Chapter 5 / Basic Imaging in Urology 63 Fig. 2. Plain-film KUB showing a round density (arrow) overlying the left renal shadow indica- tive of a left renal calculus. (From ref. 3.) Fig. 1. Normal plain-film KUB showing the renal shadows (white arrows) caused by perinephric fatty tissue, and psoas shadows (open arrows). (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM63 64 Richman and Resnick UROGRAPHY Urography involves injection or instillation of contrast material to better visualize the collecting or lumenal structures of the kidneys, ureters, bladder, and urethra. This can be done after intravenous injection or direct instillation into the urinary tract. Intravenous Urography The intravenous urogram (IVU), also called the intravenous pyelogram, is the clas- sical modality for imaging the entire urothelial tract from the pyelocalyceal system through the ureters to the bladder. Although newer imaging modalities are frequently used in place of the IVU, the IVU is an excellent study for identifying small urothelial lesions as well as the severity of obstruction from calculi. This study provides anatomical and qualitative functional information about the kidneys (Figs. 4 and 5). The IVU is performed after a gentle bowel catharsis to reduce interference from air or stool in the intestines. A preliminary KUB is taken. This film is used to demonstrate calculi or other abnormal calcifications that may be obscured by the contrast. Radio- graphic contrast is then injected, usually as a bolus, and a second image is obtained. This first contrast image is the nephrogram phase and shows enhancement of the renal shad- ows as the kidneys are perfused with contrast. Additional images are taken at timed intervals to display excretion into the collecting system, and drainage through the ure- ters. Filling of the bladder with contrast can demonstrate mucosal lesions or foreign bodies, which are represented as filling defects (Fig. 6). Nephrotomograms are fre- quently obtained to better visualize the more posterior upper and anterior lower renal poles. Tomograms can also be used to eliminate interference from overlying bowel gas. Fig. 3. Plain-film KUB showing calcific densities overlying bilateral pelvicalyceal systems indicative of “staghorn” calculi. Bilateral percutaneous nephrostomy tubes (white arrows) are seen. (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM64 Chapter 5 / Basic Imaging in Urology 65 Fig. 4. Normal excretion phase of an intravenous urogram. The kidneys, collecting systems, ureters, and bladder appear normal. Bowel catharsis before the study is to prevent obscuring bowel gas (arrows). S, spine; B, bladder. (From ref. 3.) Fig. 5. Coned-down image of the IVU in Fig. 2 showing normal nephrogram and sharply defined calyces (solid arrows), which drain to the renal pelvis (symbols) by way of the infundibula (open arrows). The ureteropelvic junctions and proximal ureters are normal. (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM65 66 Richman and Resnick The study is usually continued for 45 min or until the right and left collecting systems and ureters are adequately seen. Delayed views are often needed in obstructed systems. A postvoid image is also taken to show bladder residual volume and to allow further drainage of the upper tracts. The postvoid film can sometimes reveal small urothelial lesions of the bladder that were previously obscured when full of contrast containing urine. Cystography Cystography permits imaging of an opacified urinary bladder after retrograde instil- lation of contrast media through a urethral or suprapubic catheter. Imaging is usually performed with fluoroscopy to allow real-time imaging. This study is most often used to demonstrate a suspected urine leak, either from traumatic bladder rupture or after bladder surgery. Cystography can also be used to demonstrate the presence of a fistula between the bladder and the vagina or the bowel and to identify and characterize bladder diverticuli. Cystography is performed by first obtaining a plain film before instillation of contrast media. As with the IVU, this shows the underlying anatomy of the area to be opacified. Fig. 6. IVU of a patient showing a large filling defect in the left side of the bladder from an invasive carcinoma (white arrows). The left kidney is not functioning (there is no contrast excre- tion) because of a distal ureteral obstruction from the bladder tumor (open arrows). The right kidney appears normal. (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM66 Chapter 5 / Basic Imaging in Urology 67 Contrast material is then instilled into the bladder through the urethral or suprapubic catheter until the bladder is distended. Images may be taken in various planes to fully evaluate the bladder. The bladder is drained, and a postdrainage film is taken to evaluate for abnormalities previously obscured by the distended bladder. Bladder rupture can be extra or intraperitoneal. Extraperitoneal extravasation forms an irregular shape, and intraperitoneal extravasation follows the contour of the bowel and other visceral organs. Fistulas can be identified when adjacent, nonurinary organs are opacified with contrast. Voiding Cystourethrography Voiding cystourethrography (VCUG) can be used to evaluate for abnormal anatomy and function of the lower