Frequent urination (having to go the bathroom often). Besides blood volume and pressure regulation, kidneys also participate in the production of calcitriol (the active form of vitamin D). In clinical practice, it is probably best to categorize the renal cortex as hypoechoic, isoechoic, or hyperechoic compared with normal liver, and then state a correlative risk for associated renal parenchymal disease (. Read more. Living renal donor allografts account for more than half of the transplanted kidneys in the United States. Renal function is better evaluated by measured creatinine clearance, which takes into account not only the amount of creatinine in the blood but also the amount of creatinine within a specified volume of urine over a given period. 18-1). 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. The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption. The left kidney measured 7.8 cm, and the right kidney measured 10.9 cm. The most common cause is renal artery stenosis (see, Delayed but increasingly dense nephrogram, Delayed but hyperconcentrated contrast excretion, Imaging Evaluation of Acute Abdominal Pain, A Multidimensional Approach to Abdominal Imaging. The presence of contour irregularity usually indicates scarring, suggesting prior infection, reflux, or infarction. In other cases, both kidneys can be fused, usually at the inferior poles, which is a congenital state called the horseshoe kidney. Note number of veins by inspecting inferior vena cava along entire length of kidney. The kidneys are a pair of bean-shaped organs located below the rib cage, one on each side of the spine. Figure 18-15 Relation between the right renal artery and the inferior vena cava (IVC). The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. When simple kidney cysts do cause symptoms, they might include: Pain in the side between the ribs and hip, stomach or back. A, Enhancement of the mass is conspicuous in the corticomedullary phase. Normally, the kidney is about the size of a mouse and measures approximately 11-12 cm in length, 5-6 cm in width, and 2.5-3 cm in thickness. 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. The interpolar region is the middle of the kidney. Due to the segmental vascular supply of the kidney it is often feasible to ligate the relative arteries and veins and remove the tumour with a safe zone of healthy surrounding parenchyma ( partial nephrectomy) without removing the entire kidney or compromising its total vascular supply by ischaemia. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. 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. Figure 18-24 Normal magnetic resonance imaging appearance of the kidneys. Last reviewed: December 28, 2022 B, A small calyceal defect is seen when the same image is viewed using bone windows. 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. The region where the renal pelvis joins the ureter is called the ureteropelvic junction (UPJ). Ultrasound is usually used in the initial evaluation of the patient with newly diagnosed renal failure. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (whi. 18-14). Kidney cysts can occur with disorders that may impair kidney function. AMLs can bleed and while not cancerous are still taken very seriously. A, Axial image from contrast-enhanced computed tomography (CT) demonstrates an accessory right renal artery coursing anterior to the IVC. Created for people with ongoing healthcare needs but benefits everyone. The uniform high attenuation of the nephrographic phase provides an optimal background for detecting small, low-attenuation lesions in the renal parenchyma (Fig. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (which is in between them). normal kidney size in adults normal kidney size in children Structure In most cases, the kidneys are situated with the inferior poles slightly more lateral and anterior than the superior poles. 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. The ureter and calyces were not dilated (not shown), helping to differentiate this anatomic variant from obstruction. urinary system quizzes and labeled diagrams. and grab your free ultimate anatomy study guide! Calcifications and renal calculi are notoriously poorly demonstrated with MRI. 18-19). Ultrastructurally, the nephron is the functional representative of the kidney. 18-19). The kidneys are innervated by the renal plexus. However, T1-weighted images provide good corticomedullary differentiation. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney In addition to the renal artery, accessory renal arteries are present too. The isthmus connecting the kidneys is variable, ranging from normal renal cortex to a thin fibrous band. Figure 18-5 Illustration demonstrating the anatomy of the renal collecting system. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. 18-22). Size disparity greater than 1.5 cm between kidneys should raise suspicion that one kidney is abnormal. Jana Vaskovi MD There are many clinical states related to kidney malfunction. Luckily, the kidneys also feel this increase of pressure, and in cases when this happens, they increase the filtration rate of blood and production of urine, which subsequently leads to the increase fluid excretion and decrease of blood pressure. 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. Figure 18-19 Sagittal ultrasound image of the right kidney demonstrates increased size and echogenicity of the kidney, findings typical of human immunodeficiency virus nephropathy. Other symptoms can include abnormal urine color, blood in your urine, fever, chills, nausea, and vomiting. Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours. You can test yourself on the renal arteries with our quiz. The kidneys can be divided into three main regions from cranial to caudal. 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. 18-28). In most cases, unenhanced CT is performed when the duration and cause of renal failure are unknown because exposure to iodinated contrast media could impair recovery of renal function. This kidney measured 14 cm in length. When multiple clefts in the renal cortex are present throughout the kidney, it is described as fetal lobulation. It protects your kidneys from injury, increases their stability and connects your kidneys to surrounding tissues. Typically, one kidney sits on either side of your spine. 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. In clinical practice, it is probably best to categorize the renal cortex as hypoechoic, isoechoic, or hyperechoic compared with normal liver, and then state a correlative risk for associated renal parenchymal disease (Table 18-2). Clinical significance [ edit] 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. However, this individual is more likely to show a decline in renal function from an additional insult. Note distance from origin to the first arterial division (Fig. Figure 18-6 Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Overview. 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. 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. 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. Further testing/diagnosis is required. Relation between the right renal artery and the inferior vena cava (IVC). Sometimes, one or both kidneys fail to develop, which causes unilateral or bilateral renal agenesis. When abnormal echogenicity is detected, it is important to note whether it is unilateral or bilateral. Dialysis. 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. 18-3). In this region, the anterior and posterior hilar lip is identified (Fig. Kidneys have a special system for the excretion of hydrogen ions, and in that way consistently maintain the pH of blood at 7.4. Comparative views of the CT scan ( a axial, b coronal, and c sagittal planes) and corresponding views of the physical model ( d superior view, e median view, and f median view). Imaging must provide detailed images of the renal parenchyma and a survey of arterial, venous, and ureteral anatomy. CT scan and MRI to help diagnose and stage kidney masses. Differential diagnosis General imaging considerations include: renal cortical defect duplex kidney 18-13). The left kidney (not shown) had a similar appearance. 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. Solid masses are more likely to be cancerous but they are not all cancerous. The parenchyma of the kidney consists of the outer renal cortex, and inner renal medulla. Obstruction can cause renal failure if it is bilateral (Box 18-3) or if there is preexisting disease in the unobstructed kidney. Normal parenchymal enhancement on CT or MRI allows definitive characterization. Axial images from contrast-enhanced computed tomography demonstrate transient enhancement of a small renal cell carcinoma. Figure 25.1.2 Left Kidney. Entities for which sonography is most useful. However, sometimes ureteroscopy is required to confirm the diagnosis in patients with hematuria. 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.
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