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. Recent advances in MDCT and MRI permit cross-sectional vascular studies to replace conventional angiography before UPJ repair (Fig. Relation between the right renal artery and the inferior vena cava (IVC). 18-26). However, you may have symptoms related to the condition that's causing it. 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. Read more. The anteromedial aspect of the interpolar region is interrupted by the renal hilum to make a C shape. The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. CT scan and MRI to help diagnose and stage kidney masses. B, Transverse image of the bladder demonstrates a large bladder tumor in the region of the trigone. A second similar finely granular mass was present in the interpolar region, and it also contained . 18-28). Surgery was successful and the surgeon confirmed the anatomic survey was correct. urinary system quizzes and labeled diagrams. B, Low-attenuation lesion in the late nephrographic/early excretory phase is less suspicious in appearance. In this way, the consistency of blood is preserved and no important substances are lost. Frequent urination (having to go the bathroom often). Besides blood volume and pressure regulation, kidneys also participate in the production of calcitriol (the active form of vitamin D). February 12, 2018 - 2:17pm 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. The kidneys are innervated by the renal plexus. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. B, A curved planar reformation of the crossing vein demonstrates its course. RENAL ANATOMY Renal Parenchyma The kidneys can be divided into three main regions from cranial to caudal. I hope this helps. B, A small calyceal defect is seen when the same image is viewed using bone windows. and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. The nephrons of the kidney are responsible for maintaining balance between fluids and electrolytes, regulating levels of amino acids, overall acid-base balance, as well as removing toxins from the blood. CT angiography is occasionally performed when a vascular causative factor is suspected (renal artery stenosis or renal vein thrombosis) and MRI is contraindicated. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. 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. 18-1). The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). 18-13). Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. Figure 18-2 Annotated axial image of the right kidney from a contrast-enhanced computed tomographic scan demonstrates hilar anatomy of the kidney. Their shape resembles a bean, where we can describe the superior and inferior poles, as well as the major convexity pointed laterally, and the minor concavity pointed medially. 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. Figure 18-20 Axial image from unenhanced computed tomography of the kidneys performed 2 days after an angiographic procedure demonstrates stasis of contrast in the renal cortex, resulting in a persistent corticomedullary phase of enhancement. Creatinine is a breakdown product of creatine, found within muscle. Illustration demonstrating the anatomy of the renal collecting system. print Print this Article The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. Copyright Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (which is in between them). Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. 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. 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). But here is a neat little mnemonic to help. Cells in our body constantly produce hydrogen ions. The kidneys play a central role in homeostasis. An interpolar (an area of the kidney) solid mass of the kidney means there is a growth that needs to be examined. BOX 18-3 Causes of Bilateral Hydronephrosis. Clinical significance [ edit] Unenhanced CT can identify hydronephrosis and hydroureter, urinary stones, and some masses. 18-25). 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. Arterial stenosis was confirmed by magnetic resonance angiography. Table 18-1 Imaging the Living Renal Donor. Table 18-2 Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. Curated learning paths created by our anatomy experts, 1000s of high quality anatomy illustrations and articles. Each end of the kidney is commonly called a. 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. B, The lesion becomes more conspicuous during the nephrographic phase. Chronic obstruction, however, results in damage to the papilla, evident in the clubbed calyx of papillary necrosis (Fig. A. Junctional cortical line seen on a long-axis ultrasound image of the right kidney. 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 (. They are staged the same way as the renal pelvis. The stones can move into the ureter and literally get stuck there because the lumen of the ureter is much smaller compared to the calyces, which is very painful for the patient. The renal pelvis then tapers like a funnel to join the ureter. This apical projection is called the renal papilla and it opens to the minor calyx. The pyramids are separated by extensions of the cortex called the renal columns. 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. Table 18-7 Causes of Unilateral Small Smooth Kidney, Only gold members can continue reading. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see. Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. (Courtesy of Karl T. Rew, MD) Introduction Synonyms Epidemiology Concerning lymphatic drainage, each kidney drains into the lateral aortic (lumbar) lymph nodes, which are placed around the origin of the renal artery. A, Sagittal image of the left kidney demonstrates hydronephrosis and hydroureter. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. 18-9). Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein. Angiomyolipoma or AML for short, is a benign tumor that arises in the kidney. 18-8). 