urinary tract in both children and adults. This study is started similar to the cystogram with instillation of contrast material into the bladder through a urethral catheter. After full distension of the bladder, the patient is instructed to void either after removing the catheter or around the catheter. Abnormal findings include vesicoureteral reflux (VUR), ureterocele, posterior ure- thral valves, or strictures in males and urethral diverticula and bladder or urethral hypermobility in females. VUR (Fig. 7) predisposes the patient to upper-urinary tract infections and subsequent renal damage. There is an international grading system for VUR with a range of I to V. Grade I is the reflux of urine into the ureter without reaching Fig. 7. VCUG showing reflux of contrast material into the right pelvicalyceal system without hydroureteronephrosis (grade II). B, bladder. (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM67 68 Richman and Resnick the renal pelvis. Grade II reflux extends to the renal pelvis without abnormal dilation. Grade III reflux has dilation of the renal pelvis and ureter, and grades IV and V reflux describe increasing severity of dilation from blunting of the renal calyces to complete renal distortion and intrarenal reflux. Retrograde Urethrography Complete evaluation of the urethra includes both antegrade and retrograde urethro- graphy. The antegrade urethrogram is part of the VCUG as described above. The retro- grade urethrogram allows visualization of the anterior male urethra. This is used for evaluating a suspected traumatic urethral injury or urethral stricture. It can also be useful for diagnosis of a urethral diverticulum in females. The procedure involves placing a catheter in the fossa navicularis and occlusion of the urethral meatus with 1 to 2 mL of water in the catheter balloon. Contrast is gently instilled and images are obtained of the anterior urethra. For female retrograde urethrography, a double balloon catheter (Trattner type) with one balloon at each end of the urethra can be used to fully distend and evaluate the urethra. ULTRASONOGRAPHY Sonography uses ultrasound frequencies to image organs of the body. Images are produced by using a transducer that emits ultrasonic waves into the tissues, and then detects those that are reflected back to the transducer. Medical sonography uses frequen- cies that are between 3.5 and 10 Mhz, which is beyond the range of human hearing, hence the term ultrasound. Lower frequencies have better tissue penetration and are better for imaging deeper structures, whereas more superficial structures are better imaged with higher frequency ultrasound. Ultrasound transducers are piezoelectric crystals that use the pulse-echo principle, transforming electrical energy into ultrasonic waves and generating an electric energy potential when struck by reflected waves. This energy potential is digitized and dis- played on the monitor screen as an image. When the burst of ultrasound waves from the transducer encounter an interface between tissues of different density or stiffness, ech- oes are produced. This difference in tissues is referred to as acoustic impedence, and if the difference is small, few of the sound waves are reflected to the transducer. When the acoustic impedence is large, many of the pulsed waves are reflected to the transducer. The differing impedence of various tissues relative to surrounding tissues results in the image seen on the monitor screen. Real-time ultrasonography, which is most commonly used, is the continuous, live-image generation that occurs as the transducer is moved from one area to another. This permits dynamic imaging of the function of a single organ or the relationship between adjacent organs or structures. Doppler sonography detects a moving object, such as blood flow, moving toward or away from the transducer. The Doppler effect is the change in frequency of the sound pulse when it is reflected from a moving object. This can be used to detect the presence and degree of blood from within an artery or a vein. Color Doppler imaging takes the Doppler information from real-time gray scale imaging and converts it to color-coded imaging to facilitate differentiation between flow toward and away from the transducer. Power Doppler ultrasound has increased sensitivity for detecting blood flow in smaller vessels by displaying the integrated power of the Doppler signal. This modality does not, however, show the direction or velocity of flow. 05_Rich_061-090_F 12/2/03, 8:24 AM68 Chapter 5 / Basic Imaging in Urology 69 Ultrasound is widely used for diagnostic purposes in urology. It serves as a portable, non- or minimally invasive technique that does not produce ionizing radiation, and with a skilled operator, can produce accurate, high-quality imaging studies. It is commonly used for imaging the kidneys, ureters, bladder, prostate, testis, and scrotum. Kidney Sonography can be used to evaluate the renal parenchyma as well as the pyelocalyceal system. Ultrasound of the parenchyma can show lesions, such as cysts and tumors, and differentiate between the two. It can also be used to evaluate the thickness and echogenicity of the parenchyma. Increased echogenicity of the cortex is often an indi- cator of medical renal diseases. The normal appearance of the kidney on