Genitourinary Imaging

Chapter FOUR


Genitourinary Imaging


RICHARD A. LEDER image CHAPTER EDITOR


Kelly S. Freed


Mary T. Keogan


Anthony M. Foti


Jeremy A.L. Lawrance


Richard A. Leder


M. Gena Frederick


Daniele Marin


Vincent G. McDermott


Douglas H. Sheafor


John A. Stahl


Erik K. Paulson


CASE 1


KELLY S.FREED


HISTORY


Patient A: A 31-year-old woman who had been in a motor vehicle accident presents with gross hematuria. Patient B: A 21-year-old woman who also had been in a motor vehicle accident presents with microscopic hematuria.


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image FIGURE 4-1A Patient A: Contrast-enhanced CT through the bladder. Extravasation of contrast material is seen from the right lateral aspect of the urinary bladder. The bladder is not well distended, and it is difficult to determine if the rupture is intraperitoneal or extraperitoneal. A CT cystogram or conventional cystogram could be performed to clarify this issue.


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image FIGURE 4-1B Patient A: Anteroposterior plain film of the abdomen performed following the contrast-enhanced CT scan. Contrast material is seen superior to the bladder, tracking up along the right paracolic gutter and adjacent to the liver.


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image FIGURE 4-1C Patient B: Spot film from a conventional cystogram via a Foley catheter. There is a fracture of the left inferior pubic ramus. Contrast material is extravasating into the left inguinal region.


DIFFERENTIAL DIAGNOSIS


img The differential diagnosis for both patients includes intraperitoneal bladder rupture, extraperitoneal bladder rupture, or a combination of the two.


img In Patient A, intraperitoneal rupture is diagnosed because the contrast outlines the right paracolic gutter and liver.


img In Patient B, extraperitoneal rupture is diagnosed because the contrast material does not flow into the peritoneal cavity but extends into the proximal thigh via the left inguinal region. There is an associated fracture of the inferior pubic ramus.


DIAGNOSIS


Patient A: Intraperitoneal bladder rupture Patient B: Extraperitoneal bladder rupture


KEY FACTS


Clinical


img Bladder rupture can be seen following blunt or penetrating trauma and may be extraperitoneal, intraperitoneal, or both.


img Extraperitoneal bladder rupture is more common, composing approximately 80% of cases, and is frequently associated with pelvic fractures. The rupture usually occurs at the base of the bladder. Intraperitoneal bladder rupture occurs at the dome of the bladder when the bladder is distended. Pelvic fractures are seen less commonly in intraperitoneal bladder rupture than in extraperitoneal bladder rupture.


img Intraperitoneal rupture is more common in children than adults.


img Physical findings of bladder rupture include hematuria and the inability to urinate. Significant hematuria (> 50 red blood cells/high-power field) is a sensitive indicator of bladder trauma.


img Intraperitoneal bladder rupture requires surgery with bladder closure, whereas extraperitoneal bladder rupture can be managed with catheter drainage, antibiotics, and clinical follow-up.


Radiologic


img Radiologic diagnosis includes conventional cystography and CT of the abdomen and pelvis, including CT cystography.


img In extraperitoneal rupture, there are often associated fractures of the pubic rami or anterior pelvic ring. The extravasated contrast material can track down into the proximal thigh or scrotum. The extravasated contrast material may be ill-defined and feathery or contained.


img With intraperitoneal rupture, the contrast material flows freely into the peritoneum and may outline bowel loops or the paracolic gutters.


img CT of the abdomen and pelvis performed with the bladder only mildly or moderately distended is not as sensitive as conventional cystography for bladder injury. However, recent articles have demonstrated that CT cystography is comparably sensitive to conventional cystography. The bladder must be well distended on the CT study, either from instillation of contrast material through a Foley catheter or by using delayed images. Postdrainage CT images should also be obtained.


SUGGESTED READING


Bodner DR, Selzman AA, Spirnak JP. Evaluation and treatment of bladder rupture. Semin Urol 1995;13:62–65.


Chan DP, Abujudeh HH, Cushing GL Jr, Novelline RA. CT cystography with multiplanar reformation for suspected bladder rupture: Experience in 234 cases. AJR Am J Roentgenol 2006;187:1296–302.


Horstman WG, McClennan BL, Heiken JP. Comparison of computed tomography and conventional cystography for detection of traumatic bladder rupture. Urol Radiol 1991;12:188–193.


Morey AF, Iverson AJ, Swan A, et al. Bladder rupture after blunt trauma: guidelines for diagnostic imaging. J Trauma 2001;51:683–686.


Rehm CG, Mure AJ, O’Malley KF, Ross SE. Blunt traumatic bladder rupture: The role of retrograde cystogram. Ann Emerg Med 1991;20:845–847.


