Genitourinary Diseases

Chapter 29

Genitourinary Diseases

Beverly L. Harger

Lisa E. Hoffman

Richard Arkless

BLADDER CALCULI

NEPHROBLASTOMA (WILMS TUMOR)

NEPHROCALCINOSIS

NEPHROLITHIASIS (RENAL CALCULI)

OVARIAN DERMOID CYSTS

OTHER OVARIAN LESIONS

PHEOCHROMOCYTOMA

SMALL RENAL MASS (RENAL CELL CARCINOMA)

OTHER SMALL RENAL MASSES (ANGIOMYOLIPOMA)

UTERINE FIBROMA (LEIOMYOMA)

Portions of the genitourinary system are readily visible on plain film radiographs, which may aid in the localization of abnormal densities. This is a common site for concretions and some calcifying masses. Table 29-1 lists the common appearance of the genitourinary system and some of the abnormal findings that may be visible on plain film.

TABLE 29-1

GENITOURINARY PLAIN FILM ORGAN APPEARANCE

Organ Plain Film Visibility Plain Film Location Retroperitoneal Versus Intraperitoneal Fixed Versus Mobile Appearance Specifics Plain Film Abnormalities
Kidneys Surrounding pericapsular fat T12 to L2 level, right slightly lower than left Retroperitoneal Fixed; some translation with upright posture or inspiration Height = 2 to 2.5 vertebral bodies plus intervertebral disc; long axis oriented superomedial to inferolateral Lobulated contour; enlargement; ectopic; abnormal axis; nephrolith
Adrenals None Adjacent to body margins of T12 or L1 Retroperitoneal Fixed None Calcifications (mass-like or cystic)
Ureters None Along anterior aspect of psoas muscle to posterosuperior bladder Intraperitoneal Fixed None Nephrolith
Bladder Domed water density Midline in pelvic bowl Intraperitoneal Fixed Inferior margin <1 cm above pubic symphysis; superior margin may be indented by uterus May appear as mass; may become distended (e.g., neurogenic bladder); superiorly displaced by enlarged prostate
Prostate None Midline at pubic symphysis Intraperitoneal Fixed None Calcifications
Uterus None Midline, pelvic bowl Intraperitoneal Fixed None Calcifications (fibroids)
Ovaries None Variable Intraperitoneal Somewhat mobile None Calcifications (dermoid cyst)

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Bladder Calculi

Background

Bladder outlet obstruction from prostatic disease remains the most common cause of bladder calculi in adults with the majority occurring in elderly men.11,20 Other factors predisposing to bladder stone formation are previous lower urinary tract surgery, metabolic abnormalities, upper urinary tract calculi, intravesicular foreign bodies, spinal cord injuries, and transplant surgery.11 The presence of bladder stones is associated with an increased incidence of carcinoma.20

Clinical Comments

The presentation of vesical calculi varies from completely asymptomatic to symptoms of suprapubic pain, dysuria, intermittency, frequency, hesitancy, nocturia, and urinary retention. Bladder calculi may abrade and irritate the mucosa and predispose to infection. Bladder infections are more difficult to treat when calculi are present. Ureteral or bladder outlet obstruction may also be present.20 Approximately 15% of patients with gout, as well as hyperuricemic patients, produce uric acid stones.20

Standard treatment of bladder stones consists of endoscopic visualization and fragmentation by electrohydraulic probe.46 Massive calculi may require open surgery.46

Key Concepts

• Urinary retention with high residual urine is a common cause for formation.

• It may be difficult to detect on plain radiographs.

• Bladder calculi usually lie centrally in the pelvis on plain radiographs.

• The incidence of carcinoma of the bladder increases in the presence of stones.

