Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

effusion and brain metastases. The gastrointestinal tract is rarely involved, with an occasional recurrence presenting as an annular rectal tumor. An uncommon cancer spreads intraperitoneally and results in ascites and peritoneal carcinomatosis. If possible, a site of tumor origin should be determined because transitional cell bladder carcinomas have a worse prognosis than similar spread from the ovaries.

Surveillance: Cystoscopy and urine cytology are traditional surveillance examinations in the follow-up of bladder cancer; keep in mind that although urine cytology sensitivity is only about 30% to 50%, its specificity approaches 100%. Several other tests, including bladder tumor antigen, fibrin/fibrinogen degradation products, and nuclear matrix protein tests, are in use to a varying degree in different countries. The published evidence suggests that some of them even surpass cytology in detecting recurrence, but their role in routine follow-up is not clearly established and they are often employed as ancillary tests.

The postoperative imaging approach varies depending on the type of resection (if any). For most superficial bladder cancers no imaging follow-up is necessary unless additional risk factors are present: tumor >3cm, several tumor foci, higher than grade I tumor, or the presence of additional foci of dysplasia.

Follow-up imaging of invasive transitional cell carcinomas consists of CT, chest radiography, IV urography, and, in some centers, US. The role of MRI is still evolving. Computed tomography is recommended every 3 to 6 months initially. Because therapy causes considerable distortion, an initial posttherapy CT study is especially valuable to establish a baseline. Posttherapy edema, fibrosis, and tumor recurrence have a similar CT appearance. Edema is identified as a diffuse increase in perivesical fat density. One recommendation after successful bladder cancer therapy is that these patients be followed with an IV urogram or similar imaging study to assess for upper urinary tract cancer, on the average every 1 to 2 years, although some believe that subsequent studies should be tailored to the clinical findings.

The evidence is accumulating that MRI is more accurate than CT in detecting bladder cancer recurrences, and a gradual shift toward MR studies is evident. No firm guidelines

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are established. T2-weighted images are useful in differentiating late recurrence (isoto hyperintense) from residual fibrosis (hypointense). Within 6 to 12 months after therapy, however, these differences cannot be reliably differentiated.

The use of US for postoperative surveillance of bladder cancers is occasionally suggested, but a low sensitivity limits its use.

Adenocarcinoma

Bladder adenocarcinomas are not common. Many are primarily urachal in origin, involve the bladder dome, and are not of direct bladder origin, but a bladder carcinoma is in the differential diagnosis. An occasional bladder adenocarcinoma is associated with long-standing irritation and has developed in a defunctionalized bladder. A rare bladder adenocarcinoma is a consequence of bladder endometriosis.

A signet-ring cell adenocarcinoma or linitis plastica of the bladder is a highly malignant tumor having a poor prognosis. Most of these tumors contain signet-ring cells mixed with gland and papillary structures, at times even foci of transitional cell carcinoma. Compounding the issue is that a gastrointestinal or prostatic metastasis is often in the differential diagnosis, and thus a search for another primary is often necessary. A typical imaging appearance of a signet-ring cell adenocarcinoma is diffuse bladder wall invasion without a significant intraluminal component.

A hepatoid adenocarcinoma, representing extrahepatic hepatocellular differentiation, is a rare variant in the bladder; some of these tumors produce a-fetoprotein.

Squamous Cell Carcinoma

In most countries bladder squamous cell carcinomas represents only several percent of all primary bladder cancers, but in schistosomia- sis-endemic countries a squamous cell carcinoma is the most common primary bladder cancer. In North America and Europe a squamous cell carcinoma is more common in bladder diverticula and is often associated with chronic bladder inflammation, such as longstanding bladder calculi or the presence of indwelling catheters.

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A verrucoid carcinoma is a descriptive term for a squamous cell carcinoma having a frondlike pattern.

Computed tomography of primary squamous cell carcinoma often shows a predominantly extraluminal tumor component with invasion into adjacent structures, although some are predominantly intraluminal.

