Technetium 99m-mercaptoacetyltriglycin (MAG3) is excreted by the kidneys (mainly through secretion by proximal tubules) and provides evaluation of renal function, particularly in cases of suspected obstruction. One of the most commonly used (and least complicated) equations is shown in Box 18-1. Grounded on academic literature and research, validated by experts, and trusted by more than 2 million users. Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. This specific condition is called the nutcracker phenomenon. Perhaps of even greater importance, serum creatinine is not a sensitive test for minor insults to the kidney in otherwise healthy individuals. 18-5). Cells in our body constantly produce hydrogen ions. C, More severe hydronephrosis results in more pronounced shortening of the papilla. The interpolar region is the middle of the 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. Table 18-1 provides a quick guide itemizing key imaging findings in the potential renal donor. Kidneys are located just below your ribcage and behind your belly. 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). Because the fascia of the retroperitoneum prevents significant extravasation, the incision usually heals to form a larger lumen. 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 (. 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. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Frequent urination (having to go the bathroom often). The apex of the pyramid projects medially toward the renal sinus. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (whi. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. The vascularity of some tumors may be most apparent during this phase (Fig. Note origin of inferior accessories near inferior poles on each side. 18-24). B, Axial CT image from a different patient demonstrates the more common location of the right renal artery posterior to the IVC. Computed Tomographic Evaluation for Renal Failure, Magnetic Resonance Evaluation for Renal Failure. Each nephron contains a renal corpuscle, which is the initial component that filters the blood, and a renal tubule that processes and carries the filtered fluid to the system of calyces. 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. Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. normal kidney size in adults normal kidney size in children Structure Axial maximum intensity projection image from the arterial phase of a contrast-enhanced computed tomographic scan from a prospective renal donor demonstrates early prehilar branching of the left renal artery. 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 ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. The right kidney had a similar appearance (not shown). Creatinine is a breakdown product of creatine, found within muscle. Extraaortic origin of the renal arteries and accessory renal arteries are common. Renal cysts become fairly common as people age and usually do not cause symptoms or harm. In addition to the renal artery, accessory renal arteries are present too. 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. Table 18-2 Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. Always include unenhanced computed tomographic images to look for renal stones. However, T1-weighted images provide good corticomedullary differentiation. When this happens, the stones can block the flow of urine out of your kidneys. It is also permeable for the products of the metabolism, such are creatinine and drug metabolites. Chronic obstruction, however, results in damage to the papilla, evident in the clubbed calyx of papillary necrosis (Fig. B, A small calyceal defect is seen when the same image is viewed using bone windows. Kim Bengochea, Regis University, Denver. Register now 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. Besides blood volume and pressure regulation, kidneys also participate in the production of calcitriol (the active form of vitamin D). The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). Figure 25.1.2 Left Kidney. I would honestly say that Kenhub cut my study time in half. 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 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). Illustration demonstrating the anatomy of the renal collecting system. The small portion of the lumen surrounding the papilla is called the. A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the medulla. When simple kidney cysts do cause symptoms, they might include: Pain in the side between the ribs and hip, stomach or back. An increased amount of hydrogen ions can acidify the blood and cause a state called acidosis. Estimated creatinine clearance may be calculated using serum creatinine with adjustments made for sex, age, and body weight. Despite the complexity of renal physiology, many attempt to assess renal function with a simple quantitative measure, the serum creatinine. Entities for which sonography is most useful. Imaging must provide detailed images of the renal parenchyma and a survey of arterial, venous, and ureteral anatomy. Sometimes, one or both kidneys fail to develop, which causes unilateral or bilateral renal agenesis. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. impression is preserved. Figure 18-14 Axial maximum intensity projection image from the arterial phase of a contrast-enhanced computed tomographic scan from a prospective renal donor demonstrates early prehilar branching of the left renal artery. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. 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. 2023 The kidneys serve important . The renal cortex is part of your kidney, which itself is part of the urinary tract. Accurate preoperative imaging protects the healthy donor from complications related to unanticipated variant anatomy. 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 renal fascia which besides the kidneys also encloses the suprarenal gland and its surrounding fat. Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. Last reviewed: December 28, 2022 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. (Courtesy of Karl T. Rew, MD) Introduction Synonyms Epidemiology 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. 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. Dialysis. 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. Renal Cysts. Crossed ectopia on intravenous pyelogram. "Angio" indicates blood vessels, "myo" indicates muscle, and "lipoma" indicates fat. Some centers use diuretics or fluid bolus, or both, during CT urography to dilute the excreted contrast to improve assessment of the urothelium. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. If the renal pelvis extends out of the renal sinus, it is considered to be an extrarenal pelvis (Fig. Learn how we can help 1.2k views Reviewed Dec 09, 2022 Thank Dr. Frank Kuitems and 4 doctors agree 3 thanks 18-19). This is just a peek into the kidney physiology. The superior half of each kidney is covered by the diaphragm, which is why the kidneys move up and down during respiration. These terminal branches have no collateral circulation. 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. However, T1-weighted images provide good corticomedullary differentiation. Urine that is concentrated in the renal papilla is subsequently excreted into a lumen lined with transitional epithelium. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. 18-1). It's not clear what causes simple kidney cysts. The kidney is a very important organ in regards to body homeostasis. Annotated axial image of the right kidney from a contrast-enhanced computed tomographic scan demonstrates hilar anatomy of the kidney. But here is a neat little mnemonic to help. 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. 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. Checklist Approach to Ultrasound for Renal Failure, Absence of hydronephrosis makes postrenal causes unlikely, Cortical atrophy in one or both kidneys: suspect chronic or acute-on-chronic renal failure, Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. 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. Table 18-1 Imaging the Living Renal Donor. At that point, you may experience these symptoms: Severe, sharp pain in the side and back, below the ribs. Author: The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. Alternatively, the anterior to posterior orientation follows the same pattern: renal vein, renal artery and ureter. 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. Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. Further testing/diagnosis is required. 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. 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. A second similar finely granular mass was present in the interpolar region, and it also contained . Each end of the kidney is commonly called a pole. 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. 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. 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. 18-18). Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. When. Causes. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see Fig. The most common indication for cortical scintigraphy is to evaluate kidneys that have been injured by vesicoureteral reflux, chronic obstruction, or severe or repeated urinary infections. 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. Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. They extend from lumbar vertebra T12-L3. 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. Localized means that the tumor has not spread out from where it first started. The right kidney has a normal appearance (not shown). Overview. Learn more about the anatomy of the kidneys and the urinary system with our urinary system quizzes and labeled diagrams. Several formulas are available for this calculation, and calculators and on-line sites are available to simplify the calculations. Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. Kenhub. Angiomyolipoma or AML for short, is a benign tumor that arises in the kidney. Publication types Review MeSH terms Humans Parasympathetic innervation enhances the peristalsis while sympathetic innervation inhibits it. The normal appearance of the calyx is created by the impression of the renal papilla. Learn how we can help 1.2k views Reviewed Dec 09, 2022 Thank 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 renal pelvis then tapers like a funnel to join the ureter. This can cause varicocele of the left testicle because gravity works against the column of the blood in the left testicular vein. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. Retrograde urogram shows a calculus in the left ureter. The kidneys are reddish-brown, bean-shaped organs situated retroperitoneal on the posterior abdominal wall. 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 (. However, you may have symptoms related to the condition that's causing it. Duplication of the urinary tract is discussed in detail in Chapter 19. Living renal donor allografts account for more than half of the transplanted kidneys in the United States. 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