Kidneys are located just below your ribcage and behind your belly. During the 6th to 9th weeks of life, the kidneys begin to ascend from their position in the pelvis to the level of T12-L1, inferior to the adrenal glands. All content published on Kenhub is reviewed by medical and anatomy experts. 18-24). The highest portion of the superior pole is covered with the, The superior one-half of the anterior surface is in contact with the layer of, At exactly the center of the anterior surface, imagine a horizontal stripe that extends from the medial concavity toward the center of the lateral convexity that is the area of the kidney that is directly touched by the retroperitoneal posterior wall of the, The lateral part of the inferior pole is directly contacted with the, The rest of the inferior pole is associated with the peritoneum of the, Just like the right kidney, the highest part of the superior pole of the left is also covered with the, The inferior portion of the superior pole contacts with the peritoneum of the, Just inferior to the stomach and spleen impression, is where the left kidney directly contacts, The lateral part of the inferior half of the anterior surface is directly associated with the left colic flexure (also known as the splenic flexure) and, The medial part of the inferior half and the inferior pole are contacted by the peritoneum of the, Kidney structure (overview) - Mohammed Albakkar, Kidneys in situ (overview) - Johannes Reiss, Internal anatomy of the kidney (overview) - Mohammed Albakkar, Arteries of the kidney (overview) - Abdulmalek Albakkar, Kidneys in a cadaver - Prof. Carlos Surez-Quian. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. 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. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. Table 18-5 Checklist Approach to Ultrasound for Renal Failure. Other malfunctions of the kidney are presented through acute kidney failure, a serious and urgent medical condition. Fever. A frontal section through the kidney reveals an outer region called the renal cortex and an inner region called the medulla. A bean-like structure like the kidney has two borders: medial and lateral. The calyces, however, will have a normal appearance with an unobstructed extrarenal pelvis but will be dilated in cases of urinary obstruction. This specific condition is called the nutcracker phenomenon. 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. They are staged the same way as the renal pelvis. Each kidney should always be evaluated in long axis (coronal, sagittal, or both, depending on sonographic window) and axial to the kidney. Author: 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. Supernumerary kidney describes the presence of more than two kidneys, each surrounded by its own renal capsule. Volume rendering from a computed tomographic scan of the kidneys shows bilateral supernumerary renal arteries (three on right, two on left). Computed Tomographic Evaluation for Renal Failure, Magnetic Resonance Evaluation for Renal Failure. A, Axial image from contrast-enhanced computed tomography (CT) demonstrates an accessory right renal artery coursing anterior to the IVC. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. 18-4). If the renal pelvis extends out of the renal sinus, it is considered to be an extrarenal pelvis (Fig. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (whi. Fetal lobulation is best differentiated from renal scars during the corticomedullary phase of enhancement on computed tomography (CT) or magnetic resonance imaging (MRI) because cortex can be followed into the indentation that occurs between calyces (Fig. 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). When. Thus, the ureter is seen paravertebrally starting from the L2 and going downwards. However, small, low-attenuation lesions in the medulla are often obscured during this phase. Illustration demonstrating the anatomy of the renal collecting system. 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. 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. The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. All rights reserved. Since the abdominal organs are not paired, the left kidney is not related to the same organs as the right kidney. 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. 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. In cases of unilateral obstruction with acute renal failure, sonographic evaluation may show evidence of chronic renal parenchymal disease in the unobstructed 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). 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. Of course, if the situation is the other way around (less than 5 liters of blood), blood pressure is too low (hypotension). Urine that is concentrated in the renal papilla is subsequently excreted into a lumen lined with transitional epithelium. Note that retroaortic components are usually near the inferior poles (Fig. An interpolar (an area of the kidney) solid mass of the kidney means there is a growth that needs to be examined. Curated learning paths created by our anatomy experts, 1000s of high quality anatomy illustrations and articles. Arterial stenosis was confirmed by magnetic resonance angiography. B, Transverse image of the bladder demonstrates a large bladder tumor in the region of the trigone. Renal cysts become fairly common as people age and usually do not cause symptoms or harm. Surgery was successful and the surgeon confirmed the anatomic survey was correct. 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. Sometimes, one or both kidneys fail to develop, which causes unilateral or bilateral renal agenesis. 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. The kidneys have two functional areas that are managed and staged independently, the kidney parenchyma and the renal pelvis. Box 18-2 provides some tips regarding crossing vessels in UPJ obstruction. Literature supports the use of either multidetector computed tomography (MDCT) or MRI in donor evaluation. 18-16). Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. Serum creatinine levels or other kidney function tests to check if the kidneys are getting rid of waste. 18-13). 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. Blood supply is variable and often includes extraaortic and multiple vessel origins. Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. Causes. Occasionally, a papilla will communicate directly with an infundibulum or the renal pelvis and is considered to be an aberrant papilla. But here is a neat little mnemonic to help. Arterial stenosis was confirmed by magnetic resonance angiography. Horseshoe kidneys result from midline fusion of the kidneys, typically at the level of the origin of the inferior mesenteric artery. 18-27). I hope this helps. However, this individual is more likely to show a decline in renal function from an additional insult. Reading time: 23 minutes. Although each kidney is about the size of a fist, the approximately one million nephrons per kidney require nearly 20% of the total cardiac output to perform this multitude of functions. The phases of nephrogram development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. chronic obstruction, or severe or repeated urinary infections. Note diameter of arteries because small accessory arteries may be sacrificed in many cases. 