ultrasound is a low-echogenic, bean-shaped organ with increased echogenicity of fat within the central renal sinus (Fig. 8). The central echo complex normally has no significant lucent areas, and the presence of a hypoechoic lucency indicates hydronephrosis. The renal cortex is typically slightly less echogenic than the adjacent liver. The normal adult sonographic length of the kidney is typically between 9.5 and 13 cm. Renal cortical lesions can usually be differentiated with sonography alone or in com- bination with other imaging modalities. Ultrasound is very effective for differentiating benign cortical cysts from suspicious solid lesions. Cysts appear as anechoic structures with very thin walls and enhanced posterior acoustic transmission. Cystic masses may be hypoechoic or anechoic, with thickened walls, septa, and decreased or absent poste- Fig. 8. Sagittal sonogram of a normal right kidney. The renal parenchyma (open arrows) is less echogenic than the adjacent liver (L). The bright central sinus (symbol) is very echogenic because of the presence of fat. (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM69 70 Richman and Resnick rior acoustic transmission. Solid renal masses are variably echogenic, may have calci- fications, and have decreased through transmission. Calcifications are hyperechoic and produce acoustic shadows that block through transmission. Although sonography has very high sensitivity for detection of renal masses, staging of parenchymal and urothelial tumors is not as sensitive as computed tomography or magnetic resonance imaging in regard to detection of lymphadenopathy, capsular inva- sion, and invasion of adjacent structures. Ultrasound is useful for detecting tumor throm- bus extension into the inferior vena cava. Hydronephrosis is seen on sonography as an anechoic space within the bright echoes of the central renal sinus (Fig. 9). This anechoic space will include the ureter with hydroureteronephrosis. When infected urine with debris or hematuria with clots is present in the hydronephrotic renal pelvis, the sonographic appearance will be more hypoechoic than anechoic, and the debris can give variable echogenic shadows. Calculi, like paren- chymal calcifications are hyperechoic and block through transmission, creating acoustic shadows. Ureter The normal, nondilated ureter cannot be adequately evaluated by sonography. The ureteropelvic and ureterovesical junction can be visualized when abnormalities result in dilation of the structure. Calculi and ureteroceles, when present, can be seen with ultra- sound. Calculi in the distal ureter, like those in the renal pelvis and calyces are hyperechoic with posterior shadowing. A ureterocele appears as a round, anechoic, intravesical structure, adjacent to a dilated distal ureter. The ureterocele may contain a calculus that would appear as described above. Fig. 9. Longitudinal sonogram of a right kidney with hydronephrosis. There is dilation of the renal calyces and separation of the central sinus by nonechogenic urine (arrow). (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM70 Chapter 5 / Basic Imaging in Urology 71 Bladder Transabdominal bladder sonography is commonly performed and can be used to assess bladder volume or postvoid residual volume, bladder wall thickness, and the presence of intraluminal disorders such as tumors or calculi. Transurethral bladder ultra- sound can be used at the time of cystoscopy for staging bladder neoplasms, however this practice is not commonly used. Prostate Sonography of the prostate gland is commonly used for guidance during transrectal or transperineal core needle biopsy of the prostate. The prostate gland is examined sonographically with an endolumenal probe at a frequency of 5 to 7 Mhz using a transrectal approach. The normal gland is a symmetric, triangular, or ellipsoid organ surrounded by periprostatic fat that has a bright echogenic appearance. It normally has a sonographically measured volume of 10 to 25 cm 3 . Benign prostatic hyperplasia on ultrasound has a mixed heterogeneous transition zone that is usually somewhat hypoechoic compared with the homogeneous surrounding peripheral zone (Fig. 10). Prostate cancer usually appears as a hypoechoic lesion in the peripheral gland (Fig. 11). Advanced lesions can produce an irregular asymmetrical appearance of the prostatic capsule with possible invasion into surrounding structures. Testis and Scrotum Sonography is an important modality for imaging testicular and scrotal disorders. Because of the superficial position of these structures, high-frequency 5- to 10-Mhz Fig. 10. Transverse view of a transrectal sonogram of the prostate gland showing benign prostatic hyperplasia. The white arrows show the border between the more hypoechoic anterior transition zone and the surrounding peripheral zone. (From ref. 3.) 