CONVENTIONAL AND VIRTUAL CYSTOSCOPIES FOR DIAGNOSIS OF URINARY BLADDER GROWTH LESIONS: A SUPPLEMENTARY RATHER THAN COMPETITIVE RULES

HOSSAM IBRAHIM, ABDUL NASER GHAREEB, MOKHTAR RAGAB  AND EMADELDEEN ALI SALAH*
Radiology and urology* Departments, Al-Azhar University Hospitals, Cairo and Assiut*.

Introduction and aim of the work: Recent CT scan technology allowed three dimensional image reconstructions to precisely and accurately show fine anatomical details. The goal of this study was to evaluate the usefulness of virtual cystoscopy (VC) in diagnosis of urinary bladder neoplasm in comparison with the gold standard conventional cystoscopy (CC).

Patients and Methods: Eighty three consecutive patients (mean age 54 years) clinically presenting for gross haematuria and positive urine cytology for malignancy, were prospectively evaluated with VC after bladder air insufflation or intravenous injection of contrast medium using multi-detector helical CT (1-mm section thickness). Afterwards, all patients had been subjected to CC and examination under anaesthesia.

Results: The findings of VCs were quite comparable with the findings from the CCs except in three patients were not detected by VC (two patients with tumor sizes < 3 mm and one with carcinoma in situ). The bladders of seven patients appeared normal on both CC and VC. The sensitivity and specificity of identification of bladder mass lesions using VC were 96% and 100% respectively, while, it’s positive and negative predictive values were 100%, and 70% respectively.

Conclusion: CT virtual cystoscopy is a minimally invasive technique that could be successfully used for detection of bladder tumors ≥3 mm especially for follow up after transurethral resection of bladder tumors (TURT) cases during daily routine abdominopelvic CT work. It is not a substitute but rather supplementary to CC.

INTRODUCTION AND AIM OF THE WORK

Bladder cancer is one of the most common tumors of the urinary tract. Two out of three malignancies of the urinary tract are located in the urinary bladder (UB). Carcinoma of the urinary bladder (CB) comprises nearly 7% of all malignant tumors in men and 4% in women.1, 2 Urinary bladder cancer is the 7th leading cause of cancer death in men and the 10th in women3 and it is a common problem facing urologists worldwide. The gold standard for its diagnosis and follow-up is direct visualization of the tumor using CC. Despite having highest sensitivity and specificity for detecting bladder cancer, CC is considered invasive procedure which is associated with many complications as iatrogenic urethral or bladder injury and urinary sepsis.2 In addition, regular follow-up of patients with bladder cancer using CC is a financial burden on the health system. With the progressive development in diagnostic imaging and medical computer software technology, it is now possible to generate virtual reality images to aid the clinician to inspect the interior of the bladder in real time. This technology is considerably safe test for bladder cancer diagnosis and follow-up with detection rates comparable with CC.4

The patient with CB usually presents with haematuria, and the initial evaluation consists of cytological analysis of a urine specimen.2 Plain x-ray film of the abdomen (KUB), abdominal ultrasonography (AUS), computed tomography (CT), magnetic resonant imaging (MRI) and some other radiological modalities have been used in assessment of such cases.5 CT is usually recommended as a useful radiologic approach for assessing bladder disease, but it has low sensitivity for detection of small bladder lesions. For CT to depict a small bladder lesion, optimal imaging conditions, including adequate bladder distension and thin-slice scanning, must be satisfied. Therefore, negative findings on CT warrant performance of CC in patients with suspected bladder pathology.6

