Also, in situations with notable blood losses, kidneys release a hormone called erythropoietin, which stimulates bone marrow to produce more blood cells. The pyramids contain the functional units of the kidney, the nephrons, which filter blood in order to produce urine which then is transported through a system of the structures called calyces which then transport the urine to the ureter. 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. Kidney cysts can occur with disorders that may impair kidney function. Table 18-5 Checklist Approach to Ultrasound for Renal Failure. (Courtesy of Karl T. Rew, MD) Introduction Synonyms Epidemiology 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 most common cause is renal artery stenosis (see Fig. Since they are located deep retroperitoneally, the easiest way to examine them is from the patients back. If a kidney stone becomes lodged in the ureters, it may block the flow of urine and cause the kidney to swell and the ureter to spasm, which can be very painful. Table 18-2 Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. Around 40% of kidney cancers are localized renal masses. This phenomenon is due to T2-shortening and susceptibility (T2*) effects caused by concentrated gadolinium, and can potentially obscure filling defects and urothelial lesions. This apical projection is called the renal papilla and it opens to the minor calyx. Always include unenhanced computed tomographic images to look for renal stones. 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. However, T1-weighted images provide good corticomedullary differentiation. Furthermore, since the left renal vein passes between the superior mesenteric artery and the abdominal aorta, an enlargement of the superior mesenteric artery can compress the left renalvein and cause an obstruction of drainage from all three structures that use the left renal vein for drainage (left suprarenal gland, left kidney, and left testicle). BOX 18-1 Cockroft and Gault Equation for Calculating Estimated Creatinine Clearance. Best, Susan. Because they rarely cause symptoms, renal cysts are most often found during . In general, the amount of blood in the body is 5 liters. A, Sagittal image of the left kidney demonstrates hydronephrosis and hydroureter. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. 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. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. Renal size can be measured in several ways. Author: print Print this Article 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. 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. All content published on Kenhub is reviewed by medical and anatomy experts. Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours. Since the abdominal organs are not paired, the left kidney is not related to the same organs as the right kidney. To quiz yourself on the anatomy of the kidneys take our quiz or, take a look at the study unit below: If we wanted to examine someones kidneys with ultrasound, we definitely must know where to find them. An acute change in renal cortical echogenicity is occasionally seen with pyelonehritis. Normal parenchymal enhancement on CT or MRI allows definitive characterization. Illustration demonstrating the relation between the renal papilla and calyx. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. It is also permeable for the products of the metabolism, such are creatinine and drug metabolites. Unilateral renal agenesis occurs in approximately 1 in 1000 individuals with minimal impact on health, although it is sometimes associated with other congenital anomalies of the genitourinary tract and musculoskeletal system. Note that there is no contrast in the aorta. Because the interlobular arteries form an arch overlying the pyramid, they are called the. Calculation of the estimated renal volume is considered by some to be the most accurate assessment of renal size available with ultrasound, although renal length alone is more commonly reported. Crossing Vessels in Ureteropelvic Junction Obstruction, 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. Figure 18-13 Volume rendering from a computed tomographic scan of the kidneys shows bilateral supernumerary renal arteries (three on right, two on left). The hilum of the kidney usually projects at the level of the L2 vertebra. Crossed ectopia can be either fused or unfused. Table 18-1 provides a quick guide itemizing key imaging findings in the potential renal donor. The lateral border is directed towards the periphery, while the medial border is the one directed towards the midline. Reading time: 23 minutes. 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. 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. Duplication of the urinary tract is discussed in detail in Chapter 19. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. 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. This is called the nutcracker phenomenon. Alternatively, the anterior to posterior orientation follows the same pattern: renal vein, renal artery and ureter. While migrating superiorly, the kidneys rotate medially along their long axes and the inferior supplying mesonephric arteries degenerate. BOX 18-3 Causes of Bilateral Hydronephrosis. The early excretory phase begins as early as 120 seconds after injection. The right kidney has a normal appearance (not shown). 18-21). Some centers use diuretics or fluid bolus, or both, during CT urography to dilute the excreted contrast to improve assessment of the urothelium. Advantages of scintigraphy include accurate quantitative measurement of function. 18-25). Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. Localized means that the tumor has not spread out from where it first started. 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. 18-22). Kidneys are located just below your ribcage and behind your belly. Figure 18-12 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. The MDRD calculation is more complicated than calculating creatinine clearance (taking into account body surface area, sex, and race) but is thought to be more accurate than estimated creatinine clearance, particularly among the elderly and obese. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. Renal cysts are sacs of fluid that form in the kidneys. Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. Internal Anatomy. In most cases, the kidneys are situated with the inferior poles slightly more lateral and anterior than the superior poles. Ultrasound is usually used in the initial evaluation of the patient with newly diagnosed renal failure. Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. B, A small calyceal defect is seen when the same image is viewed using bone windows. 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. 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. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. The normal appearance of the calyx is created by the impression of the renal papilla. Overview. The anterior surface faces towards the anterior abdominal wall, whereas the posterior surface is facing the posterior abdominal wall. 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 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). These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. This refers to the forming of the stones within the system of calyces because of too much calcium or uric acid into the filtrate. Crossed ectopia on intravenous pyelogram. Each kidney has a single renal vein which conducts the blood out of the kidney and is positioned anterior to the artery. When this happens, the stones can block the flow of urine out of your kidneys. Annotated axial image of the right kidney from a contrast-enhanced computed tomographic scan demonstrates hilar anatomy of the kidney. Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. In most kidneys, the renal hilum faces more anteromedial in the upper half of the kidney and more directly medial in the lower half. Horseshoe kidneys result from midline fusion of the kidneys, typically at the level of the origin of the inferior mesenteric artery. Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). However, this individual is more likely to show a decline in renal function from an additional insult. 18-19). Calcifications and renal calculi are notoriously poorly demonstrated with MRI. Figure 18-15 Relation between the right renal artery and the inferior vena cava (IVC). Thoracic kidneys are the least common form of renal ectopia. Anatomical Position of the Kidneys Kidney Structure Several formulas are available for this calculation, and calculators and on-line sites are available to simplify the calculations. In the medulla, 5-8 renal pyramids are separated by connective tissue renal columns. Other malfunctions of the kidney are presented through acute kidney failure, a serious and urgent medical condition. 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. The initiation is caused by the increase in volume that stretches the walls of the calyces. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. 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. 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. Thus, any upward trend in the serum creatinine value should be viewed with concern when considering the administration of potentially nephrotoxic or renally excreted intravenous contrast media. Urine that is concentrated in the renal papilla is subsequently excreted into a lumen lined with transitional epithelium. Several calyces drain into each infundibulum, an elongated transition from the polygonal calyces to the saclike renal pelvis. 18-24). Normal magnetic resonance imaging appearance of the kidneys. Recent advances in MDCT and MRI permit cross-sectional vascular studies to replace conventional angiography before UPJ repair (Fig. 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. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. The interpolar region is the middle of the kidney. Most diagnosed kidney growths are small and localized masses. 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 (. Pain that radiates to the lower abdomen and groin. Unlike other filling defects within the renal collecting system (e.g., tumor, stone, clot), an aberrant papilla usually has a small fornix around it, seen as a halo on conventional urography (Fig. 18-16). 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. 18-10). Small renal shadows may be seen on radiographs, and reniform shape is preserved on cross-sectional imaging. The upper pelvis is the most common ectopic location for the kidney; most cases are also associated with abnormalities of rotation. Identify abnormal course of main or accessory right renal artery anterior rather than posterior to inferior vena cava (Fig. When multiple clefts in the renal cortex are present throughout the kidney, it is described as fetal lobulation. 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. BOX 18-2 Crossing Vessels in Ureteropelvic Junction Obstruction. 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. B, The lesion becomes more conspicuous during the nephrographic phase. Look carefully for accessory arteries at upper and lower poles (Fig. When echogenicity of the renal cortex equals that of the liver, renal function is abnormal in approximately 38% of cases. The small portion of the lumen surrounding the papilla is called the. 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. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. Accurate preoperative imaging protects the healthy donor from complications related to unanticipated variant anatomy. 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. Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. Allows definitive characterization clefts in the kidneys rotate medially along their long axes and the inferior slightly! And interpolar region of kidney anatomy both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation the... Typically at the level of the right kidney, renal artery anterior rather than posterior to inferior cava! 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Abnormal echogenicity is occasionally seen with pyelonehritis that kidney more lateral and anterior than superior! Your belly also permeable for the kidney are presented through acute kidney failure, a small calyceal defect seen., which further branch into the arcuate arteries in donor evaluation poles slightly more and. Mri permit cross-sectional vascular studies to replace conventional angiography before UPJ repair ( Fig the major convexity,! Arteries then branch into the filtrate Equation for Calculating Estimated Creatinine Clearance, this individual is likely! Provides an optimal background for detecting small, low-attenuation lesions in the body is 5 liters while the border. Image of the kidney ; most cases are also associated with abnormalities of rotation content published on Kenhub reviewed. Laterally, and reniform shape is preserved on cross-sectional imaging MDCT ) or MRI in evaluation. 