2. Doppler US of the kidneys
• Normal anatomy of the kidney
• Normal US of the kidney
• Normal Doppler US of the kidney
• Indications of renal Doppler US
3. Normal anatomy of the kidney
Paspulati RM et al. Ultrasound Clin 2006 ; 1 : 25 – 41.
Renal parenchyma: cortex & medullary pyramids
Renal sinus: arteries, veins, lymphatics, collecting system, & fat
Renal hilum: Concave, in continuity with renal sinus
4. Anatomy of renal arteries
RRA: Usually passes posterior to inferior vena cava
LRA: Usually courses posterior to left renal vein
Multiple renal arteries in 25% (inferior polar artery from aorta)
5. Arterial blood supply to the Kidney
Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
Segmental artery
Apical, upper, middle, lower, posterior
Interlobular artery
Between renal pyramids
Glomerular arteriole
Main renal artery
Arcuate artery
Between cortex & medulla
6. Left renal vein
• Longer than right renal vein
• Averages 85 mm in length (range: 60 – 110 mm)
• Joined by adrenal, gonadal, lumbar, & hemiazygous
veins before crossing the aorta
• Different types: Pre-aortic 80 – 95%
Retro-aortic 2 – 3%
Circum-aortic 7 – 9%
Sidhu R et al. Semin Ultrasound CT MRI 2009 ; 30 : 271 – 288.
7. Variants of left renal vein
Retro-aortic LRV
Incidence: 2 – 3%
Circum-aortic LRV
Incidence: 7 – 9%
Sidhu R et al. Semin Ultrasound CT MRI 2009 ; 30 : 271 – 288.
8. Left-sided IVC
Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
Normal anatomy of IVC Anomalous left-sided IVC
Persistence of embryological AV
9. Doppler US of the kidneys
• Normal anatomy of the kidney
• Normal US of the kidney
• Normal Doppler US of the kidney
• Indications of renal Doppler US
10. Gray scale imaging first
• Kidneys Maximum renal length
Echogenicity of renal cortex
Thickness of renal cortex
Masses – hydronephrosis – renal calculi
• Aorta Plaque – thrombus – dissection – aneurysm
• Adrenal glands
11. Normal kidney
Longitudinal section Cross section
Rumack CM et al. Diagnostic Ultrasound. Elsevier-Mosby, St. Louis, USA, 3rd edition, 2005.
Renal capsule: echogenic line
Renal parenchyma: outer cortex & inner medulla pyramid
Central sinus complex: high echogenicity (vessels, fat, fibrous tissue)
12. Renal dimensions
• Length of normal kidney: 9 – 14 cm
Right kidney smaller than left kidney
• Discrepancy > 2 cm between two kidneys:
Considered significant & needs further evaluation
• Renal length between 8 – 9 cm
Correlated to patient’s phenotype particularly height
• Renal length < 8 cm definitely reduced
Should be attributed to chronic renal failure
Fiorini F et al. J Ultrasound 2007 ; 10 : 161 – 167.
13. Measurement of parenchymal & cortical thickness
Cortical thickness: Normal 8 – 10 mm
Parenchymal thickness: Normal 14 – 18 mm
Tuma J et al. European course book: Genitourinary ultrasound.
European Foundation of Societies of Ultrasound in Medicine & Biology.
14. Renal volume
Length: 9 – 14 cm (longitudinal section)
Width: 4 – 6 cm (cross section)
Depth: 4 – 6 cm (cross section)
Ellipsoid formula: length . width . thickness . π/6
Derchi LE et al. Acad Radiol 1994 ; 1 : 100 – 105.
Fiorini F et al. J Ultrasound 2007 ; 10 : 161 – 167.
Adjusted to BMI
(V / BMI) . 25
Appropriate renal volume
231 50 ml
15. Classification of renal parenchymal echogenicity
4 types based of US appearance
Hypoechoic compared to liver
Isoechoic compared to liver
Hyperechoic compared to liver
Isoechoic to renal sinus
Normal
Normal
Pathological
Pathological
Grade 0
Grade I
Grade II
Grade III
16. Kidney parenchyma compared to liver parenchyma
Hypoechoic Isoechoic
Hyperechoic
Fiorini F et al. J Ultrasound 2007 ; 10 : 161 – 167.
