Learning a quickmnemonic'VAD' can help you remember these structures (renal Vein, renal Artery, Duct a.k.a ureter). The defect proved to be blood clot from papillary necrosis. This phenomenon is due to T2-shortening and susceptibility (T2*) effects caused by concentrated gadolinium, and can potentially obscure filling defects and urothelial lesions. Table 18-7 lists causes of unilateral smooth renal atrophy. Anatomy of the Kidney and Ureter Parenchyma Cortex Medulla Perirenal fat Capsule Ureter Each nephron contains a renal corpuscle, which is the initial component that filters the blood, and a renal tubule that processes and carries the filtered fluid to the system of calyces. Retrograde urogram shows a calculus in the left ureter. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Prominent extrarenal pelves are typically positioned anteriorly (Fig. The upper poles are normally oriented more medially and posteriorly than the lower poles. Ultrastructurally, the nephron is the functional representative of the kidney. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). Other symptoms can include abnormal urine color, blood in your urine, fever, chills, nausea, and vomiting. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. Kidneys are located just below your ribcage and behind your belly. The kidney is a very important organ in regards to body homeostasis. 18-4). When this happens, the stones can block the flow of urine out of your kidneys. Kidneys have a special system for the excretion of hydrogen ions, and in that way consistently maintain the pH of blood at 7.4. Typically, one kidney sits on either side of your spine. Note that there is no contrast in the aorta. Note that the left renal vein receives blood from the left suprarenal and left testicular veins. Some divide the excretory phase into the early excretory phase (contrast mainly confined to the kidney) and late excretory phase (contrast in the ureters). All rights reserved. chronic obstruction, or severe or repeated urinary infections. The Modification of Diet in Renal Disease (MDRD) is another method for estimating renal function that yields a value often called estimated glomerular filtration rate (eGFR). . In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the medulla. On axial sections, the polar regions of the kidney typically form a closed circle or donut shape, with the hole formed by renal sinus fat. Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. Imaging must provide detailed images of the renal parenchyma and a survey of arterial, venous, and ureteral anatomy. Most serum creatinine is excreted in the urine; therefore, if renal function is compromised, levels of creatinine in the serum increase. Chronic obstruction, however, results in damage to the papilla, evident in the clubbed calyx of papillary necrosis (Fig. The right kidney had a similar appearance (not shown). Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. 18-21). The pyramids contain the functional units of the kidney, the nephrons, which filter blood in order to produce urine which then is transported through a system of the structures called calyces which then transport the urine to the ureter. In the medulla, 5-8 renal pyramids are separated by connective tissue renal columns. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. Duplication of the urinary tract is discussed in detail in Chapter 19. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. All content published on Kenhub is reviewed by medical and anatomy experts. Figure 18-15 Relation between the right renal artery and the inferior vena cava (IVC). Dimitrios Mytilinaios MD, PhD Hydronephrosis is important to detect, because obstructive uropathy is often reversible if identified early. Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. The anterior surface faces towards the anterior abdominal wall, whereas the posterior surface is facing the posterior abdominal wall. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. A, Axial image demonstrates the dilated renal pelvis and crossing vessel. A prominent bar of renal cortex situated between the superior and interpolar regions of the kidney is called a column of Bertin and is occasionally mistaken on ultrasound for a renal mass. Because production of creatinine is affected by sex, age, muscle mass, protein intake, and liver function, the serum creatinine can be an inaccurate predictor of renal function, particularly in those at the extremes of age and body weight. Hypotension is a stimulus for the kidneys to increase the retention of fluid and thus increase blood pressure. B, Mild hydronephrosis results in rounding of the fornices with mild shortening of the papillary impression. The kidney tissue is protected by three layers that entirely surround the kidney: Outside the fascia is the most superficial layer a layer of fat tissue called the paranephric fat. Each pyramid creates urine and terminates into a renal papilla. The kidneys help remove waste products from the . Calculation of the estimated renal volume is considered by some to be the most accurate assessment of renal size available with