renal artery dissection occurs mainly after direct vessel injury ( such as trauma or endovascular intervention ) or in hypertensive patients with underlying arterial diseases ( such as fibromuscular dysplasia or atherosclerosis ) .
the clinical presentation with acute low back or flank pain and haematuria is readily misleading and suggests renal colic .
conventional imaging , including ultrasound and doppler explorations , is not sensitive enough to detect the dissection nor the renal infarction and patients are usually treated for urolithiasis unless a computed tomography scan ( cts ) is performed . since the first report in 1944 , almost 200 cases of srads have been published , of which 25% were diagnosed at necropsy .
the availability of non - invasive and more sensitive - contrasted imaging techniques should facilitate recognition of such cases while reducing the delay in diagnosing srad and allowing earlier treatment .
in this study , we report six patients who were referred to our nephrology department between 1997 and 2010 and presented with srad . all were men between 33 and 55 years of age .
they had no cardiovascular risk factors , except one patient who had a past history of smoking .
all patients presented acute unilateral flank pain with inguinal irradiation and sometimes haematuria on urinary dipstick testing and were most commonly diagnosed with renal colic , delaying the diagnosis of renal infarction by several days ( table 1 ) .
proteinuria was significant in two cases . among the most frequent biochemical abnormalities , we noted elevated lactate dehydrogenase concentrations and inflammatory markers including increased white blood cells , c - reactive protein and fibrinogen levels ( table 2 ) .
haemostasis was within the normal range , but the research for circulating anticoagulant was positive in two patients ( data not shown ) .
renal ultrasound was performed in all cases at admission but failed to detect renal infarction .
we performed contrast - enhanced abdominal cts to diagnose the renal infarction ( figure 1 ) and estimate the area of extension ( between 15 and 50% of the kidney surface ) .
renal infarction affected mainly the left side ( 4/6 ) but was bilateral in one patient .
we then performed angiotomodensitometry ( a - cts ) in some cases and magnetic resonance imaging angiography ( a - mri ) in others , completed by percutaneous selective renal arteriography ( figure 2 ) to identify vascular lesions and the vessels ' anatomy .
three patients had multiple renal arteries and the dissection usually affected segmental branches but concerned also the main renal artery in two cases .
only one of them was treated by angioplasty with stent implantation ( two stents ) , whilst conservative management was elected for all other patients for various reasons including the presence of a circulating false lumen , overpassed renal infarction or dissection of small branches of arteries , precluding revascularization possibilities .
all patients were treated by oral anticoagulation ( anti - vitamin k ) or anti - platelets .
two patients were lost to follow - up ; the others were followed up for a period of between 4 months and 13 years .
they had normal blood pressure ( one without any treatment and three with anti - hypertensive drug therapy ) and their renal function remained stable . demographic and baseline clinical and disease characteristics ( n = 6 ) biochemical parameters at diagnosisa 
  crp , c - reactive protein ; na , not available ; wbc , white blood cells ; alat , alanin aminotransferase ; asat , aspartate aminotransferase ; pt , prothrombin time ; aptt , activated partial thromboplastin time .
enhanced abominal cts showing median infarction of the left kidney ( patient number six ) .
renal selective angiography ; ( a ) patient number six ; ( b ) patient number five .
as illustrated by our clinical report , detection of srad is often delayed or missed because the condition is rare and its clinical presentation is non - specific .
indeed , patients with acute renal infarction commonly have abdominal , flank or low back pain as in renal colic .
the clinical presentation in our series is mainly consistent with previous reports but also illustrates new findings .
first of all , there is a male predominance with a classic male to female ratio of 4:1
. this predominance could be even stronger with a ratio of 10:1 as described by edwards et al .   in the most important series to date reporting on 35 patients .
srad occurs predominantly in the fourth decade ( mean age of our series is 39 years ) of patients without known cardiovascular risk factors except tobacco use .
another finding that our series showed was that the left renal artery was clearly more frequently involved .
some authors suggest that anatomical characteristics predispose the left renal artery to dissection in the case of traumatic injury or acceleration / deceleration [ 58 ] .
bilateral disease is encountered in 1015% of srad cases [ 911 ] usually because of underlying arterial disease .
we identified fibromuscular dysplasia in half of our cases , confirming the high prevalence reported by lacombe et al .   in their series of 22 patients treated by surgery .
the third finding that we want to underline is the fact that spontaneous dissection can occur in normal vessels under normal blood pressure , but subjected to extreme exertion , as was the case with patients five and six , who practised body building .
some authors suggest that vigourous exercise may subject the renal artery to such an unusual degree of stretching that it causes intimal tear and subsequent arterial dissection [ 1215 ] .
