Retrograde urogram shows a calculus in the left ureter. The medulla consists of multiple pyramidal tissue masses, called the renal pyramids, which are triangle structures that contain a dense network of nephrons. 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. Some of them are congenital, such as a third kidney, which is usually atrophic. Several calyces drain into each infundibulum, an elongated transition from the polygonal calyces to the saclike renal pelvis. Created for people with ongoing healthcare needs but benefits everyone. 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. Renal scintigraphy can be performed with a variety of agents to provide assessment of either function or structure of the kidneys. Hypotension is a stimulus for the kidneys to increase the retention of fluid and thus increase blood pressure. The bilateral small smooth kidney pattern describes most of what is often diagnosed on sonography as medical renal disease, although the authors prefer the term renal parenchymal disease. A healthy individual who donates a kidney is likely to maintain a normal serum creatinine despite the loss of 50% of parenchymal tissue. There are many clinical states related to kidney malfunction. The opposite situation is possible too, if the kidneys excrete too many hydrogen ions, the pH of blood becomes too alkaline, and leads to a state called alkalosis. 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. The interpolar region is the middle of the kidney. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. A, A low-attenuation lesion is difficult to identify during the corticomedullary phase. 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. The main unit of the medulla is the renal pyramid. Clinical significance [ edit] A, Axial image demonstrates the dilated renal pelvis and crossing vessel. When simple kidney cysts do cause symptoms, they might include: Pain in the side between the ribs and hip, stomach or back. Usually, there are two to three major calyces in the kidney (superior, middle, and inferior), which again unite to form the renal pelvis from which the ureter emerges and leaves the kidney through the hilum. normal kidney size in adults normal kidney size in children Structure 18-18). Most diagnosed kidney growths are small and localized masses. The minor calyces unite to form a major calyx. Note distance from origin to the first arterial division (Fig. After looking at the overview of the kidneys in situ, it may seemas they are cluttered with all abdominal organs. Creatinine is a breakdown product of creatine, found within muscle. For most of the students, the nephron is a mystical complexed structure that may be hard to understand. 18-9). 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). Cells in our body constantly produce hydrogen ions. 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). Imaging must provide detailed images of the renal parenchyma and a survey of arterial, venous, and ureteral anatomy. 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 cortex of a normal kidney is usually less echogenic than the adjacent normal liver. Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. When both kidneys are on the same side crossed ectopia is present, because the ureter from one kidney must cross the midline to insert into the bladder (Fig. 18-3). So in the filtered fluid that goes to the renal tubule, we have both necessary and unnecessary substances. "Angio" indicates blood vessels, "myo" indicates muscle, and "lipoma" indicates fat. Small renal shadows may be seen on radiographs, and reniform shape is preserved on cross-sectional imaging. 2023 Kidney cysts can occur with disorders that may impair kidney function. In most cases, the kidneys are situated with the inferior poles slightly more lateral and anterior than the superior poles. Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. Curated learning paths created by our anatomy experts, 1000s of high quality anatomy illustrations and articles. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. 18-16). Chronic glomerulonephritis usually causes bilateral increased renal echogenicity with smooth atrophy, whereas renal artery stenosis usually causes a similar but unilateral appearance (Fig. Kidneys are located just below your ribcage and behind your belly. A second similar finely granular mass was present in the interpolar region, and it also contained . BOX 18-3 Causes of Bilateral Hydronephrosis. Each segmental branch of the renal artery divides into multiple interlobar arteries that course along the periphery of the medullary pyramids and causes small interlobular branches (Fig. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. In cases of unilateral obstruction with acute renal failure, sonographic evaluation may show evidence of chronic renal parenchymal disease in the unobstructed kidney. Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. Table 18-5 summarizes a checklist approach to the ultrasound examination. Ultrasound can often identify the cause in cases of bilateral obstruction (Fig. Illustration demonstrating the relation between the renal papilla and calyx. The presence or absence of intravenous contrast media, as well as the phase of contrast enhancement, are key factors that determine the appearance of the renal parenchyma on CT (Table 18-3). Box 18-2 provides some tips regarding crossing vessels in UPJ obstruction. The most common cause is renal artery stenosis (see Fig. The kidneys can be divided into three main regions from cranial to caudal. urinary system quizzes and labeled diagrams. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see Fig. 18-12). Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. The kidneys are paired retroperitoneal structures that are normally located between the transverse processes of T12-L3 vertebrae, with the left kidney typically somewhat more superior in position than the right. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. chronic obstruction, or severe or repeated urinary infections. Size and Contour of Diffuse Renal Disease, The bilateral small smooth kidney pattern describes most of what is often diagnosed on sonography as medical renal disease, although the authors prefer the term, Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. Advantages of scintigraphy include accurate quantitative measurement of function. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. 18-22). Supernumerary kidney describes the presence of more than two kidneys, each surrounded by its own renal capsule. Renal size and cortical thickness can be assessed in a manner similar to ultrasound. Renal scintigraphy can be performed with a variety of agents to provide assessment of either function or structure of the kidneys. When this happens, the stones can block the flow of urine out of your kidneys. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. 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. 