الفهرس 
ANATOMY OF THE URINARY BLADDEROnly 14 pages are availabe for public view
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Abstract
Carcinoma of the urinary bladder is the most common tumor among the low urinary tract, accounting for 90% of cancer cases. It has high rates of recurrence at the initial tumor site and elsewhere throughout the transitional epithelium. Gross painless hematuria is the classic clinical sign of bladder carcinoma. It has the highest lifetime treatment costs per patient of all cancers.
Many imaging modalities including CT, trans-abdominal US, cystography, IVU, and MR imaging were used to evaluate the bladder.
Conventional cystoscopy remains in the clinical use the standard for evaluation of the bladder for neoplasms and may be a necessary in patients suspected of having bladder carcinoma as it has the ability of taking biopsy from suspected lesions. However it has many drawbacks such as intense discomfort for the patient and bleeding; furthermore, the high cost, invasivity, and local complications such as infections and mechanical lesions are another well-known drawbacks. Additionally, conventional cystoscopy does not provide information about extravescical extensions of the tumor.
Recent advances in CT including software developments have led to the use of three dimensional (3D) imaging reconstruction techniques and allow CT urography and virtual endoscopy to be used in daily practice.
The main goal of VC was to develop a non-invasive diagnostic tool that would be easily tolerated by the majority of patients, by producing images similar to those acquired by the conventional endoscopy. Urinary bladder is an appropriate organ for virtual endoscopy because of its simple luminal morphology, its relatively small volume and the absence of involuntary peristalsis.
At present virtual cystoscopy based on volumetric data obtained with thin section multislice CT and the use of perspective volume rendering technique, seems to be the most accurate radiological method regarding lesion detection in the urinary bladder.
In our study we tried to investigate the utility of the CT virtual cystoscopy in the detection of the bladder masses, and compared the findings to the gold standard conventional cystoscopy.
Two techniques have been used for virtual cystoscopy, either air or contrast material to fill the bladder. Virtual cystoscopy of the air-filled bladder is invasive because catheterization is required to introduce air into the bladder. Catheterization is uncomfortable and is difficult to use in cases of stricture of the urethra; however, catheterization is not required for virtual cystoscopy of the contrast material filled bladder because it can be performed as a part of the routine abdominopelvic intravenous contrast-enhanced CT examination and provide information about extravescical extensions of the tumor. Additionally, the radiation dose in the former method is doubled: virtual cystoscopy of air-filled bladders requires two sets of CT data obtained with the patient in supine and prone positions, whereas contrast material-filled virtual cystoscopy data are obtained only once. One possible complication of the air-filled method is the introduction of infection due to the use of room air. However, virtual cystoscopy with contrast material-filled bladders may be limited by a risk of contrast-induced reactions and nephrotoxicity.
Our study included 35 patients; 25 of them presented with hematuria and a recent diagnosis of bladder carcinoma, and 10 patients with a history of previous transurethral resection of superficial bladder cancer in their follow up period. They ranged in age from 12 years to 73 years with a mean of 58.68; while male to female ratio was 7.75:1.
An excellent overview of the bladder masses was obtained in all cases and the results of virtual cystoscopy and conventional cystoscopy were comparable with excellent sensitivity rates of virtual cystoscopy in detection, localization and morphology description of the bladder lesions at variable sizes. The size of the masses in both groups (n=50) ranged from 4-80 mm in diam.
The high detection rate of the lesions is mainly attributed to the CT protocol used. Acquisition with thin collimation, creation of MPR images with no artefacts and virtual images of very good quality and excellent anatomic detail facilitated detection of a large number of small tumors with a 16-MDCT scanner.
Our study showed that combined evaluation of axial, MPR and virtual images should be used to increase the performance of the technique, especially in recognition of small tumors with high sensitivity and specificity.
Virtual cystoscopy in detection of bladder masses showed sensitivity: 100%: specificity: 94.2% with two false negative (two cases of mucosal color change in UB wall) in comparison to conventional cystoscopy.
As a minimally invasive procedure, virtual cystoscopy provides many advantages. It is less time consuming than conventional cystoscopy and allows accurate localization of a lesion due to its wide field of view. The size of a tumor is measured objectively, and virtual cystoscopy can be used to monitor treatment response in a patient with a non-resectable tumor. Patients with a severe urethral stricture or marked prostatic hypertrophy, who may be poor candidates for conventional cystoscopy, can safely undergo virtual cystoscopy.
Additionally, because CT virtual cystoscopy allows imaging of the urinary bladder in multiple planes, it can be used for the evaluation of areas of the urinary bladder that are difficult to assess with conventional cystoscopy such as bladder neck, trabeculations and diverticulae. Combining evaluated virtual images with axial and MPR images could provide valuable information for extraluminal disease, such as extravesical invasion, distal ureteral obstruction, and pressure of the neighbouring organs. Combined with routine pelviabdomen CT it is has advantage of providing information for lymph nodes invasion and metastatic deposits thus aiding in grading the tumors correctly.
There are several important limitations of virtual cystoscopy. A major limitation is that it is unable to depict flat lesions (carcinoma in situ), which appear as subtle mucosal color changes at conventional cystoscopy. In addition, mucosal thickening secondary to fibrosis cannot be distinguished from a neoplasm. Of course, with conventional cystoscopy we face a similar problem because biopsy is often required to determine whether a bladder lesion is inflammatory, fibrotic, or neoplastic. The calcifications associated are seen only on the transverse images and not on the virtual images. False-positive finding of lesion may be reported due to air bubble in bladder. Many artefacts were also reported in technique of CTVC of the contrast material- filled bladder when urine and contrast could not be mixed properly.
Another disadvantage of virtual cystoscopy is that it lacks the ability to provide tissue for histological evaluation, an ability that is possible with conventional cystoscopy and biopsy.