CASE 2


MARY T. KEOGAN


HISTORY


A 56-year-old woman presents with a low-grade fever.


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image FIGURE 4-2A Noncontrast linear coronal tomogram of the renal area. Extensive calcifications are noted in the right kidney. Calcifications are also noted in the upper and lower pole calyces of the left kidney.


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image FIGURE 4-2B Five-minute anteroposterior view of the kidneys during an intravenous urogram. There is no excretion of contrast material from the right kidney. Calcifications are noted in the right proximal ureter. The left upper pole calyces are dilated, and there is no filling of the left lower pole calyces.


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image FIGURE 4-2C Tc99m-diethylenetriamine penta-acetic acid scan of the renal area in the posteroanterior projection. There is marked reduction of activity in the left lower pole, with a faint rim of cortical activity. No right renal activity is seen.


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image FIGURE 4-2D Noncontrast CT of the lower abdomen. There are dense calcifications in the right kidney and ureter. Low-attenuation areas are noted in the left lower pole consistent with a dilated collecting system.


DIFFERENTIAL DIAGNOSIS


img Renal tuberculosis (TB): This is the best diagnosis due to extensive replacement of the nonfunctioning right kidney by calcification, the so called putty kidney. Calcifications in the ureter are also typical. Pyonephrosis is present in the lower pole of the left kidney.


img Xantogranulomatosis pyelonephritis (XGP): This inflammatory process is usually related to a chronic urinary obstruction and a staghorn calculus. Calcification in the ureter is atypical.


img Schistosomiasis: This infection characteristically affects the distal ureters, causing dilation and/or stenosis. The proximal ureters and ureteropelvic junctions are rarely involved. Schistosomiasis typically causes bladder calcification, but renal calcifications are uncommon.


DIAGNOSIS


TB with right autonephrectomy and left lower pole pyonephrosis


KEY FACTS


Clinical


img Renal TB results from hematogenous spread of TB bacilli to the kidneys. Ureteral involvement is secondary to bacilluria from the kidneys.


img Although both kidneys are usually involved, the disease process is typically more severe in one kidney.


img Patients are typically >40 years and present with hematuria, frequency, dysuria, or suprapubic pain.


img About 10% of patients may be asymptomatic and have sterile urine.


Radiologic


img Radiographic findings depend on the extent of the disease process but are present in the majority of cases of renal TB.


img Papillary necrosis is common and may be extensive. Necrosis in renal granulomas may lead to the formation of communicating cavities.


img Parenchymal calcifications are present in 50% of patients. They may be amorphous in association with granulomatous masses, or dense in healed tuberculomas. Renal calculi develop in 20% of patients.


img Parenchymal scarring occurs in 20% of patients, either localized or involving the entire kidney. There are also associated calcifications and underlying calyceal abnormalities.


img Calyceal abnormalities are common, with multiple irregular strictures of the infundibula and subsequent hydrocalycosis.


img Renal function is impaired in 50% of patients. Antegrade or retrograde pyelography is often required for evaluation.


img Advanced disease eventually results in a nonfunctioning kidney (autonephrectomy or “putty” kidney). These cases are associated with extensive calcifications.


img Failure of contrast material excretion often signifies the presence of tuberculous pyonephrosis due to stricture formation.


img Abnormalities of the ureters occur in 50% of cases of renal TB due to ulceration, with fibrosis, stricture, and calcification. Alternating segments of dilation and stricture produce a characteristic beaded appearance. Shortening of the ureter may also occur, producing a “pipestem” appearance.


img Other sites of urinary tract involvement include the prostate, epididymis, scrotum, and bladder, producing calcification with abscess formation and fistulous tracts.


SUGGESTED READING


Renal inflammatory disease. In NR Dunnick, RW McCallum, CM Sandler (eds), Textbook of Uroradiology. Baltimore: Williams & Wilkins, 1991;135–157.


The ureter. In NR Dunnick, RW McCallum, CM Sandler (eds), Textbook of Uroradiology. Baltimore: Williams & Wilkins, 1991;287–319.


Craig WD, Wagner BJ, Travis MD. Pyelonephritis: Radiologic-pathologic review. Radiographics 2008;28:255–277.


Elkin M. Urogenital tuberculosis. In HM Pollock, H Elkin (eds), Clinical Urography. Philadelphia: Saunders, 1990;1020–1052.


Paterson A. Urinary tract infection: An update on imaging strategies. Eur Radiol 2004;14(Suppl 4):L89–L100.


CASE 3


ANTHONY M. FOTI


HISTORY


A 50-year-old man has back pain and an elevated serum creatinine.


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image FIGURE 4-3A Axial T1-weighted MRI of the abdomen. There is a well-circumscribed mantle of soft tissue surrounding the aorta and abutting the IVC. The mass does not displace the aorta anteriorly away from the spine and is isointense to muscle.


