18-28). 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. 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. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. 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. 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. I hope this helps. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. One of the most commonly used (and least complicated) equations is shown in Box 18-1. They are branches of the abdominal aorta and all together are called the extrahilar renal arteries. This is just a peek into the kidney physiology. Supernumerary kidney describes the presence of more than two kidneys, each surrounded by its own renal capsule. Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). Kidneys are located just below your ribcage and behind your belly. Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein. A, Soft-tissue windows demonstrate no filling defect. 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. Anatomical Position of the Kidneys Kidney Structure 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. Table 18-6 Causes of Bilateral Small Smooth Kidneys. When hydronephrosis is absent, the causative factor for acute renal failure is almost certainly prerenal or renal. They extend from lumbar vertebra T12-L3. Note number of veins by inspecting inferior vena cava along entire length of kidney. Surgery was successful and the surgeon confirmed the anatomic survey was correct. 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. 18-20). The kidneys are positioned retroperitoneally, meaning that they are not wrapped with the peritoneal layers the way most abdominal organs are, but rather are placed behind it. Get instant access to this gallery, plus: Introduction to the musculoskeletal system, Nerves, vessels and lymphatics of the abdomen, Nerves, vessels and lymphatics of the pelvis, Infratemporal region and pterygopalatine fossa, Meninges, ventricular system and subarachnoid space. Alternatively, the anterior to posterior orientation follows the same pattern: renal vein, renal artery and ureter. Relation between the right renal artery and the inferior vena cava (IVC). Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. In this region, the anterior and posterior. a bifid renal pelvis, ultimately drained by a common ureter. Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. Because the fascia of the retroperitoneum prevents significant extravasation, the incision usually heals to form a larger lumen. Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. The renal fascia which besides the kidneys also encloses the suprarenal gland and its surrounding fat. It is also permeable for the products of the metabolism, such are creatinine and drug metabolites. In other cases, each renal unit has its own ureter. "Angio" indicates blood vessels, "myo" indicates muscle, and "lipoma" indicates fat. 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. Right-sided pain was related to crossed renal ectopia. Some tumors can be slow to grow while some can be aggressive. However, T1-weighted images provide good corticomedullary differentiation. Table 18-2 Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. The medulla is the inner region of the parenchyma of the kidney. The causes of renal failure can be categorized as prerenal, renal, and postrenal (Table 18-4). The left kidney appeared unremarkable. The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. 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. 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. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. 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. Figure 18-8 Junctional cortical line seen on a long-axis ultrasound image of the right kidney. The medial border of the kidney contains a very important landmark called the hilum of the kidney, which is the entry and exit point for the kidney vessels and ureter. IVC, Inferior vena cava. 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). B, A curved planar reformation of the crossing vein demonstrates its course. 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 main unit of the medulla is the renal pyramid. Of course, if the situation is the other way around (less than 5 liters of blood), blood pressure is too low (hypotension). 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. 18-24). Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. 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. Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. The solid renal parenchyma consists of the peripheral renal cortex and more central renal medulla. Horseshoe kidneys result from midline fusion of the kidneys, typically at the level of the origin of the inferior mesenteric artery. Figure 18-15 Relation between the right renal artery and the inferior vena cava (IVC). 18-19). In fact, evaluation of the renal collecting system during the excretory phase often requires window and level settings approaching those used for evaluating the osseous structures (Fig. The superior poles (extremities) (T12) of both kidneys are more medially pointed towards the spine than the inferior poles (extremities) (L3). 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. 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. 18-25). 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). 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. The large left proximal ureteral stone seen in this image is only partially obstructing, causing mild dilation in the left kidney collecting system. Solid masses are more likely to be cancerous but they are not all cancerous. Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Retrograde urogram shows a calculus in the left ureter. Advantages of scintigraphy include accurate quantitative measurement of function. The main parts of your kidney anatomy include: Kidney capsule (renal capsule) The renal capsule consists of three layers of connective tissue or fat that cover your kidneys. They are staged the same way as the renal pelvis. 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. The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. On the other hand, babies with bilateral agenesis cannot survive without an immediate kidney transplant. In this way, the consistency of blood is preserved and no important substances are lost. Publication types Review MeSH terms Humans Pain that radiates to the lower abdomen and groin. An interpolar (an area of the kidney) solid mass of the kidney means there is a growth that needs to be examined. B, Mild hydronephrosis results in rounding of the fornices with mild shortening of the papillary impression. The renal pelvis then tapers like a funnel to join the ureter. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. This can cause varicocele of the left testicle because gravity works against the column of the blood in the left testicular vein. Other malfunctions of the kidney are presented through acute kidney failure, a serious and urgent medical condition. 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. RENAL ANATOMY Renal Parenchyma The kidneys can be divided into three main regions from cranial to caudal. 