more discordant is the fact that our patients were not all hypertensive at diagnosis . in rats
, kidney infarction induces acute hypertension associated with a transient renin elevation . in humans ,
several authors have described the occurrence of malignant hypertension in the aftermath of a renal infarction [ 13 , 1719 ] whereas other case reports suggested that hypertension is not consistently associated , some patients remaining normotensive [ 12 , 2023 ] .
it is important to note that in most of the series , patients are referred for endovascular   or surgical [ 9 , 10 , 2426 ] revascularization , whose indication relies on the presence of uncontrolled hypertension and/or kidney failure , which easily explains the nearly 100% rate of hypertension .
moreover , there was a large proportion of fibrodysplasia ( up to 90% ) [ 4 , 26 ] and/or atheroma [ 25 , 27 ] identified in the 
surgical series. the high prevalence of arterial pathology underlying the dissection may also help to explain the high frequency of hypertension in these series . in cases of srad with renal infarction
, the diagnosis must be made as early as possible to increase the chances of renal revascularization and recovery .
our experience confirms that doppler and/or ultrasound have poor diagnostic sensitivity since the dissection may affect intra - renal arterial branches and polar arteries whilst cts , on the other hand , never failed to identify the area of renal infarction .
the performance of invasive exploration by angiography is recommended at an early stage to identify the vascular lesion and propose endovascular treatment . the precise mechanism by which srad occurs still remains poorly understood .
one hypothesis raised by two small series suggests that physical exertion could be the trigger for dissection by stretching the arterial wall [ 12 , 13 ] .
the right renal artery is less often affected than the left because its greater length allows a better distribution of shear stress .
another hypothesis , as believed by some authors , suggests that srad is a clinical variant of fibromuscular dysplasia or atherosclerosis . in our series , however , the demographic characteristics of our patients are not those commonly observed in arterial dysplasia or atherosclerosis as these were men without any identified cardiovascular risk factors . additionally , in contrast to atherosclerotic lesions , the dissection occurred in the distal part of renal artery rather than the aortic ostium . finally , in half of our cases , the dissecting process also affected intra - renal arterial branches and sometimes the polar arteries .
once diagnosed , there are several options for the treatment of srad ranging from conservative treatment to endovascular and surgical intervention , depending on the stage at which the diagnosis is made and the severity of the renal lesion .
there is no therapeutic consensus and revascularization is usually proposed as a second option , for patients with medically uncontrolled hypertension or progressive renal dysfunction [ 3 , 4 , 9 , 24 , 25 ] .
anti - hypertensive treatment combined with anti - aggregate platelet therapy appears to be safe and effective in most patients , with a mean follow - up reaching almost 10 years [ 12 , 2931 ] .
although the natural history of renal artery dissection has not been well documented , it seems that remodelling of the dissected artery with re - entry points may restore a nearly normal renal flow , as it occurred with patient number six and as suggested by cases of spontaneous resolution [ 4 , 11 ] .
studied the anatomical evolution of dissections by ct angiography with three - dimensional reconstruction and found that arterial remodelling occurs in most of the dissected branches without occlusive or aneurismal evolution .
the poor outcome of surgical arterial reconstruction with a high rate of nephrectomy ( 40% ) is attributed in part to the frequent involvement of renal artery branches .
percutaneous endovascular treatment with renal artery stenting is quite appealing and appears more likely to supplant surgical intervention since it is a less invasive and a safer treatment [ 2 , 15 , 28 , 32 , 33 ] . nevertheless , endovascular approaches are indicated depending on how early the diagnosis is made and how quickly the revascularization occurs , which is crucial to reducing the area of infarction and preserve renal function . due to this short time frame for intervention
, we consider that direct non - invasive imaging by angio - cts or angio - mri is required if srad is suspected .
the clinical presentation of srad is misleading and the diagnosis should be advocated when renal crisis is not associated with urolithiasis or alternatively when hypertension is present .
such imaging techniques are invaluable for assessing renal artery morphology and area of renal infarction [ 17 , 18 ] .
the six cases reported here highlight the difficulties in establishing the diagnosis of srad and emphasize the importance of performing appropriate renal imaging , as soon as the diagnosis is considered .
 spontaneous renal artery dissection ( srad ) is a rare entity , which often presents diagnostic difficulties because of its non - specific clinical presentation . 
 we report six cases complicated with renal infarction , occurring in middle - aged male patients without risk factors , illustrating the difficulty and delay for diagnosing srad . 
 ultrasound and doppler imaging were not sensitive enough to confirm the diagnosis , and contrast - enhanced abdominal computed tomography was used to correct the diagnosis and allow the clinicians to propose appropriate treatment . 
 we conclude that considering the urgency in diagnosing and treating srad , contrast enhanced abdominal tomography and/or abdominal magnetic resonance imaging should be proposed as soon as a suspicion of srad is evoked by the clinical presentation . 
Introduction
Cases report
Discussion
Conclusion