Figure 18-24 Normal magnetic resonance imaging appearance of the kidneys. 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. During the 6th to 9th weeks of life, the kidneys begin to ascend from their position in the pelvis to the level of T12-L1, inferior to the adrenal glands. * Entities for which sonography is most useful. Sometimes, one or both kidneys fail to develop, which causes unilateral or bilateral renal agenesis. The medulla is the inner region of the parenchyma of the kidney. Some tumors can be slow to grow while some can be aggressive. 18-19). Parasympathetic innervation enhances the peristalsis while sympathetic innervation inhibits it. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. There are many clinical states related to kidney malfunction. The kidneys help remove waste products from the . and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. Approximately 1 year before presentation, the patient experienced a similar episode of right flank pain that prompted an unenhanced CT examination of the abdomen and pelvis at an outside institution. A, Soft-tissue windows demonstrate no filling defect. A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the medulla. 18-4). If the renal pelvis extends out of the renal sinus, it is considered to be an. It protects your kidneys from injury, increases their stability and connects your kidneys to surrounding tissues. BOX 18-3 Causes of Bilateral Hydronephrosis. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. A, Tips of the fornices are sharply defined. 18-19). The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. Around 40% of kidney cancers are localized renal masses. Creatinine is a breakdown product of creatine, found within muscle. Duplication of the urinary tract is discussed in detail in Chapter 19. The calcium or uric acid will precipitate and form stones. It is notable that the kidney has a very rich blood supply. Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. When the renal cortex is more echogenic than the adjacent liver, there is a high correlation with renal disease, although sensitivity is relatively low, according to Platt and colleagues (Fig. Identify abnormal course of main or accessory right renal artery anterior rather than posterior to inferior vena cava (Fig. Because the interlobular arteries form an arch overlying the pyramid, they are called the. Extraaortic origin of the renal arteries and accessory renal arteries are common. The left kidney appeared unremarkable. For most of the students, the nephron is a mystical complexed structure that may be hard to understand. Small renal shadows may be seen on radiographs, and reniform shape is preserved on cross-sectional imaging. Relation between the right renal artery and the inferior vena cava (IVC). The kidney is a very important organ in regards to body homeostasis. Note that the left renal vein receives blood from the left suprarenal and left testicular veins. However, you may have symptoms related to the condition that's causing it. The left renal vein passes anteriorly to the aorta just below the trunk of the superior mesenteric artery, which is risky because it can be compressed by one of those two. Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. Created for people with ongoing healthcare needs but benefits everyone. 18-9). 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. Thus, any upward trend in the serum creatinine value should be viewed with concern when considering the administration of potentially nephrotoxic or renally excreted intravenous contrast media. 18-13). A, Axial image from contrast-enhanced computed tomography (CT) demonstrates an accessory right renal artery coursing anterior to the IVC. The defect is the extension of sinus fat into the cortex, usually at the border of the upper pole and interpolar region of the kidney. In adults, the normal kidney is 10-14 cm long in males and 9-13 cm long in females, 3-5 cm wide, 3 cm in antero-posterior thickness and weighs 150-260 g. The left kidney is usually slightly larger than the right. If the renal pelvis extends out of the renal sinus, it is considered to be an extrarenal pelvis (Fig. The renal veins empty to the inferior vena cava, so the right vein is shorter because the inferior vena cava runs closer to the right kidney. Grounded on academic literature and research, validated by experts, and trusted by more than 2 million users. The MDRD calculation is more complicated than calculating creatinine clearance (taking into account body surface area, sex, and race) but is thought to be more accurate than estimated creatinine clearance, particularly among the elderly and obese. 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). CT scan and MRI to help diagnose and stage kidney masses. B, Low-attenuation lesion in the late nephrographic/early excretory phase is less suspicious in appearance. People with unilateral agenesis often are unaware that they lack one kidney until an accidental discovery, since the one kidney that they have is able to functionally compensate for the other. These terminal branches have no collateral circulation. When fused, the condition is described as crossed fused ectopia. Note diameter of arteries because small accessory arteries may be sacrificed in many cases. The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. Figure 25.1.2 Left Kidney. The information we provide is grounded on academic literature and peer-reviewed research. In this region, the anterior and posterior. 