RECENT ADVANCES IN RENAL ARTERY STENTING
Invasive treatment for renovascular disease. A twenty year experience from a population based registry
Bergqvist D., Björck M., Lundgren F., Troëng T.
The Journal of Cardiovascular Surgery
Year 2008 - Vol. 49 - N. 05 - October- pag. 559
Aim. To analyze time trends in invasive treatment of renovascular disease in one country.
Method. Data have been analyzed from registrations in the Swedish Vascular Registry.
Results. Invasive treatment for renovascular disease contributes around 1% of all vascular surgery within the
Swedish Vascular Registry. Over the twenty-year period 1987-2006 the population-based frequency of invasive
treatment for renovascular disease has increased; 1 597 procedures have been registered with an increase over time.
The age of the treated patients has increased over the period (P<0.001). There has been a shift from open to
endovascular procedure and from isolated percutaneous transluminal renal angioplasty (PTRA) to PTRA combined
with a stent. Complications and mortality are significantly higher in patients undergoing open reconstruction
(P<0.01). One year follow-up is incomplete and long-term results are therefore not possible to evaluate through
Conclusion. Using nation-wide registry data it is possible to analyze time-trends also concerning rare diseases or
interventions. The changing pattern toward endovascular treatment of renovascular disease is obvious. Follow-up
data at one year are incomplete.
Invasive treatment for renovascular disease
– a twenty year experience from a population based registry
D Bergqvist MD, PhD, FRCS, M Björck, MD, PhD, T Troëng MD, PhD*.
Department of Surgical Sciences, Section of Surgery, Uppsala University Hospital, SE 751 85
*Department of Surgery, Blekinge Hospital, SE- 371 85 Karlskrona, Sweden.
Professor of vascular surgery
Department of Surgical Sciences/Surgery
SE 751 85 Uppsala, Sweden
Telephone: + 46 18 611 4633
Fax: +46 18 611 4632
Running head: Invasive treatment for renovascular disease
Aim: To analyze time trends in invasive treatment of renovascular disease in one country.
Method: Data have been analyzed from registrations in the Swedish Vascular Registry.
Results: Over the twenty-year period 1987-2006 the population-based frequency of invasive
treatment for renovascular disease has increased. Invasive treatment for renovascular disease
contributes around 1% of all vascular surgery within the Swedish Vascular Registry. 1597
procedures have been registered with an increase over time. The age of the treated patients
has increased over the period (p<0.001). There has been a shift over time from open to
endovascular procedure and from isolated PTRA to PTRA combined with a stent.
Complications and mortality are significantly higher in patients undergoing open
reconstruction (p<0.01). One year follow-up is incomplete and long-term results are therefore
not possible to evaluate through registry-data only.
Conclusion: Using nation-wide registry data it is possible to analyze time-trends also
concerning rare diseases or interventions. The changing pattern toward endovascular
treatment of renovascular disease is obvious. Follow-up data at one year are incomplete.
Keywords: renal artery stenosis, renovascular disease, hypertension, kidney insufficiency,
Steering committee of the Swedish Vascular registry (Swedvasc): D Bergqvist, M Björck, K
Eliasson, C Forssell, I Jansson, L Karlström, B Kragsterman, A Lundell, J Malmstedt, J
Nordanstig, L Norgren, T Troëng.
Renal artery stenosis may be a morphological phenomenon, incidentally detected, but may
also be functional and lead to the important clinical consequences of renovascular
hypertension, and/or renovascular kidney insufficiency, or ischaemic nephropathy. In the
population of patients suffering from hypertension and/or kidney insufficiency, renal artery
stenosis is, however, responsible only for a minority of cases. The dominating causes for
renovascular disease are atherosclerosis and fibromuscular dysplasia. It is important to
identify these patients as their disease is potentially curable by open surgical or endovascular
Unfortunately the infrequency of renovascular disease caused by renal artery stenosis has
made randomized trials difficult to perform 1-6. Inclusion rate has usually been slow, which
raises the question of external validity. How have patients been selected, and do they really
represent the population of patients with renovascular disease? It is also difficult to perform
randomized studies of patients with a complex condition. To draw robust conclusions is
difficult and may be inadequate.
