Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. 18-13). Register now There are many clinical states related to kidney malfunction. Chronic obstruction, however, results in damage to the papilla, evident in the clubbed calyx of papillary necrosis (Fig. When. Look carefully for accessory arteries at upper and lower poles (Fig. 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. 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). Thoracic kidneys are the least common form of renal ectopia. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. 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. The parenchyma of the kidney consists of the outer renal cortex, and inner renal medulla. Table 18-1 Imaging the Living Renal Donor. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. 18-3). When the fine, weblike complex of ureteral arteries is recruited to contribute to collateral circulation, enlarged vessels are seen surrounding the proximal ureter, causing the classic ureteral notching seen on intravenous urogram (IVU). Most serum creatinine is excreted in the urine; therefore, if renal function is compromised, levels of creatinine in the serum increase. Concerning lymphatic drainage, each kidney drains into the lateral aortic (lumbar) lymph nodes, which are placed around the origin of the renal artery. 18-6). more lateral and anterior than the superior poles. Kidney cysts are round pouches of fluid that form on or in the kidneys. Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein. Anatomical Position of the Kidneys Kidney Structure Anatomy Where is the renal cortex? However, this individual is more likely to show a decline in renal function from an additional insult. General symptoms of kidney problems include: blood in your urine . So the pyramids represent the functional tissue that creates urine, whereas the calyces are the beginning of the ureter and transport the urine to it. 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. Caliectasis doesn't cause any symptoms on its own. Thus, an AML is a tumor that contains these 3 components. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. B, A small calyceal defect is seen when the same image is viewed using bone windows. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). Note origin of inferior accessories near inferior poles on each side. Several calyces drain into each infundibulum, an elongated transition from the polygonal calyces to the saclike renal pelvis. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see Fig. 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. All rights reserved. Computed Tomographic Appearance of the Kidneys, Utility of Different Phases of Renal Contrast Enhancement. Because an extrarenal pelvis is not confined by the renal parenchyma, there is a tendency for it to expand. 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 Dr. Frank Kuitems and 4 doctors agree 3 thanks 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. The anterior surface faces towards the anterior abdominal wall, whereas the posterior surface is facing the posterior abdominal wall. This causes them to fire impulses which stimulate rhythmical contraction and relaxation, called peristalsis. But here is a neat little mnemonic to help. The kidneys serve important . Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. 18-21). 18-26). The pyramids are separated by extensions of the cortex called the renal columns. The calcium or uric acid will precipitate and form stones. The hilum of the kidney usually projects at the level of the L2 vertebra. The visible contrast seen in the excretory phase has been concentrated many-fold. Table 18-7 lists causes of unilateral smooth renal atrophy. Renal cysts become fairly common as people age and usually do not cause symptoms or harm. print Print this Article Of course, if the situation is the other way around (less than 5 liters of blood), blood pressure is too low (hypotension). A simple calyx receives urine from a single papilla; a compound calyx receives urine from multiple papillae (Fig. It protects your kidneys from injury, increases their stability and connects your kidneys to surrounding tissues. The small portion of the lumen surrounding the papilla is called the calyx. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. 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. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. 18-3). 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). The anteromedial, aspect of the interpolar region is interrupted by the renal hilum to make a C shape. Let's see what is nephron and how it is structured,so you can remember it for good. The Modification of Diet in Renal Disease (MDRD) is another method for estimating renal function that yields a value often called estimated glomerular filtration rate (eGFR). Renal size can be measured in several ways. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. 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. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. chronic obstruction, or severe or repeated urinary infections. 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. B, A curved planar reformation of the crossing vein demonstrates its course. Table 18-7 lists causes of unilateral smooth renal atrophy. 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. Read more. 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. CT angiography is occasionally performed when a vascular causative factor is suspected (renal artery stenosis or renal vein thrombosis) and MRI is contraindicated. Duplication of the urinary tract is discussed in detail in Chapter 19. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see. 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. 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). 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. "Angio" indicates blood vessels, "myo" indicates muscle, and "lipoma" indicates fat. MR angiography can be useful for the diagnosis of renal vascular abnormalities. This kidney measured 14 cm in length. 18-25). This refers to the forming of the stones within the system of calyces because of too much calcium or uric acid into the filtrate. 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. The renal cortex is part of your kidney, which itself is part of the urinary tract. However, you may have symptoms related to the condition that's causing it. In most kidneys, the renal hilum faces more anteromedial in the upper half of the kidney and more directly medial in the lower half. 18-14). However, T1-weighted images provide good corticomedullary differentiation. If the renal pelvis extends out of the renal sinus, it is considered to be an extrarenal pelvis (Fig. Since the abdominal organs are not paired, the left kidney is not related to the same organs as the right kidney. In other cases, each renal unit has its own ureter. Unenhanced CT can identify hydronephrosis and hydroureter, urinary stones, and some masses. In this region, the anterior and posterior hilar lip is identified (Fig. 18-15). Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). 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 (. 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. Box 18-2 provides some tips regarding crossing vessels in UPJ obstruction. Some tumors can be slow to grow while some can be aggressive. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. A bean-like structure like the kidney has two borders: medial and lateral. Pain that radiates to the lower abdomen and groin. The right kidney has a normal appearance (not shown). Made. 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. 18-1). 18-27). (Courtesy of Karl T. Rew, MD) Introduction Synonyms Epidemiology Learning a quickmnemonic'VAD' can help you remember these structures (renal Vein, renal Artery, Duct a.k.a ureter). 18-8). aware of such a vessel, the urologist may choose to perform an alternate procedure to avoid hemorrhagic complications. normal kidney size in adults normal kidney size in children Structure Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. Living renal donor allografts account for more than half of the transplanted kidneys in the United States. 18-25). The left kidney appeared unremarkable. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney 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. The kidneys are located between your intestines and your diaphragm. Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. 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. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the medulla. Ultrasound performed for acute renal failure demonstrates bilateral hydronephrosis caused by a bladder tumor. Copyright The shape of the calyx is formed by the impression of the renal papilla. Last reviewed: December 28, 2022 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. It's not clear what causes simple kidney cysts. The right kidney had a similar appearance (not shown). This specific condition is called the nutcracker phenomenon. Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. Crossed ectopia can be either fused or unfused. BOX 18-2 Crossing Vessels in Ureteropelvic Junction Obstruction. 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, A low-attenuation lesion is difficult to identify during the corticomedullary phase. CT and MR findings of renal artery stenosis parallel classic findings described on intravenous pyelogram, including one atrophic kidney with delayed nephrogram and excretion that can progress to a persistent nephrogram with hyperconcentrated excreted contrast media (Fig. Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. 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. 18-16). Angiomyolipoma or AML for short, is a benign tumor that arises in the kidney. 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). Because they rarely cause symptoms, renal cysts are most often found during . Illustration demonstrating the relation between the renal papilla and calyx. 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. This is because the liver and the stomach offset the symmetry of the abdomen, with the liver forcing the right kidney a bit down, and the stomach forcing the left kidney a bit up. Extraaortic origin of the renal arteries and accessory renal arteries are common. This phenomenon is due to T2-shortening and susceptibility (T2*) effects caused by concentrated gadolinium, and can potentially obscure filling defects and urothelial lesions. The solid renal parenchyma consists of the peripheral renal cortex and more central renal medulla.
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