17. Congenital normal variants of kidney
• Dromedary hump
• Persistent fetal lobulation
• Prominent column of Bertin
• Junctional parenchymal defect
• Hypoechoic renal sinus
Paspulati RM et al. Ultrasound Clin 2006 ; 1 : 25 – 41.
18. Dromedary hump
Common renal variation
Paspulati RM et al. Ultrasound Clin 2006 ; 1 : 25 – 41.
Focal bulge on lateral border of left kidney
Result from adaptation of renal surface to adjacent spleen
Easily differentiated from renal mass by Doppler
19. Persistent fetal lobulation
Paspulati RM et al. Ultrasound Clin 2006 ; 1 : 25 – 41.
Renal surface indentations between pyramids
May be single or multiple
20. Prominent column of Bertin (PCB)
Mistaken for intrarenal tumor
Paspulati RM et al. Ultrasound Clin 2006 ; 1 : 25 – 41.
Continuity with renal cortex
Similar echo pattern as renal parenchyma
Similar vascular pattern by color & power Doppler
21. Junctional fusion defect
Paspulati RM et al. Ultrasound Clin 2006 ; 1 : 25 – 41.
Mistaken for cortical scar or angiomyolipoma
Continuity with central sinus
by echogenic line
“inter-renicular septum”
Triangular hyperechoic structure
Antero-superior or postero-inferior
surface of kidney
22. Abdominal aorta
• Normal abdominal aorta 1.5 – 2.5 cm
• Ectatic aorta 2.5 – 3 cm
• Aortic aneurysm > 3 cm
• Annual growth of aneurysms 0.33 cm/year
between 4 & 5.5 cm
* Bhatt S et al. Ultrasound Clin 2008 ; 3 : 83 – 91.
23. Cross-section at adrenal glands
Compared to seagull, Y, or V letter
Y-shaped structures lying antero-medial to kidneys
Composed of body & medial & lateral “wing” or “limb”
Tuma J et al. European course book: Genitourinary ultrasound.
European Foundation of Societies of Ultrasound in Medicine & Biology, 2011.
24. US of normal adrenal glands
Documented in 1980 1
1 Dietrich CF et al. Endoscopy 1997 ; 29 : 859 – 864.
2 Jenssen C et al. Ultraschall Med 2010 ; 31: 228 – 250.
With modern equipment (high-resolution) & good training
US can image right gland in 99% & left gland in 70%1
Transcostal scan in LLD
Between RLL, IVC & diaphragm
Right adrenal gland Left adrenal gland
Transverse scan of epigastrium
Dorsal to pancreatic tail & SV
25. Normal adrenal gland / Inverted Y-shape
Hypoechoic right adrenal gland
Horizontally inverted Y-shape
Coronal scan of right upper abdomen through MAL
Wan YL. J Med Ultrasound 2007 ;15 : 213 – 227.
26. Doppler US of the kidneys
• Normal anatomy of the kidney
• Normal US of the kidney
• Normal Doppler US of the kidney
• Indications of renal Doppler US
27. Technical points
• Fasting for at least 6 hours before the exam
• Duration of the examination: 30 – 45 min
• Rare failure: Non-cooperant patient – Gas
• Intestinal preparation: not necessary
Operator-dependent technique
Slow learning curve
Most complex & difficult Doppler examination1
28. Sites for pulsed Doppler of renal arteries
Aorta
Ostium of main renal artery
Trunk of main renal artery
Hilum of kidney
Upper pole of kidney
Middle pole of kidney
Lower pole of kidney
29. Transverse scan with probe angulations
Main renal arteries
Schäberle W. Ultrasonography in vascular diagnosis. Springer-Verlag, Berlin, 2nd edition, 2011.
