Despite the complexity of renal physiology, many attempt to assess renal function with a simple quantitative measure, the serum creatinine. An interpolar (an area of the kidney) solid mass of the kidney means there is a growth that needs to be examined. A, Steady-state free precession, (B) T2-weighted with fat saturation, (C) T1-weighted, (D) T1-weighted with fat saturation, (E) postcontrast corticomedullary phase, and (F) postcontrast nephrographic phase. Of course, if the situation is the other way around (less than 5 liters of blood), blood pressure is too low (hypotension). Urine from the calyces flows to the renal sinus via tributaries called infundibula. Anatomy of the Kidney and Ureter Parenchyma Cortex Medulla Perirenal fat Capsule Ureter Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. 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 visible contrast seen in the excretory phase has been concentrated many-fold. Figure 18-9 Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. 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. 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. Each pyramid creates urine and terminates into a renal papilla. The urinary system comprises the upper urinary tracts (kidneys and ureters), the urinary bladder, and the urethra. There are many clinical states related to kidney malfunction. The relation between the UPJ and vascular anatomy can be quite complex. Chronic glomerulonephritis usually causes bilateral increased renal echogenicity with smooth atrophy, whereas renal artery stenosis usually causes a similar but unilateral appearance (Fig. 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. Weve mentioned that the most important functions of the kidney are the regulation of the blood homeostasis and blood pressure, so acute kidney failure can lead to a quick fall of blood pressure which presents as a state of shock. Table 18-6 Causes of Bilateral Small Smooth Kidneys. 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. This specific condition is called the nutcracker phenomenon. The large left proximal ureteral stone seen in this image is only partially obstructing, causing mild dilation in the left kidney collecting system. The right kidney has a normal appearance (not shown). The defect proved to be blood clot from papillary necrosis. chronic obstruction, or severe or repeated urinary infections. 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. 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. The kidneys are located between your intestines and your diaphragm. Renal size can be measured in several ways. Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. The kidneys have two functional areas that are managed and staged independently, the kidney parenchyma and the renal pelvis. 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. Other common kidney conditions are acquired through life, and one of the most common is nephrolithiasis (kidney stones). Figure 18-21 Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. 18-7). Around 40% of kidney cancers are localized renal masses. Figure 18-15 Relation between the right renal artery and the inferior vena cava (IVC). 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). Besides blood volume and pressure regulation, kidneys also participate in the production of calcitriol (the active form of vitamin D). 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. 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. The solid renal parenchyma consists of the peripheral renal cortex and more central renal medulla. Other symptoms can include abnormal urine color, blood in your urine, fever, chills, nausea, and vomiting. Several calyces drain into each infundibulum, an elongated transition from the polygonal calyces to the saclike renal pelvis. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. B, A curved planar reformation of the crossing vein demonstrates its course. Publication types Review MeSH terms Humans 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. When hydronephrosis is absent, the causative factor for acute renal failure is almost certainly prerenal or renal. Diagnostic ultrasound uses sound wave technology to look at parts of your body, including: Brain Heart and blood vessels Breast Abdominal Organs Eyes Thyroid Skin and muscles Types of Ultrasound. 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. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see. At that point, you may experience these symptoms: Severe, sharp pain in the side and back, below the ribs. These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. 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. It is important to note, however, that the appearance of hydronephrosis does not necessarily indicate urinary obstruction (see Hydronephrosis and Its Mimics section later in this chapter). urinary system quizzes and labeled diagrams. Renal Cysts. Kidneys have a special system for the excretion of hydrogen ions, and in that way consistently maintain the pH of blood at 7.4. D, If pressure on the papilla persists, the ischemic papilla undergoes necrosis, allowing the calyx to protrude outward toward the cortex. Table 18-7 Causes of Unilateral Small Smooth Kidney, Only gold members can continue reading. Also, in situations with notable blood losses, kidneys release a hormone called erythropoietin, which stimulates bone marrow to produce more blood cells. 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. The kidneys are located between the transverse processes of T12-L3 vertebrae, with the left kidney typically positioned slightly more superiorly than the right. Table 18-5 Checklist Approach to Ultrasound for Renal Failure. 