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. Internal Anatomy. 18-8). The vessel which brings blood into the glomerulus is the afferent arteriole, whereas the vessel that carries the rest of the blood out that hasnt been filtered out of the glomerulus is called the efferent arteriole. Small renal shadows may be seen on radiographs, and reniform shape is preserved on cross-sectional imaging. Most serum creatinine is excreted in the urine; therefore, if renal function is compromised, levels of creatinine in the serum increase. Learn more about the anatomy of the kidneys and the urinary system with our urinary system quizzes and labeled diagrams. The visible contrast seen in the excretory phase has been concentrated many-fold. 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. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney However, T1-weighted images provide good corticomedullary differentiation. The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. IVC, Inferior vena cava. On the other hand, the products of cellular metabolism and drug metabolites are eliminated from the blood which prevents their depositing in the body and potential toxicity. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. A, Enhancement of the mass is conspicuous in the corticomedullary phase. Several small stones are visible in the left kidney, and the left kidney is somewhat atrophied from chronic obstruction. 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. For most people, obstruction of a single ureter does not induce renal failure. Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. In other cases, each renal unit has its own ureter. Blood supply is variable and often includes extraaortic and multiple vessel origins. 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. 18-18). The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. 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. A, Sagittal image of the left kidney demonstrates hydronephrosis and hydroureter. The superior poles (extremities) (T12) of both kidneys are more medially pointed towards the spine than the inferior poles (extremities) (L3). Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. Table 18-1 Imaging the Living Renal Donor. This layer sits posteriorly and posterolaterally to each kidney and separates it from the muscles of the abdominal wall. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. 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. 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. Comparative views of the CT scan ( a axial, b coronal, and c sagittal planes) and corresponding views of the physical model ( d superior view, e median view, and f median view). The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. MR angiography can be useful for the diagnosis of renal vascular abnormalities. 18-26). 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. Computed Tomographic Appearance of the Kidneys, Utility of Different Phases of Renal Contrast Enhancement. Sagittal ultrasound image of the right kidney demonstrates increased size and echogenicity of the kidney, findings typical of human immunodeficiency virus nephropathy. Figure 18-21 Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. C, More severe hydronephrosis results in more pronounced shortening of the papilla. On ultrasound, the renal cortex is usually echogenic in this setting. Right-sided pain was related to crossed renal ectopia. I would honestly say that Kenhub cut my study time in half. 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. Retrograde urogram shows a calculus in the left ureter. 18-25). There are many clinical states related to kidney malfunction. A, Soft-tissue windows demonstrate no filling defect. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see Fig. 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 (. The glomerular membrane is designed in a way in which it is not permeable for big and important molecules in blood, such as plasma proteins, but it is permeable to the smaller substances such as sodium, potassium, amino acids and many others. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. 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. Despite different methods of accumulation, each is sequestered by the renal cortex, providing an opportunity to quantify the volume of renal parenchymal tissue in each kidney. Thus, an AML is a tumor that contains these 3 components. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. 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. 18-4). An increased amount of hydrogen ions can acidify the blood and cause a state called acidosis. chronic obstruction, or severe or repeated urinary infections. 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 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. Sometimes, one or both kidneys fail to develop, which causes unilateral or bilateral renal agenesis. The kidneys are located between your intestines and your diaphragm. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. Since they are located deep retroperitoneally, the easiest way to examine them is from the patients back. 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. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. 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). Table 18-7 Causes of Unilateral Small Smooth Kidney, Only gold members can continue reading. 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. The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. Unlike other filling defects within the renal collecting system (e.g., tumor, stone, clot), an aberrant papilla usually has a small fornix around it, seen as a halo on conventional urography (Fig. 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. Dialysis. The kidney is a very important organ in regards to body homeostasis. Frequent urination (having to go the bathroom often). The defect proved to be blood clot from papillary necrosis. 18-18). 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. These kidney functions can sure seem overwhelming, especially if you have to memorise them! Calcifications and renal calculi are notoriously poorly demonstrated with MRI. Each time a professor says 'nephron', a student gets a headache. Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. If the renal pelvis is entirely within the confines of the renal sinus, it is considered intrarenal. Figure 25.1.2 Left Kidney. In most cases, the kidneys are situated with the inferior poles slightly more lateral and anterior than the superior poles. Figure 18-7 Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. CT is occasionally used to evaluate patients with renal failure. The renal corpuscle has two components: the glomerular (Bowmans) capsule in which sits the glomerulus. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. Identify abnormal course of main or accessory right renal artery anterior rather than posterior to inferior vena cava (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. Perhaps of even greater importance, serum creatinine is not a sensitive test for minor insults to the kidney in otherwise healthy individuals. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. (Courtesy of Karl T. Rew, MD) Introduction Synonyms Epidemiology 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. Localized means that the tumor has not spread out from where it first started. Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. Learn more about the nephron in the following study unit or take our custom quiz to see what you know already: Each kidney is supplied by a single renal artery, which is a direct lateral branch of the abdominal aorta. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. 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. Crossing Vessels in Ureteropelvic Junction Obstruction, 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. 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. 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. Several formulas are available for this calculation, and calculators and on-line sites are available to simplify the calculations. Solid masses are more likely to be cancerous but they are not all cancerous. The calcium or uric acid will precipitate and form stones. 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). 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. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (whi. CT scan and MRI to help diagnose and stage kidney masses. 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. CT angiography is occasionally performed when a vascular causative factor is suspected (renal artery stenosis or renal vein thrombosis) and MRI is contraindicated. A, Axial image from contrast-enhanced computed tomography (CT) demonstrates an accessory right renal artery coursing anterior to the IVC. Some of them are congenital, such as a third kidney, which is usually atrophic. However, this individual is more likely to show a decline in renal function from an additional insult. 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. Read more. 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. But more often, kidney cysts are a type called simple kidney cysts. Look for duplication, large extrarenal pelvis. Table 18-5 Checklist Approach to Ultrasound for Renal Failure. Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours. 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. Each end of the kidney is commonly called a pole. In most cases, the kidneys are situated with the inferior poles slightly. Learning a quickmnemonic'VAD' can help you remember these structures (renal Vein, renal Artery, Duct a.k.a ureter). more lateral and anterior than the superior poles. I hope this helps. Each pyramid creates urine and terminates into a renal papilla. "Angio" indicates blood vessels, "myo" indicates muscle, and "lipoma" indicates fat. Note that the left renal vein receives blood from the left suprarenal and left testicular veins. 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. 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). Now lets pay attention to the borders of the kidneys. development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. Copyright 18-15). 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). 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. Grounded on academic literature and research, validated by experts, and trusted by more than 2 million users. This is why the kidney is essential for the circulatory hemostasis. Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. Cells in our body constantly produce hydrogen ions. Kidney cysts are round pouches of fluid that form on or in the kidneys. A. Junctional cortical line seen on a long-axis ultrasound image of the right kidney. Demonstrates typical orientation of a horseshoe kidney variable and often includes extraaortic and multiple vessel origins laboratories! You pass with flying colours says 'nephron ', a student gets a headache inferior vena cava Fig... 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