30. Norma right renal artery
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
Transverse gray scale image
Right main renal artery
Transverse color Doppler image
Right main renal artery
31. Gray scale alone without color Doppler
Patients with difficulty to hold breath
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
Entire RRA well visualized
Color flash artifact from patient motion may obscure visualization
Better spatial resolution & and faster frame rate
Gray scale image
32. Norma left renal artery
Gray scale image Color Doppler image
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
Proximal main left renal artery Proximal main left renal artery
33. ‘‘banana peel’’ or “Isikoff” view
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
Isikoff MB et al. Am J Roentgenol 1980 ; 134 : 1177 – 1179.
Origins of right & left renal arteries
Gray scale image
Origins of right & left renal arteries
Color Doppler image
Longitudinal transhepatic view in Left lateral decubitus
34. Normal right renal artery
Coronal images of IVC
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
RRA is the only vessel to course laterally under the IVC
Often slightly indents the IVC
35. Two renal arteries or early branching?
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Longitudinal view of IVC
Two right renal arteries
Transverse view of aorta
Early branching of RRA
36. Longitudinal scan in left lateral decubitus
Multiple renal arteries (25%)
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
37. Two left renal arteries
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
PSV: 90 cm/sec
Dominant left renal artery
PSV: 60 cm/sec
Accessory left renal artery
38. Axial scan in left lateral decubitus
Using right kidney as acoustic window
Right main renal artery & vein
Color Doppler USSchematic drawing
Meola M et al. J Ultrasound 2008 ; 11 : 55 – 73.
39. Axial scan in right lateral decubitus
Using left kidney as acoustic window
Schematic drawing
Left main renal artery & vein
Color Doppler US
Zubarev AV. Eur Radiol 2001 ; 11 : 1902 – 1915.
41. Pre-aortic left renal vein (80 – 95%)
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Reduction in diameter in pre-aortic segment to IVC
with physiologic acceleration
42. Left renal vein variants
Sidhu R et al. Semin Ultrasound CT MRI 2009 ; 30 : 271 – 288.
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Retro-aortic LRV (2 – 3%) Circum-aortic LRV (7 – 9%)
Pre & retro-aortic LRV
43. Color Doppler of RRV & retro-hepatic IVC
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Righ renal vein Inferior vena cava
44. Pulsed Doppler of renal veins
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Right renal vein
Resembles pulsed Doppler of IVC
Triphasic waveform
Left renal vein
Little modulation
Wall artifact due to systolic peak
45. Limits in visualization of main renal arteries
• Obesity
• Overlying bowel gas
• Dyspnea
• Shadowing from arterial calcifications
• Cardiac arrhythmias
• Poor angle of Doppler insonation
• Accessory renal arteries (small size)
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
Expert sonographers detect 80 – 90% of main RA
CEUS improves success rate to 95%
46. Angle of insonation
Difficulty in case of tortuous or curved renal artery
Correct angleIncorrect angle
Schäberle W. Ultrasonography in vascular diagnosis.
Springer-Verlag, Berlin Heidelberg, 2nd edition, 2011.
47. Adjustment of Doppler control
Low flow settings
• Lowest pulse repetition frequency without aliasing
• Small color box
• Greatest gain without background noise
• Lowest wall filter
• High color priority
48. Normal segmental & interlobar renal arteries
Normal segmental renal arteries (long arrows)
Color Doppler image of the kidney
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
Normal inter-lobar renal arteries (short arrows)
49. Study of intra-renal arteries
Perfusion study / Low PRF
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Cortical perfusion
Tumoral vascularization
50. Study of intra-renal arteries
Morpho-hemodynamic study
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Arterio-venous fistula
Pseudo-aneurysm
Intermediate PRF
Renal stones
Vascular calcifications
High PRF
51. Normal kidney
Power Doppler
Increases sensitivity to low flow
Less angle-dependent
Good visualization of the entire renal vascular tree
Zubarev AV. Eur Radiol 2001 ; 11 : 1902 – 1915.