ultrasound, although renal length alone is more commonly reported. BOX 18-1 Cockroft and Gault Equation for Calculating Estimated Creatinine Clearance. Yet, the relations of the kidneys with other organs are often found in Anatomy tests. However, T1-weighted images provide good corticomedullary differentiation. So the pyramids represent the functional tissue that creates urine, whereas the calyces are the beginning of the ureter and transport the urine to it. Unlike the excretory phase of enhanced CT, signal intensity within the renal collecting systems is reduced on T1- and T2-weighted MR images once excreted gadolinium-based contrast media becomes sufficiently concentrated. Because an extrarenal pelvis is not confined by the renal parenchyma, there is a tendency for it to expand. Renal size can be measured in several ways. Accurate preoperative imaging protects the healthy donor from complications related to unanticipated variant anatomy. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. This is because the liver and the stomach offset the symmetry of the abdomen, with the liver forcing the right kidney a bit down, and the stomach forcing the left kidney a bit up. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. Some centers use diuretics or fluid bolus, or both, during CT urography to dilute the excreted contrast to improve assessment of the urothelium. A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the renal medulla (Figure 25.1.2). Unlike the excretory phase of enhanced CT, signal intensity within the renal collecting systems is reduced on T1- and T2-weighted MR images once excreted gadolinium-based contrast media becomes sufficiently concentrated. Illustration demonstrating the relation between the renal papilla and calyx. CT scan and MRI to help diagnose and stage kidney masses. The kidneys are innervated by the renal plexus. The anteromedial, aspect of the interpolar region is interrupted by the renal hilum to make a C shape. The vessel which brings blood into the glomerulus is the afferent arteriole, whereas the vessel that carries the rest of the blood out that hasnt been filtered out of the glomerulus is called the efferent arteriole. Figure 18-11 Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. If the renal pelvis extends out of the renal sinus, it is considered to be an. Causes. There are 8-18 renal pyramids in each kidney, that on the coronal section look like triangles lined next to each other with their bases directed toward the cortex and apex to the hilum. These terminal branches have no collateral circulation. A bean-like structure like the kidney has two borders: medial and lateral. The early excretory phase begins as early as 120 seconds after injection. The superior half of each kidney is covered by the diaphragm, which is why the kidneys move up and down during respiration. It doesn't have to be that way. Comparative views of the CT scan ( a axial, b coronal, and c sagittal planes) and corresponding views of the physical model ( d superior view, e median view, and f median view). I hope this helps. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Depending on where the cyst is located, it can affect how the kidney works. In some cases, two separate kidneys drain into a bifid renal pelvis, ultimately drained by a common ureter. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. Log In or, Click to share on Twitter (Opens in new window), Click to share on Facebook (Opens in new window), Click to share on Google+ (Opens in new window), Estimated Creatinine Clearance and Glomerular Filtration Rate, Cockroft and Gault Equation for Calculating Estimated Creatinine Clearance, The Modification of Diet in Renal Disease (MDRD) is another method for estimating renal function that yields a value often called, The kidneys can be divided into three main regions from cranial to caudal. Each time a professor says 'nephron', a student gets a headache. The right kidney has a normal appearance (not shown). CT and MR findings of renal artery stenosis parallel classic findings described on intravenous pyelogram, including one atrophic kidney with delayed nephrogram and excretion that can progress to a persistent nephrogram with hyperconcentrated excreted contrast media (Fig. The isthmus connecting the kidneys is variable, ranging from normal renal cortex to a thin fibrous band. "Angio" indicates blood vessels, "myo" indicates muscle, and "lipoma" indicates fat. If the renal pelvis extends out of the renal sinus, it is considered to be an extrarenal pelvis (Fig. Unenhanced CT can identify hydronephrosis and hydroureter, urinary stones, and some masses. February 12, 2018 - 2:17pm Cells in our body constantly produce hydrogen ions. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. Computed Tomographic Evaluation for Renal Failure, Magnetic Resonance Evaluation for Renal Failure. The main symptom is severe sharp pain that starts suddenly, usually in your belly or one side of your back, and it may go away just as quickly. B, A curved planar reformation of the crossing vein demonstrates its course. Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. The hilum of the kidney usually projects at the level of the L2 vertebra. On ultrasound, the renal cortex is usually echogenic in this setting. The main unit of the medulla is the renal pyramid. 18-10). The center of the minor concavity is marked as the hilum of the kidney where the renal artery enters the kidney, and the renal vein and ureter leave the kidney. 18-19). Crossed ectopia can be either fused or unfused. Duplication affects the axial appearance of the kidneys by dividing the renal sinus into superior and inferior components, separated by a circumferential band of cortex in the central region (Fig. Figure 18-10 Crossed ectopia on intravenous pyelogram. The kidneys serve important . IVC, Inferior vena cava. Chronic glomerulonephritis usually causes bilateral increased renal echogenicity with smooth atrophy, whereas renal artery stenosis usually causes a similar but unilateral appearance (Fig. Copyright 18-19). A, Enhancement of the mass is conspicuous in the corticomedullary phase. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. print Print this Article Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. Although ureteral contrast media is typically present before 3 minutes, longer delays provide more predictable opacification. The presence of contour irregularity usually indicates scarring, suggesting prior infection, reflux, or infarction. There are many clinical states related to kidney malfunction. Furthermore, since the left renal vein passes between the superior mesenteric artery and the abdominal aorta, an enlargement of the superior mesenteric artery can compress the left renalvein and cause an obstruction of drainage from all three structures that use the left renal vein for drainage (left suprarenal gland, left kidney, and left testicle). development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. Parasympathetic innervation enhances the peristalsis while sympathetic innervation inhibits it. Also, in situations with notable blood losses, kidneys release a hormone called erythropoietin, which stimulates bone marrow to produce more blood cells. Perhaps of even greater importance, serum creatinine is not a sensitive test for minor insults to the kidney in otherwise healthy individuals. Register now The lateral border is directed towards the periphery, while the medial border is the one directed towards the midline. The glomerulus is actually a web of arterioles and capillaries, with a special filter which filters the blood that runs through the capillaries, the glomerular membrane. The parenchyma of the kidney consists of the outer renal cortex, and inner renal medulla. Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. The corticomedullary phase is prolonged in the presence of ureteral or venous obstruction and can persist for days in cases of acute tubular necrosis (ATN; Fig. A. Junctional cortical line seen on a long-axis ultrasound image of the right kidney. In most cases, the kidneys are situated with the inferior poles slightly more lateral and anterior than the superior poles. 18-28). This illustrates the amount of reserve function that must be compromised before renal injury can be detected with a serum creatinine level. Most radiologists consider 10 to 12 cm to be an approximate reference range for renal length in adults, allowing for an additional 1 cm in either direction for patients at the extremes of height. 18-18). Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Recent advances in MDCT and MRI permit cross-sectional vascular studies to replace conventional angiography before UPJ repair (Fig. The renal pelvis then tapers like a funnel to join the ureter. For most of the students, the nephron is a mystical complexed structure that may be hard to understand. Renal Cysts. The most common cause is renal artery stenosis (see Fig. An acute change in renal cortical echogenicity is occasionally seen with pyelonehritis. 18-3). 18-25). The most superior vessel is the renal vein which exits the kidney, just under it is the renal artery that enters in, and under the artery is the exiting ureter. The glomerular membrane is designed in a way in which it is not permeable for big and important molecules in blood, such as plasma proteins, but it is permeable to the smaller substances such as sodium, potassium, amino acids and many others. It is important to note, however, that the appearance of hydronephrosis does not necessarily indicate urinary obstruction (see Hydronephrosis and Its Mimics section later in this chapter). Weve mentioned that the most important functions of the kidney are the regulation of the blood homeostasis and blood pressure, so acute kidney failure can lead to a quick fall of blood pressure which presents as a state of shock. Multidetector computed tomography examination of the kidney is a stimulus for the kidneys move and! One directed towards the anterior abdominal wall is often reversible if identified early identified early donor.. Creatinine is not confined by the diaphragm, which are the major convexity laterally, and minor concavity medially clubbed. 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