Lymphoma

Primary non-Hodgkin’s lymphoma of the bladder is rare. Hematuria is the most common presentation, although prostatic involvement results in outlet obstruction. An occasional primary bladder lymphoma presents as a large pelvic tumor. Diffuse lymphomatous involvement simply thickens the bladder wall.

Magnetic resonance signal intensities from lymphoma-involved bladder are similar to those from adjacent lymphomatous lymph nodes.

An enterovesical fistula secondary to a nonHodgkin’s lymphoma is a rare complication.

Sarcoma

In adults, nonepithelial bladder malignancies include leiomyosarcoma and rhabdomyosarcoma; both are rare. These are aggressive, rapidly growing tumors with early local invasion. Rhabdomyosarcomas occur in both the bladder and the prostate. A biopsy should establish the diagnosis.

Imaging features for most sarcomas overlap. Extensive cystitis, lymphoma, and other tumors have a similar appearance. Ultrasonography reveals a large heterogeneous tumor. Doppler US typically detects nonpulsatile low velocity flow.

Sarcoma botryoides is a rhabdomyosarcoma originating in hollow organs and growing primarily intraluminally in grape-like clusters. A rare one arises from the bladder wall (Fig. 11.10).

Most bladder tumors in younger children are rhabdomyosarcomas. They are more common in boys. They tend to occur at the trigone or posterior bladder wall and either infiltrate or grow intraluminally as a lobular, irregular bladder tumor. Superficially, an intraluminal tumor tends to mimic blood clots. Some of these tumors prolapse into the urethra and obstruct. Those originating at the bladder dome can grow

Figure 11.10. Bladder rhabdomyosarcoma in a teenage boy with hematuria. US reveals a polypoid intraluminal tumor (arrow). (Courtesy of Luann Teschmacher, M.D., University of Rochester.)

intraabdominally; determining the site of origin for some of these is difficult.

The rare bladder malignant histiocytoma and histiocytofibroma are aggressive sarcomas, at times associated with a hematologic malignancy.

Carcinosarcoma and

Sarcomatoid Carcinoma

Some bladder carcinomas contain a prominent spindle cell component and are known as sarcomatoid carcinomas. Whether these are distinct from carcinosarcomas is debated in the pathologic literature (purists argue for distinct tumors). Other terms for these tumors are malignant mixed mesodermal tumor and metaplastic carcinoma. Whether this neoplasm is secondary to collision of two tumors or whether it represents separate differentiation from a single source is speculation.

The clinical presentation is similar to that of the more typical transitional cell carcinoma.

Among 15 patients with bladder carcinosarcoma seen at the Mayo Clinic, the most common carcinomatous component was a urothelial carcinoma, less often squamous cell carcinoma or small cell carcinoma, while the sarcomatous component consisted of chondrosarcoma, leiomyosarcoma, malignant fibrous histiocytoma, and other types (33); during the same time frame 26 patients were diagnosed with a sarcomatoid carcinoma, with the tumor consisting primarily of an urothelial carcinoma.

A rare sarcomatoid carcinoma originates in a bladder diverticulum.

Both carcinosarcoma and sarcomatoid carcinoma are highly aggressive tumors having a similar outcome regardless of histologic findings and treatment. These tumors metastasize readily and mimic other neoplasms, including lymphoma. They have no characteristic imaging findings. Most are large, solid, exophytic tumors when first detected. Some bladder carcinosarcomas contain calcifications and even osseous metaplasia. The diagnosis is suggested by immunohistochemistry.

Metastases/Invasion

Invasion from an adjacent cancer is more common than metastasis to the bladder. Thus prostatic carcinoma, gynecologic malignancies, rectal and even an appendiceal carcinoma readily invade the bladder. Some of these extrinsic tumors mimic a primary bladder carcinoma.

Coincident upper tract transitional cell carcinomas and bladder cancers have already been discussed. An occasional upper tract cancer, however, metastasizes to the bladder and is not a second primary, although differentiation of these is difficult. An occasional renal cell carcinoma metastasis to the ureteral stump and bladder is detected after a nephrectomy.

