 Sonography of the Urinary Tract, the Technique, Normal Appearance and Variations. This part will cover the kidney and the renal pelvis. Now, basic technique for renal ultrasound, the position of the patient can be supine, decoupitus, one of the decoupitus, prone and position allowing optimal visualization has to be used and the times to see one kidney more than one position may be necessary. Approach can be a subcastle approach or it can be an intracastle approach and usually done with a deep suspended inspiration to bring down the kidney below the ribs. The planes used are the sagittal, coronal, transverse. So, the longitudinal scan is either sagittal or coronal and then the transverse scan. The sweep, sagittal or coronal sweep and transverse sweep has to be done to assess the whole volume of the kidney. So, the protocol is the schematic and of the sagittal scan and the sweep by moving side to side. It can be a coronal scan, a longitudinal scan with a sweep and a posterior and then the axial scan or transverse scan which can be subcastle or from the flank and move up and down for the sweep, about downwards. So, the technique involves a longitudinal scan which can be a sagittal or coronal as shown here and the transverse scan either from the subcastle anterior or from the right flank and the longitudinal sweep has to be made if it is sagittal side to side or it is coronal andro posterior under transverse sweep above downwards. So, this is the longitudinal scan of the kidney and either sagittal or coronal and the transverse scan of the kidney which can be taken from the anterior subcastle or from the right flank to get the longitudinal axis of the kidney. Now this is a coronal scan and when you attempt to take a coronal scan, you get a scan of the oblique scan of the kidney as seen here. So, then from there you rotate the probe in or swivel the probe like that to get at the long axis of the kidney. So, you have to swivel either way. So, you will get long axis again if you swivel then it will again become oblique. So, you come back to the longest axis of the kidney. So, that is the video of the technique oblique then swivel to get the long axis of the kidney. If you still further rotate it will become again oblique. So, get back to the long axis of the kidney. Here it is a coronal scan. So, once you get the longest axis here the coronal scan then you move up anterior and posterior to get the sweep of the entire volume of the kidney in the coronal or sagittal scan. Then rotate the probe 90 degrees to get the short axis or the transverse axis of the kidney as shown in the video. Once you get the transverse axis now here on the mannequin you see from the flank, but the image video is from the anterior aspect. So, either way you go above downwards to in the transverse axis to scan the entire volume of the kidney. So, the kidney has to be entire volume of the kidney should be scanned in two planes either coronal or sagittal and transverse. Now, this is the sagittal scan from the anterior subcostal approach and you see the right kidney posterior to the liver. So, when you see when you get such an image now this is the sagittal scan of the right kidney from the anterior aspect and the you see the liver and the right kidney. The kidney is being shaped and you see a perinephric fat line all around the kidney which has five structures namely the renal capsule, perinephric pad of fat, gerotus ratio, peritlperitonium, moriscan spouch and visceral peritonium and the liver capsule. So, this is the structures you see you get within this thin perinephric fat line. Then you see the parankyma, the parankyma is uniform in thickness all around and the medullary pyramids within the parankyma and then you see the central echogenic area. So, the central echogenic area as the name implies it is the echogenic area in the center of the kidney and it has the pelvic licell system, renal artery branches, renal vein branches, lymphatics and sinus fat all of these within this small area because of the interfaces between each of them it appears echogenic that is why it is called central echogenic area. Then you see the adrenal area that is adrenal above the upper pole of the right kidney and the normal adrenal we do not visualize an ultrasound in the adults. Then the longitudinal scan can be a coronal scan as shown here and the coronal scan appears like this on the schematic and the difference between sagittal and coronal. This is sagittal scan, this is coronal scan shown here for comparison what is the difference. So, in the coronal scan taken from the right flag you see the kidney and the orientation becomes little different because we place the probe in the flank near the transducer it is lateral relationship and the opposite is medial and because the probe mark is here it is the catholic and that opposite is caudal. So, from the lateral abdominal wall you see that is the