Left main renal artery entrapment by diaphragmatic crura: spiral CT angiography
Department of Medical Imaging, John Hunter Hospital, Newcastle, Australia
Entrapment of renal artery by the diaphragmatic crus is a
rare cause of renal artery stenosis. Spiral computed tomography angiography
provides a definitive diagnosis and shows the precise relationship of the
artery to the diaphragmatic crus. The authors present a case of hypertension
developing in a young 20-year-old female due to entrapment of the left renal
artery by the diaphragmatic crus. This condition should be considered in young
hypertensive patients with renal artery stenosis without cardiovascular risk
factors. � 2010 Biomedical Imaging and Intervention Journal. All rights
Keywords: renal artery stenosis, spiral computed tomography
A 20-year-old female presented with shortness of breath on
modest exertion. She described several recent episodes of lower retrosternal
chest pain at rest. She denied any other symptoms. She had no other significant
medical history but was a moderate-to-heavy smoker. There was no relevant
Physical examination was normal. Full blood count and
urea, creatinine and electrolyte levels were normal. Serial troponin levels
were also normal. Chest x-ray was normal. Electrocardiography (ECG) showed no
evidence of ischaemic change but, instead, a hypertensive response. She was
noted to become hypertensive on walking up a flight of stairs. Her resting
blood pressure was 130/70 mmHg and this increased to 200/100 mmHg on walking up
a flight of stairs. Biochemical investigations she underwent, including tests
for secondary causes of hypertension such as hyperaldosteronism and
pheochromocytoma, renin aldosterone ratio as well as urinary biogenic amine,
were normal. Lipid studies, thyroid function tests, liver function tests,
coagulation screening, blood glucose level and HbA1c were normal.
She was initially treated with perindopril and indapamide
to control her blood pressure and the treatment was effective.
A renal Doppler ultrasound suggested the presence of an
accessory left renal artery. A spiral computed tomography angiography (spiral
CTA) was performed with axial and sagittal slab MIPs, curved planar
reformation, and 3D MIPs.
The scan was performed using a Philips Brilliance 16-slice
CT scanner with 500 ml excursion 120 kV 30 mA per second. Surview image was
first obtained to locate the kidneys then a helical acquisition to include a
centimetre above and a centimetre below the upper and lower poles of the
kidneys, respectively, with 1 mm slices and 0.5 mm spaces in between. These
images were reconstructed to 2 mm by 2 mm axial and coronal images. Contrast
was injected at the rate of 4 ml per second using 75 ml of Ultravist 370.
Review of the images demonstrates two left renal arteries
and a single right renal artery. The right renal artery has a normal origin and
normal calibre throughout its course. The left main renal artery supplies the
upper pole and the mid renal parenchyma. It has a more posterior origin and
marked extrinsic compression producing a haemodynamically significant stenosis
as it passes aberrantly through the left crus of the diaphragm (Figure 1a, 1b,
1c, 1d). The left lower pole renal artery is smaller in calibre with a normal
course (Figure 2). There was decreased perfusion to the left upper pole and mid
renal parenchyma (Figure 3).
Subsequently, an aortogram with bilateral renal artery
selection was performed during suspended inspiration and expiration (Figure 4a
and 4b). The upper pole renal artery (main) is confirmed to arise posterior and
superior to the lower pole renal artery with a sharp downward bend. There was
moderate narrowing at its origin with mild post stenotic dilatation, seen best on
the inspiratory acquisition (Figure 4a and 4b). Selective angiography of the
upper pole artery was attempted, but the catheter could not be passed due to
sharp angulation at the origin. There was no evidence of pre-existing stenosis,
atherosclerosis or fibromuscular dysplasia of the left lower pole renal artery.
Unfortunately, despite best attempts, this patient was
lost to follow up.
Renal artery entrapment by the diaphragmatic crus was
first described by D�Abreu  who reported two cases proven by surgery in
1962. Since this first description, less than 20 cases have been reported in
the literature. Congenital abnormalities such as abnormal musculo-tendinous
fibres, high ectopic renal artery origin or hypertrophic diaphragmatic crus
were found to be responsible for these entrapments .
