Doppler ultrasound of the kidneys

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renal artery stenosis, renal artery thrombosis, renal vein thrombosis, nutcracker syndrome.

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  • 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. Parenchymaljunctional defects occur at site of fusion & must not be confused with pathologic processes such as renal scars & angiomyolipoma. Junctionalparenchymal 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.
  • Because of the high prevalence of hypertension in the general population and the low incidence of RVH among these patients (0.5%–5%), however, screening all hypertensive patients is neither practical nor cost effective.Screening for RAS is thus recommended only for enriched patient populations considered to be at high risk for RAS. The clinical criteria most predictive of RAS are listed in Box 1. In such patient populations the prevalence of RVH increases toapproximately 20% to 30%.
  • PSV is recommended, may be combined with RAR (and ΔRI) to improve specificity.
  • In vascular medicine, a reduction in diameter of 50% is commonly regarded as hemodynamically significant and should not be equated with clinical relevance.
  • End organ damage may have already occurred in patients who have a small kidney with a thin, echogenic renal cortex or an RI greater than 0.8 in the intraparenchymal renal arteries, and that improvement of blood pressure or renal function is less likely following intervention in such patients.
  • Patients with renal resistance-index values of at least 80 should be excluded from renal-artery angioplasty or renal-artery surgery.
  • Tardus: slowed systolic accelerationParvus: low-amplitude systolic peak
  • «bec de flûte »: فم الناي أو المزمار
  • Captopril test: measurement of plasma renin activity after captopril administration
  • Collagen deficiencies:Marfan syndrome – Ehler-Danlos syndrome – Loeys–Dietz syndrome Phakomatoses: Tuberous sclerosis – Neurofibromatosis.Loeys–Dietz syndrome Recently described autosomal dominant aortic-aneurysm syndrome that has overlapping features with Marfan & Ehlers–Danlos syndrome. The disease is characterized by the triad of arterial tortuosity and aneurysms, hypertelorism, and bifid uvula or cleft palate.Aneurysms may form at a young age and have a propensity for arterial dissection and aneurysm rupture at smaller diameters.Reference: Johnson PT, Chen JK, Loeys BL, Dietz HC, Fishman EK. Loeys–Dietz syndrome: MDCT angiography findings. Am J Roentgenol2007;189:W29–35.
  • “confetti phenomenon”: قصاصات الوق الملون تنثر على الناس في الكرنفالات والأعراس
  • Compression of LRV between aorta & superior mesenteric artery (aorto-mesenteric portion).It is known that nutcracker syndrome is an uncommon cause of gross or microscopic hematuria from non-glomerular origin and may cause orthostatic or variable degrees of proteinuria. Hematuria is believed to be caused by LRV hypertension, which may result in minute rupture of thin-walled collateral veins into the calyceal fornix.DiagnosisMeasurements of diameters of the LRV by US or CT: not satisfactory.Renal Doppler ultrasound PV ratio > 4.1Left renal venography with measurement of pressure gradient between IVC & LRV: invasive.
  • Bosniak renal cyst classification was first introduced in 1986 and has been accepted by urologists and radiologists as a way of diagnosing,discussing, and determining the management approach to cystic renal masses.Bosniak renal cyst classification was developed and based on CT findings, it is commonly applied to other imaging modalities (US & MRI).Category IIF: Slightly more complex than category II But not complex enough to fulfill the criteria for category III.Catecory III: These are surgical lesions Although some will prove to be benign (hemorrhagic cysts, chronic infected cysts, & multiloculated cystic nephroma) Some will be malignant (cystic renal cell carcinoma & multi-loculated cystic renal cell carcinoma).Calcification:Initially, thick, nodular, and irregular calcification within a lesion would have placed that lesion into category III (surgical). However, it became apparent that calcification in the wall or septa of a cystic renal mass is not as significant as once thought, and a lesion should not be placed into surgical category based solely on amount or morphology of calcification but on whether associated tissue enhancement is present.Enhancement Most important criterion used to differentiate surgical lesions from nonsurgical lesions. Categories I, II, and IIF lesions do not measurably enhance. However, the thin smooth septa and walls of these lesions will subjectively enhance if unenhanced & contrast- enhanced images are compared side by side. We refer to this phenomenon as “perceived” enhancement & believe it is due to contrast material within the tiny capillaries in the wall and septa of these benign lesions. Category III and IV lesions demonstrate unequivocal measurable enhancement of their walls, septa, or soft-tissue components & therefore are considered surgical lesions, even though some category III lesions will be benign (inflammatory lesions, multilocular cystic nephroma).Our goal should be to minimize the number of benign renal masses that are removed.US: US has limited role in evaluating cystic renal masses and should be reserved for characterizing simple or minimally complex renal cysts (containing one or two hairline thin septa). Ultrasonography should not be relied on to differentiate surgical from nonsurgical complex cystic renal masses.