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image FIGURE 4-3B Axial fat-suppressed T2-weighted MRI of the abdomen. The mantle of soft tissue is mildly hyperintense and relatively homogenous.


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image FIGURE 4-3C Axial contrast-enhanced T1-weighted MRI following the intravenous administration of a gadolinium-chelate. There is uniform enhancement of the soft tissue mass.


DIFFERENTIAL DIAGNOSIS


img Malignant retroperitoneal fibrosis (RPF): Imaging cannot differentiate malignant from nonmalignant RPF reliably; however, malignant RPF tends to be more heterogeneous on T2-weighted MR images.


img Malignant lymphadenopathy and lymphoma: These entities tend to displace the aorta anteriorly, away from the spine.


img Idiopathic RPF: The periaortic distribution and signal characteristics are classic for this entity.


DIAGNOSIS


Idiopathic (nonmalignant) RPF


KEY FACTS


Clinical


img RPF is a rare disorder in which a fibrotic plaque encases the aorta and extends laterally to engulf the inferior vena cava (IVC) and ureters. It usually begins near the aortic bifurcation and extends cephalad to the renal hila. Occasionally, it may extend cranially into the mediastinum or anteriorly into the mesentery.


img 70% of patients are 30 to 60 years of age at the time of diagnosis.


img Symptoms are nonspecific and include dull back pain, fatigue, and weight loss. Laboratory values include elevated serum creatinine levels and erythrocyte sedimentation rates.


img Two-thirds of cases are idiopathic (Ormond’s disease). The presumed mechanism is autoimmune, likely a response to leakage of ceroid, an insoluble lipid, from atherosclerotic plaques into periaortic tissue. Twelve percent of cases are secondary to methysergide administration; beta blockers, hydralazine, methyldopa, and bromocriptine have also been implicated. Other causes include malignancy, hemorrhage, and aneurysms (so-called perianeurysmal fibrosis).


img Malignant RPF is an intense desmoplastic response to retroperitoneal metastases from a variety of primary malignancies (breast, lung, thyroid, gastrointestinal tract, genitourinary tract, and Hodgkin’s lymphoma). There are only scattered malignant cells, and thus deep surgical biopsy is required to differentiate nonmalignant from malignant RPF.


img Histologically, perianeurysmal fibrosis (also referred to as an inflammatory aneurysm) is identical to RPF. The only difference is the caliber of the aorta.


img RPF usually results in ureteral dilatation by impairing peristalsis, rather than directly invading the ureter.


img RPF may obstruct the IVC and, rarely, the portal vein or common bile duct.


img Treatment consists of a combination of surgery to release the ureters (ureterolysis) and steroids.


img RPF has a similar histology and is associated with other systemic sclerosing diseases, including sclerosing cholangitis, orbital pseudotumor, mediastinal fibrosis, and Riedel’s thyroiditis. There is also an association with other immune-mediated connective tissue disorders such as ankylosing spondylitis, Wegener’s granulomatosis, systemic lupus erythematosus, Raynaud’s disease, polyarteritis nodosa, and systemic vasculitis. RPF is associated with the major histocompatibility complex HLA-B27.


Radiologic


img On intravenous urography there is hydronephrosis with medial deviation of the middle third of the ureters, which then taper near the L4 to L5 level. This is in contradistinction to most cases of lymphoma and other causes of lymphadenopathy, which are not associated with a desmoplastic response and thus cause lateral deviation of the ureters due to mass effect.


img On CT, a homogeneous mantle of soft tissue envelopes, but usually does not displace—the aorta. It extends laterally to involve the IVC and ureters, but usually does not extend >1 cm lateral to the ureters. It may obstruct the gonadal vessels. The margins are usually sharply circumscribed and not nodular. However, it may be ill-defined, although the margin characteristics cannot be used to distinguish nonmalignant from malignant RPF reliably. Precontrast, it is isoattenuating with the psoas muscles. Postcontrast, the soft tissue mass enhances uniformly, although enhancement diminishes with the chronicity of the disease.


img On ultrasound, a homogeneous hypoechoic perivascular mantle is characteristic.


img With MRI, the soft tissue mass is relatively homogeneous on all imaging sequences. It is isointense to psoas muscle on Tl-weighted images. The signal intensity on T2-weighted images and the enhancement on Tl-weighted images post-gadolinium-chelate administration vary with the stage. Early in the disease, the cellular nature of the infiltrate results in high signal intensity on T2-weighted images and discernible contrast enhancement. Late in the disease, the signal intensity on T2-weighted images and contrast enhancement decreases, reflecting the fibrotic process. Heterogeneous high signal intensity on T2-weighted images suggests malignancy, while uniformly low signal suggests late-stage benign disease.


