Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

considered to be an immunologic disorder, although a number of these children probably suffer from chronic granulomatous disease, an inherited disease characterized by recurrent bacterial or fungal infections. These children present with hematuria, urgency, and dysuria. They develop chronic bladder tumors mimicking neoplasms.

Crohn’s Disease

Cystitis in Crohn’s patients most often is secondary to an adjacent phlegmon or an enterovesical fistula. A rare patient presents with gross hematuria.

Malacoplakia

Malacoplakia is a granulomatous inflammatory reaction characterized by bladder wall thickening, at times involving adjacent structures. Pathogenesis is unknown, although many of these patients have other underlying systemic disorders.

Infection by urea splitting organisms results in deposition of inorganic salts and an alkaline encrusted cystitis. These encrustations are associated with malacoplakia, although the relationship between alkaline encrusted cystitis and malacoplakia is incompletely understood. Both malacoplakia and primary squamous cell carcinoma have developed in chronic cystitis.

Imaging reveals one or more intraluminal sessile nodules varying in size, occasionally leading to vesicoureteral junction stenosis and hydronephrosis.

If diffuse, cystitis cystica is in the imaging differential diagnosis.

ADVANCED IMAGING OF THE ABDOMEN

if present, actinomycosis or Crohn’s disease is more likely.

Radiation

Acute radiation cystitis starts 4 to 6 weeks after therapy and presents as a hemorrhagic cystitis. Imaging reveals edema and a nodular outline. Postcontrast MRI reveals an enhancing bladder wall; the appearance is similar to that of other causes of cystitis and to some neoplastic infiltrations.

Chronic cystitis develops months or years later and results in a scarred, fibrotic bladder wall with a small shrunken lumen. In general, imaging during the chronic stage is nonspecific. Radiation cystitis is one cause of a nonfunctioning hypertonic bladder.

Occasionally a vesical fistula develops secondary to radiation therapy.

Amyloidosis

Primary bladder amyloidosis is rare; more often encountered is secondary bladder amyloidosis, both presenting with hematuria. The diagnosis is made by histologic examination. Once detected, systemic amyloidosis or a malignant lymphoproliferative disorder should be excluded.

Amyloid infiltration results in a thickened, somewhat irregular bladder wall, and the imaging appearance mimics that of an infiltrating neoplasm. Magnetic resonance imaging reveals amyloid infiltration as a hypointense region on T2-weighted images (compared to a normal bladder wall).

Ischemia

Bladder overdistention can lead to ischemia and eventual gangrene. The mucosa is most sensitive to ischemia and occasionally a necrotic mucosa will slough; eventually the mucosa will regenerate.

Bladder infarction develops with bladder strangulated in an inguinal hernia.

Behçet’s Syndrome

Systemic Sclerosis

Lower urinary tract involvement with systemic sclerosis is not common. Bladder involvement results in varying degrees of wall fibrosis. While autonomic dysfunction is common, urodynamic abnormalities are not.

Tumors

Nonneoplastic Tumors

Urinary tract involvement in Behçet’s syndrome can lead to recurrent cystitis, urethritis, or epididymitis. Extensive fistulas are not common;

Interureteric Ridge Edema

Interureteric ridge edema is related to trauma or acute distal ureteral obstruction. It is best

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identified with the bladder either partially filled or almost empty.

Cystitis Cystica (Cystitis Glandularis)

A condition of unknown etiology, cystitis cystica is associated with chronic urinary tract infection. Histology reveals marked mucosal thickening, lymphatic obstruction, bladder wall edema, and intramural cysts.

Cystitis glandularis is probably a more severe form of cystitis cystica. Pathologically, considerable difficulty can be encountered in distinguishing cystitis glandularis from an adenocarcinoma, and anecdotal reports describe partial cystectomy performed because of an erroneous diagnosis of adenocarcinoma. Confusing the picture further is the occasional patient with cystitis glandularis who subsequently develops an adenocarcinoma, presumably due to the persistence of chronic irritation. At times cystitis glandularis and pelvic lipomatosis coexist.

A cystogram reveals large nodules or even a single confluent infiltrating tumor, often at the bladder base; the imaging appearance is very similar to that of a neoplasm, although the presence of several smooth bladder base nodules should suggest cystitis cystica. Both CT and US show irregular regions of bladder wall thickening in association with intraluminal tumors. Trigone involvement leads to ureter obstruction.