  • Color comet-tail artifact or “twinkling sign”Origin of the artifact poorly understood.Artifact depends on machine settings, color-write priority, pulse repetition frequency, and gray-scale gain.Use of the highest levels of color scale available on the sonography machine (i.e., increased filter and pulse repetition frequency) frequently improves visualization of the color comet-tail artifact.We do not understand why the artifact is absent or poorly seen in some cases, even when the object (calcification, stone, or surgicalclip) is clearly visualized with gray-scale imaging alone.
  • With normal drinking habits of approximately 2-3 litres a day, an occurence of two urinary jets/minute or ten urinary jets during five minutes has been observed, on both sides. A jet asymmetry is defined by < 2 jets / 5min on the ill side and > 5 jets / 5min on the other side. Next to the number of jets, the quality of jets can be assessed, too. A spectral analysis can give results on both Vmax and duration of the jets in sec. With ureters that are not completely obstructed, jets appear to run slower and to last longer, while shorter jets are being observed from time to time.
  • Vascular injury with endoscopic procedures seen in 10% of cases
  • In 1966, Elwin Fraley described four patients with nephralgia secondary to vascular compression of the superior infundibulum and proposed open surgical treatment options, including partial nephrectomy, Heineke-Mikulicz-type infundibulorrhaphy, and caliconeopyelostomy.
  • Doppler ultrasound of the kidneys

    1. 1. Doppler ultrasound of the kidneys Samir Haffar M.D. Assistant Professor of Internal Medicine
    2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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 Hricak H et al. Radiology 1982 ; 144 : 141 – 147. Fiorini F et al. J Ultrasound 2007 ; 10 : 161 – 167. Normal Normal Pathological Pathological Grade 0 Grade I Grade II Grade III
    16. 16. Kidney parenchyma compared to liver parenchyma Hypoechoic Isoechoic Hyperechoic Fiorini F et al. J Ultrasound 2007 ; 10 : 161 – 167.
    17. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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 1 Jaeger KA & Uthoff H. Ultraschall Med 2010 ; 31 : 339 – 343.
    28. 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. 29. Transverse scan with probe angulations Main renal arteries Schäberle W. Ultrasonography in vascular diagnosis. Springer-Verlag, Berlin, 2nd edition, 2011.
    30. 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. 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. 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. 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. 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. 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. 36. Longitudinal scan in left lateral decubitus Multiple renal arteries (25%) Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
    37. 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. 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. 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.
    40. 40. Pre-caval right renal artery Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
    41. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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.