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. The medial border of the kidney contains a very important landmark called the hilum of the kidney, which is the entry and exit point for the kidney vessels and ureter. Pitfall: An extrarenal pelvis may be mistaken for hydronephrosis. If the renal pelvis extends out of the renal sinus, it is considered to be an. 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. CT is occasionally used to evaluate patients with renal failure. Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. The upper pelvis is the most common ectopic location for the kidney; most cases are also associated with abnormalities of rotation. Advantages of scintigraphy include accurate quantitative measurement of function. 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. Because the interlobular arteries form an arch overlying the pyramid, they are called the. 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. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. 18-20). After looking at the overview of the kidneys in situ, it may seemas they are cluttered with all abdominal organs. 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. and grab your free ultimate anatomy study guide! For most people, obstruction of a single ureter does not induce renal failure. They are usually characterized as "simple" cysts, meaning they have a thin wall and contain water-like fluid. A, Soft-tissue windows demonstrate no filling defect. Renal size and cortical thickness can be assessed in a manner similar to ultrasound. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney The kidneys are located between the transverse processes of T12-L3 vertebrae, with the left kidney typically positioned slightly more superiorly than the right. The dynamics of obstruction and quantification of relative renal function between the two kidneys may be important considerations in two general circumstances: (1) it is unclear whether obstruction is severe enough to warrant surgical intervention; or (2) significant parenchymal atrophy exists, and the relative merits of repair and nephrectomy are being compared. Reading time: 23 minutes. Anatomy Where is the renal cortex? The small portion of the lumen surrounding the papilla is called the. 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. Figure 18-25 Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. To quiz yourself on the anatomy of the kidneys take our quiz or, take a look at the study unit below: If we wanted to examine someones kidneys with ultrasound, we definitely must know where to find them. Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. Some of them are congenital, such as a third kidney, which is usually atrophic. Kim Bengochea, Regis University, Denver. This kidney measured 14 cm in length. 18-10). Renal scintigraphy can be performed with a variety of agents to provide assessment of either function or structure of the kidneys. 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. For most of the students, the nephron is a mystical complexed structure that may be hard to understand. Estimated creatinine clearance may be calculated using serum creatinine with adjustments made for sex, age, and body weight. Internal Anatomy. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. On the other hand, babies with bilateral agenesis cannot survive without an immediate kidney transplant. Localized means that the tumor has not spread out from where it first started. Several calyces drain into each infundibulum, an elongated transition from the polygonal calyces to the saclike renal pelvis. Right-sided pain was related to crossed renal ectopia. AMLs can bleed and while not cancerous are still taken very seriously. It is notable that the kidney has a very rich blood supply. 18-15). Normal magnetic resonance imaging appearance of the kidneys. Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. 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. As the lobules of metanephric blastema coalesce to form each kidney, they do not always result in a smooth, uniform band of cortex. If the renal pelvis is entirely within the confines of the renal sinus, it is considered intrarenal. 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. Because the fascia of the retroperitoneum prevents significant extravasation, the incision usually heals to form a larger lumen. However, small, low-attenuation lesions in the medulla are often obscured during this phase. Anatomy of the Kidney and Ureter Parenchyma Cortex Medulla Perirenal fat Capsule Ureter 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. 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. 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. Retrograde urogram shows a calculus in the left ureter. Urine from the calyces flows to the renal sinus via tributaries called infundibula. Sagittal ultrasound image of the right kidney demonstrates increased size and echogenicity of the kidney, findings typical of human immunodeficiency virus nephropathy. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). more lateral and anterior than the superior poles. Created for people with ongoing healthcare needs but benefits everyone. Several formulas are available for this calculation, and calculators and on-line sites are available to simplify the calculations. Despite the complexity of renal physiology, many attempt to assess renal function with a simple quantitative measure, the serum creatinine. a bifid renal pelvis, ultimately drained by a common ureter. 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. 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. While migrating superiorly, the kidneys rotate medially along their long axes and the inferior supplying mesonephric arteries degenerate. Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. Jana Vaskovi MD 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. Recent advances in MDCT and MRI permit cross-sectional vascular studies to replace conventional angiography before UPJ repair (Fig. Serum creatinine, however, is dependent not only on its disposal but also its production. Serum creatinine levels or other kidney function tests to check if the kidneys are getting rid of waste. 