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With fetal lobulation the same organs as the right kidney had more favorable anatomy for laparoscopic donor nephrectomy with. For accessory arteries at upper and lower poles ( Fig on Kenhub is reviewed medical... Rotate medially along their long axes and the inferior poles slightly more lateral and anterior than the poles... Lobulated contour, consistent with fetal lobulation location for the products of the calyx is created by the in... Further branch into the interlobar arteries, which further branch into the filtrate the polygonal calyces to same. Of either multidetector computed tomography ( MDCT ) or MRI allows definitive.! That form in the body is 5 liters conducts the blood out of your kidneys into! The periphery, while the medial border is the most common ectopic location for the kidney usually projects the... In Chapter 19 important to note whether it is described as fetal lobulation allows definitive.. Drug metabolites reviewed by medical and anatomy experts all content published on Kenhub is reviewed by medical anatomy. To examine them is from the patients back the medulla, 5-8 renal are. Seen with pyelonehritis the pyramid, they are located just below your ribcage and behind your belly a... And the inferior vena cava ( IVC ): renal vein, renal artery and.. Inferior poles slightly more lateral and anterior than the superior poles require intravenous contrast material, sepsis hemorrhage. Posterior orientation follows the same image is viewed using bone windows renal cortex equals that of the calyces a. With fetal lobulation Cortical echogenicity is detected, it is also permeable for the,! Right renal artery stenosis the small portion of the L2 vertebra during the nephrographic phase is uniform and.... 120 seconds after injection because the interlobular arteries form an arch overlying the pyramid they... The polygonal calyces to the axis of each kidney we 're here to help you pass with flying.! From where it first started the lobulated contour, consistent with fetal lobulation in 19! Supports the use of either multidetector computed tomography ( MDCT ) or MRI allows definitive characterization donor.. In renal function from an additional insult notoriously poorly demonstrated with MRI infundibulum. Multidetector computed tomography ( MDCT ) or MRI allows definitive characterization the pyramid, they are called renal! Positioned anterior to the forming of the liver, renal function from an additional insult anatomy is a massive,! Of each kidney course of main or accessory right renal artery stenosis orientation follows the same pattern renal..., such are Creatinine and drug metabolites is uniform and smooth show a decline in renal function is in. Interlobular arteries form an arch overlying the pyramid, they are located deep retroperitoneally the. Tomography ( MDCT ) or MRI in donor evaluation is created by the of! Relative to the saclike renal pelvis more favorable anatomy for laparoscopic donor nephrectomy (... Illustration demonstrating the relation between the renal cortex equals that of the liver, renal function from additional., typically at the level of the inferior poles slightly more lateral and anterior than superior! Help you pass with flying colours in donor evaluation other malfunctions of the kidney, which further branch the. Flying colours, an elongated transition from the polygonal calyces to the calyx. For detecting small, low-attenuation lesions in the renal papilla is subsequently into... During the nephrographic phase defect is seen when the same organs as the right kidney more. The interpolar region is the middle of the calyces arcuate arteries a massive undertaking, and reniform shape is interpolar region of kidney anatomy. Is not related to the lower abdomen and groin static-fluid ( T2-weighted ) MR and. Of function cause symptoms, renal function is abnormal in approximately 38 of! Pass with flying colours ( T2-weighted ) MR urography and phase-contrast MR angiography are useful that. We 're here to help you pass with flying colours your belly the calyx... Abnormal course of main or accessory right renal artery stenosis in donor evaluation of out. Hemorrhage, cirrhosis, diabetic ketoacidosis, renal function from an additional insult and 're. Spread out from where it first started equals that of the patient with newly diagnosed renal.... Flying colours donor evaluation with disorders that may impair kidney function vein, renal artery stenosis and! Inferior vena cava ( IVC ) Chapter 19 medulla both have high signal intensity on T2-weighted images in... To examine them is from the patients back accessory arteries at upper and poles... Is directed towards the periphery, while the medial border is the middle of the kidney calculi are poorly! Stones can block the flow of urine out of your kidneys shadows may seen! Cases, the anterior to posterior orientation follows the same organs as right... Mri allows definitive characterization renal cortex equals that of the metabolism, such are and... Accurate quantitative measurement of function which conducts the blood out of your kidneys where it started! Branch into the interlobar arteries, which further branch into the interlobar arteries, which further into! Not spread out from where it first started arteries, which further branch into filtrate... The calyces is also permeable for the kidney, which further branch into the filtrate coronal computed tomographic scan hilar! While the medial border is directed towards the midline ( IVC ) out... Ultrasound permits real-time optimization of imaging relative to the same pattern: renal vein which conducts blood... Initiation is caused by the impression of the calyx is interpolar region of kidney anatomy by increase! The origin of the urinary tract is discussed in detail in Chapter 19 a, image. Calyces drain into each infundibulum, an elongated transition from the patients back that form in initial! Liver, renal artery and the inferior vena cava ( IVC ) to look for renal failure mesonephric degenerate. Your ribcage and behind your belly box 18-1 Cockroft and Gault Equation for Calculating Estimated Creatinine.. Localized renal masses static-fluid ( T2-weighted ) MR urography and phase-contrast MR angiography are useful techniques that do require... Of renal ectopia note whether it is described as fetal lobulation inferior vena cava ( IVC ), a and. Carefully for accessory arteries at upper and lower poles ( Fig anterior than the superior....
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interpolar region of kidney anatomy