Aberrant renal arteries and hypertension

Effect of Accessory Renal Arteries on Essential Hypertension and Related Mechanisms

BACKGROUND

This case-control study aimed to determine whether there were differences between patients with essential hypertension with accessory renal arteries (ARAs) and those without ARAs.

METHODS AND RESULTS

The enrolled patients with essential hypertension were divided into the ARA group (n=200) and control group without ARAs (n=238). After propensity matching, 394 patients (197 in each of the 2 groups), were included. The 24-hour BP (4.33/2.43 mm Hg) and daytime BP (4.48/2.61 mm Hg) of patients in the ARA group were significantly higher than those of the control group (P<0.05). The flow-mediated dilation was lower in the ARA group (5.98±2.70 versus 5.18±2.66; P<0.05). In correlation analysis, the horizontal plasma aldosterone concentration had the highest correlation with 24-hour, daytime, and nighttime systolic BP (r=0.263, 0.247, and 0.243, respectively; P<0.05) and diastolic BP (r=0.325, 0.298, and 0.317, respectively; P<0.05). As for multivariate regression analysis, plasma aldosterone concentration was a significant risk factor for elevated 24-hour, daytime, and nighttime systolic BP (β=0.249 [95% CI, 0.150-0.349], 0.228 [95% CI, 0.128-0.329], and 0.282 [95% CI, 0.187-0.377], respectively; P<0.05) and elevated diastolic BP (β=0.289 [95% CI, 0.192-0.385], 0.256 [95% CI, 0.158-0.353], and 0.335 [95% CI, 0.243-0.427], respectively; P<0.05). Direct renin concentration was also a risk factor for 24-hour and daytime BPs, whereas heart rate was a risk factor correlated with 24-hour, daytime, and nighttime diastolic BP (all P<0.05). For the mixed-effects model for repeated measures, the results were similar to results of the multivariate regression analysis (all P<0.05).

CONCLUSIONS

ARAs could contribute a higher BP of patients with essential hypertension and might promote the development of essential hypertension. The mechanism might be related to overactivation of the renin-angiotensin-aldosterone system and sympathetic nervous system.

Anatomic Variations of Renal Arteries as an Important Factor in the Effectiveness of Renal Denervation in Resistant Hypertension

Hypertension remains the leading cause of death worldwide. Despite advances in drug-based treatment, many patients do not achieve target blood pressure. In recent years, there has been an increased interest in invasive hypertension treatment methods. Long-term effects and factors affecting renal denervation effectiveness are still under investigation. Some investigators found that the renal arteries' morphology is crucial in renal denervation effectiveness. Accessory renal arteries occur in 20-30% of the population and even more frequently in patients with resistant hypertension. Diversity in renal vascularization and innervation may complicate the renal denervation procedure and increase the number of people who will not benefit from treatment. Based on previous studies, it has been shown that the presence of accessory renal arteries, and in particular, the lack of their complete denervation, reduces the procedure's effectiveness. The following review presents the anatomical assessment of the renal arteries, emphasizing the importance of imaging tests. Examples of imaging and denervation methods to optimize the procedure are presented. The development of new-generation catheters and the advancement in knowledge of renal arteries anatomy may improve the effectiveness of treatment and reduce the number of patients who do not respond to treatment.

Renal Volumetry-based Prediction of the Presence of Accessory Renal Artery: Computed Tomographic Angiography-based Study with Clinical Implications on Renal Doppler

Background

The objective was to validate the hypothesis and evaluate whether the presence or absence of accessory renal artery can be predicted on the basis of volumetric parameters of kidney and diameter of the main renal artery (mRA).

Methods

This retrospective analysis was performed in a total of 60 kidneys in 30 patients, who had computed tomographic (CT) angiography. The kidneys were segregated into control and study groups depending on the absence or presence of accessory renal artery. The total renal volumes were measured using renal length, breadth, and height in mm³. The renal artery diameters were also measured in mm, in the postostial segment. Renal volume/renal artery diameter (V/d) was measured for each kidney in two groups, and the difference in mean V/d values (in mm²) in two groups was measured for statistical significance.

Results

The mean V/d value in the study group with presence of the accessory renal artery was found to be 23,444.7 mm² (range: 16,229.1-32,490.0). The V/d value in the control group with the absence of accessory renal artery was found to be 19,717.15 mm² (range: 13,704.6-28,000.0). The mean values in the two groups showed a statistically significant difference in the V/d with a P value of 0.001 (P < 0.05).