Another problem is the presence of one to two kidneys, and each of them may have one to
several arteries, of which one or more may be stenosed. Although morphologically rather easy
to identify, the choice of when and how to treat is difficult, as is the evaluation of treatment
effect. Moreover, there is a possibility that a patient has other causes of pre-existing
hypertension or renal disease, and in that case only the part depending on the renal artery
stenosis is influenced by revascularization. Small vessel disease may be associated with
aging, diabetes mellitus, nephrosclerosis and/or atheroembolism. The large vessel disease,
where open or endovascular intervention can be performed, may be only a minor component
of the patient’s disease. This is important to have in mind when analyzing effects of therapy.
Other reasons why comparisons between studies are difficult and may be of limited value are
differences in target blood pressure, medical therapy, criteria for outcome and technique of
blood pressure measurement. Thus, there is a problematic situation when it comes to evidence
based recommendations. On one hand, a scarcity of randomized trials, on the other hand
experience based on clinical cases with undoubtedly successful treatment. The presence of
renal artery stenosis at angiography is moreover a strong predictor of decreased 4-year
survival 7. In the absence of randomized trials data from observational studies or population
based registries can give important information.
The aim of this paper is to analyze the development of invasive renovascular treatment during
a 20 year period as reflected in the Swedish Vascular Registry – Swedvasc.
Material and methods
Swedvasc started in 1987 in the Southern Health Care Region in Sweden, and from 1994 and
onwards all departments performing vascular surgery in Sweden have participated. Basic
principles, pros and cons, advantages and disadvantages with the registry have been reported
Between 1987 through 2006 all procedures registered in Swedvasc with the indication
renovascular hypertension and/or renovascular uraemia and/or with anatomy involving the
renal artery were analyzed. Of a total of 151 434 open and endovascular procedures
registered, 1597 (1.0%) were performed with the indication renovascular disease. The 68
emergency renovascular procedures that were registered will not be further discussed in this
report. Analysis has been made in four five-year periods to evaluate possible time trends
Ethical considerations: The Registry was ethically approved by the Swedish authorities.
Using registry data only, the individual patients were not identified. The project has been
approved by the Steering Committee of Swedvasc (Appendix).
Statistics: Time-trends were analyzed by ANOVA. Fisher’s exact test and x2 were used.
P<0.05 was considered significant.
Of the 1597 procedures 55% were performed on male and 45% on female patients. The
gender proportion has been stable over the years. The mean age was 63 years with an increase
in mean age over time (mean age and range): 59 (9-83), 61 (8-87), 63 (1-89) and 66 (15-86)
years (p<0.0001). There was no difference in age and sex between those undergoing open or
In Table I the indications for treatment are given. The relative frequencies reflect the situation
best, since during the period through 1993 there were an increasing number of departments
joining the registry to cover the whole country from 1994 onwards. There is an increase in the
number of procedures when the last two five year periods are compared (p=0.018).
Any renovascular procedures were performed in 23 departments, in 18 open surgery and in 19
endovascular. In the five hospitals with endovascular but without open renovascular surgery a
total of 12 endovascular procedures were performed. In the four hospitals where no
endovascular treatment was given, only six open operations were performed. In only six of
the 23 hospitals 80 interventions or more had been made. In four hospitals more than 150
interventions had been made in the 20 years. In eleven of the hospitals less than 20
interventions were made in the 20 years. Seventy-four percent of the procedures were
performed at university departments, 25% at county hospitals and only 0.3% (n=5) at district
In Table II the types of intervention are given. The first stents were inserted in 1997, when the
third 5-year period started. The time trends are evident. Open surgery has diminished with an
increase in endovascular procedures, where primary stenting has increasingly replaced simple
balloon dilatation. Regarding the open surgical techniques the material is too small to analyze
time trends. Bypass reconstructions dominated (n = 142), followed by endarterectomy with or
without patch (n = 83). A direct anastomosis was made on only ten occasions.
