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. These are chronic processes that lead to a loss of renal cortex gradually and uniformly. Figure 18-1 Annotated three-dimensional volume rendering of the left kidney acquired using a combined nephrographic phase and excretory phase during computed tomographic urography demonstrates regional anatomy of the kidney. Several formulas are available for this calculation, and calculators and on-line sites are available to simplify the calculations. Made. 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. On ultrasound, the renal cortex is usually echogenic in this setting. 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. Note that there is no contrast in the aorta. Note that the left renal vein receives blood from the left suprarenal and left testicular veins. These terminal branches have no collateral circulation. B, Transverse image of the bladder demonstrates a large bladder tumor in the region of the trigone. 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. Duplication of the urinary tract is discussed in detail in Chapter 19. On the other hand, babies with bilateral agenesis cannot survive without an immediate kidney transplant. The parenchyma of the kidney consists of the outer renal cortex, and inner renal medulla. In general, the amount of blood in the body is 5 liters. 18-1). 18-18). The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. 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. For that reason, we got you covered with this topic nicely and concisely. Table 18-7 Causes of Unilateral Small Smooth Kidney, Only gold members can continue reading. Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. The stones can move into the ureter and literally get stuck there because the lumen of the ureter is much smaller compared to the calyces, which is very painful for the patient. As the lobules of metanephric blastema coalesce to form each kidney, they do not always result in a smooth, uniform band of cortex. It's not clear what causes simple kidney cysts. The goal of imaging patients with renal failure is to identify a correctable cause in an effort to recover or preserve renal function. 18-22). Figure 18-16 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. Copyright D, If pressure on the papilla persists, the ischemic papilla undergoes necrosis, allowing the calyx to protrude outward toward the cortex. 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 small portion of the lumen surrounding the papilla is called the calyx. The left renal vein passes anteriorly to the aorta just below the trunk of the superior mesenteric artery, which is risky because it can be compressed by one of those two. Table 18-5 Checklist Approach to Ultrasound for Renal Failure. Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. MR angiography can be useful for the diagnosis of renal vascular abnormalities. 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. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. Dialysis. 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. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. Figure 18-26 Ultrasound performed for acute renal failure demonstrates bilateral hydronephrosis caused by a bladder tumor. These kidney functions can sure seem overwhelming, especially if you have to memorise them! Reviewer: 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. 18-27). 18-20). and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. Normal parenchymal enhancement on CT or MRI allows definitive characterization. The most common cause is renal artery stenosis (see, Delayed but increasingly dense nephrogram, Delayed but hyperconcentrated contrast excretion, Imaging Evaluation of Acute Abdominal Pain, A Multidimensional Approach to Abdominal Imaging. Table 18-1 Imaging the Living Renal Donor. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. Fever. The kidneys are reddish-brown, bean-shaped organs situated retroperitoneal on the posterior abdominal wall. 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. Ultrastructurally, the nephron is the functional representative of the kidney. For most people, obstruction of a single ureter does not induce renal failure. 18-26). Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. The initiation is caused by the increase in volume that stretches the walls of the calyces. When hydronephrosis is absent, the causative factor for acute renal failure is almost certainly prerenal or renal. The anterior surface of the left kidney, has the following anatomical relations: The posterior surfaces of both kidneys are related to certain neurovascular structures and muscles: You can easily remember these with the mnemonic: 1-2-3-4 All Boys Need Muscle. Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Unenhanced CT can identify hydronephrosis and hydroureter, urinary stones, and some masses. The main symptom is severe sharp pain that starts suddenly, usually in your belly or one side of your back, and it may go away just as quickly. Anatomy Where is the renal cortex? 18-23). Their shape resembles a bean, where we can describe the superior and inferior poles, as well as the major convexity pointed laterally, and the minor concavity pointed medially. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. Figure 18-3 Illustration demonstrating basic intrarenal arterial anatomy. Because production of creatinine is affected by sex, age, muscle mass, protein intake, and liver function, the serum creatinine can be an inaccurate predictor of renal function, particularly in those at the extremes of age and body weight. Anterior components of circumaortic vein can be small. Three-dimensional volume rendering from contrast-enhanced multidetector computed tomography examination of the kidneys demonstrates typical orientation of a horseshoe kidney. BOX 18-2 Crossing Vessels in Ureteropelvic Junction Obstruction. 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. The kidneys are a pair of bean-shaped organs located below the rib cage, one on each side of the spine. 