    52. 52. Normal pulse Doppler waveform Renal segmental artery Sharp systolic upstroke Low resistance waveform Continuous forward diastolic flow
    53. 53. Pourcelot’s resistive index RI S – ED / S Normal 50 – 70 % Abnormal > 80 %
    54. 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. 55. Acceleration Index (AI) AI = X (KHz) Probe frequency (MHz) Normal value: > 3.5 m/s2 Systolic upslope/transducer frequency
    56. 56. Measurement of PSV Early systolic peak Am J Roentgenol – Dec 1995 Biphasic with late systolic peak Monophasic with late systolic peak
    57. 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. 58. Extrasystole Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Correct RI calculated in normal sinusoidal rhythm
    59. 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
    60. 60. 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 ultrasound
    61. 61. Pheochromocytoma Uncommon – 1 % of patients with hypertension Highly vascularized right pheochromocytoma 1 Jenssen C et al. Ultraschall Med 2010 ; 31: 228 – 250. 2 Wan YL et al. J Med Ultrasound 2007 ; 15 : 213 – 227. 10% Extra-adrenal [paraganglioma] 10% of them extra-abdominal 10% Malignant 10 % Multiple masses “rules of 10” 2
    62. 62. Micronodular cortical hyperplasia of right adrenal gland Structure measuring approximately 5 mm & isoechoic to adrenal cortex Conn’s sydrome / adrenal hyperplasia Jenssen C et al. Ultraschall Med 2010 ; 31: 228 – 250.
    63. 63. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    64. 64. Renal artery stenosis 1 – 5% of hypertensive population • Atherosclerosis • Fibromuscular dysplasia (FMD) • Dissection • Embolization • Aortic coarctation • Renal Artery Aneurysm • Arteritis • Congenital • Neurofibromatosis • Irradiation > 95 % of cases
    65. 65. Renal artery stenosis Atherosclerosis > 90% FMD < 10% Age After age of 50 Young Gender More common in males More common in females Location Proximal 1 cm of main RA Branching points Middle of renal artery Others (carotids) Post-stenotic dilatation Rare Frequent
    66. 66. Clinical risk factors for renovascular HTN • Abrupt onset of severe HTN: diastolic >120 mm Hg • Accelerated or malignant HTN: grade III or IV retinopathy • HTN refractory to appropriate three-drug regimen • Onset of hypertension before age 30 or after age 60 • HTN with rapidly progressive renal failure • Renal failure that develops in response to ACE inhibitor • HTN associated with upper abdominal bruit • Episodes of recurrent severe HTN & pulmonary edema Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
    67. 67. Renal artery stenosis Direct signs Focal color aliasing Color bruit Turbulence PSV > 180 cm/sec Renal Aortic Ratio > 3.5 Indirect signs AT > 0.07 sec AI < 3 m/s2 Δ RI (right – left) > 5 % Significant stenosis (50 – 85% diameter reduction) Sensitivity: 79 – 91% Specificity: 73 – 97% Severe stenosis (> 85 % diameter reduction) Sensitivity: 95% Specificity: 97%
    68. 68. Renal artery stenosis / Direct criteria Non-significant stenosis (< 50% diameter stenosis) Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Plaque in anterior wall of LRA PSV: 148 cm/sec Color Doppler US Power Doppler US Better visualization of plaque
    69. 69. Renal artery stenosis / Direct criteria PSV: 275 cm/sec High-grade stenosis Aliasing in left renal artery Schäberle W. Ultrasonography in vascular diagnosis. Springer-Verlag, Berlin Heidelberg, 2nd edition, 2011.
    70. 70. Renal artery stenosis / First Generation CEUS Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Baseline color Doppler RRA not identified Aliasing of SMA origin Pulse Doppler image PSV > 300 cm/s Severe stenosis of RRA IV contrast agent RRA visualized Focal color aliasing
    71. 71. PSV: 293 cm/sec – RI : 0.91 Controversial indication of PTA2 Aliasing in left renal artery Retro-aortic course of LRV 1 Schäberle W. Ultrasonography in vascular diagnosis. Springer-Verlag, Berlin, 2nd edition, 2011. 2 Jaeger KA et al. Ultraschall in Med 2007 ; 28 : 28 – 31. Renal artery stenosis / Direct criteria
    72. 72. Creatinine clearance after correction of RAS according to RI before revascularization Radermacher J et al. N Engl J Med 2001 ; 344 : 410 – 417. 131 pts with unilateral or bilateral RAS > 50 % of luminal diameter Renal angioplasty or surgery
    73. 73. Renal artery stenosis / Renal Aortic Ratio Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Small right kidney (8.4 cm) PSV (aorta): 102 cm/s PSV (RRA): 465 cm/s High grade stenosis of RRA RAR: 4.5
    74. 74. Renal artery stenosis / Indirect criteria Schäberle W. Ultrasonography in vascular diagnosis. Springer-Verlag, Berlin, 2nd edition, 2011. PSV: 85.7 cm/s EDV: 47.2 cm/s RI: 0.64 Left renal hilumRight renal hilum PSV: 125 cm/sec EDV: 58.1 cm/s RI: 0.75 Δ RI (right – left) > 0.05 → RA stenosis in side of lower RI
    75. 75. Renal artery stenosis / Tardus-Parvus wave Severe stenosis (> 85 % diameter reduction) Tardus: Longer rise time Parvus: Low PSV Freeman SJ. Ultrasound 2004 ; 12 : 69 – 74.