Surgical complications within 30 days are shown in Table III. Data are missing in five
percent. The complication rate was significantly higher in the surgical group (p<0.01). Two
nephrectomies were made in the surgical group, none in the others. General complications are
listed in Table IV. Thirty day mortality in the three groups were 5.0 %, 0.8 % and 1.2 %
respectively, again mortality being significantly higher in the open surgical group (p < 0.001).
Follow-up was reported in 88% after 30 days but only 54% after one year. Of those with
follow-up data, at 30 days 93.4% were in their homes, 4.6% were in hospital or geriatric
institution and 2% were dead. The corresponding proportions at one year were 91.5%, 1.7%
and 6.7% respectively.
Invasive treatment of symptomatic renal artery stenosis is not common. Only around 1% of all
vascular procedures registered in the Swedvasc have the indication renovascular disease.
Probably there is a certain degree of underreporting, which is more pronounced among
patients undergoing endovascular treatment when not being hospitalized in vascular surgical
wards. This problem must be solved by closer cooperation and better reporting routines from
departments of interventional radiology, where the treatment is performed. Nonetheless, the
decreasing proportion of open surgical procedures is obvious.
As a consequence, very few departments perform a reasonable volume of open surgery. It is
our opinion that open renovascular surgery belongs to the more difficult parts of vascular
surgery, with a need of great experience and possibility for rapid decisions and
improvisations. This would seem a good reason to centralize elective renovascular surgery to
few centres. It is always difficult to establish the number of operations needed to obtain good
quality, but four renal artery reconstructions per year seem far too low. Although
complications requiring surgery after endovascular procedures are infrequent, an adequate
care of those patients with often demanding surgery also motivates centralization. When
occlusion occurs, the time until adequate perfusion must be restored is often very short,
making transportation unsafe. The increased frequency of complications observed after open
surgery could be due to an unfavourable case-mix, the more difficult cases undergoing open
repair, but is also supported by results in the only existing small randomized trial 1.
The increasing proportion of endovascular procedures at the expense of open surgery seems
reasonable, results from one randomized trial supporting such a development 1. One
prerequisite, however, is a strict follow-up program for at least one year after the intervention.
This is necessary to be able to re-intervene at re-stenosis, thereby maintaining secondary
patency comparable to the primary patency after open surgery. This requires a well-
functioning organization of follow-up. The need for first redo procedure occurs earlier after
balloon dilatation than after open surgery 1,12,13. A previous balloon dilatation does not exclude
successful open surgery at failure or complications 14.
Considering endovascular treatment there has been a change from balloon dilatation to the use
of stents, a technical modification that at first sight seems reasonable, but the scientific
evidence behind such a development is very poor. One small randomized trial speaks in
favour of stenting 4, but little is known about long term effects of stenting and how this
procedure influences the possibility to perform an open surgical reconstruction should it be
necessary. One problem with endovascular treatment is the risk of distal atheroembolism with
potential destruction of parenchymal tissue 15. This risk has been considered an indication to
use “protection” devices, although the effect of such devices is still unproven.
Unfortunately, there are only a few small randomized trials evaluating invasive treatment of
renovascular disease. Several trials are ongoing 16 and results are eagerly awaited. Other
important sources of information are population-based registries, which complement
randomized trials 10. Such a registry must cover all procedures with a near to 100% follow up
and high validity of data. For most procedures the follow up in Swedvasc is adequate and
good, renovascular reconstruction being an unfortunate exception. There are reasons to
believe that the majority of procedures are reported, but urgent measures must be taken to
improve follow-up. Follow-up must cover the patients´ blood pressure and renal function as
well as the patency of the reconstruction.
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Clinical diagnosis and indication for treatment of renal artery stenosis.
Principle types of intervention
N.B. 20 were classified as other types of reconstructions.
Surgical complications within 30 days after intervention (%). One patient can have
Occlusion, thrombosis 18.104.22.168
Infection of the reconstruction0.40 0.2
Bowel ischaemia 22.214.171.124
Total19.5 7.7 10.2
Individual patients with surgical
General complications within 30 days after intervention. Number (per cent).
(n = 241)
(N = 904)
(n = 432)