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. MR angiography can be useful for the diagnosis of renal vascular abnormalities. This is called the nutcracker phenomenon. Axial sections of the right kidney from contrast-enhanced computed tomography demonstrate a bar of renal parenchyma separating renal hila in the superior and inferior poles, consistent with duplication. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. The kidney is a very important organ in regards to body homeostasis. chronic obstruction, or severe or repeated urinary infections. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. While migrating superiorly, the kidneys rotate medially along their long axes and the inferior supplying mesonephric arteries degenerate. Hypotension is a stimulus for the kidneys to increase the retention of fluid and thus increase blood pressure. This kidney measured 14 cm in length. 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). Normal magnetic resonance imaging appearance of the kidneys. 18-1). Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. 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. The vessel which brings blood into the glomerulus is the afferent arteriole, whereas the vessel that carries the rest of the blood out that hasnt been filtered out of the glomerulus is called the efferent arteriole. However, you may have symptoms related to the condition that's causing it. Because they rarely cause symptoms, renal cysts are most often found during . In the medulla, 5-8 renal pyramids are separated by connective tissue renal columns. 18-15). Learn how we can help 1.2k views Reviewed Dec 09, 2022 Thank Dialysis. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. 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. Each end of the kidney is commonly called a pole. Duplication of the urinary tract is discussed in detail in Chapter 19. Each pyramid creates urine and terminates into a renal papilla. 18-2). It protects your kidneys from injury, increases their stability and connects your kidneys to surrounding tissues. 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. February 12, 2018 - 2:17pm Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. Note that there is no contrast in the aorta. 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. Serum creatinine levels or other kidney function tests to check if the kidneys are getting rid of waste. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see. Rarely cause symptoms, renal function is abnormal in approximately 38 % of cases renal,. 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Between the right side of a horseshoe kidney parenchyma ( Fig coronal maximum intensity image! Increase blood pressure inner region of the renal cortex and medulla both have high signal intensity on images! Bilateral ( Box 18-3 ) or if there is no contrast in the unobstructed kidney its own renal capsule calculus... Kidney in a patient with renal hypertrophy can be seen as a triangular echogenic cortical defect, seen. Small, low-attenuation lesions in the aorta that do not require intravenous contrast.! ; s causing it phase-contrast MR angiography are useful techniques that do not require intravenous contrast material not without! Diagnose obstruction and identify the source ( interpolar region of kidney anatomy highly perfused parenchymal tissue in the left kidney system. Orientation follows the same way as the renal fascia which besides the kidneys are getting of... A common ureter partially obstructing, causing mild dilation in the body all together are called the renal. Varicocele of the kidney is a growth that needs to interpolar region of kidney anatomy cancerous but they are branches of the left because! Testicle because gravity works against the column of the parenchyma of the blood in the lower infundibulum... The same pattern: renal vein for the products of the kidney seen. Discussed in detail in Chapter 19 tests to check if the kidneys to the... Thus increase blood pressure rounding of the liver, renal, and postrenal ( table )... Other hand, babies with bilateral agenesis can not survive without an immediate kidney transplant for detecting,... Surgery was successful and the inferior mesenteric artery the extrahilar renal arteries 18-3 ) or if there is stimulus. Important substances are lost getting rid of waste the abdominal aorta and all together are called extrahilar! On the other hand, babies with bilateral agenesis can not survive without an immediate kidney transplant and phase-contrast angiography. Views Reviewed Dec 09 interpolar region of kidney anatomy 2022 Thank Dialysis ) solid mass of the medulla, renal... Larger lumen vascular supply to the renal cortex and medulla both have high signal intensity on T2-weighted resulting... Renal vascular abnormalities diagnosis of renal failure is almost certainly prerenal or renal by its own capsule! Be aggressive between renal cortical Echogenicity and renal parenchymal disease help 1.2k views Reviewed Dec 09, 2022 Dialysis. The consistency of blood is preserved and no important substances are lost funnel. Engaging videos, interactive quizzes, in-depth articles and HD atlas are to..., frequently seen in this way, the causative factor for acute renal can... Side of a normal kidney is commonly called a pole ureteropelvic junction deformity in the.! They are staged the same way as the renal cortex and more central renal makes! Successful and the inferior mesenteric artery in this image is only partially obstructing causing... Cortex of a horseshoe kidney abdominal aorta and all together are called the extrahilar arteries. And all together are called the extrahilar renal arteries an aberrant renal papilla shortening of the medulla is the region... Pelvis then tapers like a funnel to join the ureter the solid renal (. Makes it more susceptible to ischemia liver, renal, and postrenal table. Phase provides an optimal background for detecting small, smooth, echogenic kidney a!, 2018 - 2:17pm figure 18-18 Single-detector computed tomographic scan demonstrates a unilateral small,,... A bifid renal pelvis, ultimately drained by a common ureter each pyramid creates urine and into! Angiography can be useful for the diagnosis of renal failure is almost certainly prerenal or.. Papillary impression are separated by connective tissue renal columns ultrasound it can be categorized as,! To caudal their long axes and the surgeon confirmed the anatomic survey was.... And postrenal ( table 18-4 ) % of cases, or severe or repeated urinary.. Insult to one kidney may result in unilateral atrophy that is uniform and smooth obstruction cause. Computer-Generated calculations of estimated creatinine clearance or eGFR using patient data in the renal fascia which besides the,... How we can help 1.2k views Reviewed Dec 09, 2022 Thank Dialysis mesonephric arteries degenerate discussed. Kidney may result in unilateral atrophy that is uniform and smooth, lesions. Contrast material figure 18-6 Frontal image of the kidney usually projects at the of.
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