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. 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. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. Chronic obstruction, however, results in damage to the papilla, evident in the clubbed calyx of papillary necrosis (Fig. Since they are located deep retroperitoneally, the easiest way to examine them is from the patients back. Note that retroaortic components are usually near the inferior poles (Fig. Pain that radiates to the lower abdomen and groin. Some centers use diuretics or fluid bolus, or both, during CT urography to dilute the excreted contrast to improve assessment of the urothelium. Blood in the urine, or dark urine. Look for retroaortic or circumaortic left renal vein. 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. Bone scan and chest x-ray to find out if the cancer has spread. Solid masses are more likely to be cancerous but they are not all cancerous. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. Each end of the kidney is commonly called a pole. The small portion of the lumen surrounding the papilla is called the calyx. Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. If the renal pelvis extends out of the renal sinus, it is considered to be an extrarenal pelvis (Fig. Note origin of inferior accessories near inferior poles on each side. 18-21). It protects your kidneys from injury, increases their stability and connects your kidneys to surrounding tissues. 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. The left kidney (not shown) had a similar appearance. Hydronephrosis is important to detect, because obstructive uropathy is often reversible if identified early. 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. This can cause varicocele of the left testicle because gravity works against the column of the blood in the left testicular vein. When fused, the condition is described as crossed fused ectopia. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. 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. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Prominent extrarenal pelves are typically positioned anteriorly (Fig. Renal artery Increasing pressure within the lumen initially distends the fornices (acutely angled portions of the calyx along the sides of the papillae), whereas the central portion of the papillary impression is preserved. Most diagnosed kidney growths are small and localized masses. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. Renal scintigraphy can be performed with a variety of agents to provide assessment of either function or structure of the kidneys. Table 18-6 Causes of Bilateral Small Smooth Kidneys. Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. This illustrates the amount of reserve function that must be compromised before renal injury can be detected with a serum creatinine level. D, If pressure on the papilla persists, the ischemic papilla undergoes necrosis, allowing the calyx to protrude outward toward the cortex. 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 renal cortex is part of your kidney, which itself is part of the urinary tract. There is no specific treatment for fused kidneys and the only option is to treat the pathologies that affect them during life. 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 (. Each end of the kidney is commonly called a pole. 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. 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. Eliminating toxic metabolites through urine, regulation of blood homeostasis and blood pressure, production of some hormones, Positioned retroperitoneally, consists of the cortex and medulla, empties urine into the ureter (which carries urine to the urinary bladder), Renal artery (branch of the abdominal aorta), Renal vein (drains to the inferior vena cava), Third kidney, horseshoe kidney, kidney agenesis, kidney stones, acute kidney failure, Regulates the amount of fluid in the body by increasing or decreasing the urine production, Maintain the pH of blood at 7.4 by decreasing or increasing the excretion of hydrogen ions, Medial part of the lower half of superior pole, Lateral part of the lower half of superior pole, Lateral part of inferior half of anterior surface, Medial part of inferior half of anterior surface, The perinephric fat (perirenal fat capsule). In other cases, each renal unit has its own ureter. 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. 18-18). 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. Figure 18-11 Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. One of the most commonly used (and least complicated) equations is shown in Box 18-1. Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. In most kidneys, the renal hilum faces more anteromedial in the upper half of the kidney and more directly medial in the lower half. Imaging must provide detailed images of the renal parenchyma and a survey of arterial, venous, and ureteral anatomy. Because the interlobular arteries form an arch overlying the pyramid, they are called the arcuate arteries. 18-11). Lets start with the right kidney anterior surface. 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. Their shape resembles a bean, where we can describe the superior and inferior poles, as well as the major convexity pointed laterally, and the minor concavity pointed medially. Table 18-3 Utility of Different Phases of Renal Contrast Enhancement. The renal corpuscle has two components: the glomerular (Bowmans) capsule in which sits the glomerulus. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see Fig. In general, the amount of blood in the body is 5 liters. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours. The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. The visible contrast seen in the excretory phase has been concentrated many-fold. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. Other malfunctions of the kidney are presented through acute kidney failure, a serious and urgent medical condition. 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.
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