream extent of the lesion is difficult to evaluate using CTA (Fig. 3A) [23]. Notably, the sensitivity and specificity of Doppler ultrasound in evaluating lesion extent are not well established, except in centers with considerable expertise using this method [6].

Fig. 3.

Technical considerations and steps following validation of a fibromuscular dysplasia (FMD)-affected kidney donation. (A) The red arrows indicate the downstream boundary between arterial segments appearing healthy and those affected by dysplasia on angiography. (B) The white arrow denotes the length of the healthy portion of the main renal artery branching division, which is too short for direct reimplantation in the recipient. (C) Vascular graft harvested from the ipsilateral hypogastric artery. (D) Excised segment of the dysplastic artery. (B, E) The black arrows highlight the longitudinal section of the dysplastic artery up to the healthy arterial wall.

Considerations for Bilateral Renal Fibromuscular Dysplasia

Some transplant teams encountering asymptomatic bilateral renal FMD (Fig. 4) do not automatically exclude donation, provided the donor retains the kidney with the less severe dysplastic involvement [24–26]. However, renal FMD has long been regarded as a lesion with potential for progression. Its anatomical evolution and hemodynamic impact can lead to serious clinical consequences, such as poorly controlled hypertension or renal failure. Although the risk of progression remains poorly quantified, case studies suggest it occurs. Given the absolute principle of donor safety upheld by all transplant centers, medical and surgical teams must ensure that postdonation renal function remains optimal, as it will depend entirely on the remaining kidney. Therefore, authorizing donation from an individual with bilateral renal FMD remains risky because even a seemingly mild lesion in the retained kidney may become clinically significant or symptomatic over time.

Fig. 4.

Bilateral renal fibromuscular dysplasia. Reproduced from Plouin et al. [30] under the Creative Commons License.

Indeed, two different teams have reported cases of progressive arterial FMD affecting the retained kidney after donation. In one case, progression occurred 1-year postdonation, while in the other, it occurred 8 years later. In both cases, progression became symptomatic and hemodynamically significant, ultimately requiring interventional treatment [27,28].

Prior to these studies, Felts et al. [29] described the case of a 33-year-old woman who had been excluded from kidney donation due to unilateral renal FMD that was considered mild and asymptomatic at the time of evaluation. Three years later, she developed malignant renovascular hypertension due to the progression of this dysplastic lesion, requiring surgical intervention.

In a study assessing hypertension risk in donors, Cragg et al. [24] compared a group of 49 potential donors with renal FMD (71% of whom had bilateral involvement) to a matched control group without FMD. Over a mean follow-up period of 7.1 years, the risk of developing hypertension was significantly higher in the FMD group (26%) versus control participants (6%) [24].

The ARCADIA registry also raised concerns regarding bilateral renal FMD, reporting a significant association between bilateral renal involvement and multisite disease. In this registry, bilateral renal lesions were present in 60% of individuals with multisite FMD [5]. In addition to these risks and concerns related to bilateral involvement, two key questions must be asked. First, what is the natural history of the lesion in the remaining kidney of a (usually young) donor, considering that the kidney will undergo compensatory hypertrophy and increased glomerular filtration, thereby increasing blood flow in an artery already weakened by pre-existing dysplasia? Second, what are the anatomical limits—in terms of the degree of stenosis and the extent of the asymptomatic lesion in the kidney not selected for donation—beyond which the contralateral kidney becomes ineligible for donation? Currently, teams that accept donations from individuals with bilateral renal FMD rely on qualitative radiological descriptions such as “mild,” “moderate,” or “severe.” However, these terms are based on local experience rather than standardized expert guidelines or evidence-based thresholds [24,31,32].

Gender and Pregnancy-Related Risks

Another key concern, raised by Chrysochou et al. [33], involves specific risks associated with this condition in female potential kidney donors of childbearing age who may consider pregnancy after donation. The author cites a recent report from a European registry on renal FMD, clearly demonstrating higher rates of gestational hypertension and, to a lesser extent, preterm birth, in patients with renal FMD compared to women without this vascular anomaly [34]. For this reason, the same author emphasizes the need for further studies to determine whether these obstetric risks remain elevated after kidney donation [33]. If confirmed, these risks could be even greater in women with bilateral renal involvement.

Extrarenal Screening

During the predonation vascular evaluation, it is essential to recognize the systemic nature of FMD [6,22], as involvement of other arterial territories, particularly those supplying the brain, is not uncommon. Therefore, identifying renal FMD warrants a systematic angiographic workup to detect possible extrarenal dysplastic lesions, as well as associated aneurysms or dissections that may have remained clinically silent until the time of evaluation. This screening should encompass all small- and medium-caliber arteries, from the intracranial and supra-aortic vessels to the visceral arteries and the proximal segments of the lower limb arteries.