Conclusion

The study suggests that the possibility of the presence of the accessory renal artery is directly proportional to the total renal volume and inversely proportional to the diameter of mRA. The use of integrated volumetric parameter (V/d) is therefore likely to play a key role in the prediction of the presence of accessory renal artery on imaging studies. Renal volumetry on CT angiography may help predict the presence of accessory renal artery and thus may have implications on renal Doppler studies.

Renin dependent hypertension caused by accessory renal arteries

Background

Hypokalemia in the presence of hypertension is often attributed to primary hyperaldosteronism as a cause of secondary hypertension, however secondary hyperaldosteronism may present similarly. Accessory renal arteries are variants in the vascular anatomy which are often thought to be innocuous but in some circumstances can cause renovascular hypertension leading to secondary hyperaldosteronism.

Case presentation

We report 2 cases of hypertension with secondary hyperaldosteronism associated with accessory renal arteries. Both patients presented with hypokalemia and further investigations revealed hyperaldosteronism with unsuppressed renin levels. Imaging studies showed the presence of accessory renal artery.

Conclusion

Accessory renal arteries are a potential cause renovascular hypertension which can be detected via CT angiography or magnetic resonance angiography. Hormonal evaluation should be undertaken to determine whether its presence contributes to hypertension in the patient as targeted treatment such as aldosterone antagonist can be initiated. Surgical intervention or renal denervation may be considered in resistant cases.

Accessory renal arteries: Prevalence in resistant hypertension and an important role in nonresponse to radiofrequency renal denervation

OBJECTIVE

The aim of this study was to understand the role of accessory renal arteries in resistant hypertension, and to establish their role in nonresponse to radiofrequency renal denervation (RDN) procedures.

BACKGROUND

Prior studies suggest a role for accessory renal arteries in hypertensive syndromes, and recent clinical trials of renal denervation report that these anomalies are highly prevalent in resistant hypertension. This study evaluated the relationships among resistant hypertension, accessory renal arteries, and the response to radiofrequency (RF) renal denervation.

METHODS

Computed Tomography Angiography (CTA) and magnetic resonance imaging (MRI) scans from 58 patients with resistant hypertension undergoing RF renal denervation (RDN) were evaluated. Results were compared with CT scans in 57 healthy, normotensive subjects undergoing screening as possible renal transplant donors. All scans were carefully studied for accessory renal arteries, and were correlated with long term blood pressure reduction.

RESULTS

Accessory renal arteries were markedly more prevalent in the hypertensive patients than normotensive renal donors (59% vs 32% respectively, p=0.004). RDN had an overall nonresponse rate of 29% (response rate 71%). Patients without accessory vessels had a borderline higher response rate to RDN than those with at least one accessory vessel (83% vs 62% respectively, p=0.076) and a higher RDN response than patients with untreated accessory arteries (83% vs 55%; p=0.040). For accessory renal arteries and nonresponse, the sensitivity was 76%, specificity 49%, with positive and negative predictive values 38% and 83% respectively.

CONCLUSIONS

Accessory renal arteries were markedly over-represented in resistant hypertensives compared with healthy controls. While not all patients with accessory arteries were nonresponders, nonresponse was related to both the presence and non-treatment of accessory arteries. Addressing accessory renal arteries in future clinical trials may improve RDN therapeutic efficacy.

Renal artery anatomy affects the blood pressure response to renal denervation in patients with resistant hypertension

BACKGROUND

Renal denervation (RDN) has been shown to reduce blood pressure (BP), muscle sympathetic nerve activity (MSNA) and target organ damage in patients with resistant hypertension (RH) and bilateral single renal arteries. The safety and efficacy of RDN in patients with multiple renal arteries remains unclear.

METHODS

We measured office and 24-hour BP at baseline, 3 and 6 months following RDN in 91 patients with RH, including 65 patients with single renal arteries bilaterally (group 1), 16 patients with dual renal arteries on either one or both sides (group 2) and 10 patients with other anatomical constellations or structural abnormalities (group 3). Thirty nine out of 91 patients completed MSNA at baseline and follow-up.

RESULTS

RDN significantly reduced office and daytime SBP in group 1 at both 3 and 6 months follow-up (P<0.001) but not in groups 2 and 3. Similarly, a significant reduction in resting baseline MSNA was only observed in group 1 (P<0.05). There was no deterioration in kidney function in any group.

CONCLUSION

While RDN can be performed safely irrespective of the underlying renal anatomy, the presence of single renal arteries with or without structural abnormalities is associated with a more pronounced BP and MSNA lowering effect than the presence of dual renal arteries in patients with RH. However, when patients with dual renal arteries received renal nerve ablation in all arteries there was trend towards a greater BP reduction. Insufficient renal sympathetic nerve ablation may account for these differences.

