"Angio" indicates blood vessels, "myo" indicates muscle, and "lipoma" indicates fat. 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. However, T1-weighted images provide good corticomedullary differentiation. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. 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). 18-3). A second similar finely granular mass was present in the interpolar region, and it also contained . Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. Renal scintigraphy can be performed with a variety of agents to provide assessment of either function or structure of the kidneys. The small portion of the lumen surrounding the papilla is called the calyx. The kidneys help remove waste products from the . Crossed ectopia on intravenous pyelogram. Table 18-2 Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. The superior half of each kidney is covered by the diaphragm, which is why the kidneys move up and down during respiration. Urine from the calyces flows to the renal sinus via tributaries called infundibula. 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. 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. 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. The information we provide is grounded on academic literature and peer-reviewed research. Figure 18-8 Junctional cortical line seen on a long-axis ultrasound image of the right kidney. 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. Renal size and cortical thickness can be assessed in a manner similar to ultrasound. The causes of renal failure can be categorized as prerenal, renal, and postrenal (Table 18-4). An increased amount of hydrogen ions can acidify the blood and cause a state called acidosis. Each end of the kidney is commonly called a pole. However, this individual is more likely to show a decline in renal function from an additional insult. Perhaps of even greater importance, serum creatinine is not a sensitive test for minor insults to the kidney in otherwise healthy individuals. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. 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. Figure 18-5 Illustration demonstrating the anatomy of the renal collecting system. Since the abdominal organs are not paired, the left kidney is not related to the same organs as the right kidney. The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. Kidneys are located just below your ribcage and behind your belly. Each end of the kidney is commonly called a pole. The vascularity of some tumors may be most apparent during this phase (Fig. I would honestly say that Kenhub cut my study time in half. When this happens, the stones can block the flow of urine out of your kidneys. Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. 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. The hilum of the kidney usually projects at the level of the L2 vertebra. Pain that radiates to the lower abdomen and groin. Table 18-1 provides a quick guide itemizing key imaging findings in the potential renal donor. 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. Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. On axial sections, the polar regions of the kidney typically form a closed circle or donut shape, with the hole formed by renal sinus fat. B, A curved planar reformation of the crossing vein demonstrates its course. 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. The anteromedial, aspect of the interpolar region is interrupted by the renal hilum to make a C shape. A bean-like structure like the kidney has two borders: medial and lateral. Use of MR contrast agents in renal failure poses a lower risk than iodinated contrast material for exacerbating renal failure, but there is evidence that gadolinium-based MR contrast media pose some risk for systemic complications (nephrogenic systemic fibrosis) and should be used with caution in patients with severe or acute renal insufficiency. When fused, the condition is described as crossed fused ectopia. Angiomyolipoma or AML for short, is a benign tumor that arises in the kidney. 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. CT scan and MRI to help diagnose and stage kidney masses. The main function of the kidney is to eliminate excess bodily fluid, salts and byproducts of metabolism this makes kidneys key in the regulation of acid-base balance, blood pressure, and many other homeostatic parameters. At that point, you may experience these symptoms: Severe, sharp pain in the side and back, below the ribs. 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. In addition to the renal artery, accessory renal arteries are present too. For most people, obstruction of a single ureter does not induce renal failure. For that reason, we got you covered with this topic nicely and concisely. 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. Several formulas are available for this calculation, and calculators and on-line sites are available to simplify the calculations. Blood supply is variable and often includes extraaortic and multiple vessel origins. Creatinine is a breakdown product of creatine, found within muscle. The interpolar region is the middle of the kidney. Renal artery Ultrastructurally, the nephron is the functional representative of the kidney. 18-8). A, A low-attenuation lesion is difficult to identify during the corticomedullary phase. Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. The phases of nephrogram development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. When hydronephrosis is absent, the causative factor for acute renal failure is almost certainly prerenal or renal. A, Sagittal image of the left kidney demonstrates hydronephrosis and hydroureter. 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. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. 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 right kidney had a similar appearance (not shown). The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. 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). Table 18-3 Utility of Different Phases of Renal Contrast Enhancement. 18-19). Any excessive amount of fluid will increase the pressure on the arterial wall and cause the blood pressure to rise (hypertension). Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. The anteromedial aspect of the interpolar region is interrupted by the renal hilum to make a C shape. 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. a bifid renal pelvis, ultimately drained by a common ureter. February 12, 2018 - 2:17pm Thus, the ureter is seen paravertebrally starting from the L2 and going downwards. Table 18-7 lists causes of unilateral smooth renal atrophy. Other common kidney conditions are acquired through life, and one of the most common is nephrolithiasis (kidney stones). Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. A, Soft-tissue windows demonstrate no filling defect. BOX 18-3 Causes of Bilateral Hydronephrosis. The kidneys are bilateral organs placed retroperitoneally in the upper left and right abdominal quadrants and are part of the urinary system. 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. B, The lesion becomes more conspicuous during the nephrographic phase. Despite different methods of accumulation, each is sequestered by the renal cortex, providing an opportunity to quantify the volume of renal parenchymal tissue in each kidney. 18-18). 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. 18-9). 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). Hypotension is a stimulus for the kidneys to increase the retention of fluid and thus increase blood pressure. Urine that is concentrated in the renal papilla is subsequently excreted into a lumen lined with transitional epithelium. Grounded on academic literature and research, validated by experts, and trusted by more than 2 million users. 18-22). 18-1). Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. In most cases, the kidneys are situated with the inferior poles slightly. Although ureteral contrast media is typically present before 3 minutes, longer delays provide more predictable opacification. Ultrasound is usually used in the initial evaluation of the patient with newly diagnosed renal failure. Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. For most of the students, the nephron is a mystical complexed structure that may be hard to understand. 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. * Entities for which sonography is most useful. 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). 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. 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. A furosemide challenge is often administered after initial excretion is observed to measure the impact of diuresis on the clearance of radiotracer from the renal pelvis. The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption. The apex of the pyramid projects medially toward the renal sinus. This causes them to fire impulses which stimulate rhythmical contraction and relaxation, called peristalsis. Imaging must provide detailed images of the renal parenchyma and a survey of arterial, venous, and ureteral anatomy. The left testicular vein must ascend higher and it drains to the left renal vein at a right angle, unlike the right testicular vein which joins the inferior vena cava directly. Normal parenchymal enhancement on CT or MRI allows definitive characterization. The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. Learn how we can help 1.2k views Reviewed Dec 09, 2022 Thank A simple calyx receives urine from a single papilla; a compound calyx receives urine from multiple papillae (Fig. Pancake kidney describes a more severe fusion anomaly with a single, flat kidney positioned low in the pelvis with an anterior collecting system drained by either one or two ureters. Anatomical Position of the Kidneys Kidney Structure Pearl: Any upward trend in serum creatinine value should be viewed with concern because it implies renal reserve function has already been affected. This is why the kidney is essential for the circulatory hemostasis. The renal cortex is part of your kidney, which itself is part of the urinary tract. This article will discuss the anatomy and major functions of the kidney.

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