Only a few metastatic melanomas to the bladder have been reported.

Local invasion is from the outer wall inward; thus cystoscopy will not detect early invasion. Computed tomography and MR evidence of an asymmetric bladder wall thickening and increased MR signal intensity of the involved bladder wall segment are signs of invasion. Eventual intraluminal extension is evident.

Small Cell Carcinoma

The rare bladder small cell carcinoma appears to be less aggressive than a similar lung carcinoma. One should keep in mind that neuroendocrine tumors also have a small cell appearance but are characterized by their immunohistochemical properties; in some publications a distinction between small cell carcinomas and some neuroendocrine tumors is blurred. Histologically, these tumors also tend

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to mimic lymphoma. Occasionally bladder metastases from lung cancer has a similar appearance. Imaging simply reveals a solid tumor.

Most of these tumors result in hematuria. Adding chemotherapy to radical surgery appears to improve survival.

Neuroendocrine Tumors

The bladder trigone contains cells of neural crest origin.

Neurofibroma

The most common genitourinary involvement by neurofibromatosis is in the bladder.Although an occasional single neurofibroma is detected, more often these tumors are part of neurofibromatosis type I. Only a rare bladder neurofibroma is malignant. A trigone neurofibroma can obstruct an adjacent ureter.

These tumors range from a focal, wellmarginated one to diffuse infiltration by a plexiform neurofibroma. Some neurofibromas have an imaging appearance similar to that of bladder leiomyomas, although neurofibromas often are more hyperintense on T2-weighted images than leiomyomas.

Paraganglioma (Pheochromocytoma)

Paragangliomas are uncommon catecholamineproducing tumors originating from chromaffin cells in the bladder paraganglion system. They can be multicentric. The most common location is in the trigone, followed by the bladder dome. Only an occasional one is malignant.

Hematuria is common. Some patients develop atypical hypertension, including palpitations, excessive sweating, paroxysmal hypertension, or even a hypertensive crisis during micturition due to release of epinephrine or norepinephrine.

Similar to other sites, bladder paragangliomas are solid, hypervascular tumors readily detected by CT and angiography. At times selective venous blood sampling is helpful in localizing these tumors. An occasional paraganglioma contains curvilinear calcification. Ultrasonography shows a solid, echogenic mass containing low-impedance flow. These tumors are interme-

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diate to hypointense on T1and hyperintense on T2-weighted MR images.

Long-term follow-up is necessary after resection of these tumors because recurrences or metastases can develop years later.

Intraluminal Mass

Causes of intraluminal bladder masses not attached to the bladder wall include blood clots, stones, fungus balls, and foreign bodies/ bezoars.

Bladder calculi either form in the kidney and migrate to the bladder, or form de novo in the bladder. In certain parts of Asia and Africa bladder stones develop in children, called endemic bladder stones. Primary bladder calculi develop in a setting of stasis or the presence of a foreign body. Most small stones are mobile, with an occasional one adhering to the bladder wall due to adjacent inflammation. Thickening of the bladder wall is common. Stasis in an hourglass bladder incarcerated within a hernia has led to stone formation.

Occasionally giant bladder calculi fill almost the entire bladder lumen. Most of these stones contain calcium and are relatively radiopaque.

Bladder and urethral stones can be treated by ultrasonic lithotripsy, using either a transurethral or a percutaneous cystolithotripsy approach.

The most common entry site for bladder foreign bodies is through the urethra, with the foreign body being either self-introduced or introduced during a transurethral surgical procedure. Items mentioned in the literature range from bizarre household products to various surgical instruments. A second access route is during laparotomy or laparoscopic procedures. Least common are foreign bodies migrating from a site outside the bladder; these include such foreign bodies as synthetic gum used to protect a surgical ureterostomy and an intrauterine device migrating into the bladder lumen. Shotgun pellets have been passed spontaneously during voiding.

Clinical presentations range from recurrent infections to acute obstruction, depending on the type and location of a foreign body.