SUGGESTED READING


Amis ES Jr. Retroperitoneal fibrosis. AJR Am J Roentgenol 1991;157: 321-329.


Arrive L, Hricak H, Tavares NJ, Miller TR. Malignant versus nonmalignant retroperitoneal fibrosis: differentiation with MR imaging. Radiology 1989;172:139–143.


Brooks AP, Reznek RH, Webb JA. Aortic displacement on computed tomography of idiopathic retroperitoneal fibrosis. Clin Radiol 1989;40:51–52.


Brun B, Laursen K, Sorensen IN, et al. CT in retroperitoneal fibrosis. AJR Am J Roentgenol 1981;137:535–538.


Cronin CG, Lohan DG, Blake MA, et al. Retroperitoneal fibrosis: a review of clinical features and imaging findings. AJR Am J Roentgenol 2008;191:423–431.


Degesys GE, Dunnick NR, Silverman PM, et al. Retroperitoneal fibrosis: use of CT in distinguishing among possible causes. AJR Am J Roentgenol 1986;146:57–60.


Kottra JJ, Dunnick NR. Retroperitoneal fibrosis. Radiol Clin North Am 1996;34:1259–1275.


CASE 4


JEREMY A.L.
LAWRANCE


HISTORY


A 67-year-old woman who was previously healthy presents with a 6-week history of epigastric pain.


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image FIGURE 4-4A Axial T2-weighted MRI of the upper abdomen. There is a 5-cm left-upper quadrant mass. It is of relatively high signal intensity and heterogeneous in nature. In addition, a highsignal intensity mass is noted in the IVC.


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image FIGURE 4-4B Coronal T2-weighted MRI of the upper abdomen. The mass is superior to and clearly separate from the left kidney.


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image FIGURE 4-4C Axial T1-weighted gradient echo MRI of the upper abdomen shows a crescent of flow around the IVC filling defect.


DIFFERENTIAL DIAGNOSIS


img Renal cell carcinoma: The mass is separate from the kidney; therefore, this diagnosis is excluded.


img Pheochromocytoma: These tumors usually demonstrate very high signal on T2-weighted MR images. They are usually > 3 cm and are frequently necrotic and hemorrhagic. The IVC invasion, however, is not a feature of pheochromocytomas.


img Adrenal metastasis: Tumors > 5 cm are more likely malignant. Furthermore, metastases are usually of higher signal intensity than adenomas. Apart from an adrenal metastasis in a patient with renal cell carcinoma, IVC invasion by an adrenal metastasis would be uncommon. The kidneys show no evidence of tumor in this case.


img Adrenal adenoma: This diagnosis is extremely unlikely unless IVC thrombosis is coincidental.


img Adrenal carcinoma: Although these tumors typically are larger at presentation, direct IVC invasion makes this the most likely diagnosis.


DIAGNOSIS


Adrenal carcinoma with inferior vena cava invasion


KEY FACTS


Clinical


img Adrenal carcinomas are rare malignant tumors with an annual incidence of 0.5 to 2.0 cases per million per year.


img The average age in one large study was 47 years.


img There is a slight female preponderance.


img In a series of 156 cases, 53% had a functional endocrine syndrome. Cushing’s syndrome is the most common, with virilization, hypertension, and feminization occurring less frequently.


img Up to 5% of cases are bilateral.


Radiologic


img Adrenal carcinomas tend to be large at presentation, usually > 5 cm in diameter. Functional tumors tend to be smaller at presention than nonfunctioning tumors. The range of sizes in one study was 3 to 30 cm, with a mean diameter of 12 cm.


img The problem with small adrenal carcinomas is that it is often impossible to differentiate benign from malignant tumors. Tumors > 5 cm are more likely malignant, while evidence of local invasion into adjacent organs or distant metastases are features of malignant tumors.


img In recent studies, metastases from adrenal carcinoma were present in 22%, while older studies reported higher incidences of metastases. The most common sites are liver, lymph nodes, bone, and lungs.


img Areas of necrosis, hemorrhage, and calcification are common. The latter is best detected by CT and found in approximately 30% of cases.


img By MRI, adrenal carcinoma shows low signal intensity on T1-weighted images and signal intensity greater than liver on T2-weighted images. Pheochromocytomas tend to have very high signal intensity on T2-weighted images and can be difficult to distinguish from adrenal carcinomas with MRI. Detection and delineation of vascular invasion, as well as multiplanar capability, make MRI a useful diagnostic tool in cases of adrenal carcinoma.


SUGGESTED READING


Dunnick NR. Adrenal carcinoma. Radiol Clin North Am 1994;32:99–108.


Icard P, Chapuis Y, Andreassian B, et al. Adrenocortical carcinoma in surgically treated patients: a retrospective study on 156 cases. French Assoc Endocrine Surg 1992;112:972–980.


