Kidneys, Our Body's Trash Collectors - USA

Upon completion of this course, you will be able to: Name anatomy, and vascularity specific to the kidney Explain the three orthogonal measurements of the kidney Describe normal color and spectral Doppler findings in the urinary system Congratulations! You have completed the Kidneys, Our Body’s Trash Collectors course. Listed below are the key points presented in this course. Take time to review the material before you try the final quiz.   Download and print a copy of the detailed Course Review   In this course you have learned to: List anatomy and vascularity specific to the kidney. Explain the three orthogonal measurements of the kidney. Describe normal color and spectral Doppler findings in the urinary system. The intra-abdominal urinary system includes two bean-shaped kidneys, ureters, bladder with arteries and veins to each. Located lateral to the twelfth thoracic and the third lumbar vertebrae, these retroperitoneal structures lie between the parietal peritoneum and posterior abdominal wall.2    Usually found in the right and left upper quadrant, surrounding organs, patient position, and respiration change their location. The right kidney, slightly lower due to the large anterior liver, and lies within Morison’s pouch.   The renal arteries originate laterally from the aorta inferior to the superior mesenteric artery (SMA)2 with most of us having a single artery.3 The incidence of duplicated renal arteries varies with each population, however, up to a third of individuals show this normal anatomic difference.4  The right renal artery (RRA) courses from the aorta passing posterior to the inferior vena cava (IVC) and posterior to the liver hilum. The left renal artery (LRA) passes from the aorta to the kidney posterior to the renal vein and pancreatic tail.2    When viewing anatomy in medical imaging, we orientate as if we are facing the patient (anatomical position). The result is the patient’s right side is on our left and vice versa. Learn More about Transverse Anatomy Learn more about transverse anatomy Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal-Renal-Simulation-001b/index.htmlPDF File: Learn More about Vascular Anatomy Learn more about vascular anatomy Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal_Renal_Simulation-002/index.htmlPDF File: Upon entering the renal hilum, the renal artery divides into four or five segmental arteries. These branch into the interlobar arteries coursing along the sides of the renal pyramids. The arcuate arteries arch over the base of the pyramids with the interlobular arteries extending into the cortex.5    The arcuate arteries provide the origin for the interlobular arteries which enter the renal glomeruli. Once the gas and waste exchange occur at the cellular level, blood exits the kidney via veins.    This diagram shows the arterial divisions within the kidney. Learn More About Intrarenal Vasculature Learn more about intrarenal vasculature Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal_Renal_Simulation-003b/index.htmlPDF File: Most sonographic exams of the kidneys begin with grayscale or 2D-mode imaging.  Structures surrounding and within the kidney have a characteristic sonographic appearance. The renal capsule images as a strongly echogenic structure surrounding the kidney. The renal cortex has mid-level echoes when compared to the liver or spleen. The triangular pyramids appear as hypoechoic, when compared to the renal cortex. The renal sinuses appear echogenic due the fat, blood vessels, and the collecting system.6 Renal sinuses lie within the central portion of the kidney.  These structures contain the collection system (major and minor calyces) arteries, and veins, lymphatics, peripelvic fat, fibrous tissues, and part of the renal pelvis. Learn More about Longitudinal Renal Anatomy Learn more about longitudinal renal anatomy Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal-Renal-Simulation-004e/index.htmlPDF File: Learn More about Left Renal Anatomy Learn more about left renal anatomy Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal_Renal_Simulation-005b/index.htmlPDF File: Learn More about Transverse Renal Anatomy Learn more about transverse renal anatomy Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal_Renal_Simulation-006/index.htmlPDF File: The normal kidney varies in size showing differences with each person. A child’s kidney changes as they grow while the adult kidney has normal ranges depending on gender, body habitus, age, and hydration.6 In the adult the normal longitudinal kidney varies from 9 to 13 centimeters in length.3 Keep in mind we always measure both kidneys and a difference of more than two centimeters in length is a significant finding.6 Learn more about measuring the kidney Learn More about Measuring the Kidney Tab TitleTextLength Measurement3, 6, 7Finding the greatest length of the kidney requires careful transducer angling and rotation. Any imaging plane, anterior, coronal (lateral), posterior or oblique, allows for lengthening of the kidney.   