18-1). 18-14). The kidneys are bilateral organs placed retroperitoneally in the upper left and right abdominal quadrants and are part of the urinary system. 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. Extraaortic origin of the renal arteries and accessory renal arteries are common. RENAL ANATOMY Renal Parenchyma The kidneys can be divided into three main regions from cranial to caudal. Figure 18-4 Illustration demonstrating the relation between the renal papilla and calyx. 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. The normal appearance of the calyx is created by the impression of the renal papilla. The renal fascia which besides the kidneys also encloses the suprarenal gland and its surrounding fat. Figure 18-3 Illustration demonstrating basic intrarenal arterial anatomy. The phases of nephrogram development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. A, Enhancement of the mass is conspicuous in the corticomedullary phase. A. Junctional cortical line seen on a long-axis ultrasound image of the right kidney. Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. 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. Note distance from origin to the first arterial division (Fig. 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. If the renal pelvis is entirely within the confines of the renal sinus, it is considered intrarenal. Pitfall: An extrarenal pelvis may be mistaken for hydronephrosis. 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. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. The shape of the calyx is formed by the impression of the renal papilla. 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. An increased amount of hydrogen ions can acidify the blood and cause a state called acidosis. 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. Each end of the kidney is commonly called a. 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. 18-5). 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. Table 18-7 lists causes of unilateral smooth renal atrophy. Figure 18-25 Sagittal ultrasound image of the left kidney demonstrates a unilateral small, smooth, echogenic kidney in a patient with renal artery stenosis. 18-24). 18-4). Read more. Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. 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. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney But here is a neat little mnemonic to help. Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. 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. Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. 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 (. 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. On the superior aspect of each kidney is the adrenal gland. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. Anatomy Where is the renal cortex? So in the filtered fluid that goes to the renal tubule, we have both necessary and unnecessary substances. Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). This causes them to fire impulses which stimulate rhythmical contraction and relaxation, called peristalsis. Thus, an AML is a tumor that contains these 3 components. On the other hand, babies with bilateral agenesis cannot survive without an immediate kidney transplant. The kidneys can be divided into three main regions from cranial to caudal. However, T1-weighted images provide good corticomedullary differentiation. But more often, kidney cysts are a type called simple kidney cysts. The genital system consists of the testes, epididymides, deferent ducts, seminal vesicles, ejaculatory ducts, the prostate, and the penis in males; and the ovaries, uterine tubes, uterus, and vagina in females. 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. 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. For most people, obstruction of a single ureter does not induce renal failure. Look for retroaortic or circumaortic left renal vein. Hypotension is a stimulus for the kidneys to increase the retention of fluid and thus increase blood pressure. It participates in vital processes such as regulation of blood osmolarity and pH, regulation of blood volume and blood pressure, production of hormones, and filtration of foreign substances. Because the fascia of the retroperitoneum prevents significant extravasation, the incision usually heals to form a larger lumen. Figure 18-20 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. Enlargement of a congenitally unilateral kidney is typical and presumed to be compensatory. BOX 18-1 Cockroft and Gault Equation for Calculating Estimated Creatinine Clearance. Illustration demonstrating the anatomy of the renal collecting system. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. 18-3). 18-21). More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. The solid renal parenchyma consists of the peripheral renal cortex and more central renal medulla. Typically, one kidney sits on either side of your spine. Read More Created for people with ongoing healthcare needs but benefits everyone. After looking at the overview of the kidneys in situ, it may seemas they are cluttered with all abdominal organs. The minor calyces unite to form a major calyx. An acute change in renal cortical echogenicity is occasionally seen with pyelonehritis. In the medulla, 5-8 renal pyramids are separated by connective tissue renal columns. 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. Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. The ureters are the tubes that carry urine from the renal pelvis to the bladder. 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