мошонка, мочевой пузырь уретра

viral (i.e., mumps). Testicular enlargement, decreased echogenicity, and hypervascularity are all typical findings (Fig. 6-35A and B). As with epididymitis, hypervascularity may be the only abnormal finding, so color Doppler analysis is more sensitive in the diagnosis of orchitis than is gray-scale sonography alone (see Fig. 6-35C and D). In addition to orchitis, the differential diagnosis

for an enlarged, hypoechoic testis includes torsion, diffuse lymphoma or leukemia, and diffuse seminoma (Table 6-2). Orchitis is much less frequently focal than is epididymitis. In such cases it can be difficult to distinguish a hypoechoic hypervascular tumor from focal orchitis (see Fig. 6-35E and F). Clues to look for that make orchitis more likely include the finding of

174 ULTRASOUND: THE REQUISITES

Table 6-2 Causes of an Enlarged Hypoechoic Testis

pain and tenderness without a palpable mass on physical examination and the sonographic finding of associated involvement of the epididymis. Orchitis may progress to a testicular abscess if appropriate therapy is not instituted. Testicular abscesses will appear as complex

fluid collections that are avascular but have intense peripheral hyperemia (Fig. 6-36). Scrotal wall abscesses may develop from testicular abscesses, or they may arise primarily within the soft tissues of the scrotum (Fig. 6-37).

One other role of sonography is in the evaluation of testicular trauma. An important clinical question is the status of the tunica albuginea. If it is intact, surgery is usually not indicated. If it is ruptured, surgery is required within 72 hours to maintain testicular viability. Fractures of the testis rarely appear as linear testicular defects on sonography. More commonly, nonspecific-appearing areas of increased or decreased echogenicity are seen within the testis or the testis becomes misshapen and distorted (Fig. 6-38). This is usually due to a combination of hemorrhage and extrusion of seminiferous tubules.

It is important to keep in mind that trauma can serve as an event that leads to a careful self-examination and uncovers a preexisting testicular tumor. Therefore, posttraumatic intratesticular abnormalities whose sonographic characteristics overlap with tumors should be viewed with suspicion and either evaluated surgically or with careful ultrasound follow-up. Trauma can also induce testicular torsion. Therefore, a careful Doppler examination should be a routine part of the evaluation of the traumatized patient.

BLADDER

The urinary bladder is usually well seen with sonography and determination of post-void residuals, using the formula for an ellipsoid (length × width × height × 0.53),

is a common request. However, a number of other abnormalities can be visualized.

The most common abnormality seen on sonography is bladder wall thickening. This is most commonly due to bladder outlet obstruction. Other causes include neurogenic bladder, cystitis, edema from adjacent inflammatory processes, radiation, and primary or secondary neoplasms. Detection with cross-sectional imaging is somewhat subjective because thickening will vary with the degree of bladder distention (Fig. 6-39). Reasonable guidelines for upper limits of normal are 3 mm for a well-distended bladder and 5 mm for a poorly distended bladder.

Bladder tumors are frequently detected on sonography, usually in patients who are having renal sonograms for hematuria. Ninety percent are transitional cell carcinoma. Smoking, analgesic abuse, and industrial carcinogen exposure all predispose to transitional cell

cancer. Five percent are squamous cell cancer. These occur in patients with bladder schistosomiasis, neurogenic bladders, or chronic inflammatory conditions of the bladder. Two percent of bladder tumors are adenocarcinoma, which tend to occur in urachal remnants and in bladder exstrophy. Bladder carcinoma is three times more common in men and tends to occur in middle-aged and older populations. The prognosis is dependent on the depth of invasion and, in particular, the degree of involvement of the muscularis.

The majority of transitional cell cancers of the bladder arise along the posterior wall, in the region of the trigone. Sonographically, the majority are polypoid with a mass arising from the bladder wall extending into the bladder lumen (Fig. 6-40A and B). Less often they are infiltrative with diffuse or localized thickening of the bladder wall (see Fig. 6-40C). The presence of a transitional cell cancer in the bladder or in the upper tracts places the entire urothelium at risk and periodic imaging is required.

The primary differential diagnosis for bladder cancer is blood clots (Fig. 6-41). The useful findings that distinguish bladder cancer from blood clot are immobility and presence of blood flow. The differential diagnosis also includes other intraluminal lesions such as stones and fungus balls; other causes of focal wall thickening

such as invasion by adjacent tumors (prostate, rectum, cervix), involvement by adjacent inflammatory processes, fistulas with adjacent organs, wall trabeculation, benign prostatic hypertrophy, endometriosis, malakoplakia, leukoplakia, tuberculosis, and schistosomiasis; and rare tumors such as adenocarcinoma, squamous cell carcinoma, and pheochromocytoma. Bladder stones are easily distinguished from other abnormalities by the combination of shadowing and mobility (Fig. 6-42). Benign prostatic hypertrophy may produce a prominent mass in the base of the bladder that simulates a transitional cell cancer (Fig. 6-43). In most cases, lesions of benign prostatic hypertrophy will be located in the midline and continuity with the prostate will be apparent.