    76. 76. Tardus-Parvus wave • Mimics Abdominal coarctation William syndrome Aortic/mitral valve disease Left ventricle dysfunction CV medications: after-load reducers • Exaggerating 25 mg captopril 1 hour before exam • Minimizing Age – HTN – DM (vessel compliance) Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
    77. 77. Abdominal aortic aneurysm & renal arteries Zubarev VZ. Eur Radiol 2001 ; 11 : 1902 – 1915. Aneurysm arises below origin of both renal arteries
    78. 78. Fibromuscular dysplasia Moniliform aspect of RRA Typical FMD in middle third of RRA Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. PSV 250 cm/sec No parallelism of RRA walls
    79. 79. Etiologies of renal artery dissection Stenotic or occlusive lesion • Atherosclerosis • Fibromuscular dysplasia • Extension of aortic dissection • Marfan syndrome & Ehlers-Danlos syndrome • Trauma & iatrogenic causes • Idiopathic Sidhu R et al. Semin Ultrasound CT MRI 2009 ; 30 : 271 – 288.
    80. 80. Renal artery dissection Flank pain & hematuria – Stenotic or occlusive lesion Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Interruption of LRA « bec de flûte » Associated thrombosis of LRV Occlusion of LRA at its origin Complete necrosis of LK
    81. 81. Coarctation of abdominal aorta Severe hypertension in a 6-year-old boy Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Bilateral & symmetric tardus parvus waveform Sagital view of aorta Severe narrowing at level of CA & SMA
    82. 82. Guidelines for diagnosis of RAS • Recommended as screening test Duplex US followed by CT angiography (except RF) & MR angiography • Not recommended as screening test Captopril renal scintigraphy Plasma renin activity Captopril test Selective renal vein renin measurements Hirsch AT et al. J Am Coll Cardiol 2006 ; 47 : 1239 – 1312.
    83. 83. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    84. 84. Renal artery thrombosis • Causes Embolism: most common Thrombosis – trauma – hypercoagulable state • Symptoms Acute flank pain + hematuria • Impression Renal stone Leaking abdominal aortic aneurysm • Doppler US Normal side: normal arterial & venous flow Affected side: no arterial flow – venous flow
    85. 85. Renal artery thrombosis / Complete Irshad A et al. Semin Ultrasound CT MRI 2009 ; 30 : 298 – 314. Absence of flow within kidney Power Doppler US Power Doppler US more medially Flow in iliac artery & proximal anastomotic artery
    86. 86. Renal artery thrombosis / Partial Caia S et al. Clinical Imaging 2008 ; 32 : 367 – 371. Slender flow in main renal artery Color Doppler US Pulsed Doppler US Low velocity: PSV 40 cm/s Low resistance: RI 0.5
    87. 87. Renal artery embolism Caia S et al. Clinical Imaging 2008 ; 32 : 367 – 371. Low PSV in main renal artery No blood flow in upper pole Normal blood flow in lower pole
    88. 88. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    89. 89. Doppler US in acute renal vein thrombosis Acute flank pain & hematuria • High RI in intra-renal arteries Reversed flow in diastole • Absence of flow in intra-renal veins • Enlarged main renal vein with no flow
    90. 90. Acute renal vein thrombosis Absence of color signal in main right renal vein Reversed diastolic flow in main renal artery Kraft JK.& Brandão LR. Pediatr Radiol 2011 ; 41 : 299 – 307. LRV more commonly involved (longer length)
    91. 91. Acute renal vein thrombosis / Poor outcome • Reduced perfusion at diagnosis • Subcapsular fluid collections • Profoundly hypoechoic & irregular renal pyramids • Patchy cortical echotexture Likely reflecting cortical infarction & hemorrhage Kraft JK.& Brandão LR. Pediatr Radiol 2011 ; 41 : 299 – 307.