Renal denervation in multiple renal arteries

BACKGROUND

In most previous studies investigating efficacy of renal denervation (RDN), patients with multiple renal arteries are generally excluded from treatment. This study was designed to determine the prevalence of multiple renal arteries in patients referred for RDN, to propose a classification for anatomical eligibility and to investigate the relation between the presence of multiple arteries and blood pressure (BP)-lowering effect.

MATERIALS AND METHODS

Patients referred for RDN who underwent noninvasive imaging of the renal arteries before treatment were included in present analysis. Eligible patients were treated. Renal function and BP were evaluated 6 months after treatment.

RESULTS

Hundred and twenty-six patients referred for RDN were included in present analysis. Thirty-four per cent had multiple arteries. Sixty-nine patients underwent RDN. Office BP significantly reduced from 195 (± 26)/106 (± 14) mmHg to 165 (± 24)/95 (± 14) mmHg (P < 0·001). BP reduction in patients with multiple arteries which were all treated was comparable to patients with solitary arteries. However, patients with multiple which were not all treated showed a trend towards a less pronounced effect of RDN (β: 11·6, P = 0·11). The proposed classification appeared useful by identifying eligible anatomy. Renal function at 6 months did not differ from baseline in all subgroups.

CONCLUSIONS

Based on our results and the high prevalence of multiple arteries, it seems reasonable not to exclude patients with multiple renal arteries from RDN. Current analysis suggests that BP reduction may be less pronounced in patients with multiple renal arteries of whom not all arteries were treated.

Renal denervation in a patient with two renal accessory arteries: a case report

Percutaneous renal denervation has emerged as an effective adjunct in the management of resistant hypertension. However, the limits of the renal anatomical criteria that can be successfully treated are still unknown. In this report, we describe the case of a middle-aged man with essential resistant hypertension and two small left accessory renal arteries that underwent renal denervation of both principal renal arteries. He responded well with a progressive reduction in blood pressure measuring of 16/10, 32/17 and 45/24 mmHg at 1, 6 and 12 months, respectively. At 12 months, 94% of ambulatory measurements were below 140/90 mmHg and the number of anti-hypertensive medications had decreased from six to three. Thus, it would appear that the presence of two non-ablated left accessory renal arteries does not influence the response to renal denervation.

Outcome of living kidney donors left with multiple renal arteries

Individuals with kidneys having ≥ 2 arteries appear to have an increased incidence of hypertension. Whether kidney donors in whom the remaining kidney has ≥ 2 arteries are at increased risk of hypertension is unknown. Therefore, we studied 3685 kidney donors to determine whether donors left with a kidney having ≥ 2 arteries were at increased risk of hypertension, impaired renal function, or death. Cohorts were assigned based on our practice pattern and the anatomy of the donated kidney. Of the 3685 donors, 1211 were estimated to have a remaining kidney with ≥ 2 arteries. Mean follow-up time for the single-artery group was 14.1 (± 11.0) yr and 15.3 (± 11.2) yr for the ≥ 2 artery group. Six-month hospital readmission rate was 1.4% and 1.2%, hypertension was noted in 22.4% and 21.8% and proteinuria in 9.7% and 9.6%, and estimated glomerular filtration rate at last follow-up was 62 (± 28) and 62 (± 16) for single vs. ≥ 2 renal artery groups, respectively. Our data suggest no adverse clinical sequelae nor any decrease in long-term survival for donors left with a kidney having ≥ 2 renal arteries.

Do multiple renal arteries in the remnant kidney have a negative influence on kidney donors after kidney donation?

AIM

To investigate whether the presence of multiple renal arteries in the remnant kidney has implications for lower renal function or increased incidence of hypertension.

METHODS

We reviewed the intraoperative and follow-up data of 101 live kidney donors who underwent nephrectomies at our institution. Sixty-nine donors (68.3%) had single artery in the remnant kidney (Group A), while 32 donors (31.7%) had multiple renal arteries in the remnant kidney (Group B). We compared the demographic and intraoperative data between the two groups. The follow-up data of donors in each group were divided into three subgroups based on the length of the follow-up period (12-24 months, 24-48 months and ≥48 months). Subgroups were created based on blood pressure and serum creatinine level. The δblood pressure (follow-up blood pressure minus preoperative blood pressure) and δserum creatinine (follow-up serum creatinine minus preoperative serum creatinine) in each subgroup in Group A were compared with the counterparts in Group B.