The imaging strategy for donors with renal FMD includes both abdominal CTA and cerebrovascular imaging. Abdominal CTA, performed as part of the predonation evaluation, generally provides adequate visualization of the abdominal aorta and its branches, particularly the renal and visceral arteries, as well as the entire iliac arterial system. Regarding cerebrovascular imaging, according to Gornik et al. [6], all individuals diagnosed with FMD, regardless of the initially involved vascular bed, should undergo at least one screening for intracranial aneurysms using either brain CTA or magnetic resonance angiography. These examinations simultaneously enable evaluation of the supra-aortic trunks and intracranial arteries.

If extrarenal involvement is confirmed, it is essential to determine whether the asymptomatic lesion requires vascular intervention. When intervention is indicated, it should be managed at a specialized vascular or endovascular center. Even in the absence of immediate indications for treatment, an asymptomatic extrarenal dysplastic lesion carries a potential risk of progression, which may compromise the donor’s long-term vascular health. In this context, deferring donation appears to be a justified and cautious approach, pending further evidence from longitudinal studies to better define risk stratification. However, some authors suggest that living kidney donation may still be considered in selected cases, provided the extrarenal lesion does not currently warrant revascularization and that the donor is fully informed and agrees to adhere to regular, targeted follow-up, particularly through serial vascular imaging [33].

In contrast, kidney donation must be categorically rejected in cases where extrarenal arterial dysplastic lesions have already become symptomatic. This includes lesions that have led to a transient ischemic attack, stroke, myocardial infarction, or ischemic complications due to dissection or aneurysmal rupture in other vascular territories, even if these conditions were successfully treated.

Ethical Aspects and Informed Consent

Obtaining informed consent from an individual intending to donate an FMD-affected kidney requires that the supervisory ethics committee explain not only the standard risks of donation [35], but also those specifically associated with this systemic condition. This is especially important in transplant centers that consider living donations from individuals whose predonation evaluation reveals asymptomatic bilateral renal involvement or associated asymptomatic extrarenal manifestations.

It is equally essential to inform the donor of potential risks to the recipient, particularly those related to vascular reconstruction and possible progression of FMD due to incomplete resection of the dysplastic lesion. In this context, the role of the ethics committee becomes critically important in several respects. On the one hand, committee members, aware of organ shortages, can appreciate the commendable motivations of transplant teams willing to accept risks they deem manageable to provide certain patients with their only opportunity for transplantation. This is particularly relevant for recipients at risk of losing access to dialysis due to exhausted vascular sites or those facing irreversible delays in growth and weight gain while on dialysis. On the other hand, the ethics committee cannot simply endorse these risks based solely on the transplant team’s approval. Rather, the committee must weigh these risks in light of data published in robust studies with the strongest available information regarding outcomes.

Importantly, particularly in countries where deceased donor programs remain underdeveloped [36], the transplant team in cases of living donation becomes an indirect beneficiary of the donation, in addition to the recipient. The donated kidney represents an essential therapeutic resource enabling transplant teams to conduct their activities; thus, while these teams place great emphasis on donor safety, this concern inevitably coexists with another crucial priority: sustaining their transplant program within the global context of graft scarcity.

Hence, the ethics committee plays a central role in maintaining a delicate balance between medical needs—particularly the demand for grafts—donor safety, and scientific integrity until professional or scientific societies establish formal guidelines defining and validating the acceptance criteria for these donor kidneys.

TECHNICAL CHALLENGES

The two main technical considerations in the transplantation of grafts affected by FMD are: the resection of the arterial segment involved by the dysplastic lesion; and the management of excessive shortening of the renal artery after this resection, which must be performed under cold ischemia (Fig. 3B–E).

According to Berardinelli et al. [37], most postoperative complications reported in the literature involving FMD-affected grafts occurred when the dysplastic artery was either left unresected and directly anastomosed to recipient vessels, or resected without subsequent vascular reconstruction [13,16,38,39]. In contrast, the best outcomes were observed when the dysplastic segment was resected and arterial reconstruction was performed—particularly when done under cold ischemic conditions—prior to implantation in the recipient [20,39,40].

Technical Approach

After the graft is harvested and placed on the back table, care must be taken to introduce the perfusion cannula gently and atraumatically into the renal artery during cold perfusion, to avoid inducing dissection of the dysplastic segment.

Complete resection of the arterial segment affected by dysplasia is a critical early step, performed immediately after perfusing and flushing the graft with cold preservation solution at 4 °C. The extent of the lesion is usually already well-defined through predonation imaging and should not extend beyond the distal main renal artery or the proximal portion of its first two branches (Fig. 3A). Depending on the extent of resection, the graft will either retain a stump of the main renal artery in the case of partial resection, or present with two separate arteries (specifically, the first two branches) if the main trunk has been completely resected (Fig. 3B and E).