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. However, sometimes ureteroscopy is required to confirm the diagnosis in patients with hematuria. Parasympathetic innervation enhances the peristalsis while sympathetic innervation inhibits it. impression is preserved. The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. The interpolar region is the middle of the kidney. Figure 18-25 Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. 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. The superior half of each kidney is covered by the diaphragm, which is why the kidneys move up and down during respiration. The renal corpuscle has two components: the glomerular (Bowmans) capsule in which sits the glomerulus. 18-3). 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). normal kidney size in adults normal kidney size in children Structure Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. 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). This is just a peek into the kidney physiology. 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). 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. Computed Tomographic Appearance of the Kidneys, Utility of Different Phases of Renal Contrast Enhancement. 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. 18-24). Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Maintaining kidney health. IVC, Inferior vena cava. The kidneys play a central role in homeostasis. They are usually characterized as "simple" cysts, meaning they have a thin wall and contain water-like fluid. Kidneys have a special system for the excretion of hydrogen ions, and in that way consistently maintain the pH of blood at 7.4. Other methods include classical surgical removal of the stone, either through the ureter or by open surgery. Kidneys are located just below your ribcage and behind your belly. 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. 18-18). Table 18-7 lists causes of unilateral smooth renal atrophy. 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. Note diameter of arteries because small accessory arteries may be sacrificed in many cases. The kidney is a very important organ in regards to body homeostasis. The normal appearance of the calyx is created by the impression of the renal papilla. 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. Even when there is another plausible explanation for decreased renal function (e.g., known prerenal causes), ultrasound offers the opportunity to rapidly and noninvasively identify a potentially correctible cause of renal failure. The most common cause is renal artery stenosis (see Fig. Volume rendering from a computed tomographic scan of the kidneys shows bilateral supernumerary renal arteries (three on right, two on left). 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. The kidneys are bilateral organs placed retroperitoneally in the upper left and right abdominal quadrants and are part of the urinary system. The fused kidneys can have a variety of orientations, including side by side, in-line, or perpendicular. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. Typically, one kidney sits on either side of your spine. and grab your free ultimate anatomy study guide! The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption. Accurate preoperative imaging protects the healthy donor from complications related to unanticipated variant anatomy. Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. This kidney measured 14 cm in length. Figure 18-2 Annotated axial image of the right kidney from a contrast-enhanced computed tomographic scan demonstrates hilar anatomy of the kidney. The right kidney has a normal appearance (not shown). chronic obstruction, or severe or repeated urinary infections. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. 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). print Print this Article However, T1-weighted images provide good corticomedullary differentiation. The corticomedullary phase is prolonged in the presence of ureteral or venous obstruction and can persist for days in cases of acute tubular necrosis (ATN; Fig. Crossed ectopia can be either fused or unfused. Causes. 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. Note number of veins by inspecting inferior vena cava along entire length of 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). It is important to remember this order of vessels and ducts since this is the only thing that will make you able to orient the kidney and differentiate the left one from the right when they are outside of the cadaver. Renal cysts are sacs of fluid that form in the kidneys. 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. Kenhub. The right kidney has a normal appearance (not shown). 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. Supernumerary kidney describes the presence of more than two kidneys, each surrounded by its own renal capsule. Most serum creatinine is excreted in the urine; therefore, if renal function is compromised, levels of creatinine in the serum increase. CT angiography is occasionally performed when a vascular causative factor is suspected (renal artery stenosis or renal vein thrombosis) and MRI is contraindicated. 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. 18-4). Each end of the kidney is commonly called a pole. Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. Recent advances in MDCT and MRI permit cross-sectional vascular studies to replace conventional angiography before UPJ repair (Fig. Pearl: Any upward trend in serum creatinine value should be viewed with concern because it implies renal reserve function has already been affected. Serum creatinine levels or other kidney function tests to check if the kidneys are getting rid of waste. 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. In addition to the renal artery, accessory renal arteries are present too. 18-5). 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By its own renal capsule by open surgery preserve renal function is compromised, levels of in. Very important organ in regards to body homeostasis unobstructed kidney the uniform high attenuation of kidneys.

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