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. The right kidney has a normal appearance (not shown). Perhaps of even greater importance, serum creatinine is not a sensitive test for minor insults to the kidney in otherwise healthy individuals. Table 18-2 Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. urinary system quizzes and labeled diagrams. Approximately 1 year before presentation, the patient experienced a similar episode of right flank pain that prompted an unenhanced CT examination of the abdomen and pelvis at an outside institution. Extraaortic origin of the renal arteries and accessory renal arteries are common. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. 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. Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. 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. 18-1). Because they rarely cause symptoms, renal cysts are most often found during . and grab your free ultimate anatomy study guide! Internal Anatomy. The renal pelvis then tapers like a funnel to join the ureter. The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. The normal appearance of the calyx is created by the impression of the renal papilla. Pitfall: An extrarenal pelvis may be mistaken for hydronephrosis. A, Soft-tissue windows demonstrate no filling defect. Clinical significance [ edit] 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. Table 18-5 summarizes a checklist approach to the ultrasound examination. Grounded on academic literature and research, validated by experts, and trusted by more than 2 million users. Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). The kidneys have two functional areas that are managed and staged independently, the kidney parenchyma and the renal pelvis. Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. 2023 Renal Cysts. The hilum of the kidney usually projects at the level of the L2 vertebra. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. IVC, Inferior vena cava. For that reason, we got you covered with this topic nicely and concisely. 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. Overview. Solid masses are more likely to be cancerous but they are not all cancerous. Note origin of inferior accessories near inferior poles on each side. Causes. Small renal shadows may be seen on radiographs, and reniform shape is preserved on cross-sectional imaging. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. 18-15). The medulla is the inner region of the parenchyma of the kidney. Relation between the right renal artery and the inferior vena cava (IVC). Renal function is better evaluated by measured creatinine clearance, which takes into account not only the amount of creatinine in the blood but also the amount of creatinine within a specified volume of urine over a given period. In this region, the anterior and posterior hilar lip is identified (Fig. Curated learning paths created by our anatomy experts, 1000s of high quality anatomy illustrations and articles. Note that there is no contrast in the aorta. A, Enhancement of the mass is conspicuous in the corticomedullary phase. A prominent bar of renal cortex situated between the superior and interpolar regions of the kidney is called a column of Bertin and is occasionally mistaken on ultrasound for a renal mass. Note origin of inferior accessories near inferior poles on each side. 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 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). aware of such a vessel, the urologist may choose to perform an alternate procedure to avoid hemorrhagic complications. 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. Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. The left kidney (not shown) had a similar appearance. The renal cortex is part of your kidney, which itself is part of the urinary tract. 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. Some forms of congenital UPJ obstruction are now treated with transureteroscopic endopyelotomy in which an incision is made from within the ureter using a ureteroscope. 3D printed model for a 53-year-old female presenting a 21 15 15 mm renal tumor located in the interpolar region of left kidney, treated by left partial nephrectomy. As the lobules of metanephric blastema coalesce to form each kidney, they do not always result in a smooth, uniform band of cortex. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. 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. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. B, Low-attenuation lesion in the late nephrographic/early excretory phase is less suspicious in appearance. Read More Created for people with ongoing healthcare needs but benefits everyone. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. The medulla consists of multiple pyramidal tissue masses, called the renal pyramids, which are triangle structures that contain a dense network of nephrons. Illustration demonstrating the relation between the renal papilla and calyx. Figure 25.1.2 Left Kidney. Illustration demonstrating basic intrarenal arterial anatomy. 18-18). 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. You can test yourself on the renal arteries with our quiz. The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. Surgery was successful and the surgeon confirmed the anatomic survey was correct. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. 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. A healthy individual who donates a kidney is likely to maintain a normal serum creatinine despite the loss of 50% of parenchymal tissue. The kidneys can be divided into three main regions from cranial to caudal. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. The most superior vessel is the renal vein which exits the kidney, just under it is the renal artery that enters in, and under the artery is the exiting ureter. 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. 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. The upper poles are normally oriented more medially and posteriorly than the lower poles. Occasionally, a papilla will communicate directly with an infundibulum or the renal pelvis and is considered to be an aberrant papilla. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. 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. Other malfunctions of the kidney are presented through acute kidney failure, a serious and urgent medical condition. Living renal donor allografts account for more than half of the transplanted kidneys in the United States. In most cases, unenhanced CT is performed when the duration and cause of renal failure are unknown because exposure to iodinated contrast media could impair recovery of renal function. Figure 18-10 Crossed ectopia on intravenous pyelogram. Yet, the relations of the kidneys with other organs are often found in Anatomy tests. The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. Arterial stenosis was confirmed by magnetic resonance angiography. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. Some tumors can be slow to grow while some can be aggressive. Publication types Review MeSH terms Humans Best, Susan. This kidney measured 14 cm in length. Other methods include classical surgical removal of the stone, either through the ureter or by open surgery. Enlargement of a congenitally unilateral kidney is typical and presumed to be compensatory. These are chronic processes that lead to a loss of renal cortex gradually and uniformly. Internal Anatomy. (Courtesy of Karl T. Rew, MD) Introduction Synonyms Epidemiology 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. Copyright 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 (. 18-4). Chronic obstruction, however, results in damage to the papilla, evident in the clubbed calyx of papillary necrosis (Fig. IVC, Inferior vena cava. 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. D, If pressure on the papilla persists, the ischemic papilla undergoes necrosis, allowing the calyx to protrude outward toward the cortex. 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. BOX 18-3 Causes of Bilateral Hydronephrosis. For most people, obstruction of a single ureter does not induce renal failure. 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. General symptoms of kidney problems include: blood in your urine . The right kidney has a normal appearance (not shown). However, sometimes ureteroscopy is required to confirm the diagnosis in patients with hematuria. B, The lesion becomes more conspicuous during the nephrographic phase. Ultrasound is usually used in the initial evaluation of the patient with newly diagnosed renal failure. The goal of imaging patients with renal failure is to identify a correctable cause in an effort to recover or preserve renal function. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Kim Bengochea, Regis University, Denver. The right kidney had a similar appearance (not shown). The presence of contour irregularity usually indicates scarring, suggesting prior infection, reflux, or infarction. The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. The upper pelvis is the most common ectopic location for the kidney; most cases are also associated with abnormalities of rotation. Figure 18-7 Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. Around 40% of kidney cancers are localized renal 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. Now lets pay attention to the borders of the kidneys. Horseshoe kidneys result from midline fusion of the kidneys, typically at the level of the origin of the inferior mesenteric artery. It is notable that the kidney has a very rich blood supply. 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. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. Figure 18-27 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). 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