After resection, it is essential to evaluate the remaining length of the renal artery stump or its two primary branches, as this length is often insufficient to permit tension-free direct anastomosis to the recipient’s iliac arteries, necessitating vascular reconstruction. This reconstruction involves lengthening the renal artery or its two branches using a vascular substitute.

This vascular substitute is most commonly an autologous graft [13,16,37–43], the quality of which is confirmed by preoperative imaging. It can be harvested from the saphenous vein or the ipsilateral hypogastric artery (Figs. 3C, 5, and 6), provided the contralateral hypogastric artery has not previously been used. More rarely, it is harvested from the contralateral superficial femoral artery (Fig. 7); the vessel is then reconstructed using either a prosthetic graft or a segment of the saphenous vein. Cryopreserved arterial allografts may be used depending on their availability [43].

Fig. 5.

Close-up view of the final arterial configuration. Arterial reimplantation was performed via interposition of an autologous hypogastric graft harvested from the homolateral side of the transplant. The black arrows indicate the proximal anastomosis, performed under warm ischemia. The yellow arrow denotes the distal anastomosis between the main branch of the renal artery and the hypogastric graft, previously performed under cold ischemia. The white dashed circle highlights the location of the hypogastric artery ostium, previously harvested and used as the vascular extension in this reconstruction.

Fig. 6.

Overview of renal graft reimplantation. Arterial reimplantation was performed via interposition of an autologous hypogastric graft harvested from the homolateral side of the transplant. The black arrows indicate the proximal anastomosis, performed under warm ischemia. The yellow arrow denotes the distal arterial anastomosis, previously performed under cold ischemia. The blue arrow indicates the venous anastomosis.

Fig. 7.

Arterial reimplantation via interposition of two autologous arterial grafts harvested from the contralateral superficial femoral artery. The yellow arrows indicate the distal prehilar anastomosis, previously constructed and leak-tested under cold ischemia. The black arrows highlight the proximal arterial anastomosis, performed under warm ischemia. The blue arrow indicates the venous anastomosis.

Among these options, the ipsilateral hypogastric artery is generally considered ideal for several reasons. First, its compliance closely matches that of the renal artery, and it is anatomically near the site of the graft’s arterial anastomosis. Second, it carries minimal to no long-term risk of aneurysmal dilation, unlike venous grafts, which are constantly exposed to high arterial pressure. This is because the hypogastric artery graft is reimplanted onto the common or external iliac artery and thus remains under similar hemodynamic conditions as before. Third, compared to prosthetic grafts, it carries a significantly lower risk of infection, and fourth, compared to grafts harvested from the femoral artery, it avoids compromising vascular supply to the ipsilateral lower limb. However, a relatively high atheromatous burden may be a limiting factor in older recipients.

Once vascular reconstruction is complete, a critical final step performed on the back table is to check for anastomotic leaks. This is done by perfusing cold preservation solution through the renal artery or the first two branches of its arterial division, now extended by graft material. This leak test is essential to prevent pre-hilar anastomotic bleeding during reperfusion in the recipient.

Our Experience

Among the 850 kidney transplants from living donors performed at our center, two grafts presented with FMD (Fig. 2). Both were successfully implanted into the recipients. Resection of the dysplastic lesions and subsequent management of the shortened renal arteries or their two primary branches were accomplished through vascular reconstruction performed under cold ischemia. This enabled safe arterial implantation onto the recipient’s iliac artery, resulting in tension-free, watertight arterial anastomoses with hemodynamically satisfactory flow, achieved through the interposition of one or two vascular grafts serving as arterial extensions. At this point, the distal anastomosis had already been completed under cold ischemia. Thus, the duration of warm ischemia related to the vascular implantation of the graft in the recipient was limited to the time required for the proximal arterial anastomosis, along with that required for the venous anastomosis.

POSTTRANSPLANT MANAGEMENT AND OUTCOMES

Donor and Recipient Follow-Up

After transplantation, both the donor and the recipient should undergo specific long-term monitoring for FMD, in addition to standard posttransplant care. For donors whose predonation evaluation excluded bilateral or multisite FMD, follow-up should include clinical assessment, renal function testing, and noninvasive imaging of the remaining kidney using renal ultrasound, complemented by Doppler when indicated. As the existing literature does not provide sufficient evidence to support standardized imaging protocols or follow-up intervals in this context, we propose follow-up at 1 and 6 months after donation, then at least annually.

