But here is a neat little mnemonic to help. It doesn't have to be that way. A, Tips of the fornices are sharply defined. The portion of the kidney between the poles is called the interpolar region and contains the renal hilum (Fig. Urine that is concentrated in the renal papilla is subsequently excreted into a lumen lined with transitional epithelium. The superior poles (extremities) (T12) of both kidneys are more medially pointed towards the spine than the inferior poles (extremities) (L3). 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. Frontal image of the left kidney from an intravenous urogram demonstrating an aberrant renal papilla in the lower pole infundibulum. Radiologists divide the kidney into three parts: the upper pole, lower pole, and the interpole (which is in between them). The kidneys help remove waste products from the . At the Brady Urological Institute, we believe in the adage, "An ounce of prevention is worth a pound of cure," so we place great emphasis on a thorough metabolic evaluation, so that therapies can be appropriately directed towards reducing the risk of recurrent stone disease. 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. 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. The renal pelvis then tapers like a funnel to join the ureter. This refers to the forming of the stones within the system of calyces because of too much calcium or uric acid into the filtrate. Static-fluid (T2-weighted) MR urography and phase-contrast MR angiography are useful techniques that do not require intravenous contrast material. The patient had right flank pain but had a solitary calcification in the left pelvis on plain radiograph (not shown). normal kidney size in adults normal kidney size in children Structure The isthmus connecting the kidneys is variable, ranging from normal renal cortex to a thin fibrous band. Calcifications and renal calculi are notoriously poorly demonstrated with MRI. 18-19). General symptoms of kidney problems include: blood in your urine . 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. But more often, kidney cysts are a type called simple kidney cysts. Each time a professor says 'nephron', a student gets a headache. 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. Caliectasis doesn't cause any symptoms on its own. 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 (. 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). The large left proximal ureteral stone seen in this image is only partially obstructing, causing mild dilation in the left kidney collecting system. 18-21). Extraaortic origin of the renal arteries and accessory renal arteries are common. 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). Technetium 99m-mercaptoacetyltriglycin (MAG3) is excreted by the kidneys (mainly through secretion by proximal tubules) and provides evaluation of renal function, particularly in cases of suspected obstruction. 18-24). Other methods include classical surgical removal of the stone, either through the ureter or by open surgery. The renal veins empty to the inferior vena cava, so the right vein is shorter because the inferior vena cava runs closer to the right kidney. Ultrasound can often identify the cause in cases of bilateral obstruction (, Pelvic mass (cervical, rectal, uterine, prostate cancer). The dynamics of obstruction and quantification of relative renal function between the two kidneys may be important considerations in two general circumstances: (1) it is unclear whether obstruction is severe enough to warrant surgical intervention; or (2) significant parenchymal atrophy exists, and the relative merits of repair and nephrectomy are being compared. The renal cortex and medulla both have high signal intensity on T2-weighted images resulting in poor corticomedullary differentiation. BOX 18-1 Cockroft and Gault Equation for Calculating Estimated Creatinine Clearance. The normal appearance of the calyx is created by the impression of the renal papilla. Many clinical laboratories now provide computer-generated calculations of estimated creatinine clearance or eGFR using patient data in the medical information system. development and contrast excretion parallel those seen on contrast-enhanced CT with one notable exception (Fig. Pain that radiates to the lower abdomen and groin. Duplication of the urinary tract is discussed in detail in Chapter 19. The patient had acute renal failure; therefore, contrast-enhanced CT was not performed. 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. Hydronephrosis is important to detect, because obstructive uropathy is often reversible if identified early. 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. The segmental arteries then branch into the interlobar arteries, which further branch into the arcuate arteries. It's not clear what causes simple kidney cysts. 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 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. 18-27). The adrenal cortex directly influences renal function through the production of the hormone aldosterone to stimulate sodium reabsorption. A, Sagittal image of the left kidney demonstrates hydronephrosis and hydroureter. 18-3). 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. Bone scan and chest x-ray to find out if the cancer has spread. A, Soft-tissue windows demonstrate no filling defect. The early excretory phase begins as early as 120 seconds after injection. Normal parenchymal enhancement on CT or MRI allows definitive characterization. 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. 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. You can test yourself on the renal arteries with our quiz. Unenhanced MRI can also be used to diagnose obstruction and identify the source (Fig. Right-sided pain was related to crossed renal ectopia. 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. B, Transverse image of the bladder demonstrates a large bladder tumor in the region of the trigone. Note origin of inferior accessories near inferior poles on each side. B, A small calyceal defect is seen when the same image is viewed using bone windows. This phenomenon is due to T2-shortening and susceptibility (T2*) effects caused by concentrated gadolinium, and can potentially obscure filling defects and urothelial lesions. RENAL ANATOMY Renal Parenchyma The kidneys can be divided into three main regions from cranial to caudal. 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. 18-2). 18-25). AMLs can bleed and while not cancerous are still taken very seriously. Coronal maximum intensity projection image from a contrast-enhanced computed tomographic scan demonstrates a dilated and tortuous lumbar veins joining the left renal vein. 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. Blood in the urine, or dark urine. Ultrasound is usually used in the initial evaluation of the patient with newly diagnosed renal failure. and parenchymal mass without the risks for nephrotoxicity associated with iodinated contrast media or nephrogenic systemic fibrosis associated with gadolinium contrast agents. Solid masses are more likely to be cancerous but they are not all cancerous. Other common kidney conditions are acquired through life, and one of the most common is nephrolithiasis (kidney stones). Living renal donor allografts account for more than half of the transplanted kidneys in the United States. Because they rarely cause symptoms, renal cysts are most often found during . Figure 18-13 Volume rendering from a computed tomographic scan of the kidneys shows bilateral supernumerary renal arteries (three on right, two on left). 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. 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