Johnson PT, Horton KM, Fishman EK. Adrenal mass imaging with multi-detector CT: pathologic conditions, pearls, and pitfalls. Radiographics 2009;29:1333–1351.


Slattery JM, Blake MA, Kalra MK, et al. Adrenocortical carcinoma: Contrast washout characteristics on CT. AJR Am J Roentgenol 2006;187:W21-W24.


Zografos GC, Driscoll DL, Karakousis CP, Humen RP. Adrenal adenocarcinoma: a review of 53 cases. Surg Oncol 1994;55:160–164.


CASE 5


RICHARD A.
LEDER


HISTORY


A 46-year-old man presents with urinary frequency.


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image FIGURE 4-5A Anteroposterior supine 10-minute film of the bladder from an intravenous urogram demonstrates an oval to round filling defect along the left side of the bladder with no evidence of ureteral obstruction on that side.


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image FIGURE 4-5B Anteroposterior postvoid film from the same intravenous urogram shows a smooth filling defect involving the left lateral wall of the bladder.


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image FIGURE 4-5C Contrast-enhanced CT through the urinary bladder shows a smooth, round filling defect in the left posterolateral wall of the bladder. The filling defect is of soft tissue attenuation.


DIFFERENTIAL DIAGNOSIS


img Transitional cell carcinoma (TCC): TCC must be included in the differential diagnosis of this lesion, but some features mitigate against this as the most likely diagnosis. Large intravesical transitional cell tumors are frequently of the papillary variety. They have a stippled surface and are unlikely to appear as smooth, as in this case. The location will dictate whether a large lesion of this size will obstruct the ureter. In this case, no ureteral obstruction was present.


img Hematoma or fungus ball: There are a multitude of nonfixed filling defects that can occur within the bladder. It is useful in cases where hematomas or fungus balls are being considered to image the patient using ultrasound to document that these are not fixed to the bladder wall. While ultrasound was not performed in this patient, it is essential to document whether filling defects within the bladder are likely to be mobile or fixed.


img Bladder calculus: Almost all urinary calculi are hyper-attenuating on CT (> +100 Hounsfield units [HU]). This filling defect measured soft tissue attenuation.


img Cystitis: Bullous cystitis can appear as a bladder wall lesion. Cystitis glandularis is a proliferative lesion in which glandular elements of the bladder mucosa occur in the submucosa. Many patients have infections and associated cystitis cystica. These masses are typically villous. Submucosal fluid-filled cysts describe cystitis cystica, which can cause filling defects within the bladder. Chronic infection is postulated as the chief etiologic factor.


img Bladder leiomyoma: Smooth muscle tumors of the bladder wall may have this appearance and should be considered in the differential diagnosis of a smooth bladder wall filling defect.


DIAGNOSIS


Leiomyoma of the bladder


KEY FACTS


Clinical


img Leiomyomas may occur in any site in the genitourinary tract. These lesions occur in all age groups and affect both sexes equally.


img Lesions may be endovesical (63%), intramural (7%), or extravesical (30%).


img The cause of these tumors is unknown.


img The tumor is usually asymptomatic and may be detected incidentally on physical examination or cystoscopy.


img The endovesical form may present with irritative urinary symptoms, gross hematuria, or obstructive symptoms.


img Small endovesical lesions can be managed with transurethral resection and fulguration. Larger endovesical, intramural, or extravesical tumors are best treated with segmental resection.


img The prognosis of this tumor is excellent. No malignant degeneration has been reported.


Radiologic


img Intravenous urography or cystography usually reveals a smooth filling defect within the bladder.


img CT is useful to determine consistency (attenuation), size, location, and possible adjacent organ involvement.


img The endovesical form can be sessile or pedunculated on cystoscopy and is usually covered with normal bladder mucosa.


SUGGESTED READING


Fasih N, Prasad Shanbhogue AK, Macdonald DB, et al. Leiomyomas beyond the uterus: unusual locations, rare manifestations. Radiographics 2008;28:1931–1948.


Illescas FF, Baker ME, Weinerth JL. Bladder leiomyoma: Advantages of sonography over computed tomography. Urol Radiol 1986;8:216–218.


Knoll LD, Segura JW, Scheithauer BW. Leiomyoma of the bladder. J Urol 1986;136:906–908.


Wong-You-Cheong JJ, Woodward PJ, Manning MA, Sesterhenn IA. From the Archives of the AFIP: neoplasms of the urinary bladder: Radiologic-pathologic correlation. Radiographics 2006;26:553–580.


CASE 6


M. GENA
FREDERICK


HISTORY


A 63-year-old woman has microscopic hematuria.


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image FIGURE 4-6A Anteroposterior supine 5-minute film of the urinary bladder from an intravenous urogram. There is bilateral columnation of both ureters to the level of the ureterovesical junction, with a rounded distal configuration.