Dilation/Obstruction

Bladder outlet and urethral obstruction is discussed in Chapters 12 and 13.

Prolonged bladder outlet obstruction does lead to renal failure. An overdistended bladder resulted in bilateral iliac vein obstruction and bilateral urinary obstruction, and led to a pulmonary embolus (34).

Occasionally a patient with urinary retention has no anatomic obstruction, but “functional” bladder neck obstruction is believed to be responsible. Some of these patients with functional obstruction have normal cystourethrography and retrograde urethrography. The external sphincter opens during voiding but the bladder neck relaxes either intermittently or inadequately.

Neurogenic Bladder

Normal bladder intraluminal pressure is less than 10 to 15cm of water. In general, a chronic constant pressure of greater than about 40cm of water leads to bladder wall thickening, trabeculations, and outpouchings.

Bladder dysfunction is classified into an uninhibited neurogenic bladder, hyperreflexive detrusor (reflex neurogenic, contractile bladder), areflexic detrusor (autonomous neurogenic, flaccid bladder), and sensory or motor paralysis (Table 11.2).

In an uninhibited neurogenic bladder voluntary external sphincter contraction prevents voiding during uninhibited voiding. As a result, the posterior urethra is dilated to the external sphincter level and the imaging appearance is similar to a spinning top. These findings occur in infants with an immature bladder and adults with a cerebral cortical lesion (stroke, brain tumor). In infants the imaging appearance tends to be similar to that seen with posterior urethral valves.

Patients with a lesion above the lower lumbar level have detrusor hyperreflexia and develop a trabeculated thick-walled bladder. Such a hyperreflexive detrusor is found in patients with multiple sclerosis and lesions inducing spinal cord damage (trauma, tumor, syringomyelia). A large postvoid residue is common.

Bladder contractions result in bladder neck opening, but the striated external sphincter does not open and thus bladder pressure increases. Associated vesicoureteral reflux is common in these patients, and if not corrected often results in loss of renal function.

Lower motor neuron involvement leads to detrusor areflexia. These patients develop a large, thin-walled bladder. No detrusor contractions are evident with an areflexic detrusor. The bladder neck remains open, external sphincter does not constrict normally, and these patients are incontinent.

Additional variants of a neurogenic bladder include sensory and motor paralysis. The former is most often found in diabetics. An association exists between gastroparesis and bladder dysfunction; patients with both idiopathic gastroparesis and diabetic gastroparesis are affected. Presumably a similar autonomic neuropathy is responsible for both gastric and bladder involvement.

Motor paralysis develops in some multiple sclerosis and polio patients. Urinary incontinence and retention are common problems in multiple sclerosis, often presenting a complex appearance. A majority of multiple sclerosis patients have detrusor hyperreflexia and a minority areflexia; these patients also develop bladder diverticula, urinary infection, hydronephrosis, and reflux.

Voiding dysfunction develops in patients with lumbar spinal stenosis. Dysfunction improves in some after a decompressive laminectomy, but others continue with a poor outcome.

A neurogenic bladder has been reported in Wolfram’s syndrome (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness) (35).

Autonomic dysreflexia, encountered in patients with a neurogenic bladder and similar conditions, is discussed later (see Examination Complications).

Calcifications

Bladder lumen calcifications consist of calculi and foreign bodies. Bladder wall calcifications include infections (schistosomiasis and tuberculosis), neoplasms, therapy related (radiation, chemo-, and immunotherapy, cyclophosphamide, BCG, thiotepa, and mitomycin C), phleboliths, arteriosclerosis, alkaline cystitis, and amyloidosis. Some calcifications are readily apparent with conventional radiography while others are detected only with a higher radiographic contrast imaging modality such as CT.

Fistula

Vesicovaginal

Common causes of vesicovaginal fistulas are prior gynecologic procedure, such as hysterectomy, and, in rural North Africa, obstetrical trauma (36). Less common etiologies include adjacent neoplasms and radiation therapy.

Cystography is the procedure of choice to detect these fistulas. A vaginogram is less often