18-24). It is also permeable for the products of the metabolism, such are creatinine and drug metabolites. Entities for which sonography is most useful. This causes them to fire impulses which stimulate rhythmical contraction and relaxation, called peristalsis. Parasympathetic innervation enhances the peristalsis while sympathetic innervation inhibits it. Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. Because the interlobular arteries form an arch overlying the pyramid, they are called the arcuate arteries. A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the medulla. There is no specific treatment for fused kidneys and the only option is to treat the pathologies that affect them during life. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. The initiation is caused by the increase in volume that stretches the walls of the calyces. Serum creatinine, however, is dependent not only on its disposal but also its production. In most kidneys, the renal hilum faces more anteromedial in the upper half of the kidney and more directly medial in the lower half. The renal pelvis then tapers like a funnel to join the ureter. Solid masses are more likely to be cancerous but they are not all cancerous. The region where the renal pelvis joins the ureter is called the, If the renal pelvis is entirely within the confines of the renal sinus, it is considered intrarenal. 18-20). Finally, the arcuate arteries branch into the interlobular arteries which branch off even further by giving afferent arterioles to run blood past the glomerulus for blood filtration. Kidney stones are most often treated by ultrasound shock therapy, during which high-frequency radio waves break the stone into smaller pieces that can be passed naturally into the urine. It's not clear what causes simple kidney cysts. A, Soft-tissue windows demonstrate no filling defect. B, Mild hydronephrosis results in rounding of the fornices with mild shortening of the papillary impression. In other cases, each renal unit has its own ureter. Pancake kidney describes a more severe fusion anomaly with a single, flat kidney positioned low in the pelvis with an anterior collecting system drained by either one or two ureters. 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. I would honestly say that Kenhub cut my study time in half. Crossed ectopia can be either fused or unfused. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. 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). Pain that radiates to the lower abdomen and groin. In most cases, the kidneys are situated with the inferior poles slightly. 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. The apex of the pyramid projects medially toward the renal sinus. 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. Occasionally, a papilla will communicate directly with an infundibulum or the renal pelvis and is considered to be an aberrant papilla. The solid renal parenchyma consists of the peripheral renal cortex and more central renal medulla. CT scan and MRI to help diagnose and stage kidney masses. 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. Figure 18-11 Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. The left kidney (not shown) had a similar appearance. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (whi. When fused, the condition is described as crossed fused ectopia. This kidney measured 14 cm in length. The pyramids are separated by extensions of the cortex called the renal columns. Normally, the kidney is about the size of a mouse and measures approximately 11-12 cm in length, 5-6 cm in width, and 2.5-3 cm in thickness. Differential diagnosis General imaging considerations include: renal cortical defect duplex 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. Arterial stenosis was confirmed by magnetic resonance angiography. 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. When multiple clefts in the renal cortex are present throughout the kidney, it is described as fetal lobulation. An acute change in renal cortical echogenicity is occasionally seen with pyelonehritis. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. Annotated axial image of the right kidney from a contrast-enhanced computed tomographic scan demonstrates hilar anatomy of the kidney. AMLs can bleed and while not cancerous are still taken very seriously. Figure 18-21 Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. The axes of the renal moeities are abnormal with the inferior poles angled medially. Luckily, the kidneys also feel this increase of pressure, and in cases when this happens, they increase the filtration rate of blood and production of urine, which subsequently leads to the increase fluid excretion and decrease of blood pressure. 18-25). Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. Ultrastructurally, the nephron is the functional representative of the kidney. 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). The renal pelvis then tapers like a funnel to join the ureter. Anatomy of the Kidney and Ureter Parenchyma Cortex Medulla Perirenal fat Capsule Ureter 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. The left testicular vein must ascend higher and it drains to the left renal vein at a right angle, unlike the right testicular vein which joins the inferior vena cava directly. This illustrates the amount of reserve function that must be compromised before renal injury can be detected with a serum creatinine level. Table 18-7 Causes of Unilateral Small Smooth Kidney, Only gold members can continue reading. In addition to the renal artery, accessory renal arteries are present too. The large left proximal ureteral stone seen in this image is only partially obstructing, causing mild dilation in the left kidney collecting system. 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. Renal Cysts. The goal of imaging patients with renal failure is to identify a correctable cause in an effort to recover or preserve renal function. On the superior aspect of each kidney is the adrenal gland. Note number of veins by inspecting inferior vena cava along entire length of kidney. On ultrasound, the renal cortex is usually echogenic in this setting. The renal fascia which besides the kidneys also encloses the suprarenal gland and its surrounding fat. Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. They are staged the same way as the renal pelvis. Caliectasis doesn't cause any symptoms on its own. 18-13). Arterial stenosis was confirmed by magnetic resonance angiography. Aggressive tumors form, grow and spread very quickly. In fact, evaluation of the renal collecting system during the excretory phase often requires window and level settings approaching those used for evaluating the osseous structures (Fig. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. The relation between the UPJ and vascular anatomy can be quite complex. Table 18-5 Checklist Approach to Ultrasound for Renal Failure. Figure 18-26 Ultrasound performed for acute renal failure demonstrates bilateral hydronephrosis caused by a bladder tumor. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. Normal serum creatinine level acute change in renal cortical echogenicity is detected, is. 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