Hemangioma

Bladder hemangiomas are not common. They occur in all age groups but are more prevalent in children and young adults. Especially in children, they manifest with hematuria.

Hemangiomas range from a focal, sessile tumor to a diffuse intramural infiltration. Some are multiple. Similar to hemangiomas at other sites, MR shows them to be hypointense on T1and hyperintense on T2-weighted images.

The role of selective arterial embolization is not well established for these rare tumors.

Pseudosarcoma

A fibroblastic proliferation of unknown etiology, called a pseudosarcomatous myofibroblastic (fibromyxoid) tumor or inflammatory pseudotu-

mor, develops in a number of organs, including the bladder. This tumor has some characteristics of a desmoid tumor; indeed, whether these are all the same entity is conjecture. It occurs in both children and adults. It is not associated with prior trauma. Some patients present with hematuria or progressive anemia. Associated pain suggests a hematoma or even intraperitoneal hemorrhage.

The bladder wall and, at times, surrounding tissues are infiltrated by a tumor superficially resembling a sarcoma. These are highly vascular myxoid stroma tumors showing both early and delayed CT contrast enhancement. In children, both clinically and radiologically this tumor has been mistaken for an embryonal rhabdomyosarcoma or some other type of sarcoma. The diagnosis is established by histology; no cytologic atypia or increase in number of mitoses should be evident. Immunohistochemistry reveals myofibroblast proliferation. Immunoreactivity with vimentin is positive in some patients.

Condyloma

A bladder condyloma is rare. These tumors are induced by human papilloma virus infection, result in a proliferation of squamous epithelium, and are associated with an increased risk of malignancy.

A cystogram reveals one or more intraluminal tumor. Imaging identifies an irregular bladder wall thickening and, in fact, a large condyloma mimics a neoplasm.

Endometriosis

Bladder endometriosis is rare. Most often it is contiguous with an extrinsic endometrioma and presents as an infiltrating tumor at the bladder dome. Several reports describe malignant transformation in bladder endometriosis; most often these are clear cell adenocarcinomas.

Some women with bladder endometriosis develop dysuria and hypogastric pain. Bladder and ureteral endometriosis was associated with recurrent acute pyelonephritis (14).

Computed tomography or MR should define the often present extrinsic soft tissue component (Fig. 11.5). Nevertheless, a neoplasm cannot be excluded from the imaging appearance.

Figure 11.5. Bladder endometriosis. Computed tomography identifies an irregular intramural tumor posterior and to the left of the bladder (arrow). The appearance mimics a neoplasm. (Courtesy of Patrick Fultz, M.D., University of Rochester.)

Benign Neoplasms

Papilloma

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Many of these patients are asymptomatic, and these tumors are detected incidentally. Some manifest with hematuria, and less often bladder outlet obstruction or ureteral obstruction.

Intraluminal growth is most common; a minority grow extravesically, while a dumbbell appearance is relatively rare. Some extravesical leiomyomas reach a large size before being detected.

A cystogram reveals leiomyomas as smooth, sessile tumors. Magnetic resonance typically identifies a well-marginated tumor having an intermediate signal intensity on T1and inter- mediate-to-hypointense signal on T2-weighted images. Leiomyomas exhibit variable MR contrast enhancement. Tumor degeneration leads to a varied appearance.

An imaging-guided suprapubic biopsy can often establish the diagnosis, although most of these tumors are resected.

A papilloma consists of a fibrovascular bundle covered by either transitional or squamous cells. As discussed in Chapter 10, papilloma etiology is unknown and their histopathologic diagnosis difficult.

A type of transitional cell papilloma is the inverted papilloma, found throughout the urothelial tract, but most often in the bladder. An initial diagnosis of an inverted papilloma should be made with care; papillomas mimic and are readily misdiagnosed as transitional cell carcinomas. These tumors are believed to be related to human papillomavirus type 18 infection, chronic irritation, and subsequent metaplasia. An occasional one is associated with a more proximal urothelial carcinoma or a superficial bladder tumor.