Renal artery stenosis (RAS) is a common, correctable cause
of hypertension and renal impairment. In the general hypertensive population
the prevalence of this condition varies between 1 and 5%. The most common
causes of RAS are atherosclerosis and fibromuscular dysplasia .
Extrinsic compression of the renal arteries leading to
hypertension has been associated with abdominal aortic aneurysm , tumour,
hypertrophic adrenal tissue, and psoas muscle band anomaly . However,
extrinsic compression of one or both renal arteries by the diaphragmatic crura,
which is known as renal entrapment syndrome, is rare [6-10]. Compression is by
fibres forming part of the crus of the diaphragm or psoas muscle impinging on the
renal artery by verticalisation of the root of the renal artery. This results
in stenosis (usually at the ostium of the artery). The artery follows an
unusual acutely angled (sigmoid) course. This anomaly is also associated with a
high origin of the renal artery from the aorta and is more common on the left
side. The mechanism evoked is an anomaly of migration of the kidneys .
Clinical features suggestive of RAS include abdominal
bruit, severe retinopathy, unexplained hypokalaemia, and unexplained renal
impairment . Early detection of RAS is necessary for effective treatment and
to prevent end-stage renal disease .
Renal artery entrapment may be suspected on angiographic
views and proven by cross-sectional imaging . Thony et al 
demonstrated two angiographic features suggesting renal artery entrapment:
renal arteries descending down and close to the aorta, and a concentric ostial
stenosis in a patient free of atheroma.
Although Duplex ultrasound is an accurate examination for
screening RAS , it does not allow the analysis of the relationship between
the renal artery and muscular structures . This is clearly shown in
angiographic reconstructions using CT .
Although surgery and stenting have been used for treatment
of renal entrapment syndrome, they are associated with surgical morbidity and
stent-related complications such as bending or rupture of stents. Surgical
treatment needs to be considered on a case-by-case basis in relation to the
anatomy and the biological and functional data. The use of an arterial stent in
the situation of muscular compression leads to a risk of bending or rupture of
the stent . In addition, movement of the diaphragm induces significant
displacement of kidneys during respiration which induces both bending and
torsional forces on the renal arteries. This bending may lead to stent fracture
and restenosis . An alternative is to treat with balloon angioplasty and
cutting balloon angioplasty, which may have lower patency rate but fewer
stent-related complications in these patients .
Bilici et al  have investigated the use of
botulinum toxin injection directly into the diaphragmatic crus under CT
guidance as an alternative to surgical treatment and stenting. This method
still requires further evaluation.
Compression of a renal artery by the crus of the diaphragm
(renal entrapment syndrome) should be investigated in proximal renal artery
stenosis in young hypertensive patients without other cardiovascular risk
factors, and where fibromuscular dysplasia is unlikely. Spiral CTA is a key
investigation for identification of the renal entrapment syndrome. Once the
renal entrapment syndrome is confirmed, surgical management should be a
consideration. New treatment methods are being evaluated including botulinum
injection, which may provide an alternative to surgical management.
Figure 1 (a) Axial, (b) sagittal and (c) coronal slab MIP and (d) curved planar reformatted images. The left main renal artery has marked extrinsic compression with haemodynamically significant stenosis due to an aberrant and posterior course through the left crus of the diaphragm (arrows).
Figure 2 Coronal slab MIP. The lower pole of the left kidney is supplied by an accessory small calibre renal artery (white long arrow).
Figure 3 Coronal image demonstrates decreased perfusion to the upper pole and mid left kidney (white arrow). There is normal perfusion to the left lower pole and right kidney.
Figure 4 Abdominal angiogram in (a) inspiration, and (b) expiration. Images demonstrate a single right normal renal artery and a normal left lower pole renal artery. The left main renal artery to the upper pole of the left kidney was moderately narrowed (white arrow) at the origin with mild post stenotic dilation.
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|Received 19 June 2009; received in revised form 1 November
2009; accepted 16 November 2009
Correspondence: John Hunter Hospital, Lookout Rd, New Lambton, NSW Australia. E-mail: Please contact Managing Editor
Please cite as: Singham S, Murugasu P, MacIntosh J, Deshpande A,
Left main renal artery entrapment by diaphragmatic crura: spiral CT angiography, Biomed Imaging Interv J 2010; 6(2):e11