    92. 92. Acute renal vein thrombosis / Poor outcome Kraft JK.& Brandão LR. Pediatr Radiol 2011 ; 41 : 299 – 307. Severely decreased renal perfusion Right kidney Normal perfusion for comparison Left kidney
    93. 93. Subcapsular fluid collections Hypoechoic & irregular pyramids Patchy hypoechoic areas in cortex Kraft JK.& Brandão LR. Pediatr Radiol 2011 ; 41 : 299 – 307. Acute renal vein thrombosis / Poor outcome
    94. 94. Chronic renal vein thrombosis / Collateral flow No flow in main right renal vein Collateral flow clearly seen Zubarev VZ. Eur Radiol 2001 ; 11 : 1902 – 1915. Kraft JK.& Brandão LR. Pediatr Radiol 2011 ; 41 : 299 – 307. Capsular collateral veins Linear calcifications in parenchyma
    95. 95. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    96. 96. Renal artery aneurysms Extraparenchymal in 90% of cases • Causes Atherosclerosis – FMD Collagen deficiencies – Phacomatosis • Gender More common in females • Age Young patients • Location Main renal artery or at bifurcation • Wall Thin (risk of rupture) • Treatment > 2.5 cm in diameter Surgery (nephrectomy – kidney-sparing)
    97. 97. Aneurysm of left renal artery Gao J et al. Clinical Imaging 2006 ; 30 ; 140 – 142. Gray-scale US Color Doppler US Angiography
    98. 98. Micro-aneurysms Contraindication of renal biopsy (bleeding) • Location Distal branches of cortex Segmental arteries rarely • Size 1 mm, 2-3 mm rarely • Cause PAN (micoaneurysms in 100%) • Clinic Fever – Abdominal pain – Hematuria – RF • Diagnosis Arteriography – Not visible by Doppler Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
    99. 99. Renal pseudo-aneurysm • Causes Iatrogenic (percutaneous procedure) – Trauma • Incidence Unknown • Clinic Silent Small & resolve uneventfully Hematuria Communicate with collecting syst Bleeding Rupture in perirenal space • Rx Small Monitoring until they resolve Large Transcatheter embolization
    100. 100. Pseudo-aneurysm Sampling at neck To-and-fro waveform “To” Systole “Fro” Diastole
    101. 101. “to and fro waveform” within neck of the lesion Cystic lesion in middle of RK Bi-directional flow “yin -yang pattern” Rashid M et al. Emerg Radiol 2007 ; 14 : 257 – 260. Renal pseudo-aneurysm
    102. 102. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    103. 103. Arterio-venous communication Direct communication from artery to vein without capillary bed • Congenital A-V malformation 25% Multiple large arterial feeding vessels Numerous A-V communications • Acquired A-V fistula 75% Single communication of artery & vein 0.3 – 4 % after kidney biopsy Sidhu R et al. Semin Ultrasound CT MRI 2009 ; 30 : 271 – 288.