A typical papilloma appearance is that of an isolated, endophytic tumor. On immediate postcontrast MRI papillomas appear as enhancing polyps arising from a less enhancing bladder wall and surrounded by intraluminal signalvoid urine.

Leiomyoma

Bladder leiomyomas are the most common benign bladder neoplasm but still represent less than 1% of all bladder tumors. They are detected in a younger patient age group than are carcinomas.

Nephrogenic Metaplasia/Adenoma

Nephrogenic metaplasia is a rare condition occurring throughout the urothelium but most often involving the bladder. The pathogenesis is unknown, but prior stone disease or some type of trauma appears to be the predisposing factor. Whether the occasionally reported nephrogenic adenoma simply represents further cell differentiation or is the same entity is speculation.

Nephrogenic adenomas occur in the bladder, bulbar urethra, urethral diverticula, and prostatic urethra. Most are discovered incidentally. A history of prior instrumentation or inflammation is not uncommon; these adenomas probably represent a metaplastic response to prior urothelial trauma. Select examples include a 4-year-old girl with a bladder nephrogenic adenoma (15); she had a ureterocele resection and bilateral ureter reimplantations at 3 months of age. Cystoscopy in a 76-year-old man revealed a papillary nephrogenic adenoma (16); he had received intravesical BCG therapy for recurrent bladder transitional cell carcinoma.

Most of these adenomas are polypoid, and imaging simply reveals a sessile tumor, although some are flat.

Recurrence is common after resection, but most authors agree that little risk of malignant transformation exists; nevertheless, some

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nephrogenic metaplasias and adenomas are associated with bladder cancer. A rare report describes a bladder villous adenoma, at times with foci of adenocarcinoma.

Malignant Neoplasms

Transitional Cell Carcinoma

Clinical Aspects

Primary bladder cancer is three times more common in men than women and more common in whites than blacks. In the West, most bladder cancers are transitional cell carcinomas. They range from carcinoma in situ to diffuse infiltration and metastasis. Adenocarcinoma and squamous cell carcinoma are considerably less common and tend to occur in certain settings, discussed later.

Epithelial origin bladder neoplasms are uncommon in the second decade of life and rare in the first. Most bladder neoplasms at these ages are of mesodermal origin. Some studies suggest that patients under 40 years of age with bladder transitional cell carcinoma have a lower recurrence rate and a better prognosis compared to older patients, but other studies conclude that the prognosis depends primarily on tumor stage and is not correlated with age. In children, transitional cell carcinomas tend to be low grade and have a low recurrence rate.

The most common clinical presentation is painless hematuria, ranging from gross to microscopic and often intermittent. Ureteral obstruction due to an adjacent cancer is often silent. Spontaneous perforation of a bladder carcinoma is a curiosity. An occasional bladder cancer manifests first via spread to other structures, at times to unusual sites.

The Leser-Trelat sign consists of an association of multiple seborrheic keratoses with an internal malignancy. It occurs with transitional cell bladder carcinomas.

Etiology

A familial form of bladder transitional cell carcinoma exists, with two genetic patterns: a minor autosomal-dominant pattern and a more common multifactorial pattern involving both genetic and environmental factors. Some papillary and invasive tumors harbor a chromosome 9 allelic loss, while others contain a p53 gene

mutation without alterations of chromosome 9. Immunohistochemical study of bladder tumors in patients younger than 30 years reveals p53 gene product overexpression in a majority (17); aneuploidy of chromosome 17 is common. The p53 gene mutations are associated with highgrade, high-stage urothelial cancers, and these gene mutations suggest a monoclonal origin for multicentric cancers. An extremely early age at onset, in particular, should suggest a genetic factor.

Infection, the presence of stones, smoking, various direct-acting chemicals, and a number of environmental factors are associated with these cancers. Carcinogenic chemicals implicated include benzidine and 4-aminobiphenyl; cyclophosphamide also appears to increase the risk of bladder cancer. Some affected individuals are infected with human type 18 papillomavirus.

Bladder carcinoma is the most common malignancy in those parts of the Middle East and Africa where schistosomiasis is endemic. The specific relationship is not clear, but N- nitrosamine compounds appear involved because urine levels of these compounds are increased in patients with schistosomiasisassociated bladder cancer.