This image shows an example of caliper placement for a longitudinal measurement of the right kidney.  Note: Calipers do not represent the display on an ultrasound system.  Transverse Measurement6, 7To ensure three orthogonal measurements, obtain two (anteroposterior (AP) and coronal) on the transverse view of the kidney at the hilum. Accurate measurements of the kidneys become important if the clinician uses renal volume to determine normalcy in either the adult or pediatric patient.    This image shows an example of caliper placement for a transverse measurement of the right kidney. When measuring, place the calipers perpendicular to the hilum and lateral edge and the anteroposterior (AP) borders rather than in alignment with the transducer. Make sure to include the complete medial edge of the kidney (open arrows) on the transverse measurement. Note: Calipers do not represent the display on an ultrasound system. The intrarenal arteries, due to their size, visualize poorly when using 2D-mode imaging. However, the extrarenal vessels appear as hypoechoic, tubular structures extending from the aorta or to the IVC.   Duplication of renal arteries is a normal variation; however, we must obtain both 2D-mode images and spectral Doppler tracings of each vessel.3, 4 Learn More About Upper Abdomen Vasculature Learn more about upper abdomen vasculature Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal_Renal_Simulation-009/index.htmlPDF File: Learn More About a Single Renal Artery Learn more about a single renal artery     This longitudinal image, obtained by placing the transducer on the mid abdomen, shows the RRA (orange) posterior to the IVC (yellow). Hepatic vein – red; Portal vein – blue; Gallbladder – green.   Learn More About a Duplicated Renal Artery Learn more about a duplicated renal artery Duplication of renal arteries is a normal variation; however, we must obtain both 2D-mode images and spectral Doppler tracings of each vessel.3, 4     The duplicated RRA (orange) image posterior to the IVC (yellow_ Narrowing the sector width increases the line density, and thus, also increasing image detail.8 Like 2D-mode image creation, the ultrasound system sends a signal along a single line to produce the overlay we know as a color image. To obtain the data needed to generate the color Doppler image, the ultrasound system sequences lines. One contains 2D-mode information, and an alternate obtaining color Doppler information. Repeated sampling of the color line results in a color region of interest (ROI) often called the color box. Differences in structure position, in our case the blood flow, allow assignment of a color value to the pixel by the ultrasound system.8 Color Doppler imaging uses the mean frequency shift information from blood flow.8, 9 This mode is a qualitative method of demonstrating blood flow.  Learn More About Color Doppler Learn more about color Doppler Tab TitleTextRenal Artery The left 2D-mode image shows artifactual RRA filling. The lumen fills (right) with the activation of color Doppler confirming flow. Use the smallest 2D-mode and color Doppler region of interest (ROI) to maximize the image frame rate and line density.9 Renal Vein This is a transverse view of the right kidney. The left 2D-mode image shows the renal hilum. Color Doppler Velocity (CDV) shows filling of renal vessels within the hilum (right).  