Intracavitary Mass

Sediment found in the bladder usually consists of urinary precipitates or pus. It presents a shifting or mobile sludge structure much like that seen in the gallbladder. The mobility of bladder sludge will generally distinguish it from flat, sessile bladder-wall tumors and areas of hypertrophic wall thickening. The best diagnostic procedure may be CEUS (Fig.11.70).

Fig. 11.70 Purulent bladder sediment in a patient with pyonephrosis.

Most benign and malignant bladder tumors appear sonographically as exophytic intraluminal masses or as plaque-like lesions infiltrating the bladder wall. Benign bladder papilloma is an example of an exophytic tumor. Other than the loose correlation between tumor size and biological behavior, there are no sonographic criteria that can confidently distinguish a benign papilloma from papillary carcinoma. Detectable wall infiltration is suggestive of carcinoma, however. This requires differentiation from an adenoma of the prostatic median lobe protruding into the bladder (Figs. 11.71, 11.72, 11.73).

Fig. 11.72 Bladder papilloma (arrow): lobulated, narrow polypoid mass occupying a constant position in the bladder. Next to it is a hyperechoic mass with an acoustic shadow (S): bladder stone. HB = bladder.

Fig. 11.71 a and b Polypoid bladder tumor (images courtesy of Professor C. Goerg, University Hospital Giessen and Marburg, Marburg, Germany).

a Gray-scale image: lobulated hypoechoic mass on the bladder floor.

Fig. 11.73 Median-lobe adenoma (benign prostatic hyperplasia), color Doppler.

a Polypoid mass extending into the bladder lumen. Apparent wall infiltration, scant peripheral vascularity.

b CEUS: intensive enhancement (arrow): bladder tumor.

b Longitudinal scan angled slightly downward shows that the tumor is connected to the median lobe of the prostate. HB = bladder.

Most benign and malignant bladder tumors arise from the transitional epithelium (urothelium). Other tumor types include squamous cell carcinomas (often associated with schistosomiasis), adenocarcinomas, and mesenchymal tumors (rhabdomyosarcoma, seen mainly in children). The Union for International Cancer Control (UICC) staging system is shown in Fig.11.98, p. 412. The most common malignant bladder tumor is urothelial carcinoma. Morphologically, approximately 70% of malignant bladder tumors display a papillary, almost villous type of growth. A small percentage are

solid or nodular. Bladder carcinomas metastasize chiefly to the regional lymph nodes along the iliac vessels. They can also seed hematogenously to the liver, lung, and bone marrow.

Bladder carcinomas may become ulcerated, and therefore typical complaints such as urgency are usually accompanied by hematuria.

Sonographic features. Polypoid bladder carcinoma is easily detected sonographically in a well-distended bladder when the lesion is larger than 5 mm. Exceptions are tumors located on the floor or roof of the bladder. Ultra-

sound demonstrates a nonhomogeneous internal echo pattern with smooth or lobulated, often hyperechoic, margins (Fig.11.74, Fig.11.75). Some tumors are pedunculated and exhibit a cauliflower-like structure. An intensely echogenic “hood” suggests a fibrous or partially calcified tumor surface, which is reportedly more characteristic of squamous cell carcinoma.9 The sonographic staging10 of a presumed or detected bladder carcinoma requires evaluating the deeper wall structures.

Sensitivity of ultrasound. Ultrasound has only about a 50% sensitivity in the diagnosis of bladder tumors.11 This results from the low detection rate of small tumors and precancerous lesions confined to the mucosa, tumors located on the bladder roof or anterior wall, and multiple tumors. Other lesions that usually escape sonographic detection are foci of simple or atypical hyperplasia, small urothelial papillomas, carcinoma in situ, plaque-like urothelial carcinomas, and small papillary carcinomas. Wall infiltration (mucous layer, infiltration into the muscle layer) is not detectable in abdominal ultrasound.

Fig. 11.74 Polypoid bladder tumor (T; papillary urothelial carcinoma).

a Intravesical mass with irregular margins (blooming effect causes the surface to appear more echogenic).

Fig. 11.75 Polypoid bladder tumor (T). Histology (after transurethral resection) indicated urothelial carcinoma without bladder wall infiltration (stage pTa).

a Hypoechoic tumor with an echogenic rim and no detectable bladder wall infiltration. HB = bladder.

Differentiation from clot. It is difficult to distinguish bladder carcinoma from intravesical clots. The following criteria are helpful in this regard:

●A mass on the bladder roof or side walls is suggestive of neoplasia.

●Movement of the mass when the patient is repositioned suggests a clot (no movement is more consistent with a neoplasm).

●Swirling echoes and a change in shape and size on rapid filling of the bladder suggest a blood clot.

b Irregular tumor vessels are detected, proving that the mass is not a clot.

b Color Doppler shows spotty vascularity.

●Color Doppler examination: vascularity suggests a tumor, while lack of vascularity (low flow velocity) is more consistent with a clot.

●Wall infiltration positively identifies the mass as a tumor.

●Repeat scans should always be obtained to check the constancy of the finding.

A bladder tumor is rarely the result of invasion by prostatic carcinoma, because that tumor arises from the outer zone of the prostate and does not extend toward the bladder floor like a median-lobe adenoma (Fig.11.76).

c Infiltration of the seminal vesicle (SB) is detected, indicating a stage T4a tumor by ultrasound (see Fig. 11.98).

Fig. 11.76 Known local metastatic prostatic carcinoma, histologically confirmed. The tumor (T) has infiltrated the bladder floor and obstructed the ureter (U). The tumor regressed completely after combined hormonal and chemotherapy. HB = bladder.