Potentially, symptoms suggestive of renal FMD [27] or involvement of other arterial territories—such as new-onset hypertension, headaches, or pulsatile tinnitus—may arise during follow-up. In such cases, the choice of imaging modality and its timing should be adjusted to detect, monitor, and manage any previously undiagnosed or newly developed dysplastic lesion.

For the recipient, particularly after complication-free vascular reconstruction and arterial implantation following resection of a dysplastic lesion, follow-up should include clinical evaluation, assessment of graft function, and noninvasive imaging of the renal graft with Doppler ultrasound. This should occur during the early posttransplant period, at 3 and 6 months, and at least annually thereafter, in accordance with our proposed schedule.

In situations where clinical or radiological findings raise suspicion of vascular complications—particularly those related to arterial reconstruction or to possible disease progression in recipients with incomplete lesion resection (e.g., stenosis, aneurysm, or renal artery dissection)—the imaging strategy should be promptly tailored to the nature, severity, and therapeutic implications of the complication.

Donor Outcomes

In a candidate with an isolated, unilateral renal dysplastic lesion—where assessment of the kidney not selected for donation revealed no imaging abnormalities and biological and radioisotopic functional tests were optimal—it is reasonable to assume that any additional risk is low and likely comparable to that of a donor without FMD. Moreover, even potential benefits are possible. For approved donors, nephrectomy of the FMD-affected kidney removes the dysplastic arterial segment and thus prevents subsequent renovascular hypertension. For excluded candidates, identifying the lesion facilitates its monitoring and, if necessary, medical management and revascularization once the stenosis becomes hemodynamically significant.

Adrogue et al. [44] recently conducted a retrospective analysis of cardiovascular and renal events in kidney donors diagnosed with renal FMD, comparing them to donors without the condition. The study included 8,922 living donors from three US transplant centers, with a mean follow-up period of 15.5±8.9 years. The FMD cohort comprised 113 donors, while the control group included 452 matched donors without FMD [44].

The results revealed no significant differences between the FMD and control groups in rates of hypertension, proteinuria, or chronic renal failure. Moreover, none of the donors with FMD progressed to end-stage renal failure. Similarly, the rates of cardiovascular events—defined as myocardial infarction, congestive heart failure, transient ischemic attack, stroke, or the need for coronary or peripheral arterial intervention—were comparable between groups, as were mortality rates [44]. That highly relevant study represented the largest series to date on the outcomes of donors with renal FMD, with the longest follow-up period. Nevertheless, it has been critiqued [33] for certain limitations [44]. Notably, these include its lack of data regarding: (1) the anatomical characteristics of the dysplastic lesion (multifocal versus unifocal; proximal versus extending along the main renal artery); (2) the unilateral versus bilateral nature of the lesion; and (3) the presence or absence of concomitant extrarenal lesions.

Consequently, the present authors had no information on the selection approaches used by these three transplant centers to distinguish those accepted for donation from those excluded among potential donors with renal FMD.

Recipient Outcomes

Similarly, for a graft that demonstrated optimal function on predonation evaluation—particularly based on biological and radioisotopic testing—with a dysplastic lesion that was proximal, limited, and completely resected, and for which vascular reconstruction and arterial implantation in the recipient were technically sound, it is reasonable to assume that its functional outcomes and survival will be comparable or nearly comparable to those of grafts unaffected by FMD.

Although limited in number and often based on case reports [40,43,45], studies evaluating the function and survival of such grafts have generally reported very satisfactory results. Notably, Kolettis et al. [25] followed 36 adult patients who received kidney transplants from donors with FMD, reporting a 3-year graft survival rate of 89%, comparable to the 86% seen in transplants from donors without FMD. In an earlier study, the same group noted that none of their donors with FMD-affected kidneys developed hypertension, proteinuria, or significant changes in serum creatinine levels over a 4.5-year follow-up period [26].

CONCLUSION

In the absence of alternative donor options and based on current evidence, a living-donor kidney affected by FMD can be considered a safe option, provided that two essential conditions are met. First, a rigorous selection process must be applied to this category of donors. In addition to meeting standard criteria for living kidney donation, the pretransplant evaluation must include: (1) confirmation that the contralateral kidney shows no morphological abnormalities on imaging and demonstrates optimal function on both biological and radioisotopic assessments; (2) assessment of the extent of arterial dysplasia, including confirmation that no extrarenal dysplastic lesions are present that could pose future risks to the donor; (3) characterization of the dysplasia in the kidney to be donated, ensuring that it is proximal and limited in extent; and (4) the donor’s fully informed consent, along with a clear understanding of the specific risks associated with this systemic condition.

Second, a high level of surgical expertise is required to perform any necessary vascular reconstruction and to ensure tension-free, hemodynamically sound arterial anastomoses in the recipient.