Bladder diverticula are other common abnormalities that are visible on sonography. They usually occur due to outlet obstruction and often coexist with a thick bladder wall. They appear as a fluid-filled structure adjacent to the bladder. In the majority of cases, careful scanning will demonstrate the connection between the bladder and the diverticulum (Fig. 6-44A and B). When the connection is not visible on gray-scale sonography, compression of the bladder with the transducer may demonstrate urine flow between the bladder and diverticulum on color Doppler imaging (see Fig. 6-44C and D).

Figure 6-42 Bladder calculus. Transverse view of the bladder shows a hyperechoic intraluminal lesion with a posterior acoustic shadow located along the dependent aspect of the bladder.

Figure 6-43 Prostatic hypertrophy simulating a bladder cancer. Longitudinal power Doppler view of the bladder shows a polypoid intraluminal mass similar in appearance to the transitional cell carcinoma seen in Fig. 6-40A. Readily detectable internal blood flow indicates that this is vascularized soft tissue and not a blood clot. Continuity with an enlarged prostate was identified on other views.

Urinary stasis in the diverticulum predisposes to infection, stone formation, and cancer. Because it may be difficult for the urologist to pass a cystoscope through the neck of a diverticulum, it is important to scan them carefully to exclude these potential complications.

Another unusual perivesicular fluid collection is the urachal diverticulum or cyst. These form if there is incomplete closure of the urachus. If the umbilical segment closes but the vesicular segment does not, a diverticulum is formed. If the segment between the bladder and umbilicus fails to close then a urachal cyst forms (Fig. 6-45). Both abnormalities are characterized by their location adjacent to the anterior dome of the bladder.

Simple ureteroceles are easy to detect with sonography. They are caused by dilatation of the intramural portion of the distal ureter protruding into the bladder lumen. In adults, they are usually incidental findings and are located in the expected location of the ureteral orifice. They are formed by mild stenosis of the ureteral orifice presumably due to limited resorption of Chwalla’s membrane during embryologic ureteral recanalization. On sonography they appear as round or oval, thin-walled cystic structures on the posterior wall of the bladder. On real-time scanning they can be observed to change size as they fill and empty and ureteral jets can be observed intermittently emanating from their orifice (Fig. 6-46). Pseudoureteroceles caused by some pathologic process that obstructs the ureteral orifice, such as stones, tumors, and recent manipulation, can mimic simple ureteroceles, but the wall is usually thicker and the obstructing lesion should be visible. Box 6-4 reviews the causes of bladder wall lesions.

Box 6-4 Causes of Bladder Wall Lesions

Primary neoplasms

Transitional cell

Adenocarcinoma

Squamous cell

Pheochromocytoma

Invasion from adjacent neoplasms

Rectum

Prostate

Cervix

Uterus

Inflammation from adjacent organs

Diverticulitis

Crohn’s disease

Pelvic inflammatory disease

Appendicitis

Ureteroceles

Urachal cysts

Cystitis cystica

Endometriomas

Fistulas

Malakoplakia

Leukoplakia

Tuberculosis

Schistosomiasis

URETHRA

Sonography is not a primary modality used to evaluate most urethral abnormalities. However, it can be quite valuable in some instances. The normal female urethra

can routinely be identified on transvaginal and transperineal scans as a hypoechoic linear structure arising from the base of the bladder and passing inferior to the symphysis pubis (Fig. 6-47). Because of the anisotropic properties of the urethral wall muscles, the urethral wall may appear very hypoechoic or even anechoic when it is oriented parallel to the direction of the sound. This should not be confused with urine in the lumen of the urethra.

A combination of transvaginal and transperineal scanning is very effective in identifying urethral diverticula in women. These appear as simple or complex collections of fluid that are intimately related to the urethra. They usually arise from the mid urethra and initially extend posteriorly. However, they frequently wrap around one or both lateral aspects of the urethra (Fig. 6-48). They can be complicated by both stones and cancer. Periurethral abscesses simulate diverticula but are more remote from the urethra and are usually associated with a hyperemic inflammatory reaction (Fig. 6-49).

In men, sonography is occasionally used to evaluate urethral strictures. The main purpose is to accurately

Figure 6-47 Normal female urethra. Sagittal transvaginal scan in the pelvic midline shows the urinary bladder (B) in the deep aspect of the field of view. The urethra (arrows) is seen as a hypoechoic linear structure exiting from the base of the bladder and traveling inferior to the synthesis pubis (S).

determine the location and measure the length and thickness of the stricture to determine the type of treatment that is required. To visualize the stricture, the urethra must be injected with saline or with viscous lidocaine at the time of the examination (Fig. 6-50).

PENIS

Several penile abnormalities can be evaluated with sonography. One primary role of sonography is

diagnosing vascular causes of erectile dysfunction. This can be done with pulsed Doppler analysis after the injection of vasoactive drugs such as papaverine and prostaglandin E into the corpora cavernosa. In normal men, there is an increase in arterial flow to the bilateral cavernosal arteries that can be quantified by measuring systolic velocities. The recommended criteria for a normal response vary somewhat. Most would agree that systolic velocities exceeding 35 cm/sec can be considered normal (Fig. 6-51) and that maximum velocities below 25 cm/sec indicate arterial insufficiency. Velocities