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image FIGURE 4-6B Anterosuperior supine 15-minute film of the urinary bladder from an intravenous urogram. Within the bladder, there is a “cobra head” appearance bilaterally. Note the lucent outline of the bulbous ureteral termination.


DIFFERENTIAL DIAGNOSIS


img Pseudoureterocele: This appearance is caused by a TCC of the bladder or a stone obstructing the ureter. It is unlikely because of the lack of a filling defect or mass, as well as the bilaterality of the defects. Other less common causes of the “pseudoureterocele” appearance include cervical carcinoma invading the ureterovesical orifice, radiation cystitis, or edema of the ureterovesical junction from recent stone passage. However, these are unlikely in this case because the former are identified by asymmetry of the distal lumen and irregularity of the wall and generally do not have intravesicular protrusion. However, they are capable of distending the distal ureter and thus mimicking an orthotopic ureterocele.


img Bilateral simple ureteroceles: This is the most likely diagnosis given the lack of a bladder mass or irregularity, the intravesicular protrusion, the absence of upper tract dilatation, and the bilaterality.


DIAGNOSIS


Bilateral simple ureteroceles


KEY FACTS


Clinical


img An orthotopic ureterocele forms in a ureter with a normal insertion into the trigone, as opposed to an ectopic ureterocele.


img Orthotopic ureteroceles usually occur in single collecting systems, as opposed to ectopic ureteroceles, which occur in duplicated collecting systems.


img Orthotopic ureteroceles are usually unilateral, asymptomatic, and incidental. However, a calculus may lodge or form in the ureterocele.


img A ureterocele is a congenital deformity.


img A ureterocele consists of a prolapse of the distal ureter into the bladder with associated dilation of the distal ureter.


img The wall of the ureterocele is composed of a thin layer of muscle between the outer surface of the bladder uroepithelium and the inner surface of the ureteral uroepithelium.


Radiologic


img The typical radiographic appearance is the so-called cobra head deformity, which is formed by the projection of the minimally dilated distal ureter into the lumen of the bladder, with opacified urine surrounding the ureterocele.


img The thin line of radiolucency represents the wall of the ureterocele.


SUGGESTED READING


Berrocal T, López-Pereira P, Arjonilla A, Gutiérrez J. Anomalies of the distal ureter, bladder, and urethra in children: embryologic, radiologic, and pathologic features. Radiographics 2002;22:1139–1164.


Davidson AJ, Hartman DS. Radiology of the Kidney and Urinary Tract (2nd ed). Philadelphia: Saunders, 1994;520-523.


Mitty HA, Schapira HE. Ureterocele and pseudoureterocele: cobra versus cancer. J Urol 1977;117:557–561.


CASE 7


M. GENA
FREDERICK


AND


DANIELE MARIN


HISTORY


A 54-year-old man presents with abdominal pain.


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img FIGURE 4-7A Noncontrast CT of the abdomen demonstrates a small, well-defined lesion in the lateral portion of the right kidney with increased attenuation (+59 Hounsfield units [HU]) compared to the adjacent renal tissue.


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img FIGURE 4-7B On corresponding contrast-enhanced CT image, the lesion demonstrates lack of contrast enhancement (attenuation increase compared to the noncontrast scan = +1 HU).


DIFFERENTIAL DIAGNOSIS


img Hemorrhagic renal cell carcinoma (RCC): This diagnosis is unlikely because the entire lesion is of uniform increased attenuation on the noncontrast study.


img Hemorrhagic angiomyolipoma: This diagnosis is unlikely due to the absence of macroscopic fat on the noncontrast CT.


img Hemorrhagic renal cyst: This is the most likely diagnosis due to the small size, uniform appearance, and lack of enhancement of this renal lesion.


DIAGNOSIS


Hemorrhagic renal cyst


KEY FACTS


Clinical


img Renal cysts account for approximately 60% of all renal masses.


img Renal cysts increase in frequency with age (approximately 50% of cases occur past the age of 50).


img Most renal cysts are asymptomatic, whether hemorrhagic or not.


img Hemorrhagic cysts are frequently seen in patients with autosomal dominant polycystic kidney disease and acquired renal cystic disease.


Radiologic


img Noncontrast CT is necessary to evaluate the attenuation of the lesion before contrast material administration.


img Cysts that are “hyperdense” exhibit attenuation values between +50 and +80 HU. The high attenuation is due to a high content of protein, blood breakdown products, or iodine. To be considered a benign hyperdense cyst, the lesion must be sharply marginated, homogeneous, and nonenhancing (< 10 HU increase postcontrast).


img Because of the thickness of the wall and the internal structure of the lesion, these cysts cannot be evaluated reliably with ultrasound, and only 50% of hyper-attenuating lesions demonstrate typical sonographic cyst criteria. CT is necessary to assess or rule out lesion enhancement.