18-10). Figure 18-16 Coronal reformation from contrast-enhanced computed tomography performed for renal donation demonstrates a retroaortic left renal vein crossing the aorta well inferior to the level of the renal hila. B, Axial CT image from a different patient demonstrates the more common location of the right renal artery posterior to the IVC. A, Steady-state free precession, (B) T2-weighted with fat saturation, (C) T1-weighted, (D) T1-weighted with fat saturation, (E) postcontrast corticomedullary phase, and (F) postcontrast nephrographic phase. On ultrasound, the renal cortex is usually echogenic in this setting. When simple kidney cysts do cause symptoms, they might include: Pain in the side between the ribs and hip, stomach or back. When the fine, weblike complex of ureteral arteries is recruited to contribute to collateral circulation, enlarged vessels are seen surrounding the proximal ureter, causing the classic ureteral notching seen on intravenous urogram (IVU). Look for duplication, large extrarenal pelvis. Figure 18-4 Illustration demonstrating the relation between the renal papilla and calyx. Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. The kidneys are bilateral organs placed retroperitoneally in the upper left and right abdominal quadrants and are part of the urinary system. Crossed ectopia on intravenous pyelogram. Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. MR angiography can be useful for the diagnosis of renal vascular abnormalities. and grab your free ultimate anatomy study guide! This plexus provides input from: The sensory nerves from the kidney travel to the spinal cord at the levels T10-T11, which is why the pain in the flank region always rises suspicions that something is wrong with the corresponding kidney. Figure 18-11 Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. Table 18-7 lists causes of unilateral smooth renal atrophy. They are staged the same way as the renal pelvis. Horseshoe kidneys result from midline fusion of the kidneys, typically at the level of the origin of the inferior mesenteric artery. Concerning lymphatic drainage, each kidney drains into the lateral aortic (lumbar) lymph nodes, which are placed around the origin of the renal artery. Note that there is no contrast in the aorta. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. 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. Table 18-6 lists the most common causes of bilateral smooth renal atrophy. Any excessive amount of fluid will increase the pressure on the arterial wall and cause the blood pressure to rise (hypertension). However, T1-weighted images provide good corticomedullary differentiation. Reviewer: This causes them to fire impulses which stimulate rhythmical contraction and relaxation, called peristalsis. This layer sits posteriorly and posterolaterally to each kidney and separates it from the muscles of the abdominal wall. The ureters are the tubes that carry urine from the renal pelvis to the bladder. Simple kidney cysts aren't cancer and rarely cause problems. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. While migrating superiorly, the kidneys rotate medially along their long axes and the inferior supplying mesonephric arteries degenerate. 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. Anatomy of the Kidney and Ureter Parenchyma Cortex Medulla Perirenal fat Capsule Ureter Serum creatinine, however, is dependent not only on its disposal but also its production. Overview. Table 18-7 lists causes of unilateral smooth renal atrophy. Made aware of such a vessel, the urologist may choose to perform an alternate procedure to avoid hemorrhagic complications. Technetium 99m dimercaptosuccinic acid (DMSA) and glucoheptonate (GHA) are both used for evaluation of renal parenchyma. In some cases, two separate kidneys drain into a bifid renal pelvis, ultimately drained by a common ureter. Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. The lateral border is directed towards the periphery, while the medial border is the one directed towards the midline. The large left proximal ureteral stone seen in this image is only partially obstructing, causing mild dilation in the left kidney collecting system. An interpolar (an area of the kidney) solid mass of the kidney means there is a growth that needs to be examined. It doesn't have to be that way. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (which is in between them). Advantages of scintigraphy include accurate quantitative measurement of function and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. Most diagnosed kidney growths are small and localized masses. CT is occasionally used to evaluate patients with renal failure. Aggressive tumors form, grow and spread very quickly. Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. The small portion of the lumen surrounding the papilla is called the calyx. 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. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. Figure 18-26 Ultrasound performed for acute renal failure demonstrates bilateral hydronephrosis caused by a bladder tumor. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Pain that radiates to the lower abdomen and groin. Extraaortic origin of the renal arteries and accessory renal arteries are common. 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). An acute change in renal cortical echogenicity is occasionally seen with pyelonehritis. 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). Of course, if the situation is the other way around (less than 5 liters of blood), blood pressure is too low (hypotension). In other cases, each renal unit has its own ureter. Kenhub. Figure 18-25 Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. The main parts of your kidney anatomy include: Kidney capsule (renal capsule) The renal capsule consists of three layers of connective tissue or fat that cover your kidneys. Dimitrios Mytilinaios MD, PhD In other cases, each renal unit has its own ureter. 