2023 Blood supply is variable and often includes extraaortic and multiple vessel origins. Figure 18-4 Illustration demonstrating the relation between the renal papilla and calyx. 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. Renal size can be measured in several ways. Anterior components of circumaortic vein can be small. Crossed ectopia on intravenous pyelogram. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. Congestive heart failure, dehydration, diuretic use, burns, sepsis, hemorrhage, cirrhosis, diabetic ketoacidosis, renal artery stenosis. Illustration demonstrating the anatomy of the renal collecting system. Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein. Table 18-6 lists the most common causes of bilateral smooth renal atrophy. The anteromedial aspect of the interpolar region is interrupted by the renal hilum to make a C shape. In other cases, each renal unit has its own ureter. But more often, kidney cysts are a type called simple kidney cysts. 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. Anatomical Position of the Kidneys Kidney Structure These are chronic processes that lead to a loss of renal cortex gradually and uniformly. Any excessive amount of fluid will increase the pressure on the arterial wall and cause the blood pressure to rise (hypertension). 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. The kidney tissue is protected by three layers that entirely surround the kidney: Outside the fascia is the most superficial layer a layer of fat tissue called the paranephric fat. Read More Created for people with ongoing healthcare needs but benefits everyone. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. 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. 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. This plexus provides input from: The sensory nerves from the kidney travel to the spinal cord at the levels T10-T11, which is why the pain in the flank region always rises suspicions that something is wrong with the corresponding kidney. RENAL ANATOMY Renal Parenchyma The kidneys can be divided into three main regions from cranial to caudal. 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. Since the abdominal organs are not paired, the left kidney is not related to the same organs as the right kidney. 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. 18-11). The small portion of the lumen surrounding the papilla is called the. The renal fascia which besides the kidneys also encloses the suprarenal gland and its surrounding fat. The solid renal parenchyma consists of the peripheral renal cortex and more central renal medulla. This specific condition is called the nutcracker phenomenon. 18-25). In other cases, each renal unit has its own ureter. Supernumerary kidneys are quite rare and have been associated with aortic coarctation, vaginal atresia, and urethral duplications. The corticomedullary phase is prolonged in the presence of ureteral or venous obstruction and can persist for days in cases of acute tubular necrosis (ATN; Fig. The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. 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. Made. Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. 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. The nephrons within the cortex comprise some of the most highly perfused parenchymal tissue in the body. The renal pelvis then tapers like a funnel to join the ureter. 18-20). Global insult to one kidney may result in unilateral atrophy that is uniform and smooth. The kidneys serve important . Estimated creatinine clearance may be calculated using serum creatinine with adjustments made for sex, age, and body weight. 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 patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). In this region, the anterior and posterior hilar lip is identified (Fig. A second similar finely granular mass was present in the interpolar region, and it also contained . Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Figure 18-5 Illustration demonstrating the anatomy of the renal collecting system. Kidney cysts are round pouches of fluid that form on or in the kidneys. Illustration demonstrating the relation between the renal papilla and calyx. On the other hand, babies with bilateral agenesis cannot survive without an immediate kidney transplant. Even when there is another plausible explanation for decreased renal function (e.g., known prerenal causes), ultrasound offers the opportunity to rapidly and noninvasively identify a potentially correctible cause of renal failure. If the renal pelvis extends out of the renal sinus, it is considered to be an extrarenal pelvis (Fig. 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. 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. Advantages of scintigraphy include accurate quantitative measurement of function. Duplication of the urinary tract is discussed in detail in Chapter 19. The cortex of a normal kidney is usually less echogenic than the adjacent normal liver. However, small, low-attenuation lesions in the medulla are often obscured during this phase. The visible contrast seen in the excretory phase has been concentrated many-fold. 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. These terminal branches have no collateral circulation. 18-22). Bilateral echogenic kidneys with renal hypertrophy can be seen associated with human immunodeficiency virus disease (see Fig. 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. They are branches of the abdominal aorta and all together are called the extrahilar renal arteries. Kidney cysts can occur with disorders that may impair kidney function. Ultrasound It can be seen as a triangular echogenic cortical defect, frequently seen in upper lobe parenchyma. 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. I would honestly say that Kenhub cut my study time in half. Table 18-1 provides a quick guide itemizing key imaging findings in the potential renal donor. The bilateral small smooth kidney pattern describes most of what is often diagnosed on sonography as medical renal disease, although the authors prefer the term renal parenchymal disease. If this appearance were present bilaterally, chronic renal disease such as chronic glomerulonephritis would be a more likely explanation. 18-13). Because the interlobular arteries form an arch overlying the pyramid, they are called the. Renal Cysts. Now lets pay attention to the borders of the kidneys. Some tumors can be slow to grow while some can be aggressive. Retrograde urogram shows a calculus in the left ureter. Urine that is concentrated in the renal papilla is subsequently excreted into a lumen lined with transitional epithelium. Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). If the renal pelvis extends out of the renal sinus, it is considered to be an. Association between Renal Cortical Echogenicity and Renal Parenchymal Disease. Right-sided pain was related to crossed renal ectopia. Note origin of inferior accessories near inferior poles on each side. Ultrasound permits real-time optimization of imaging relative to the axis of each kidney. In this way, the consistency of blood is preserved and no important substances are lost. In this case, the right kidney had more favorable anatomy for laparoscopic donor nephrectomy. Because the fascia of the retroperitoneum prevents significant extravasation, the incision usually heals to form a larger lumen. When the renal cortex is more echogenic than the adjacent liver, there is a high correlation with renal disease, although sensitivity is relatively low, according to Platt and colleagues (Fig. 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). They extend from lumbar vertebra T12-L3. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. Maintaining kidney health. 18-24). For most people, obstruction of a single ureter does not induce renal failure. The interpolar region is the middle of the kidney. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. Besides blood volume and pressure regulation, kidneys also participate in the production of calcitriol (the active form of vitamin D). and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. The presence of significant renal parenchyma may justify surgical repair to maximize the functional contribution of that kidney. 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. The left kidney appeared unremarkable. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. 18-10). Each nephron contains a renal corpuscle, which is the initial component that filters the blood, and a renal tubule that processes and carries the filtered fluid to the system of calyces. All content published on Kenhub is reviewed by medical and anatomy experts. Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. Axial image of the left kidney from a contrast-enhanced computed tomographic scan demonstrates an extrarenal pelvis. Box 18-2 provides some tips regarding crossing vessels in UPJ obstruction. 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