Unenhanced CT can identify hydronephrosis and hydroureter, urinary stones, and some masses. When. General symptoms of kidney problems include: blood in your urine . There are many clinical states related to kidney malfunction. Summary: A variety of factors, including patient body habitus, local renal anatomy, cost and patient preference, must be taken into consideration when determining the optimal treatment modality for lower pole renal calculi. The parenchyma of the kidney consists of the outer renal cortex, and inner renal medulla. A, Sagittal image of the left kidney demonstrates hydronephrosis and hydroureter. For most people, obstruction of a single ureter does not induce renal failure. The kidneys are bilateral organs placed retroperitoneally in the upper left and right abdominal quadrants and are part of the urinary system. Enlargement of a congenitally unilateral kidney is typical and presumed to be compensatory. However, T1-weighted images provide good corticomedullary differentiation. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. A, Tips of the fornices are sharply defined. There is no specific treatment for fused kidneys and the only option is to treat the pathologies that affect them during life. Figure 18-1 Annotated three-dimensional volume rendering of the left kidney acquired using a combined nephrographic phase and excretory phase during computed tomographic urography demonstrates regional anatomy of the kidney. 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). Volume rendering from a computed tomographic scan of the kidneys shows bilateral supernumerary renal arteries (three on right, two on left). The left kidney appeared unremarkable. AMLs can bleed and while not cancerous are still taken very seriously. 18-24). In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. 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. RENAL ANATOMY Renal Parenchyma The kidneys can be divided into three main regions from cranial to caudal. Table 18-1 Imaging the Living Renal Donor. 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. The right kidney had a similar appearance (not shown). On ultrasound, the renal cortex is usually echogenic in this setting. Kidneys are located just below your ribcage and behind your belly. Note number of veins by inspecting inferior vena cava along entire length of kidney. 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. A bean-like structure like the kidney has two borders: medial and lateral. The upper pelvis is the most common ectopic location for the kidney; most cases are also associated with abnormalities of rotation. The region where the renal pelvis joins the ureter is called the ureteropelvic junction (UPJ). Identify abnormal course of main or accessory right renal artery anterior rather than posterior to inferior vena cava (Fig. 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. Note that retroaortic components are usually near the inferior poles (Fig. Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. IVC, Inferior vena cava. normal kidney size in adults normal kidney size in children Structure B, Transverse image of the bladder demonstrates a large bladder tumor in the region of the trigone. 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. Note that there is no contrast in the aorta. 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. 18-23). The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. 18-25). When this happens, the stones can block the flow of urine out of your kidneys. Because the fascia of the retroperitoneum prevents significant extravasation, the incision usually heals to form a larger lumen. Extraaortic origin of the renal arteries and accessory renal arteries are common. 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 renal pelvis then tapers like a funnel to join the ureter. Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. Also, in situations with notable blood losses, kidneys release a hormone called erythropoietin, which stimulates bone marrow to produce more blood cells. Look for retroaortic or circumaortic left renal vein. Thoracic kidneys are the least common form of renal ectopia. In most cases, unenhanced CT is performed when the duration and cause of renal failure are unknown because exposure to iodinated contrast media could impair recovery of renal function. 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. Kidney cysts can occur with disorders that may impair kidney function. The kidneys are positioned retroperitoneally, meaning that they are not wrapped with the peritoneal layers the way most abdominal organs are, but rather are placed behind it. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney 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. Fetal lobulation is best differentiated from renal scars during the corticomedullary phase of enhancement on computed tomography (CT) or magnetic resonance imaging (MRI) because cortex can be followed into the indentation that occurs between calyces (Fig. Typically, one kidney sits on either side of your spine. Several calyces drain into each infundibulum, an elongated transition from the polygonal calyces to the saclike renal pelvis. print Print this Article Some tumors can be slow to grow while some can be aggressive. Table 18-7 lists causes of unilateral smooth renal atrophy. A junctional cortical line is a common septum of capsule typically seen on ultrasound as an echogenic line at the site of fusion between the superior pole and middle third of the kidney (Fig. Right-sided pain was related to crossed renal ectopia. Pitfall: An extrarenal pelvis may be mistaken for hydronephrosis. 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. 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. Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. Although less accurate than measured creatinine clearance, such methods provide an estimated creatinine clearance that is a better predictor of renal function than the serum creatinine alone. Figure 18-3 Illustration demonstrating basic intrarenal arterial anatomy. This article will discuss the anatomy and major functions of the kidney. BOX 18-1 Cockroft and Gault Equation for Calculating Estimated Creatinine Clearance. The initiation is caused by the increase in volume that stretches the walls of the calyces. more lateral and anterior than the superior poles. Medullary cystic disease is encountered only rarely, and in addition to the echogenic atrophic cortex, the medullary pyramids are particularly hypoechoic. Learn how we can help 1.2k views Reviewed Dec 09, 2022 Thank 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. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see Fig. 