Intrarenal Vessels-CDV This CDV image shows the segmental (double arrows) and the interlobar (open arrow) arteries.3, 6 The color-coding for this image shows arterial flow (red) towards the transducer and venous flow (blue) away from the transducer (shown by the color bar on the upper right of the image).8, 9 Adjust the color scale and gain to optimize the CDV vascular filling.Intrarenal Vessels-CDE Color Doppler Energy (CDE) is often simply called power Doppler, uses color coding to show the amplitude, or strength, of blood flow.8 The more flow in a vessel the higher the amplitude increasing the signal. CDE does not show velocity changes, however, this mode has greater flow sensitivity in low flow states such as the small arcuate and interlobar vessels.8 This is an image of the small interlobular (down white arrow) arteries and connecting arcuate (up open arrow) arteries.3, 6   Learn More About Color Doppler with Videos Learn more about color Doppler with videos Tab TitleTextIntrarenal Vessels:  Renal Vein Renal ArteryThis video shows a CDV taken on a coronal plane resulting in an image showing both renal arteries originating from the aorta.  This view is often called the banana peel image.    All Doppler imaging relies on detecting the frequency shift from blood flow. While color Doppler provides a qualitative method to assess flow; spectral Doppler provides a method of quantitative assessment. Additionally, a sample volume allows positioning of the sampling area where we wish to obtain the spectral tracing.9 Thus, we can measure the acceleration time, velocity, pulsatility index (PI), A / B ratio, and resistance of flow within the vessel (aka resistive index [RI]).  Learn More About Spectral Doppler Learn more about spectral Doppler Tab TitleTextRenal Artery The sample gate (arrow) indicates the sample area within the left renal artery.9 The optimal Doppler angle is at less than 60 degrees. The ultrasound system allows us to set the angle with the resulting angle displayed on the image (box).  Most clinicians prefer to see the spectral tracing above the baseline as in this example. The inverted (double arrows) text explains the color Doppler (away from the transducer) and spectral tracing discrepancy. The speed (velocity) of the flow displays to the right of the spectral tracing (bracket). Note: Flow direction varies between ultrasound systems and utilized color maps.Renal Vein This 2D-mode reference image and spectral tracing of the RRV shows flow away from the kidney towards the IVC.  Flow away from the transducer has a blue hue (shown in the color bar in the upper left) and the spectral tracing shows inverted (box) flow above the baseline. Venous flow has a phasic pattern (arrows) due to the increase and decrease of abdominal pressure during respiration.3Intrarenal WaveformNormal vessels within (intrarenal) and outside (extrarenal) the kidney display similar low resistance flow characteristics as arteries and veins located in other areas of the body. This waveform shows a normal intrarenal spectral tracing.  There is a rapid increase from diastole to the early systolic peak (aka compliance peak) with gradual decrease throughout the heart cycle.3Intrarenal Vessels This image shows a spectral tracing of an arcuate artery in the mid to lower section of the kidney. Decreasing the depth, 2D-mode field of view (FOV) and color box increases the frame rate.8 Adjusting the sweep speed to show two cardiac cycles allows for identification of the waveform appearance. This spectral tracing uses a tint which can increase visibility of subtle waveform changes.  Optimizing the spectral Doppler tracing allows for evaluation of the waveform shape and measurement of flow velocities. Controls that allow you to adjust the appearance of the tracing include the sweep speed, edge, dynamic range, and filter.   Each ultrasound system has unique technique parameters to aid in optimizing the spectral tracing. Please refer to the User Manual for further information on your system. Learn More About Optimizing Spectral Doppler Learn more about optimizing the spectral Doppler tracing Tab TitleTextSweep SpeedUltrasound systems allow you to adjust the speed of a spectral tracing. Called the sweep speed, increasing the speed displays fewer flow cycles. This is a handy adjustment when performing a renal Doppler exam.  Showing two or three cycles allows easier visualization of the waveform shape.  This shows the changes in the spectral tracing when using sweep while sampling the lower pole arcuate artery flow. Edge FilterSometimes referred to as reject, the filter function reduces the amount of noise and clutter surrounding the baseline. Filter suppresses the lower level signals that are the result of tissue and vessel wall motion. Increasing the filter decreases the echoes displayed at the baseline The filter value (F) changes when adjusted. Dynamic RangeYou can adjust the range of grays that display on the spectral tracing and thus change the overall contrast resolution by using the dynamic range feature. This control allows you to change the highest to lowest grayscale values. Using a lower dynamic range results in a high contrast tracing while the opposite is true of a high dynamic range image.   