05_Rich_061-090_F 12/2/03, 8:24 AM71 72 Richman and Resnick transducers are used. The sonogram of a normal testis shows homogeneous echogenicity and a smooth contour (Fig. 12). There should be no distinct hypo- or hyperechoic areas within the tunica albuginea. The epididymis is observed as a separate structure and has similar echogenicity as the testis. Color Doppler sonography can characterize blood flow to the testes and can be used to identify the etiology of acute scrotal pain. Ischemic pain, as would present with testicular torsion, can be separated from hyperemic pain, associated with inflamma- tion or infection. Traumatic injury to the scrotum can be assessed sonographically. Findings can include hematoma, hydrocele, hematocele, and testicular fracture. Fig. 12. Sonogram of a normal testis (From ref. 3.) Fig. 11. Transverse view of transrectal sonogram of the prostate showing hypoechoic lesions in the left peripheral zone with distortion of the capsule (white arrow), suspicious for carcinoma. (Picture courtesy of Dr. Elizabeth Anoia.) 05_Rich_061-090_F 12/2/03, 8:24 AM72 [...]... delicate, Chapter 5 / Basic Imaging in Urology 75 Fig 14 Contrast-enhanced axial CT of the mid-abdomen demonstrates a simple cyst in the right kidney (symbol) This lesion has a smooth border and did not enhance with contrast compared to noncontrasted images of the same lesion A, aorta; K, kidney; L, liver; and S, spine (From ref 3.) Fig 15 Contrast-enhanced axial CT of the mid-abdomen demonstrates a solid enhancing... sedated Kidney With MRI of the normal kidney, the medulla is lighter than the cortex on T1-weighted imaging (Fig 26), and the same density as the medulla on T2-weighted imaging Fat is bright on both T 1- and T2-weighted images unless fat suppression is used Urine and Chapter 5 / Basic Imaging in Urology 83 Fig 26 Coronal T1-weighted MRI showing normal right and left kidneys Retroperitoneal fat appears bright... MRI produces better soft-tissue differentiation than 82 Richman and Resnick Fig 25 Contrast-enhanced axial CT of the mid-abdomen demonstrates retroperitoneal lymphadenopathy (white arrow) from metastatic testicular carcinoma (From ref 3.) CT and generates image reconstructions in multiple perspectives, such as cross-sectional, sagittal, coronal, and oblique, as well as three-dimensional orientations... Contrast-enhanced axial CT of the mid-abdomen demonstrates a large heterogeneous left renal cell carcinoma with tumor thrombus in the left renal vein (white arrowheads) and in the inferior vena cava (white arrow) The vena cava is normally flat (see Fig 13) and a round, full appearance indicates thrombus (From ref 3.) Chapter 5 / Basic Imaging in Urology 77 Fig 18 Contrast-enhanced axial CT of the mid-abdomen... depending on the stage of the tumor COMPUTED TOMOGRAPHY CT scanning produces high-definition images of a patient’s anatomy by passing a thin collimated beam of x-rays through the patient from multiple sources, which are then absorbed by a linear array of detectors These x-ray images are assembled by a computer, generating cross-sectional views of the patient on a monitor The images can then be stored digitally... This study is an excellent low-radiation means to evaluate a patient after ureteroneocystostomy or after expected spontaneous resolution of VUR Adrenal The adrenal cortex and medulla can be assessed with radionuclide imaging Adrenal cortical functioning tumors can be identified by intravenous injection of radiolabeled derivatives of cholesterol, such as 7-iodomethyl-19-norcholesterol, labeled with... carcinoma of the prostate (From ref 3.) Chapter 5 / Basic Imaging in Urology 81 Fig 24 Axial CT scan of the upper abdomen shows normal right and left adrenal glands (arrows) L, liver; Sp, spleen (From ref 3.) Retroperitoneum CT is routinely used for staging of urological malignancies and other retroperitoneal tumors Pelvic and para-aortic lymphadenopathy from bladder, prostate, testicular, and renal... imaging in three phases, noncontrast imaging, imme- 74 Richman and Resnick Fig 13 Axial CT scan of normal kidneys Right and left renal arteries are identified (solid symbols) as is the left renal vein (open symbol) Other adjacent structures identified include the aorta (A), inferior vena cava (I), liver (L), spleen (Sp), and spine (S) (From ref 3.) diate post-contrast bolus imaging, and delayed postcontrast... Contrast-enhanced axial CT of the mid-abdomen demonstrates a large mass in the collecting system of the left kidney (arrowheads) This lesion is a transitional cell carcinoma of the renal pelvis urothelium S, spine; L, liver; I, inferior vena cava; A aorta (From ref 3.) Renal Pelvis, Ureters, and Bladder Urothelial tumors appear as filling defects seen during the excretion phase of a contrast-enhanced... Adrenocortical carcinomas often have focal collections of macroscopic lipid, which can result in focal regions of signal intensity loss on opposed-phase chemical shift MRI In contrast to adrenocortical lesions, pheochromocytomas typically are high-intensity adrenal masses on T2-weighted MRI Female Pelvis MRI is used to accurately evaluate pelvic organ prolapse because it provides a multiplanar global view of the . and spine (S). (From ref. 3.) 05_Rich_06 1-0 90_F 12/2/03, 8: 24 AM 74 Chapter 5 / Basic Imaging in Urology 75 Fig. 14. Contrast-enhanced axial CT of the mid-abdomen demonstrates a simple cyst in the right. flow. 05_Rich_06 1-0 90_F 12/2/03, 8: 24 AM68 Chapter 5 / Basic Imaging in Urology 69 Ultrasound is widely used for diagnostic purposes in urology. It serves as a portable, non- or minimally invasive. involves imaging in three phases, noncontrast imaging, imme- 05_Rich_06 1-0 90_F 12/2/03, 8: 24 AM73 74 Richman and Resnick diate post-contrast bolus imaging, and delayed postcontrast bolus imaging,