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. Anatomical Position of the Kidneys Kidney Structure The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. This significantly affects the testicle, since an obstruction of drainage causes an obstruction of fresh arterial blood inflow, which can result in the infarction of testicular tissue. Simple kidney cysts aren't cancer and rarely cause problems. The superior poles (extremities) (T12) of both kidneys are more medially pointed towards the spine than the inferior poles (extremities) (L3). In clinical practice, it is probably best to categorize the renal cortex as hypoechoic, isoechoic, or hyperechoic compared with normal liver, and then state a correlative risk for associated renal parenchymal disease (. Overview. Table 18-7 lists causes of unilateral smooth renal atrophy. Aggressive tumors form, grow and spread very quickly. It is notable that the kidney has a very rich blood supply. Other common kidney conditions are acquired through life, and one of the most common is nephrolithiasis (kidney stones). These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. The axes of the renal moeities are abnormal with the inferior poles angled medially. Figure 18-12 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. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. Right-sided pain was related to crossed renal ectopia. In addition to the renal artery, accessory renal arteries are present too. Living renal donor allografts account for more than half of the transplanted kidneys in the United States. It is important to remember this order of vessels and ducts since this is the only thing that will make you able to orient the kidney and differentiate the left one from the right when they are outside of the cadaver. The kidneys serve important . Table 18-1 provides a quick guide itemizing key imaging findings in the potential renal donor. In clinical practice, it is probably best to categorize the renal cortex as hypoechoic, isoechoic, or hyperechoic compared with normal liver, and then state a correlative risk for associated renal parenchymal disease (Table 18-2). 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). The interpolar region is the middle of the kidney. 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. B, Low-attenuation lesion in the late nephrographic/early excretory phase is less suspicious in appearance. Hypotension is a stimulus for the kidneys to increase the retention of fluid and thus increase blood pressure. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Figure 18-22 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. Sometimes, one or both kidneys fail to develop, which causes unilateral or bilateral renal agenesis. Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. 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. 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. Curated learning paths created by our anatomy experts, 1000s of high quality anatomy illustrations and articles. Occasionally, a papilla will communicate directly with an infundibulum or the renal pelvis and is considered to be an aberrant papilla. This kidney measured 14 cm in length. Table 18-6 lists the most common causes of bilateral smooth renal atrophy. 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. 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). 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. Unilateral renal agenesis occurs in approximately 1 in 1000 individuals with minimal impact on health, although it is sometimes associated with other congenital anomalies of the genitourinary tract and musculoskeletal system. 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). The kidneys are bilateral organs placed retroperitoneally in the upper left and right abdominal quadrants and are part of the urinary system. Most serum creatinine is excreted in the urine; therefore, if renal function is compromised, levels of creatinine in the serum increase. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. BOX 18-3 Causes of Bilateral Hydronephrosis. The normal appearance of the calyx is created by the impression of the renal papilla. and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. The calcium or uric acid will precipitate and form stones. Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (whi. Urine from the calyces flows to the renal sinus via tributaries called infundibula. a bifid renal pelvis, ultimately drained by a common ureter. Other malfunctions of the kidney are presented through acute kidney failure, a serious and urgent medical condition. Table 18-6 Causes of Bilateral Small Smooth Kidneys. This apical projection is called the renal papilla and it opens to the minor calyx. . Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. Because of this, the tubules are designed in a way that they reabsorb the necessary substances, (sodium, potassium, and amino acids as mentioned before) and carries them back to the blood; whereas they do not absorb but rather secrete unnecessary substances such as creatinine and drug metabolites for excretion from the body. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. Some centers use diuretics or fluid bolus, or both, during CT urography to dilute the excreted contrast to improve assessment of the urothelium. 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. 18-7). Renal scintigraphy can be performed with a variety of agents to provide assessment of either function or structure of the kidneys. In most cases, the kidneys are situated with the inferior poles slightly. Table 18-3 Utility of Different Phases of Renal Contrast Enhancement. 18-4). In other cases, each renal unit has its own ureter. Recent advances in MDCT and MRI permit cross-sectional vascular studies to replace conventional angiography before UPJ repair (Fig. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. 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). However, small, low-attenuation lesions in the medulla are often obscured during this phase. Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. Small renal shadows may be seen on radiographs, and reniform shape is preserved on cross-sectional imaging. Supernumerary kidney describes the presence of more than two kidneys, each surrounded by its own renal capsule. The goal of imaging patients with renal failure is to identify a correctable cause in an effort to recover or preserve renal function. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. The lateral border is directed towards the periphery, while the medial border is the one directed towards the midline. The renal corpuscle has two components: the glomerular (Bowmans) capsule in which sits the glomerulus. Estimated creatinine clearance may be calculated using serum creatinine with adjustments made for sex, age, and body weight. Author: Anatomy Where is the renal cortex? 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. 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