TintsChanging the displayed tint allows you to select a color hue to apply to the spectral tracing. Ureters begin at the renal pelvis traveling inferior to the bladder. Each ureter inserts into the bladder at the trigone with slit-like openings preventing retrograde flow of urine.   The full urinary bladder images as an anechoic, fluid-filled structure located in the pelvis. Image the bladder on both the transverse and longitudinal planes with 2D-mode imaging. A full urinary bladder helps image organs located posterior or inferior, such as the uterus and prostate. As the ureters move the urine from the kidneys to the bladder they contract resulting in ‘flow’ into the bladder. We use CDV or CDE to identify the urinary inflow, often called jets, to confirm function of the kidneys.10 Learn more about the longitudinal urinary bladder Learn more about the longitudinal urinary bladder Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal_Renal_Simulation-010/index.htmlPDF File: Learn More About the Transverse Urinary Bladder Learn more about the transverse urinary bladder Instructions:Flash File:HTML5 File:/content/generator/Course_90021741/Normal_Renal_Simulation-011/index.htmlPDF File: Learn more about urinary jets Learn more about urinary jets Tab TitleTextUrinary JetsUrinary jets image as low-level echoes entering the bladder at the level of the trigone on the 2D-mode image. Occurring approximately every 5 to 20 seconds, an easier method to confirm jets is using CDV.6 Confirmation of both jets helps rule out obstruction from calculi or abdominal pathology.10 Urinary Jets-Video  Explore the links below for the Glossary, References, and Further Reading opportunities. Glossary Glossary Anatomical position – The patient position facing the viewer with face, palms, and feet rotated forward (anterior).   Anterior – Towards the front of the body.   Anteroposterior (AP) – The anatomic axis extending from the front to the back of the body.   Caudal – Towards the feet.   Column of Bertin – A normal variant showing an extension of the renal cortex between the renal pyramids.   Coronal – A plane dividing the body into front and back sections.   Diastole – Relaxation of the heart resulting in filling of the chambers with blood.   Echogenic – Having brighter appearance than the surrounding tissue.   Extrarenal – Outside of the kidney.   Hypoechoic – Having a darker appearance than the surrounding tissue.   Hypertrophy - Cellular enlargement resulting in an increase in the size of an organ.   Intrarenal – Within the kidney.   Longitudinal – A plane that divides the body into right and left sides (aka sagittal or parasagittal).   Morison’s pouch – The potential anatomic space between the right kidney and liver.   Orthogonal – Planes at right angles to each other.   Parenchyma – Functional area of an organ i.e., cells.   Peripelvic – Around the renal pelvis.   Posterior – Towards the back of the body.   Quantitative – The ability to measure and assign a numerical value.   Qualitative – Display of the quality of flow within a range of frequencies.   Renal capsule – Fibrous layer surrounding the kidney.   Renal cortex – Portion of the kidney between the renal medulla and capsule.   Renal hilum – The location of vessels and ureter within a recessed central area of the kidney.   Renal pelvis – The broad origin of the ureter within the renal hilum.   Renal pyramids – Cone-shaped structures within the medulla.   Renal sinus – Echogenic central area of the kidney containing the vessels, major and minor calyces, renal pelvis and fatty tissue.   Retroperitoneum – Anatomic space located posterior, or deep, to the peritoneum.   Systole – Cardiac contraction which moves the blood from the heart into the body.   Superior mesenteric artery (SMA) – Vessel originating from the anterior aorta inferior to the diaphragm which supplies intrabdominal organs (i.e., colon, duodenum, pancreas).   Transverse – Plane dividing the body into top and bottom sections.  References / Further Reading References / Further Reading 1. Shih, H., Wu, C., and Lin, S. (2018). Physiology and pathophysiology of renal erythropoietin-producing cells. Journal of the Formosan Medical Association. 117(11): 955-963.   2. Moore, K.L., Dalley, A.F., and Agur, A.M. (2017). Abdomen. (Eds.), Clinically oriented anatomy (pp. 406-452). Philadelphia: Wolters Kluwer.   