Associated Conditions

In patients with renal pelvis and ureteral transitional cell carcinomas, almost half have synchronous or will develop metachronous bladder tumors, and these patients should undergo regular cytologic evaluation and radiologic screening for a prolonged time period in order to detect these associated bladder carcinomas. On the other hand,only in a small minority does a bladder tumor antedate an upper tract tumor, and in these patients the primary bladder tumor tends to be multifocal. Whether patients with a bladder cancer should undergo regular upper urinary tract follow-up is not clear from the literature, although among patients with stages Ta, T1, and Tis bladder tumors entered in a prospective trial of BCG therapy and followed for 15 years or longer, 21% developed upper tract tumors (18); some of these tumors occurred between 10 and 15 years later, and thus these patients need lifelong follow-up. Intravenous urography is useful for screening upper urinary tracts; retrograde pyelography provides

alternate visualization if IV urography is inconclusive. Some investigators, on the other hand, believe that IV urography at the initial diagnosis of bladder cancer is unnecessary because of a low upper urinary tract tumor detection rate with urography.

In patients with a prostate or bladder cancer, the risk of having or developing the other cancer is considerably greater than expected. Patients with a bladder carcinoma are also at increased risk for renal cell carcinomas and bronchopulmonary carcinoma.

Pathology

Histologically, a diagnosis of transitional cell carcinoma is not always straightforward. Mimicry by benign cystitis glandularis has already been mentioned. The reverse is also true; even an invasive bladder transitional carcinoma can be composed of cells and glands having relatively bland cytologic features suggesting a benign condition.

Metaplastic changes, at times extensive, are often observed in a setting of a bladder cancer. Epithelial dysplasia is found in most resected bladders with a bladder cancer. Incidental carcinoma in situ is also common, and up to one third of cancers are multifocal. An occasional bladder carcinoma exhibits osseous or cartilaginous metaplasia or osteoclast-like giant cells.

The World Health Organization grading system for transitional cell carcinomas consists of grade I lesions, which are low grade (welldifferentiated), and grade III lesions, which are poorly differentiated. Grade II lesions are intermediate. Grade I tumors rarely invade, and the vast majority of invasive tumors are grade III.

Detection

Urinary cytology detects low-grade bladder cancers with about 50% sensitivity, although currently the diagnosis is generally established by cystoscopy and biopsy. Bladder wash cytology at the time of cystoscopy also aids in diagnosis.

Proposed tests to detect urothelial neoplasms include tumor antigen, fibrin/fibrinogen degradation products, and nuclear matrix protein (NMP-22); these require further study to establish their place in cancer detection.

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Bladder transitional cell carcinomas range from exophytic (papillary) to infiltrating or a combination of both. Exophytic tumors are either polypoid or frond-like. Demonstration of intraluminal extension, although helpful in localizing a tumor, does not aid tumor staging. A carcinoma can originate in a bladder diverticulum.

Computed tomography identifies a soft tissue tumor arising from the bladder wall (Fig. 11.6). Depending on growth, these tumors range from a sessile polyp to bladder wall thickening. The least common is a pedunculated polyp. Tumors at the bladder dome or trigone are poorly imaged with CT, the limitation being the axial slices used. Because of partial volume averaging, these lesions tend to blend into the bladder wall and surrounding structures. Likewise, tumors at the bladder base tend to blend into the prostate. In general, CT misses lesions smaller than about 1 to 2cm in diameter. Computed tomography also cannot distinguish adherent blood clots from a tumor. Coronal views are often helpful.

Contrast enhanced multidetector CT reveals bladder cancers enhancing more than the surrounding bladder wall, best seen on 60–80 sec delayed scans (19); tumors <4cm in diameter tend to have homogeneous enhancement, larger ones become more heterogeneous. A urine distended bladder aids tumor detection.

Computer tomography cystoscopy, with the bladder opacified with contrast, can also detect

Figure 11.6. Bladder transitional cell carcinoma. Excretory phase CT identifies a right bladder tumor (arrow). The bladder base tumor (arrowheads) is due to prostatic enlargement. (Source: Joffe SA, Servaes S, Okon S, Horowitz M. Multi-detector row CT urography in the evaluation of hematuria. RadioGraphics 2003;23(6):1441–1456, with permission from the Radiological Society of North America.)