lateral abdominal wall then you see the liver, medial to the lateral abdominal wall then you see the right kidney medial to the right lateral aspect of the right lobe of the liver and then you see the sauvus muscle medial to the right kidney and then the lateral surface of the vertebra seen as a white light with shadow. So, because the probe mark is here then this is the catholic so, which is the upper pole towards the head end is the upper pole. So, that is the upper pole and above the upper pole we get the adrenal area and that is the lower pole and you see that the lower pole is actually in the upper part of the image, but the orientation is it is lateral. So, the lower pole is more laterally placed than the upper pole that is normal that is because of the sauvus becoming bulky lower down it is thin near the upper pole it becomes bulky. So, it takes the lower pole more lateral than the upper pole. So, that is the normal orientation of the kidney and that is the sauvus marked by the triangle. Now, coming to the difference between sagittal and coronal you see the kidney the sagittal section is taken like that and so, the you see the parenchyma all round whereas coronal scan is taken in this plane as shown in the schematic and the parenchyma there is a discontinuity in the medial aspect because of the escape of the vascular pedicle. So, the that is the discontinuity in the of the parenchyma mediady. So, you see that the central echogenic area is continuous with the perinefric fat or retropitin fat and the hilum that is that differentiate this from the sagittal scan. So, as a result when you get a section sagittal section like that the kidney looks as the image shows with parenchyma all round, but when you take a coronal scan of the kidney it looks this like this seen in this schematic where the parenchyma is all round except the renal hilum. So, that is the central echogenic area continuous with the retropitinil fat. So, that is because the collecting system and the vessels escape reach the retropitinium through the hilum. So, when you see the collecting system these are the chelises communicate with the renal pelvis and the continuous as the ureter. So, that is the chelises renal pelvis and continuous as the ureter. Now, these are seen when the collecting system is dilated when there is obstruction, but because the collecting system is collapsed with no fluid in between it cannot be made out normally. So, as a result to see the collecting system the coronal scan is crucial. So, the significance of some certain diagnosis are section specific. So, they will be seen only in a particular section. Here we will see how the coronal scan is significant. Now, here you see an image of a kidney in the sagittal scan where you see multiple cysts in the a kidney. So, it mimics a multistick kidney, but when you do a coronal scan you see that the typical appearance of the peripheral dilated peripheral chelises communicating with the more dilated medially placed large renal pelvis. So, making a diagnosis of hydronephrosis. So, you see how crucial the coronal scan is. We will see another example. Here again multiple cysts of varying size typical of multistick kidney and in coronal scan also it remains as multiple cysts non communicating cysts of varying size. So, typical of multistick kidney. Another example here you see the kidney in the lower half of the kidney you see multiple cysts, but when you do a coronal scan you see that the upper half of the kidney is normal whereas in the lower half you see the peripheral dilated chelises communicating with the medially placed renal pelvis and continues as the ureter. So, that makes the diagnosis of hydronephrosis of the lower moiety in a double collecting system with upper moiety being normal. So, here again this diagnosis is possible only on a coronal scan. A few more examples of the significance of coronal scan. Here this is a sagittal scan of a kidney showing a cyst in the upper pole in this sagittal scan, but when you do a coronal scan you see that it is not a cyst it is the dilated upper moiety of a double collecting system which continues SF ureter down. So, then it is diagnosis double collecting system with the hydronephrosis of the upper moiety. Another example you see a small cyst in the upper pole of the kidney and when you do coronal scan you see that it is continuous this huge dilated ureter making asymmetrical double collecting system of the kidney with a small upper moiety with hydronephrosis and dilated ureter. Now, here you see a sagittal scan the kidney absolutely looks normal, but when you do a coronal scan you see that there is a similar to here you see a double collecting system with asymmetrically small upper moiety with dilated collecting system continues as the dilated ureter. So, again here it is a double collecting system with hydronephrosis of the upper moiety. These are examples of the significance