    104. 104. A-V malformation Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. A-V malformation with pseudo-aneurismal dilatation Low resistance arterial flow Arterialized venous flow Hydronephrosis or cyst with calcified wall Aneurismal dialatation with peri-vascular artifact
    105. 105. A-V fistula First described in 1962 1 • Cause Iatrogenic (percutaneous procedure) –Trauma • Clinic Asymptomatic (80%) Gross hematuria – High output cardiac failure Thrombo-embolic episodes – RF – HTN • Evolution Most regress spontaneously in 6 months Some progress to life-threatening complication • Rx Asymptomatic: follow-up by Doppler Symptomatic: embolization Routine post-biopsy Doppler US & 6 months later 1 Fernstrom I et al. J Urol 1962 ; 88 : 709. 2 J Clin Ultrasound 2008 ; 36 : 377 – 380.
    106. 106. Arterio-venous fistula Feeding artery Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Perivascular artifact in inferior pole “confetti phenomenon” Color Doppler US / High PRF Low resistance arterial flow Arterialized venous flow Feeding artery & draining vein
    107. 107. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    108. 108. Doppler US in nutcracker syndrome Hilar portion & aorto-mesenteric portion Cut-off value in supine position 3.8 Cut-off value in upright position 5.5 Fitoz S et al. J Ultrasound Med 2007 ; 26 : 573. Ratio of A-P diameter of LRV Ratio of peak velocities of LRV Aorto-mesenteric portion & hilar portion Cut-off value in supine position 4.2 Cut-off value in upright position 5.1
    109. 109. Nutcracker syndrome / Ratio of A-P diameter Oblique transverse sonograms Peker A et al. J Clin Ultrasound 2011 ; 39 : 418 – 421. Hilar portion: 25 mm Aorto-mesenteric portion: 2mm Ratio: 12.5 Supine position Hilar portion: 24 mm Aorto-mesenteric portion: 2mm Ratio: 12 Upright position
    110. 110. Nutcracker syndrome / Ratio of peak velocities Cho BS et al. Nephrol Dial Transplant 2001 ; 16 : 1620 – 1625. Peak velocity ratio: 6 LRV near hilum Peak velocity: 19.9 cm/sec LRV between aorta & SMA Peak velocity: 99.7 cm/sec
    111. 111. Nutcracker syndrome / SMA angle Peker A et al. J Clin Ultrasound 2011 ; 39 : 418 – 421. Upright position 14 ° Supine position 33° Cut-off value 41° in supine position – 21° in upright position
    112. 112. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    113. 113. Doppler in renal Mass Limited role compared to CT • Pseudo-tumors Prominent column of Bertin Persistent fetal lobulation Dromedary hung • Renal tumors Tumoral vascularization CEUS: solid or cystic mass • Venous invasion Renal veins IVC Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
    114. 114. Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Normal interlobular arteries at periphery of PCB Prominent column of Bertin (PCB) Mistaken for intra-renal tumor Prominent column of Bertin or mass
    115. 115. Vascularization of renal tumors Jinzaki’s classification Intratumoral focal vessels Penetrating vessels Peripheral vessels Penetrating & peripheral Angiomyolipoma Angiomyolipoma Carcinoma Carcinoma Pattern 1 Pattern 2 Pattern 3 Pattern 4 Jinzaki M et al. Radiology 1998 ; 209 : 543 – 550.
    116. 116. Vascularization of renal tumors Jinzaki M et al. Radiology 1998 ; 209 : 543 – 550. Pattern 3 Peripheral vessels Carcinoma Pattern 4 Penetrating & peripheral vessels Carcinoma
    117. 117. Solid renal mass / CEUS Hypervascular lesion CEUS / 34 sec MSCT / arterial phase Hypervascular lesion Gray-scale US Subtle deformation of renal contour Clear renal cell tumor at surgery Setola SV et al. Abdom Imaging 2007 ; 32 : 21 – 28.