RESULTS

Renal arterial stenosis and calcification of renal arterial wall were not observed in all donors. There were no significant differences in the intraoperative characteristics (e.g. age, body mass index, operative duration and estimated blood loss) between the two groups. In addition, the blood pressure and serum creatinine level among subgroups within each group were similar. Furthermore, significant differences in δblood pressure and δserum creatinine were not observed between subgroups within the same follow-up period. Recipient survival rate and serum creatinine level were similar and acceptable in both groups.

CONCLUSIONS

The presence of multiple renal arteries in the remnant kidney does not have additional negative influence on kidney donors after kidney donation.

Accessory or additional renal arteries show no relevant effects on the width of the upper urinary tract: a 64-slice multidetector CT study in 1072 patients with 2132 kidneys

OBJECTIVE

The aim of this study was to find out on an unselected patient group whether crossing vessels have an influence on the width of the renal pelvis and what independent predictors of these target variables exist.

METHODS

In this cross-sectional study, 1072 patients with arterially contrasted CT scans were included. The 2132 kidneys were supplied by 2736 arteries.

RESULTS

On the right side, there were 293 additional and accessory arteries in 286 patients, and on the left side there were 304 in 271 patients. 154 renal pelves were more than 15 mm wide. The greatest independent factor for hydronephrosis on one side was hydronephrosis on the contralateral side (p<0.0001 each). Independent predictors for the width of the renal pelvis on the right side were the width of the renal pelvis on the left, female gender, increasing age and height; for the left side, predictors were the width of the renal pelvis on the right, concrements, parapelvic cysts and great rotation of the upper pole of the kidney to dorsal. Crossing vessels had no influence on the development of hydronephrosis. Only anterior crossing vessels on the right side are associated with widening of the renal pelvis by 1 mm, without making it possible to identify the vessel as an independent factor in multivariate regression models.

CONCLUSION

The width of the renal pelvis on the contralateral side is the strongest independent predictor for hydronephrosis and the width of the renal pelvis. There is no link between crossing vessels and the width of the renal pelvis.

Accessory Renal Arteries Are Not Related to Hypertension Risk:A Review of MR Angiography Data

OBJECTIVE

It has been hypothesized that accessory renal arteries are related to the risk of hypertension. Our goal was to determine the prevalence of accessory renal arteries in hypertensive patients using MR angiography and to assess the relationship between accessory renal arteries and hypertension risk.

MATERIALS AND METHODS

From 1996 to 2002, 185 hypertensive patients underwent MR angiography of the renal arteries at our institution for assessment of renal artery stenosis. MR angiograms were obtained using a 1.5-T magnet, IV gadolinium, and 3D gradient-echo sequences. Interpretations of the MR angiograms were retrospectively reviewed.

RESULTS

Of 185 hypertensive patients, 45 (24%) showed accessory renal arteries. Of these 45 patients, nine (20%) showed renal artery stenosis and 36 (80%) showed no significant stenosis. Of the 140 patients with a single renal artery, 42 (30%) showed renal artery stenosis and 98 (70%) showed no stenosis. The odds ratio of renal artery stenosis in the accessory renal artery group versus the single renal artery group was 0.58 (95% confidence interval, 0.26-1.3%), which is not statistically significant at a power of 0.85 (chi(2) = 1.705; p = 1.0).

CONCLUSION

We found no statistically significant difference in the prevalence of renal artery stenosis between patients with accessory renal arteries and those without accessory renal arteries. Assuming that the presence of two separate causes of hypertension in the same patient would be unlikely, this finding implies that accessory renal arteries are a vascular anomaly and not a direct cause of hypertension. The findings are potentially relevant in refuting the theory of accessory renal arteries as an anatomically treatable cause of hypertension.

Congenital familial vascular anomalies: a study of patients with an anomalous inferior vena cava, and of their first-degree relatives

With magnetic resonance angiography and computed tomography, congenital anomalies of the inferior vena cava are diagnosed more frequently than they used to be. Accessory renal arteries identified by magnetic resonance angiography in a patient with an anomalous inferior vena cava indicated a combination of arterial and venous abnormalities. The study was initiated to screen consecutive patients with an anomalous inferior vena cava for concomitant abdominal and pelvic arterial abnormalities, and their first-degree relatives for congenital vascular anomalies. Magnetic resonance angiography identified in 2 of 5 patients with an anomalous inferior vena cava concomitant accessory renal arteries and in 5 of 11 first-degree relatives major abdominal vascular anomalies including accessory renal arteries, accessory renal veins, and anomalies of the hepatic artery. None of the relatives showed abnormalities of the inferior vena cava. The familial occurrence of vascular anomalies strongly suggests an underlying pathogenetic component in affected family members. In patients with a congenital anomaly of the inferior vena cava, concomitant arterial abnormalities should be considered. First-degree relatives may be at risk for congenital vascular anomalies.

