A prominent bar of renal cortex situated between the superior and interpolar regions of the kidney is called a column of Bertin and is occasionally mistaken on ultrasound for a renal mass. impression is preserved. 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. In most cases, the kidneys are situated with the inferior poles slightly more lateral and anterior than the superior poles. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. The renal cortex is part of your kidney, which itself is part of the urinary tract. The ureters are the tubes that carry urine from the renal pelvis to the bladder. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. Jana Vaskovi MD The lateral border is directed towards the periphery, while the medial border is the one directed towards the midline. However, you may have symptoms related to the condition that's causing it. The anterior surface faces towards the anterior abdominal wall, whereas the posterior surface is facing the posterior abdominal wall. Increased cortical echogenicity is associated with many forms of chronic renal parenchymal disease and indicates a renal cause for renal failure. This article will discuss the anatomy and major functions of the kidney. Kidney cysts are round pouches of fluid that form on or in the kidneys. This phenomenon is due to T2-shortening and susceptibility (T2*) effects caused by concentrated gadolinium, and can potentially obscure filling defects and urothelial lesions. Table 18-1 provides a quick guide itemizing key imaging findings in the potential renal donor. These surfaces are separated by the edges of the kidney, which are the major convexity laterally, and minor concavity medially. They are usually characterized as "simple" cysts, meaning they have a thin wall and contain water-like fluid. 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). 18-27). 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. Despite the complexity of renal physiology, many attempt to assess renal function with a simple quantitative measure, the serum creatinine. Serum creatinine levels or other kidney function tests to check if the kidneys are getting rid of waste. B, Low-attenuation lesion in the late nephrographic/early excretory phase is less suspicious in appearance. B, Transverse image of the bladder demonstrates a large bladder tumor in the region of the trigone. 18-13). The left artery has a short way to the left kidney, whereas the right has to go behind the inferior vena cava in order to reach the right kidney. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. A. Junctional cortical line seen on a long-axis ultrasound image of the right kidney. Read more. The kidneys are innervated by the renal plexus. Alternatively, the anterior to posterior orientation follows the same pattern: renal vein, renal artery and ureter. B, A small calyceal defect is seen when the same image is viewed using bone windows. Read more. Duplication of the urinary tract is discussed in detail in Chapter 19. The vascularity of some tumors may be most apparent during this phase (Fig. 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. Kidney stones are most often treated by ultrasound shock therapy, during which high-frequency radio waves break the stone into smaller pieces that can be passed naturally into the urine. The kidneys have two functional areas that are managed and staged independently, the kidney parenchyma and the renal pelvis. 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. The apex of the pyramid projects medially toward the renal sinus. Box 18-2 provides some tips regarding crossing vessels in UPJ obstruction. 18-25). Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. 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. 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. The interpolar region is the middle of the kidney. It can be caused by a variety of factors, but most often arises because of the ischemia of the kidney and the toxic effect of some medications, resulting in the failure of all kidney functions. The presence of contour irregularity usually indicates scarring, suggesting prior infection, reflux, or infarction. Usually, there are two to three major calyces in the kidney (superior, middle, and inferior), which again unite to form the renal pelvis from which the ureter emerges and leaves the kidney through the hilum. 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. This method is the standard in evaluation of UPJ obstruction and often is used for other types of chronic obstruction. 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. Always include unenhanced computed tomographic images to look for renal stones. Although ureteral contrast media is typically present before 3 minutes, longer delays provide more predictable opacification. Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). 18-4). Figure 18-18 Single-detector computed tomographic images from ureteropelvic junction deformity in the right side of a horseshoe kidney. 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. Look for duplication, large extrarenal pelvis. Entities for which sonography is most useful. The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. Prominent extrarenal pelves are typically positioned anteriorly (Fig. 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. Thoracic kidneys are the least common form of renal ectopia. More tenuous vascular supply to the renal medulla makes it more susceptible to ischemia. This refers to the forming of the stones within the system of calyces because of too much calcium or uric acid into the filtrate. 18-6). Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney 18-16). The defect proved to be blood clot from papillary necrosis. MR angiography can be useful for the diagnosis of renal vascular abnormalities. In most cases, the kidneys are situated with the inferior poles slightly. Around 40% of kidney cancers are localized renal masses. 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. Localized means that the tumor has not spread out from where it first started. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. 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 left kidney appeared unremarkable. CT angiography is occasionally performed when a vascular causative factor is suspected (renal artery stenosis or renal vein thrombosis) and MRI is contraindicated. 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. Because the fascia of the retroperitoneum prevents significant extravasation, the incision usually heals to form a larger lumen. While migrating superiorly, the kidneys rotate medially along their long axes and the inferior supplying mesonephric arteries degenerate. Most radiologists consider 10 to 12 cm to be an approximate reference range for renal length in adults, allowing for an additional 1 cm in either direction for patients at the extremes of height. The left kidney (not shown) had a similar appearance. Look for retroaortic or circumaortic left renal vein. The kidney also has endocrine functions, helping to control blood pressure, bone mineralization, and erythrocyte production. Figure 18-9 Coronal computed tomographic image in the corticomedullary phase shows normal corticomedullary differentiation along the lobulated contour, consistent with fetal lobulation. Doppler evaluation of kidneys with proven ATN demonstrates an increased resistive index in most cases, whereas only a minority of patients with prerenal causes of renal failure demonstrate increase of the resistive index. 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. Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein. In most kidneys, the renal hilum faces more anteromedial in the upper half of the kidney and more directly medial in the lower half. 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. Note origin of inferior accessories near inferior poles on each side. Register now The glomerulus is actually a web of arterioles and capillaries, with a special filter which filters the blood that runs through the capillaries, the glomerular membrane. 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. The kidneys are located between your intestines and your diaphragm. 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. B, A curved planar reformation of the crossing vein demonstrates its course. Since they are located deep retroperitoneally, the easiest way to examine them is from the patients back. 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. The kidneys play a central role in homeostasis. Crossed ectopia can be either fused or unfused. 18-21). Now lets pay attention to the borders of the kidneys. Other common kidney conditions are acquired through life, and one of the most common is nephrolithiasis (kidney stones). 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. Table 18-5 Checklist Approach to Ultrasound for Renal Failure. 18-19). The renal pelvis then tapers like a funnel to join the ureter. Because an extrarenal pelvis is not confined by the renal parenchyma, there is a tendency for it to expand. Yet, the relations of the kidneys with other organs are often found in Anatomy tests. The small portion of the lumen surrounding the papilla is called the calyx. Kidney cysts can occur with disorders that may impair kidney function. 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