    118. 118. Bosniak renal cyst classification Category CT features Significance I Thin wall, water density & does not enhanced No septa, calcification, or solid component Benign Israel GM & Bosniak MA. Urology 2005 ; 66 : 484 – 488. II Thin septa with “perceived” enhancement Fine or slightly thick calcification High attenuation non-enhancing cyst < 3 cm Benign IIF Thick regular septa with “perceived” enhancement Thick regular wall with “perceived” enhancement Thick, nodular, & irregular calcification High attenuation non-enhancing cyst > 3 cm Likely benign Follow-up III Thick smooth or irregular septa Thick smooth or irregular wall With measurable enhancement Some benign Some malignant IV Criteria of category III Enhancing mass independent of wall or septa Malignant Cystic carcinoma
    119. 119. Cystic renal mass / CEUS Thin-walled cyst No septa or solid component Bosniak category I CECT scan Enhancing mural nodule within cyst Bosniak category IV CEUS Park BK et al. Eur J Radiol 2007 ; 61 : 310 – 314. Renal cell carcinoma after partial nephrectomy
    120. 120. Invasion of IVC in RCC Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Color Doppler US Localization of upper extremity of thrombus Power Doppler US Tumoral vascularization of thrombus
    121. 121. Indications of renal Doppler ultrasound  Renal artery stenosis  Renal artery thrombosis & emboli  Renal vein thrombosis  Aneurysm & pseudo-aneurysm  Arterio-venous communications  Nutcracker syndrome  Renal mass  Miscellaneous indications
    122. 122. • Nephropathies • Kidney stones • Hydronephrosis • Uretero-pelvic junction obstruction • Fraley syndrome (Upper calix syndrome) Miscellaneous indications
    123. 123. Renal Doppler in nephropathies • Acute tubular necrosis • Tubulo-interstitial nephropathy • Micro-angiopathy • Nephro-angiosclerosis • Diabetic nephropathy Glomerulo-nephritis (↑ RI in end stage disease) Elevated RI Normal RI
    124. 124. Diabetic nephropathy Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Increased resistive index: 0.89 Renal insufficiency
    125. 125. Kidney stone / Twinkling artifact Tchelepi H et al. Am J Roentgenol 2009 ; 192 : 11 – 18. Twinkling sign from large stone Presence of small stone Large stone causing hydronephrosis Presence of posterior shadowing Useful for evaluation of small kidney stones High PRF & gain just below artifact limit
    126. 126. Hydronephrosis RI of LK: 0.45RI of RK: 0.65Hydronephrosis of right UPJ Δ RI (right – left) > 0.05 Sensibility: 10 – 40%, Specificity > 80% Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Obstruction without dilatation Indications Dilatation without obstruction Hydronephrosis in pregnancy
    127. 127. Renal colic in pregnancy Physiological hydronephrosis or stone? Retrospective study of 262 patients (2 local hospitals) Data on clinical presentation, imaging, & interventions Clinical & laboratory features unhelpful to predict stone Left-sided colic more likely to indicate stone Improved accuracy of Doppler in predicting stone (55 – 72%): Elevated resistive index Absence of urinary jet Andreoiu M et al. Urology 2009 ; 74 : 757 – 761.
    128. 128. Urinary jet Obstructed ureter if no jet seen after 15 min of observation Presence of jet do not exclude incomplete obstruction Tuma J et al. European course book: Genitourinary ultrasound. European Foundation of Societies of Ultrasound in Medicine & Biology, 2011.
    129. 129. Uretero-pelvic junction obstruction Most common cause of UT obstruction in children Multiples proposed factors Delayed recanalization of fetal ureter Abnormal development of ureteral muscle Abnormal ureteral peristalsis Aberrant vessels or bands Sivit CJ. Ultrasound Clin 2006 ; 1 : 67 – 75. Bilateral in 25%
    130. 130. Uretero-pelvic junction obstruction Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Sidhu R et al. Semin Ultrasound CT MRI 2009 ; 30 : 271 – 288. Hilar artery seen in 30 – 45% of patients Crossing vessel usually located anterior to UPJ obstruction
    131. 131. Fraley syndrome / Upper calyx syndrome Vascular compression of superior calyx Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. IV pyelography Superior calyx obstruction due to extrinsic compression Color Doppler US Segmental artery crossing the dilated calyx CT Angiography before tt: polar nephrectomy – reimplantation
    132. 132. References Springer-Verlag – 2011 Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. EFSUMB – 2011
    133. 133. Thank You

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