At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. Each time a professor says 'nephron', a student gets a headache. Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. 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). The goal of imaging patients with renal failure is to identify a correctable cause in an effort to recover or preserve renal function. Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. The kidneys are located between your intestines and your diaphragm. However, T1-weighted images provide good corticomedullary differentiation. 18-25). A bean-like structure like the kidney has two borders: medial and lateral. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. Identify abnormal course of main or accessory right renal artery anterior rather than posterior to inferior vena cava (Fig. Note diameter of arteries because small accessory arteries may be sacrificed in many cases. Concerning lymphatic drainage, each kidney drains into the lateral aortic (lumbar) lymph nodes, which are placed around the origin of the renal artery. Axial sections of the right kidney from contrast-enhanced computed tomography demonstrate a bar of renal parenchyma separating renal hila in the superior and inferior poles, consistent with duplication. Poorly functioning kidneys with little residual parenchymal volume may be removed because preservation offers opportunities for future complications (infection, hypertension) without contributing significantly to renal function. Both renal arteries, left and right, arise just below the superior mesenteric artery, with the left renal artery positioned slightly superiorly to the right one. and grab your free ultimate anatomy study guide! The axes of the renal moeities are abnormal with the inferior poles angled medially. The genital system consists of the testes, epididymides, deferent ducts, seminal vesicles, ejaculatory ducts, the prostate, and the penis in males; and the ovaries, uterine tubes, uterus, and vagina in females. The presence of contour irregularity usually indicates scarring, suggesting prior infection, reflux, or infarction. Figure 18-14 Axial maximum intensity projection image from the arterial phase of a contrast-enhanced computed tomographic scan from a prospective renal donor demonstrates early prehilar branching of the left renal artery. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. February 12, 2018 - 2:17pm Relation between the right renal artery and the inferior vena cava (IVC). Figure 18-27 T2-weighted maximum intensity projection image from a magnetic resonance urogram performed to evaluate urinary obstruction identified in a patient with an obstructing soft tissue mass in the pelvis on unenhanced computed tomography (CT). Some divide the excretory phase into the early excretory phase (contrast mainly confined to the kidney) and late excretory phase (contrast in the ureters). RENAL ANATOMY Renal Parenchyma The kidneys can be divided into three main regions from cranial to caudal. The renal corpuscle has two components: the glomerular (Bowmans) capsule in which sits the glomerulus. The kidneys are highly vascular (contain a lot of blood vessels) and are divided into three main regions: the renal cortex (outer region which contains about 1.25 million renal tubules), renal medulla (middle region which acts as a collecting chamber), and renal pelvis (inner region which receives urine through the major calyces). A, Axial image demonstrates the dilated renal pelvis and crossing vessel. Arterial stenosis was confirmed by magnetic resonance angiography. If, however, a vessel crosses the UPJ at the level of obstruction, a blind incision made from the inside of the ureteral lumen can result in severe hemorrhage. The kidneys have two functional areas that are managed and staged independently, the kidney parenchyma and the renal pelvis. Volume rendering from a computed tomographic scan of the kidneys shows bilateral supernumerary renal arteries (three on right, two on left). 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. The relation between the UPJ and vascular anatomy can be quite complex. Note origin of inferior accessories near inferior poles on each side. However, you may have symptoms related to the condition that's causing it. Figure 18-11 Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. However, small, low-attenuation lesions in the medulla are often obscured during this phase. Normal magnetic resonance imaging appearance of the kidneys. Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. 18-18). The hilum of the kidney usually projects at the level of the L2 vertebra. Causes. A potential benefit of MRI is the lack of exposure to ionizing radiation, although unenhanced CT would still be required to detect stones (the presence of stones increases the donors risk for renal insufficiency later in life and could disqualify them as a donor candidate). Internal Anatomy. 18-13). 18-19). Use of MR contrast agents in renal failure poses a lower risk than iodinated contrast material for exacerbating renal failure, but there is evidence that gadolinium-based MR contrast media pose some risk for systemic complications (nephrogenic systemic fibrosis) and should be used with caution in patients with severe or acute renal insufficiency. Ultrasound can often identify the cause in cases of bilateral obstruction (Fig. normal kidney size in adults normal kidney size in children Structure Because repeat imaging does not expose the patient to additional radiation, multiple phases including delayed images may be obtained and allow the creation of quantitative curves that define the initial filling and then clearing of dilated collecting system structures. In some cases, two separate kidneys drain into a bifid renal pelvis, ultimately drained by a common ureter. The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. Figure 18-15 Relation between the right renal artery and the inferior vena cava (IVC). Pitfall: An extrarenal pelvis may be mistaken for hydronephrosis. The renal cortex is part of your kidney, which itself is part of the urinary tract. 