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). On the other hand, kidneys do have relations with peritoneum, or precisely with the specific organs that are covered with peritoneum which are placed directly adjacent to the kidneys. 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). Table 18-5 Checklist Approach to Ultrasound for Renal Failure. 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. Arterial stenosis was confirmed by magnetic resonance angiography. Computed Tomographic Evaluation for Renal Failure, Magnetic Resonance Evaluation for Renal Failure. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. The defect is the extension of sinus fat into the cortex, usually at the border of the upper pole and interpolar region of the kidney. 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. This is called the nutcracker phenomenon. Some centers use diuretics or fluid bolus, or both, during CT urography to dilute the excreted contrast to improve assessment of the urothelium. Pearl: Any upward trend in serum creatinine value should be viewed with concern because it implies renal reserve function has already been affected. At the Brady Urological Institute, we believe in the adage, "An ounce of prevention is worth a pound of cure," so we place great emphasis on a thorough metabolic evaluation, so that therapies can be appropriately directed towards reducing the risk of recurrent stone disease. Axial images of the left kidney from a three-phase renal computed tomographic scan demonstrate improved conspicuity of low-attenuation lesions of the renal medulla during the nephrographic phase. These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. So in the filtered fluid that goes to the renal tubule, we have both necessary and unnecessary substances. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. On the other hand, babies with bilateral agenesis cannot survive without an immediate kidney transplant. a bifid renal pelvis, ultimately drained by a common ureter. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. The main function of the kidney is to eliminate excess bodily fluid, salts and byproducts of metabolism this makes kidneys key in the regulation of acid-base balance, blood pressure, and many other homeostatic parameters. When the renal cortex is more echogenic than the adjacent liver, there is a high correlation with renal disease, although sensitivity is relatively low, according to Platt and colleagues (Fig. Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Other malfunctions of the kidney are presented through acute kidney failure, a serious and urgent medical condition. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. normal kidney size in adults normal kidney size in children Structure It participates in vital processes such as regulation of blood osmolarity and pH, regulation of blood volume and blood pressure, production of hormones, and filtration of foreign substances. These are chronic processes that lead to a loss of renal cortex gradually and uniformly. 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). Even when there is another plausible explanation for decreased renal function (e.g., known prerenal causes), ultrasound offers the opportunity to rapidly and noninvasively identify a potentially correctible cause of renal failure. In adults, the normal kidney is 10-14 cm long in males and 9-13 cm long in females, 3-5 cm wide, 3 cm in antero-posterior thickness and weighs 150-260 g. The left kidney is usually slightly larger than the right. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. Renal artery You can test yourself on the renal arteries with our quiz. Localized means that the tumor has not spread out from where it first started. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. Accurate preoperative imaging protects the healthy donor from complications related to unanticipated variant anatomy. Table 18-7 Causes of Unilateral Small Smooth Kidney, Only gold members can continue reading. 18-19). 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. If the renal pelvis is entirely within the confines of the renal sinus, it is considered intrarenal. Renal function is better evaluated by measured creatinine clearance, which takes into account not only the amount of creatinine in the blood but also the amount of creatinine within a specified volume of urine over a given period. In most kidneys, the renal hilum faces more anteromedial in the upper half of the kidney and more directly medial in the lower half. In order to understand the functions of the kidney, we must first learn its anatomy. development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. Estimated creatinine clearance may be calculated using serum creatinine with adjustments made for sex, age, and body weight. Internal Anatomy. Depending on where the cyst is located, it can affect how the kidney works. 18-25). Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. For that reason, we got you covered with this topic nicely and concisely. As the lobules of metanephric blastema coalesce to form each kidney, they do not always result in a smooth, uniform band of cortex. Read More Created for people with ongoing healthcare needs but benefits everyone. 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. Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. 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. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. Anterior components of circumaortic vein can be small. Since they are located deep retroperitoneally, the easiest way to examine them is from the patients back. 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). Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. Renal size can be measured in several ways. Diabetes, hypertension, acute tubular necrosis, Increased echogenicity has high association with parenchymal disease, Acute tubular necrosis usually results in an increased RI, whereas prerenal causes usually do not have an increased RI; postrenal causes often increase the RI, but hydronephrosis should be present in those cases, If present, suspect neurogenic bladder or outlet obstruction, Often severe aortic disease or fibromuscular dysplasia. 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). The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. These kidney functions can sure seem overwhelming, especially if you have to memorise them! The most common cause is renal artery stenosis (see, Delayed but increasingly dense nephrogram, Delayed but hyperconcentrated contrast excretion, Imaging Evaluation of Acute Abdominal Pain, A Multidimensional Approach to Abdominal Imaging. Renal Cysts. Because they rarely cause symptoms, renal cysts are most often found during . The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. 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. Dialysis. Conventional surgery for congenital UPJ obstruction involves an open pyeloplasty, in which some tissue is removed from the wall of the saclike renal pelvis to form a more tapered, efficient, funnel-shaped renal pelvis. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see. The anteromedial aspect of the interpolar region is interrupted by the renal hilum to make a C shape. 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. 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. Now that weve mastered the borders, it will be easier to take a closer look at the anatomical relations that the kidneys share with other abdominal structures. The left artery has a short way to the left kidney, whereas the right has to go behind the inferior vena cava in order to reach the right kidney. Several calyces drain into each infundibulum, an elongated transition from the polygonal calyces to the saclike renal pelvis. 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. B, Mild hydronephrosis results in rounding of the fornices with mild shortening of the papillary impression. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. However, this individual is more likely to show a decline in renal function from an additional insult. This kidney measured 14 cm in length. A. Junctional cortical line seen on a long-axis ultrasound image of the right kidney. 18-1). 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. The normal appearance of the calyx is created by the impression of the renal papilla. This phenomenon is due to T2-shortening and susceptibility (T2*) effects caused by concentrated gadolinium, and can potentially obscure filling defects and urothelial lesions. 18-20). Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. Right-sided pain was related to crossed renal ectopia. It can be caused by a variety of factors, but most often arises because of the ischemia of the kidney and the toxic effect of some medications, resulting in the failure of all kidney functions. The phases of nephrogram. For most people, obstruction of a single ureter does not induce renal failure. The vascularity of some tumors may be most apparent during this phase (Fig. The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. Some forms of congenital UPJ obstruction are now treated with transureteroscopic endopyelotomy in which an incision is made from within the ureter using a ureteroscope. 18-16). The most common cause is renal artery stenosis (see Fig. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. Kidney cysts are round pouches of fluid that form on or in the kidneys. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). I hope this helps. Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. Maintaining kidney health. CT angiography is occasionally performed when a vascular causative factor is suspected (renal artery stenosis or renal vein thrombosis) and MRI is contraindicated. Note origin of inferior accessories near inferior poles on each side. Read more. This is why the kidney is essential for the circulatory hemostasis. 2023 Right-sided pain was related to crossed renal ectopia. Sagittal ultrasound image of the right kidney demonstrates increased size and echogenicity of the kidney, findings typical of human immunodeficiency virus nephropathy. Figure 18-23 Axial image of the left kidney obtained in the excretory phase of a computed tomographic urogram demonstrates the effects of window settings on visualizing structures near excreted contrast. Publication types Review MeSH terms Humans When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. It is also permeable for the products of the metabolism, such are creatinine and drug metabolites. Table 18-5 summarizes a checklist approach to the ultrasound examination. Learn how we can help 1.2k views Reviewed Dec 09, 2022 Thank Dr. Frank Kuitems and 4 doctors agree 3 thanks Medullary cystic disease is encountered only rarely, and in addition to the echogenic atrophic cortex, the medullary pyramids are particularly hypoechoic. Figure 18-17 Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein.
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interpolar region of kidney anatomy