SUGGESTED READING


Israel GM, Bosniak MA. How I do it: evaluating renal masses. Radiology 2005;236:441–450.


Israel GM, Bosniak MA. Pitfalls in renal mass evaluation and how to avoid them. Radiographics 2008;28:1325–1338.


Bosniak MA. The small (≤ 3.0 cm) renal parenchymal tumor: detection, diagnosis, and controversies. Radiology 1991;179:307–317.


CASE 8


RICHARD A.
LEDER


AND


DANIELE MARIN


HISTORY


A 33-year-old man has a history of urinary tract infections.


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image FIGURE 4-8A Anteroposterior film of the kidneys, ureters, and bladder from an intravenous urogram shows two collecting systems on the left side of the abdomen. On this film, only the distal left ureter is seen


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image FIGURE 4-8B Anteroposterior coned view of the pelvis from the intravenous urogram shows normal insertion into the bladder trigone of both the left and right ureters.


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img FIGURE 4-8C Contrast-enhanced CT of the midabdomen shows enhancement of the left kidney, with absence of renal tissue in the right renal fossa.


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img FIGURE 4-8D Contrast-enhanced CT of the lower abdomen. The right kidney is present in the left lower quadrant.


DIFFERENTIAL DIAGNOSIS


img Retroperitoneal mass with displacement of the kidney: This diagnosis is unlikely due to the absence of an obvious abdominal mass.


img Renal duplication with agenesis of the contralateral kidney: Although renal duplication may cause enlargement of the kidney and could account for the presence of two left ureters, this diagnosis can be ruled out with a careful inspection of the course of both ureters, which demonstrates crossing of one ureter into the opposite side of the pelvis and normal insertion in the bladder trigone.


img Crossed renal ectopia: This is the most likely diagnosis, given the position of the kidneys and the insertion of the ureters.


DIAGNOSIS


Crossed renal ectopia


KEY FACTS


Clinical


img There are four types of crossed renal ectopia: (i) crossed renal ectopia with fusion, (ii) crossed renal ectopia without fusion, (iii) solitary crossed renal ectopia, where monolateral renal agenesis is associated with ureteral insertion on the opposite side of the solitary kidney, and (iv) bilateral crossed renal ectopia, where both kidneys are crossed to the opposite side of the abdomen with their ureters inserting into the contralateral ureterovesicle junction.


img The most common varieties are fused and unfused ectopia; crossed fused ectopia occurs in 85% to 90% of cases.


img Crossed renal ectopia is seen more commonly in males than females.


img The most common scenario is the left kidney crossing to the right side of the abdomen.


img There are associated urinary tract abnormalities, including obstruction, stones, infection, vesicoureteral reflux, primary megaureter, hypospadius, cryptorchi-dism, urethral valves, and multicystic dysplastic kidney.


img There are associated abnormalities of other organ systems, including skeletal anomalies, unilateral ovarian and fallopian tube agenesis, and cardiac and gastrointestinal anomalies.


img Theories of occurrence include faulty development of the ureteral bud with crossing of the midline to contact the contralateral metanephric blastema, obstruction of renal ascent by blood vessels, and local environmental factors involving surrounding tissues and organs.


Radiologic


img The most common form of crossed renal ectopia is a crossed fused ectopia. Radiographically, this can be diagnosed on either ultrasound, CT, or intravenous urography when renal tissue lies on the opposite side of the abdomen from its ureteral insertion, and renal tissue from the crossed kidney fuses with the kidney native to that side of the abdomen. Helical CT, particularly using coronal reformation, or MRI may be useful in distinguishing fused from unfused ectopia.


img CT is also useful for excluding secondary causes of renal displacement, such as large retroperitoneal masses.


img Patients with this abnormality are usually asymptomatic, although they may present with a palpable abdominal mass or a history of repeated urinary tract infections.


SUGGESTED READING


Gay SB, Armistead JP, Weber ME, Williamson BR. Left infrarenal region: anatomic variants, pathologic conditions, and diagnostic pitfalls. Radiographics 1991;11:549–570.


Silva JM, Jafri SZH, Cacciarelli AA, et al. Abnormalities of the kidney: embryogenesis and radiologic appearance. Appl Radiol 1995;24:19–24.


CASE 9


RICHARD A.
LEDER


AND


DANIELE MARIN


HISTORY


A 60-year-old man presents with a palpable right-sided abdominal mass, flank pain, and hematuria.


img

image FIGURE 4-9A Transabdominal ultrasound of the right kidney in the longitudinal plane shows a solid, hyperechoic, partially exophytic mass at the lower pole.