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. The information we provide is grounded on academic literature and peer-reviewed research. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. Other methods include classical surgical removal of the stone, either through the ureter or by open surgery. This refers to the forming of the stones within the system of calyces because of too much calcium or uric acid into the filtrate. Thoracic kidneys are the least common form of renal ectopia. The anterior surface faces towards the anterior abdominal wall, whereas the posterior surface is facing the posterior abdominal wall. A, Axial image demonstrates the dilated renal pelvis and crossing vessel. MR angiography can be useful for the diagnosis of renal vascular abnormalities. Dimitrios Mytilinaios MD, PhD Creatinine is a breakdown product of creatine, found within muscle. 18-10). The vascularity of some tumors may be most apparent during this phase (Fig. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. Kidney cysts are round pouches of fluid that form on or in the kidneys. The region where the renal pelvis joins the ureter is called the, If the renal pelvis is entirely within the confines of the renal sinus, it is considered intrarenal. When fused, the condition is described as crossed fused ectopia. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see. B, A curved planar reformation of the crossing vein demonstrates its course. Each segmental branch of the renal artery divides into multiple interlobar arteries that course along the periphery of the medullary pyramids and causes small interlobular branches (Fig. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Always include unenhanced computed tomographic images to look for renal stones. This is called the nutcracker phenomenon. Although this dilatation of the renal pelvis may occasionally mimic hydronephrosis, delicate and sharply defined calyces and thin infundibula can be used to differentiate an extrarenal pelvis from obstruction. 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 opposite situation is possible too, if the kidneys excrete too many hydrogen ions, the pH of blood becomes too alkaline, and leads to a state called alkalosis. While migrating superiorly, the kidneys rotate medially along their long axes and the inferior supplying mesonephric arteries degenerate. So in the filtered fluid that goes to the renal tubule, we have both necessary and unnecessary substances. 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. However, you may have symptoms related to the condition that's causing it. 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. Renal cysts are sacs of fluid that form in the kidneys. In most kidneys, the renal hilum faces more anteromedial in the upper half of the kidney and more directly medial in the lower half. The left kidney (not shown) had a similar appearance. Anatomy Where is the renal cortex? The large left proximal ureteral stone seen in this image is only partially obstructing, causing mild dilation in the left kidney collecting system. Note that the left renal vein receives blood from the left suprarenal and left testicular veins. Eliminating toxic metabolites through urine, regulation of blood homeostasis and blood pressure, production of some hormones, Positioned retroperitoneally, consists of the cortex and medulla, empties urine into the ureter (which carries urine to the urinary bladder), Renal artery (branch of the abdominal aorta), Renal vein (drains to the inferior vena cava), Third kidney, horseshoe kidney, kidney agenesis, kidney stones, acute kidney failure, Regulates the amount of fluid in the body by increasing or decreasing the urine production, Maintain the pH of blood at 7.4 by decreasing or increasing the excretion of hydrogen ions, Medial part of the lower half of superior pole, Lateral part of the lower half of superior pole, Lateral part of inferior half of anterior surface, Medial part of inferior half of anterior surface, The perinephric fat (perirenal fat capsule). 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. 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. A, A low-attenuation lesion is difficult to identify during the corticomedullary phase. IVC, Inferior vena cava. CT angiography is occasionally performed when a vascular causative factor is suspected (renal artery stenosis or renal vein thrombosis) and MRI is contraindicated. Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. 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). It protects your kidneys from injury, increases their stability and connects your kidneys to surrounding tissues. It's not clear what causes simple kidney cysts. The muscular relations of the inferior half are easy to remember by dividing the kidney surface into three vertical stripes, where the medial stripe represents the impression of the psoas major muscle, the central stripe the quadratus lumborum, and the lateral stripe the transversus abdominis muscle. Some tumors can be slow to grow while some can be aggressive. Urine from the calyces flows to the renal sinus via tributaries called infundibula. Further testing/diagnosis is required. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. AMLs can bleed and while not cancerous are still taken very seriously. Right-sided pain was related to crossed renal ectopia. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. Note that there is no contrast in the aorta. Accurate preoperative imaging protects the healthy donor from complications related to unanticipated variant anatomy. Medullary cystic disease is encountered only rarely, and in addition to the echogenic atrophic cortex, the medullary pyramids are particularly hypoechoic. This phenomenon is due to T2-shortening and susceptibility (T2*) effects caused by concentrated gadolinium, and can potentially obscure filling defects and urothelial lesions. Other symptoms can include abnormal urine color, blood in your urine, fever, chills, nausea, and vomiting. 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. Technetium 99m dimercaptosuccinic acid (DMSA) and glucoheptonate (GHA) are both used for evaluation of renal parenchyma. 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. Duplication of the urinary tract is discussed in detail in Chapter 19. At one end of each nephron, in the cortex of the kidney, is a cup-shaped structure called the Bowman's capsule. Each pyramid creates urine and terminates into a renal papilla. Simple kidney cysts aren't cancer and rarely cause problems. The solid renal parenchyma consists of the peripheral renal cortex and more central renal medulla. 18-24). When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. Best, Susan. 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). I would honestly say that Kenhub cut my study time in half. An acute change in renal cortical echogenicity is occasionally seen with pyelonehritis. Cancer and rarely cause problems it is considered to be examined virus (! 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