Conn's syndrome and bilateral renal artery stenosis in the presence of multiple renal arteries

We report the case of a 42-year-old male who was admitted to our hospital after an acute hypertensive crisis despite four-way anti-hypertensive therapy. The renal scintigraphy, the excretory urogram and the biochemical profile performed two years before were unremarkable, except for slightly elevated serum creatinine and plasma aldosterone, in presence of normal aldosterone/renin ratio. The renal arterial angiography that was performed despite a second unremarkable scintigraphy revealed high-grade bilateral arterial stenosis in the presence of multiple renal arteries. Following dilatation of the left stenosis, the aldosterone/renin ratio was pathologic. Recumbent and orthostatic aldosterone values were 830 pg/ml and 1824 pg/ml, respectively, and recumbent and orthostatic renin values were 0.82 and 1.21 ng angiotensin I/ml/h, respectively. The abdominal computed tomography performed to investigate a possible concomitant Conn's syndrome resulted in the detection of a left adrenal tumor. After resection of the lesion, plasma-aldosterone levels normalized and a pronounced rise in serum potassium levels was observed. Following angioplasty of the right renal artery stenosis, blood pressure could easily be managed with combined beta and calcium channel blocker therapy. Particularly in cases of bilateral (but also in the presence of unilateral) renal artery stenosis in association with Conn's syndrome, all the available screening methods for these disorders can fail. In cases of poor response to combination hypertensive therapies, renal arteriography and a fludrocortisone-suppression test should be performed in order to rule out both renal arterial stenosis and Conn's syndrome, even in the absence of clinical and biochemical findings suspicious for either disorder.

A possible explanation for the frequent concomitance of arterial hypertension and multiple renal arteries

In more than 20% of subjects, at least one kidney is found to be supplied by more than one artery arising from the aorta. This aberrant renovascular anatomy has been reported in the literature to occur in up to 80% of patients who suffer from essential hypertension. Predominant numbers of the so-called 'accessory' vessels are longer and narrower than the segmental arteries arising in the main renal artery. As a result (in accordance with Poiseuille's law of fluid flow), the renal segments supplied by these 'accessory' vessels may have lower levels of blood pressure than the remainder of the parenchyma, thereby increasing the renin secretion. This hypothesis could be significant in terms of finding a causal treatment for a disorder induced by such a mechanism. We first review the literature in which the frequency of these vascular anomalies in normotensive and hypertensive patients is described, and then advance a hypothesis explaining the frequent incidence of essential hypertension in these subjects, as well as the ramifications of this phenomenon.

Hypertension associated with multiple renal arteries may be renin-dependent

OBJECTIVE

Subjects with multiple renal arteries have been shown to suffer more frequently from hypertension and to have higher blood pressures than subjects whose kidneys are supplied by single renal arteries. This study was carried out to determine whether subjects with multiple renal arteries also have higher renin activity.

METHODS

We studied 62 consecutive patients who had undergone angiography for various reasons. They were divided into two groups. Group A comprised 29 patients whose kidneys were supplied by single arteries (male :female ratio 1.63, mean age 51.8 +/- 1.9 years) while Group B comprised 33 patients with multiple renal arteries (male:female ratio 2, mean age 47.3 +/- 2.3 years).

RESULTS

Before stimulation with frusemide, the plasma renin in Group A was 0.79 +/- 0.13 ng angiotensin l/ml per h, while in Group B the corresponding figure was 1.73 +/- 0.38 ng angiotensin l/ml per h. This difference was statistically significant (P= 0.0127). Thirty minutes later the plasma renin level in Group A was 2.43 +/- 0.37 ng angiotensin l/ml per h versus a level of 3.86 +/- 0.53 ng angiotensin l/ml per h in Group B (P= 0.0169). Again, 30 minutes later the level was 2.59 +/- 0.4 ng angiotensin l/ ml per h in Group A, versus 3.79 +/- 0.59 ng angiotensin l/ ml per h in Group B (P= 0.0495).

CONCLUSIONS

We conclude that patients with multiple renal arteries constitute a group who have high plasma renin activity and may therefore be prone to develop arterial hypertension.

Innocent aberrant renal vessels producing ureteropelvic junction obstruction

Hydronephrosis caused by a triad of weight loss, renal ptosis, and the presence of lower pole aberrant renal vessels in two adults, with review of literature and surgical approach to this problem, is discussed.