Nephroblastoma (Wilms Tumor)

Background

Nephroblastoma (Wilms tumor) is the most common abdominal malignancy in childhood.9,17 Overall, leukemia and lymphoma, brain tumors (astrocytoma and medulloblastoma), and neuroblastoma have a higher incidence in pediatric populations when other sites of the body are also considered.27 The highest incidence occurs in 3- and 4-year-old children, with 80% of Wilms tumors occurring in children 1 to 5 years old.3,6,27

Imaging Findings

Wilms tumor appears radiographically as a complex renal mass (Fig. 29-2). Approximately 5% to 10% of these lesions show areas of calcification, but calcium, when seen in a mass in this area, is much more likely to be in a neuroblastoma of the adrenal or other similar tissue.27 Intravenous pyelography shows either a displaced or a nonfunctioning kidney. Ultrasonography typically reveals a well-defined tumor, often surrounded by a hyperechoic halo of compressed normal renal tissue.17,21 Noncontrast computed tomography (CT) usually reveals a large intrarenal mass of lower attenuation than the adjacent normal kidney. Cystic spaces or areas of tumor necrosis appearing as inhomogeneous, low-density areas are seen in most tumors.17

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FIG 29-2 Nephroblastoma (Wilms tumor). A, Intravenous urogram anteroposterior projections show diffuse amorphous calcification of a large right upper quadrant mass in a pediatric patient. B, Intravenous urogram lateral view of the same patient demonstrates the retroperitoneal location of this mass. Nephroblastoma is the most common abdominal malignancy of children, with 80% occurring between 1 and 5 years of age.

Clinical Comments

Patients with Wilms tumor present with an abdominal mass in more than 90% of cases.17 Approximately 50% of patients experience hypertension or fever. Hematuria is relatively uncommon.17,27 No male or female predominance is noted.17 Up to 30% with the rare condition of aniridia (congenital absence of the iris) develop nephroblastoma.27 A total of 4% to 5% of cases show bilateral tumors.27

Key Concepts

• Wilms tumor is the most common abdominal malignancy of children.

• Abdominal mass is the most common clinical presentation.

• Radiographically, Wilms tumor is seen as a complex renal mass; 5% to 10% have internal calcification.

Nephrocalcinosis

Background

Calcifications in the kidney are generally thought of as systemic conditions influenced by the concentration of a calcium, phosphate, oxalate, and on environment factors such as pH, osmolarity, and the concentration a variety of inhibitory molecules and proteins (e.g., citrate).39 Based on its location, calcification in the kidney can be classified broadly into two categories: calcification within the pyelocalyceal lumina, known as nephrolithiasis, and intraparenchymal calcification, termed nephrocalcinosis. Nephrocalcinosis also can be categorized with respect to its predominant location. A limited group of diseases, cortical nephrocalcinosis, may produce calcification confined to, or predominantly located in, the renal cortex. Other conditions, such as medullary nephrocalcinosis, spare the cortex and cause calcium salt deposition in the medulla, interstitium, or lumina of the nephrons.

Imaging Findings

Radiographically, cortical nephrocalcinosis can be differentiated from the medullary variety by the peripheral location of the calcification. Medullary calcification is typically that of bilateral, diffuse, fan-shaped clusters of stippled calcifications, primarily in the renal pyramids (Fig. 29-3). Although precipitating conditions are most often systemic, the presentation of calcification is not universally bilateral and symmetrical. Unilateral and focal presentations are common (Fig 29-4), suggesting that intrinsic factors, such as vascularity, may be involved.

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FIG 29-3 Medullary sponge kidney. A, Faint calculi are seen in the renal pyramids (arrows). Medullary sponge kidney is characterized by ectatic collecting ducts and associated small cysts communicating with these ducts. B, Renal tubular acidosis. This parenchymal renal calcification results from renal tubular acidosis. The calcifications occur within the tubules surrounding the calyces (arrows).
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FIG 29-4 A and B, Diffuse clusters of calcification consistent with nephrocalcinosis.

Clinical Comments

The two most common etiologies of cortical nephrocalcinosis are acute cortical necrosis and chronic glomerulonephritis, although radiographically evident calcification is rare in both conditions. Persons on chronic dialysis may have similar calcifications.