of a coronal scan. Few more examples now coronal scan why it is important we will see here the kidney sagittal scan looks normal, but when you do a coronal scan you see even though the kidney looks normal you see a calculus medial to it. So, this is because of a non-dilated renal pelvis with a calculus at the Pug. So, this calculus is missed on the sagittal scan and here you see hydronephrosis of the kidney and you see the renal pelvis and as if the renal pelvis is ending blindly without dilation of the ureter may making a diagnosis of Pug abstraction, but when you do tilt the probe in a coronal plane anteriorly you see that the pelvis is continuing as a dilated ureter and which bends and turns upwards which is very characteristic of an upturned perurator of retrocaval ureter a very classical finding as a sea horse sign. Then we come to the transverse scan. Now, the transverse scan as I said can be taken from the anterior aspect or from the flank. So, this is from the anterior aspect kind of the kidney the same patient you see from the flank you get the transverse scan of the kidney. So, it can be done anteriorly or from the flank. Now, once you see the transverse scan of the kidney and the gallbladder, you see the liver, you see the gallbladder and then you see the right kidney with the perinephric fat line, the parenchyma, the pyramids, the central echogenic area extending continuous with the retropetanil echogenic area, the infirminacheva, head of pancreas and the antherm of the ureterum. These are the structures in relation to the right kidney. Now, as I said certain diagnosis or section specific. So, certain diagnosis will be obvious in a transverse scan. Now, here this is a coronal scan you see a calculus in the lower pole and when you do a coronal scan, you see a cyst in left lateral decubitus position. You see in fact that there is a cyst in the lower pole with a fluid fluid level indicating that it is milk of calcium within a cyst. In anteriorly different diagnosis which does not need any intervention while a diagnosis of calculus will need an intervention to remove it. That is about the right kidney and coming to the left kidney, the protocol is a coronal scan of the left flank which is done like this in this schematic and you see the coronal scan of the canymage and sagittal scan of the left kidney is not obtainable in most situations because of gas in the stomach prevents the solution of the left kidney from anterior aspect. So, most of the times you take a coronal scan from the left flank. So, here again the relationship is lateral, median, upper kephalic and chordal and you see the lateral abdominal wall and the image is similar to coronal scan of the right kidney but the structures are different. So, instead of right lobe of liver we see the spleen, instead of right kidney you get the left kidney, instead of right sovers you get the left sovers and instead of right lateral surface of the vertebra, you get the left lateral surface of the vertebra casting a shadow and protocol for each organ you have seen in the basics it should cover a sweep of minimum two planes and to cover the entire volume of the kidney. So, first get at the long axis make a long axis sweep from side to side then turn 90 degrees rotation to the short axis and then move up down to cover the entire volume of the kidney. So, at least in two planes we should do that. So, then we come to the real-time observation in the technique and protocol. So, we have to observe the movement of the kidney with respiration which is even though the kidney is in vertebrate structure we see the movement of the kidney with respiration and the liver also moves with respiration, but many times you will appreciate a differential movement a sliding movement of the liver over the kidney as seen here, but which is brought out with a forced movement as seen in this image in this video you see that the liver slides over the right kidney. So, these are two important observations in the movement of the kidney which is which is the importance of which will be illustrated in the normal section and which is the movement will be restricted when there is inflammation and adherence of the kidney to surrounding structures either by infection or infiltration. Now, coming to the ecogenicity of the renal parankema this is the relative ecogenicity of the different structures in the abdomen. Kidney is less ecogenic than spleen and liver spleen is less ecogenic than liver and then pancreas the liver and spleen are less ecogenic than pancreas which is less ecogenic than the retropertonal fat. So, that is the relative ecogenicity. Now, coming to the kidney what are the normal parameters we look for you have to look for all these parameters we will see one by one. Now, normal appearance the size the length of the kidney is varies from 9 to 12 centimeters width 4 to 5 centimeters and the parankimal thickness 