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. Anatomical Position of the Kidneys Kidney Structure Curated learning paths created by our anatomy experts, 1000s of high quality anatomy illustrations and articles. When multiple clefts in the renal cortex are present throughout the kidney, it is described as fetal lobulation. Imaging must provide detailed images of the renal parenchyma and a survey of arterial, venous, and ureteral anatomy. The muscular relations of the inferior half are easy to remember by dividing the kidney surface into three vertical stripes, where the medial stripe represents the impression of the psoas major muscle, the central stripe the quadratus lumborum, and the lateral stripe the transversus abdominis muscle. If the renal pelvis extends out of the renal sinus, it is considered to be an. Illustration demonstrating the relation between the renal papilla and calyx. Computed Tomographic Evaluation for Renal Failure, Magnetic Resonance Evaluation for Renal Failure. 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. They are branches of the abdominal aorta and all together are called the extrahilar renal arteries. Hydronephrosis is important to detect, because obstructive uropathy is often reversible if identified early. The phases of nephrogram. Solid masses are more likely to be cancerous but they are not all cancerous. Figure 18-21 Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. Most serum creatinine is excreted in the urine; therefore, if renal function is compromised, levels of creatinine in the serum increase. The information we provide is grounded on academic literature and peer-reviewed research. Each pyramid creates urine and terminates into a renal papilla. The right kidney had a similar appearance (not shown). The apex of the pyramid projects medially toward the renal sinus. Author: Computed Tomographic Appearance of the Kidneys, Utility of Different Phases of Renal Contrast Enhancement. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Chronic glomerulonephritis usually causes bilateral increased renal echogenicity with smooth atrophy, whereas renal artery stenosis usually causes a similar but unilateral appearance (Fig. This layer sits posteriorly and posterolaterally to each kidney and separates it from the muscles of the abdominal wall. Ultrastructurally, the nephron is the functional representative of the kidney. The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. You can test yourself on the renal arteries with our quiz. The upper pelvis is the most common ectopic location for the kidney; most cases are also associated with abnormalities of rotation. This kidney measured 14 cm in length. normal kidney size in adults normal kidney size in children Structure Axial maximum intensity projection image from the arterial phase of a contrast-enhanced computed tomographic scan from a prospective renal donor demonstrates early prehilar branching of the left renal artery. The posterior branch supplies the posterior part of the kidney, whereas the anterior branch arborizes into five segmental arteries, each supplying a different renal segment. The phases of nephrogram development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. Copyright 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. This is called the nutcracker phenomenon. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. 18-6). Each end of the kidney is commonly called a pole. more lateral and anterior than the superior poles. and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. Table 18-6 lists the most common causes of bilateral smooth renal atrophy. Lets start with the right kidney anterior surface. 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. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). Learn more about the anatomy of the kidneys and the urinary system with our urinary system quizzes and labeled diagrams. The anterior surface of the left kidney, has the following anatomical relations: The posterior surfaces of both kidneys are related to certain neurovascular structures and muscles: You can easily remember these with the mnemonic: 1-2-3-4 All Boys Need Muscle. 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. Diagnostic ultrasound uses sound wave technology to look at parts of your body, including: Brain Heart and blood vessels Breast Abdominal Organs Eyes Thyroid Skin and muscles Types of Ultrasound. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. Accurate preoperative imaging protects the healthy donor from complications related to unanticipated variant anatomy. When fused, the condition is described as crossed fused ectopia. B, Mild hydronephrosis results in rounding of the fornices with mild shortening of the papillary impression. Living renal donor allografts account for more than half of the transplanted kidneys in the United States. Although this dilatation of the renal pelvis may occasionally mimic hydronephrosis, delicate and sharply defined calyces and thin infundibula can be used to differentiate an extrarenal pelvis from obstruction. 18-16). 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. Figure 18-19 Sagittal ultrasound image of the right kidney demonstrates increased size and echogenicity of the kidney, findings typical of human immunodeficiency virus nephropathy. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. Figure 18-13 Volume rendering from a computed tomographic scan of the kidneys shows bilateral supernumerary renal arteries (three on right, two on left). The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. Although each kidney is about the size of a fist, the approximately one million nephrons per kidney require nearly 20% of the total cardiac output to perform this multitude of functions. Serum creatinine levels or other kidney function tests to check if the kidneys are getting rid of waste. 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