54. Accleration time (AT)
or Rise time (RT)
• Length of time in sec from
onset of systole to peak systole
• Normal value: < 0.07 second
55. Acceleration Index (AI)
AI =
X (KHz)
Probe frequency (MHz)
Normal value: > 3.5 m/s2
Systolic upslope/transducer frequency
56. Measurement of PSV
Early systolic peak
Am J Roentgenol – Dec 1995
Biphasic with late systolic peak
Monophasic with late systolic peak
57. Early systolic notch
Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
Some normal waveforms have early systolic notch
1. Measuring to point of PSV results in prolonged AT & AI
2. Excellent negative predictive value of stenosis > 60%
58. Extrasystole
Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
Correct RI calculated in normal sinusoidal rhythm
59. Spectral Doppler of renal arteries
Normal values
• PSV < 180 cm/sec
• Renal Aortic Ratio (RAR) < 3
• Resistive index (RI) < 0.70
• ∆ RI (right – left) < 0.05
• Acceleration Time (AT) < 0.07 sec
• Acceleration Index (AI) > 3.5 m/s2
Editor's Notes
The normal adult kidney is bean shaped with a smooth convex contour anteriorly, posteriorly, andlaterally. Medially, the surface is concave and known as the renal hilum. The renal hilum is continuous with a central cavity called the renal sinus. The collecting system (renal pelvis) lies posterior to the renal vessels in the renal hilum.
● The right renal artery is longer than the left, and passes posterior to the IVC.● The left renal artery has a more horizontal course to the kidney.
Anomalous left-sided IVC from persistence of the embryological azygos vein.
Discrepancy of more than 2 cm between the lengths of two kidneys is considered significant and needs further evaluation.The renal parenchyma is composed of cortex and medullary pyramids.The renal medullary pyramids are hypoechoic relative to the renal cortex and can be identified in most normal adults.The normal renal cortex has classically been described as being less echogenic than adjacent liver and spleen. Platt et al. evaluated 153 patients and found that 72% of patients with renal cortical echogenicity equal to that of the liver had normal renal function.If renal echogenicity greater than the liver were used as the criterion, both specificity and positive predictive value for abnormal renal function rose to 96% and 67%, respectively. However, sensitivity is poor-only 20%.
Easily differentiated from renal mass:1- similar echotexture to adjacent renal parenchyma on gray-scale ultrasound.2- CFD and PD will demonstrate similar perfusion to that of adjacent renal parenchyma.
Another common renal variant that can be mistaken for renal scarring, a consequence of chronic infective process of the kidneys. Persistent fetal lobulation can be differentiated from scarred kidneys by the location of the renal surface indentations, which do not overlie the medullary pyramids as in true renal scarring, but overlie the space between the pyramids.The underlying medulla and the cortex are normal
Prominent cortical tissue that is present between the pyramids and projects into the renal sinus. Prominent columns of Bertin are usually seen in the middle third of the kidney and are more common on the left side.
During normal development, there is partial fusion of two parenchymal masses called renunculi. Parenchymal junctional defects occur at site of fusion & must not be confused with pathologic processes such as renal scars & angiomyolipoma. Junctional parenchymal defect is most typically located anteriorly and superiorly and can be traced medially & inferiorly into renal sinus. Usually, it is oriented more horizontally than vertically; therefore, it is best appreciated on sagittal scans.It is seen more often on the right; however, when a good acoustic window is present (splenomegaly), it can also be seen on the left.
Normally, the glands are 0.3 to 0.6 cm in thickness, 4 to 6 cm in length, and 2 to 3 cm in width.
The traditional view resulting from studies in the 1970’s and 1980’s that successful ultrasound imaging of the adrenal glands is the exception has been invalidated by the development of modern ultrasound diagnostics and should no longer affect the application of US.
One of the most complex and difficult sonographic examination.
Accessory renal arteries from the aorta to the upper or lower poles of the kidney in 15 -24 %.In a study performed by Bude and colleagues, a hemodynamically significant stenosis isolated to an accessory renal artery was found inonly 1.5% of patients undergoing angiography for evaluation of RVH. This study concluded that failure to evaluate accessory renal arteries should not negatively affect the usefulness of a noninvasive study for detecting RVH.
Even expert sonographers detect only 80–90 per cent of renal arteries.Ultrasound contrast agents improve the technical success rate to 95 per cent.