2.5 to 3 centimeters. The left kidney is slightly larger compared to the right kidney. So, how is the kidney measured? Measure they take the longest axis of the kidney and take the measurement to from pole to pole. The renal length correlates best with the body weight decreases with advancing age lesser in females vary with the state of to some extent with the state of hydration and there is an increase slight increase in the length with pregnancy. Now, there can be error in renal measurement and the source of error is one is how it is measured. So, this is an oblique scan the right kidney and even though the section will look the same but the measurement is will be less as shown in this illustration. So, when you take the longest axis it will look longer. So, how to avoid this error a trick is to get the longest bipolar length by real time ultrasound by a vertical swivel of the probe as I have described earlier in the earlier part of the lecture. So, here you see oblique scan the kidney looks normal morphologically but the length is only 9.6 whereas, when you rotate the probe and get the longest axis it is actually 10.9. So, if you do not do this then you will by mistake make a shorter length of the kidney. So, how to do that you get a long axis of the kidney I have described earlier. So, get at the coronal scan it is you get oblique scan then rotate the probe to get the long axis of the kidney then measure and other sources of error in the renal measurements on the lower pole of the kidney upscrewed by bowel gas and you get a smaller length and to avoid that you must avoid the gas and get the longest axis of the kidney. When the parent camel thickness is uniform around the kidney and you should see the clear margins of the kidney like that all around you must be clearly seeing to avoid mistakes in measurement and avoid missing a pathology. Now, coming to the contour of the kidney it is smooth and harmonious it is corn mix laterally anteriorly and posteriorly and corn came medially that is the hilum of the kidney and coming to the parenchyma parenchyma is contains both cortex and medulla. The medulla is seen as triangular echopore structure pyramids in the parenchyma which is more medial than the cortex and echogenicity gradient as said earlier the cortex is echopore less echogenic than the liver adjacent liver spleen and the cortex is more echogenic compared to the medullary pyramids. So, we assume that liver and spleen are normal before you come to a conclusion and then there is a difference between the cortical echogenicity and the medullary pyramids. So, that is called the cortical medullary differentiation which is again has to be looked for to rule out some pathology of the kidney and the parenchyma rind is all round seen all round except at the hilum as shown here. Then we come to the central echogenic area it is the contents which has been described earlier. You see a prominent or large sinus in obesity because of more fat, steroid therapy and sinus lipomatosis. You see a thin sinus, thin central echogenic area in the neonates as seen here and in catexia and when there is parenchyma swelling and compression of the central echogenic area which happens abnormally. When there is parenchyma, edema or infiltration. This is an example of a ket pareniferate is causing compression of the central echogenic area. Even lymphomatosis infiltration of the parenchyma will produce the same effect. Then we come to the perinephric fat line describe the contents of this thin white line and this may not be made out in a normal patient but when there is abnormality when there is fluid collection the layers will be seen separately as seen here the renal capsule, the perinephric fat of fat, the gerotasphatia and the peritoneum and Morrison's pouch with fluid in it in the form of ascites and then the liver capsule. So, all are made out in this case of viral hemorrhagic fever where there is fluid in between the layers. The perinephric fat line is usually thin and echogenic but it can be thick and echogenic because of fat. Fat, the echogenicity of fat varies depending on the location and content and content of fibrous tissue. So, here it appears echogenic in this patient it looks ecopower. So, it can be thick ecopower fat also can be seen. This is a normal variation. The question of the kidney is in supine it extends from T12 to L3, the left kidney, right kidney slightly inferior to the left kidney by about 1 to 2 centimeters and there is a little mobility with the change in position maybe in erect it will come down a little mobility with respiration. Normal appearance of the kidney is different in the neonate where the cortex is hyperacoic compared to the liver and this hyperacoic becomes hyperacoic by about 3 months and in premature infants the echogenicity is more and the medulla strikingly echopower mimics this in the neonate and there are contour lobulations