The anteromedial, aspect of the interpolar region is interrupted by the renal hilum to make a C shape. Crossed ectopia on intravenous pyelogram. The kidneys are reddish-brown, bean-shaped organs situated retroperitoneal on the posterior abdominal wall. However, sometimes ureteroscopy is required to confirm the diagnosis in patients with hematuria. 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. This refers to the forming of the stones within the system of calyces because of too much calcium or uric acid into the filtrate. The main unit of the medulla is the renal pyramid. Figure 18-11 Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. Several small stones are visible in the left kidney, and the left kidney is somewhat atrophied from chronic obstruction. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Computed Tomographic Evaluation for Renal Failure, Magnetic Resonance Evaluation for Renal Failure. 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. 18-14). Thoracic kidneys are the least common form of renal ectopia. Because the interlobular arteries form an arch overlying the pyramid, they are called the arcuate arteries. 18-7). Reading time: 23 minutes. Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney 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). 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. 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. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. Always include unenhanced computed tomographic images to look for renal stones. The normal appearance of the calyx is created by the impression of the renal papilla. 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. 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. Hydronephrosis is important to detect, because obstructive uropathy is often reversible if identified early. Recent advances in MDCT and MRI permit cross-sectional vascular studies to replace conventional angiography before UPJ repair (Fig. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. The shape of the calyx is formed by the impression of the renal papilla. 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. Identify abnormal course of main or accessory right renal artery anterior rather than posterior to inferior vena cava (Fig. These are chronic processes that lead to a loss of renal cortex gradually and uniformly. The right kidney has a normal appearance (not shown). Extraaortic origin of the renal arteries and accessory renal arteries are common. D, If pressure on the papilla persists, the ischemic papilla undergoes necrosis, allowing the calyx to protrude outward toward the cortex. If a kidney stone becomes lodged in the ureters, it may block the flow of urine and cause the kidney to swell and the ureter to spasm, which can be very painful. The calcium or uric acid will precipitate and form stones. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). The kidneys are innervated by the renal plexus. If the renal pelvis is entirely within the confines of the renal sinus, it is considered intrarenal. Renal cysts are sacs of fluid that form in the kidneys. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. The left kidney appeared unremarkable. 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. Chronic obstruction, however, results in damage to the papilla, evident in the clubbed calyx of papillary necrosis (Fig. Each pyramid creates urine and terminates into a renal papilla. Technetium 99m dimercaptosuccinic acid (DMSA) and glucoheptonate (GHA) are both used for evaluation of renal parenchyma. 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. Renal size and cortical thickness can be assessed in a manner similar to ultrasound. 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). When the renal arteries enter the kidney through the hilum, they split into anterior and posterior branches. Table 18-1 Imaging the Living Renal Donor. The large left proximal ureteral stone seen in this image is only partially obstructing, causing mild dilation in the left kidney collecting system. MR angiography can be useful for the diagnosis of renal vascular abnormalities. 18-28). 18-24). 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. 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. Read more. Figure 18-8 Junctional cortical line seen on a long-axis ultrasound image of the right kidney. Yet, the relations of the kidneys with other organs are often found in Anatomy tests. Anatomy of the Kidney and Ureter Parenchyma Cortex Medulla Perirenal fat Capsule Ureter In cases of unilateral obstruction with acute renal failure, sonographic evaluation may show evidence of chronic renal parenchymal disease in the unobstructed kidney. However, T1-weighted images provide good corticomedullary differentiation. Concerning lymphatic drainage, each kidney drains into the lateral aortic (lumbar) lymph nodes, which are placed around the origin of the renal artery. Urine that is concentrated in the renal papilla is subsequently excreted into a lumen lined with transitional epithelium. 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. 18-25). Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours. Duplication of the urinary tract is discussed in detail in Chapter 19. Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Renal size can be measured in several ways. 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). February 12, 2018 - 2:17pm 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. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. Sagittal ultrasound image of the right kidney demonstrates increased size and echogenicity of the kidney, findings typical of human immunodeficiency virus nephropathy. This layer sits posteriorly and posterolaterally to each kidney and separates it from the muscles of the abdominal wall. 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). 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. * Entities for which sonography is most useful. 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). 18-13). The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Illustration demonstrating the relation between the renal papilla and calyx. Ultrasound is usually used in the initial evaluation of the patient with newly diagnosed renal failure. Figure 18-10 Crossed ectopia on intravenous pyelogram. 18-18). This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. 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. This is just a peek into the kidney physiology. Living renal donor allografts account for more than half of the transplanted kidneys in the United States. a bifid renal pelvis, ultimately drained by a common ureter. Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. C, More severe hydronephrosis results in more pronounced shortening of the papilla. Note distance from origin to the first arterial division (Fig. CT scan and MRI to help diagnose and stage kidney masses. 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