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image FIGURE 4-9B Contrast-enhanced CT shows a large, solid mass in the right kidney. Within the central and lateral portion of the mass, there is a broad area of decreased attenuation, corresponding to areas of cystic tumor necrosis.


DIFFERENTIAL DIAGNOSIS


img Renal cell carcinoma (RCC): The imaging features in this case reveal the presence of a solid, enhancing right renal mass with features that are consistent with RCC. The broad area of low attenuation within the mass could represent internal hemorrhage or necrosis.


img Oncocytoma: There are no imaging features that confidently allow for the diagnosis of a benign oncocytoma. However, this diagnosis belongs in the differential diagnosis of a solitary renal mass in a patient who has no evidence of metastatic disease (no retroperitoneal lymphadenopathy and no osseous, hepatic, or pulmonary parenchymal metastases).


img Renal metastasis: Metastatic disease to the kidney is uncommon and would be only included in the differential diagnosis of patients with a known primary malignancy, most commonly lung, breast, or colon cancer. No such history existed in this patient.


img Angiomyolipoma: The diagnosis of angiomyolipoma is made when fat is detected within a renal mass. It is possible that given sufficient hemorrhage within an angiomyolipoma, no fat may be detected. No fat was detected within this mass, and there was no evidence of subcapsular or perinephric hemorrhage.


img Lymphoma: This patient has no history of non-Hodg-kin’s lymphoma. Furthermore, no retroperitoneal lymphadenopathy is present, although lymphomatous masses may exist within the kidneys in the absence of lymphadenopathy.


DIAGNOSIS


Renal oncocytoma


KEY FACTS


Clinical


img An “oncocyte” is a transformed epithelial cell with an enlarged, homogeneous, dense cytoplasm filled with acidophilic granules.


img Microscopically, a renal oncocytoma is characterized by eosinophilic epithelial cells with protuberant mitochondria within the cytoplasm.


img A renal oncocytoma has a distal tubular or collecting duct origin.


img On gross examination, lesions are well circumscribed, often encapsulated, without necrosis or hemorrhage. A central stellate scar may be present.


img The right kidney is affected as often as the left kidney. Cases of bilateral synchronous tumors have been reported.


img The tumor size ranges from 0.1 to 26.0 cm.


img The age at diagnosis ranges from 26 to 94 years.


img There is a 1.63 to 1.0 male-to-female ratio.


img Less than one-third of patients will present with the classic triad of renal cell tumors, including flank pain, hematuria, with a palpable abdominal mass.


img Rarely, renal oncocytomas may demonstrate a malignant growth pattern with distant metastatic disease.


Radiologic


img Ultrasound shows a homogeneous, isoechoic to hyperechoic, well-marginated mass. These are indistinguishable from RCC.


img Although rarely performed, angiography may demonstrate a “spoke-wheel” appearance due to the characteristic vascular architecture of the tumor. Other common but less specific angiographic findings include a dense parenchymal blush and no contrast media puddling, arteriovenous shunting, or renal vein invasion as commonly seen in RCC.


img On CT, oncocytomas demonstrate well-defined and smooth margins, with or without a central stellate scar. Lesions demonstrate intense and homogeneous enhancement after dynamic administration of contrast material.


img Only 67% of large oncocytomas (> 3 cm) and 82% smaller tumors (< 3 cm) demonstrate typical imaging findings at CT (i.e., homogeneous attenuation throughout the tumor, a central, sharply marginated stellate area of low attenuation). In the remaining cases (33% and 18%, respectively), CT in unable to differentiate oncocytomas from RCC.


img On MRI, oncocytomas show homogenous, low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. The presence of a capsule or a central stellate scar and the absence of either internal hemorrhage or necrosis also favor this diagnosis.


SUGGESTED READING


Davidson AJ, Hayes WS, Hartman DS, et al. Renal oncocytoma and carcinoma: failure of differentiation with CT. Radiology 1993;186:693–696.


Hélénon O, Merran S, Paraf F, et al. Unusual fat-containing tumors of the kidney: a diagnostic dilemma. Radiographics 1997;17:129–144.


Velasquez G, Glass TA, D’Souza VJ, Formanek AG. Multiple oncocytomas and renal carcinoma. AJR Am J Roentgenol 1984;142:123–124.


CASE 10


RICHARD A.
LEDER


AND


DANIELE MARIN


HISTORY


A 48-year-old man was referred for CT after seeing his ophthalmologist.


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image FIGURE 4-10A Noncontrast CT of the abdomen shows enlargement of both the head and tail of the pancreas, although it is difficult to determine whether there are solid or cystic lesions present. There is marked deformity of the right kidney, with a hydrocalyx containing a small calculus in the upper pole, exophytic renal masses, and a solid mass medially.

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Jan 7, 2017 | Posted by in GENERAL RADIOLOGY | Comments Off on Genitourinary Imaging
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