3. Neumyer, M.M. (2018). The renal vasculature. 2 ed. Diagnostic medical sonography: The vascular system, ed. Kapinski, A.M., Philadelphia: Wolters Kluwer. 335-351.   4. Gulas, E., Wysiadecki, G., Cecot, T., Majos, A., Stefańczyk, L., Topol, M., and Polguj, M. (2016). Accessory (multiple) renal arteries - Differences in frequency according to population, visualizing techniques and stage of morphological development. Vascular. 24(5): 531-537.   5. Weber, T.M., Robbin, M.L., and Lockhart, M.E. (2013). The kidneys. In Pozniak, M.A. and Allan, P.L., (Eds.), Clinical Doppler ultrasound (pp. 193-213). Edinburgh: Churchill Livingstone Elsevier.   6. Baker, S.M. and Walker, D.C. (2017). The kidneys. In Kawamura, D. and Nolan, T., (Eds.), Diagnostic medical sonography: Abdomen and superficial structures (pp. 271-334). Philadelphia: Wolters Kluwer.   7. Paltiel, H.J. and Babcock, D.S. (2017). The pediatric urinary tract and adrenal glands. In Rumack, C.M. and Levine, D., (Eds.), Diagnostic ultrasound (pp. 1775-1832). Philadelphia: Elsevier.   8. Miele, F.R. (2013). Ultrasound physics and instrumentation. 5 ed.: Miele Enterprises, Inc.   9. McDicken, W.N. and Hoskins, P.R. (2013). Physics: Principles, practice and artefacts. In Pozniak, M.A. and Allan, P.L., (Eds.), Clinical Doppler ultrasound (pp. 1-25). Edinburgh: Churchill Livingstone.   10. Walker, D.C. and Baker, S.M. (2017). The lower urinary system. In Kawamura, D. and Nolan, T., (Eds.), Diagnostic medical sonography: Abdomen and superficial structures (pp. 335-356). Philadelphia: Wolters Kluwer. The reproduction, transmission or distribution of this training or its contents is not permitted without express written authority. Offenders will be liable for damages.   All names and data of patients, parameters and configuration dependent designations are fictional and examples only.   All rights, including rights created by patent grant or registration of a utility model or design, are reserved.   Please note that the learning material is for training purposes only!   For the proper use of the software or hardware, please always use the Operator Manual or Instructions for Use (hereinafter collectively “Operator Manual”) issued by Siemens Healthineers. This material is to be used as training material only and shall by no means substitute the Operator Manual. Any material used in this training will not be updated on a regular basis and does not necessarily reflect the latest version of the software and hardware available at the time of the training.   The Operator Manual shall be used as your main reference, for relevant safety information like warnings and cautions. Note: Some functions shown in this material are optional and might not be part of your system. The information in this material contains general technical descriptions of specifications and options as well as standard and optional features that do not always have to be present in individual cases.   Certain products, product related claims or functionalities described in the material (hereinafter collectively “Functionality”) may not (yet) be commercially available in your country. Due to regulatory requirements, the future availability of said Functionalities in any specific country is not guaranteed. Please contact your local Siemens Healthineers sales representative for the most current information.   ACUSON Sequoia is a trademark of Siemens Medical Solutions USA, Inc.   Copyright © Siemens Healthcare GmbH, 2019.  The main purpose of the kidneys is to eliminate metabolic waste or, garbage, from the blood such as extra water, carbon dioxide, and nitrogenous waste. This filtering process results in the kidneys excreting urine which travels to the bladder via ureters.   Kidneys also recycle chemicals such as sodium, phosphorus, and potassium. This helps maintain normal levels of these electrolytes in our system to keep us healthy.   Low levels of oxygen in our blood stimulates the kidneys to secrete erythropoietin (EPO). This hormone assists creation of red blood cells (RBC) in the bone marrow. Additionally, the RBC’s contain hemoglobin which transport oxygen to our cells.1   In the event kidney function changes, clinicians routinely request a sonographic evaluation for morphology and vascular flow. This course begins with a review of pertinent renal and vascular anatomy.  We then discuss the 2D-mode, color Doppler, and the spectral Doppler appearance of the normal kidney.