which is normal and the central echogenic area is thin because of very thin fat in the neonates. The renal length in neonates ranges from 3 to 5 centimeters and there are a nomogram of the pediatric kidney length and width available. Now, there are some anatomic variants, normal variants which can be malrotation, fetal lobulations, parankamal junctional defeat, hypertrophic column of protein and dromedary hump, extracellular pelvis. Now, here malrotation we see in sagittal scan you see the renal hyalum anteriorly instead of being medially it is anterior. So, here normal the hyalum in sagittal scan hyalum is not seen because it is medial but here in the malrotated kidney you see anteriorly and in the transverse scan again you see the hyalum anteriorly normally it should be medial as seen here. So, this is a malrotated kidney right kidney and persistent fetal lobulation which we saw in the neonate can persist. So, these are renal lobules in neon clay begin to diffuse in late second trimester to yield a progressively smooth contour. Sometimes this fusion could be incomplete and contour shows small indentations which is inter medullary there is no parankamal thinning. So, the contour shows small indentations which is inter medullary between the medullary pyramids and the parankamal remains thick there is no parankamal thinning to differentiate it from a scar. There is a normal variation in the form of parankamal junctional defect which is seen as a thin echogenic line from perinefric fat to renal extending from perinefric fat to reelsinus between upper and mid third junction more commoner in the right side than the left kidney. And differential diagnosis is a parankamal scar how to differentiate if the differentiation is in the the contour defect is acute versus obtuse in in junctional defect it is acute like this whereas in the parankamal scar it is obtuse like that. And the chelicea blunting underlying chelix is normal here, but there will be blunting of the chelix in a parankamal scar. Hypotrophic column of protein you see is a normal variation. You see that the there is a parankamal indentation on the renal central echogenic area laterally and the junction of upper and mid third junction and the that will be continuous with the adjacent cortex as seen here and it will contain the normal morphology containing renal pyramids as seen here and it will be less than 3 centimeters in size and there will not be any contour change in the kidney. So, that is the hypertrophic column of protein in contrast here also you see a similar appearance, but only thing is the morphology is different and it can be a TCC though so difficult to differentiate sometimes. And the another where normal variation is dromedary hump as shown here in the schematic the hump on the left kidney can make city it is a contour adaptation to the spleen and the differential diagnosis will be a mass. So, how it is differentiated the parankamal thickness is maintained as shown in the schematic diagram you see the and contains normal renal pyramids whereas if it is a mass it will not be the renal pyramids will not be there and vasculature they will be normal in the hump whereas in the mass it will be split. So, here you see the parankamal thickness maintained in hump whereas it is lost in and the mass normal pyramids are seen in the normal hump whereas it is absent in the mass. Then central echogenic area the most important structure as we have seen is the pelvic lacyl system. So, once you in normally the pelvic lacyl system remains collapsed so it cannot be visualized normally. So, when you see like this we assume that the pelvic lacyl system is normal whereas if it is dilated then the central echogenic area will be split by the dilated collecting system as seen in the sagittal scan and in coronal scan you will see the make of the chelices communicating with the medial pelvis. So, that is the dilatation of the collecting system and in the central echogenic area may be enlarged and this may be normal or due to sinus lipometasis or it can be abnormal as seen here there is fluid between indicating that there are multiple polypied masses in coronal scan you see the mass extending into the ureter. It can be a blood clot or a sloughed papilla or fungus ball or a papillary TCC here this turned out to be papillary TCC. So, all this appearance can be produced by all these conditions. Then we come to the extranetal pelvis which is a normal variation where the renal pelvis is mainly extranetal in location and because there is no support of parenchyma it is baggy. So, this has to be recognized and it is appreciated in transverse scan and you see the extranetal pelvis with thickening of the wall and you see huge obstruction with a huge dilated extranetal pelvis whereas the chelices are not much dilated because the pressure is taken by the extranetal pelvis. Thank you very much for your attention.