Roughly 40% of cases of medullary nephrocalcinosis are attributable to primary hyperparathyroidism, another 20% to renal tubular acidosis, and the remaining 40% divided among many other causes.

Key Concepts

• Renal intraparenchymal calcification is known as nephrocalcinosis.

• Two categories of nephrocalcinosis are cortical and medullary.

• A peripheral location is seen with cortical nephrocalcinosis.

• Cortical nephrocalcinosis is rare.

• Usually bilateral, diffuse, fan-shaped clusters of stippled calcifications typically are seen with medullary nephrocalcinosis.

• Primary hyperparathyroidism and renal tubular acidosis are the most common causes of medullary nephrocalcinosis.

Nephrolithiasis (Renal Calculi)

Background

Whereas nephrocalcinosis is calcification in renal parenchyma, nephrolithiasis is concretion calcification in the luminal portion of the urinary tract (Figs. 29-5 and 29-6). The composition of renal stones varies with geography. In the United States, approximately 75% of renal stones are calcium oxalate. The remaining 25% of renal calculi are noncalcareous and are composed of uric acid, struvite, or cystine.

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FIG 29-5 A and B, Focal, homogeneous appearing calcifications likely representing stones (nephrolithiasis) formed in the distal lumen. However, at times, as is the case here and in Figure 29-4, the presentation is not obviously diffuse and stippled, as one would expect with nephrocalcinosis or well-formed and homogeneous, as is typical of nephrolithiasis, making differentiation difficult. By contrast, another case, C, clearly exhibits the well-formed homogenous stones typical of nephrolithiasis. A–C, Courtesy Ian D. McLean, LeClaire, IA.
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FIG 29-6 Staghorn calculus in two different patients. A, Plain film of the abdomen demonstrates a calculus that conforms to the shape of the calyces, infundibulum, and pelvis. B, Intravenous pyelogram showing bilateral duplication of the collecting systems with a staghorn calculus obstructing the upper collecting system on the right (arrow).

Imaging Findings

Ultrasonographically, most stones larger than a few millimeters show shadowing. However, ultrasonography is not the procedure of choice in diagnosis because too many false-negative studies exist. In intravenous pyelography, the radiolucent stones can be difficult to differentiate from blood clots or sloughed tissue. (All of these can obstruct drainage from the kidney.) With CT, all stones are denser than unenhanced renal parenchyma and urine.

Segments of the urinary tract proximal to the stone may show varying degrees of dilatation depending on the degree and chronicity of occlusion created by the stone (Fig. 29-7). Not all dilated drainage systems are from stones and other intrinsic filling defects; crossing bands of vessels or congenital narrowing can give the same appearance on intravenous pyelograms. Up to 90% of renal calculi are opaque enough to be seen on plain film radiographs.

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FIG 29-7 Nephrolithiasis. Ureteral stone (arrow) with associated proximal ureter dilatation and hydronephrosis.

Clinical Comments

Low urine volume and stasis contribute to formation of both calcareous and noncalcareous stones by increasing the urinary concentration of stone-forming constituents.

Renal calculi in the ureters cause renal colic, which has a dramatic clinical presentation, often with severe flank pain. Stones remaining in the renal pelvis may lead to obstruction. If they pass into the bladder, on unusual occasions, they may act as the nidus of a bladder calculus.

Key Concepts

• Nephrolithiasis is produced in conditions causing urinary stasis or providing a nidus for stone formation.

• Symptoms usually are produced by obstruction.

• Nearly 90% are opaque enough to be seen on plain film radiographs.

Ovarian Dermoid Cysts (Mature Cystic Teratoma)

Background

Mature cystic teratoma is the most common germ cell neoplasm and the most common childhood ovarian tumor comprising 10% to 25% of all ovarian tumors.42

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Feb 2, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Genitourinary Diseases

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