Recently, three-dimensional computer-rendering techniques with rapid image acquisition have led to the development of virtual-reality imaging. With commercially available software, virtual reality imaging allows interactive intra-luminal navigation through any hollow viscous, simulating CC. This technique of virtual endoscopy has been applied to many organs, including the colon, bronchus, stomach, and bladder.7-11 As a new diagnostic tool, VC provides many advantages; it allows accurate localization of the lesion due to its wide field of view and depiction of extravesical anatomic landmarks. The size of a mass is measured objectively, and VC can be used to monitor radiation or chemotherapy treatment responses in a patient with a non-resectable tumor.7,12 CT virtual cystoscopy (CT-VC) can be obtained either with gas-filled bladder or with contrast-material-filled bladder.13,14 Multi-detector CT with volume acquisition and rapid scan speed can avoid motion artifact and the retrospective thin slice reconstruction is useful in detecting smaller lesions. Contrast enhanced studies facilitate the evaluation of the relation between the tumors and their surrounding structures and the confirmation of pelvic lymphadenopathy.15 The main goal of this study was to assess the usefulness of VC using a volume rendering algorithm performed with multidetector CT in diagnosis of urinary bladder neoplasm compared to the CC.

MATERIALS AND METHODS

Eighty three patients were included in this study from the urology outpatient clinics at Al-Azhar University Hospitals, over the period from May 2006 till Dec 2008. Sixty four of them were males and 19 were females. Their age range from 33 to 67 years old with the mean age ± SD was 54 ± 7.9 years old. The majority of cases were in their 5th decade of life (48%). The main presenting complaints were haematuria (gross in 80%) and /or other lower urinary tract symptoms. All patients were subjected to detailed history, full clinical examinations, and laboratory investigations (urine analysis with cytology plus renal function tests). Medical imaging included KUB, AUS, chest X-ray as well as CT scanning of the abdomen and pelvis was done for all cases. CC examination was performed for every patient, under general/spinal anesthesia with transurethral resection (TUR) biopsy obtained from the bladder growths. The endourologists, who were not pre-minded with the virtual cystoscopic findings, performed cystoscopic examinations using rigid wide angle telescopes. They were instructed to determine the number, location, and size of the bladder lesions by drawing, video-recording or photographing.

Virtual cystoscopic examinations were done after filling of UB either by room air insufflation (N: 45) or IV contrast material injections (N: 38). When air contrast was used, the catheterized bladder was completely evacuated from urine followed by insufflation of bladder with 100-300 ml room air via the catheter using a 60 ml syringe and a clamp, according to bladder capacity and patient’s tolerance. On the other technique of IV contrast media, 10 ml of non-ionic contrast material intravenously injected 30 minutes prior to the scan. Thereafter, routine helical CT was performed using GE multislice 4 detectors system in single breath hold after IV injection of contrast media (using automatic injector at a rate of 2ml/sec with the dose 1 ml/kg; maximum used dose was 100ml). The CT parameters were 280 mAs, l20 Kv, 1 mm collimation, 1 mm reconstruction interval and 3 mm slice thickness. The obtained data were downloaded to an independent workstation (Millentech workstation) for post-processing. Using multi-planar reformate from the source axial images, a central reference point was set in the center of the bladder lumen.

The camera for VC was placed in the center of the bladder lumen and thereafter was advanced to each quadrant in turn. The findings were then evaluated from various angles. This was held at the medical imaging department of Al-Azhar University Hospital (CT & MRI unit). On the monitor, 3 windows were simultaneously displayed, the global view (3D picture), the local view (virtual image), and the nearest axial CT imaging slice. The obtained data was subsequently processed for reconstructing VC (by volume-rendering algorithm) and multi-planar images reconstruction (transverse, coronal and sagittal planes at a slice thickness of 1 mm). Three radiologists interpreted the images independently with consensus if any data difference was noted. The site, size, shape and number of the bladder lesions were documented on separate worksheets. The lesions were categorized into polypoidal (if its length was larger than width), sessile (if their width were larger than length) and diffuse wall thickening. The findings of VC were then compared to the findings of CC.

RESULTS

Both CCs and VCs were well tolerated by all patients without complications. Images in all virtual cystoscopic examinations were of excellent quality with adequate bladder distension. On CC, 100 tumor lesions were identified in 76 patients (7 cases were tumor free although cytologically positive for cellular atypia); single tumor lesion was documented in 57 patients (75%), two lesions in 14 patients (18.4%), triple lesions in 4 patients (5.3%) and one patient (1.3%) was diagnosed as carcinoma in situ (CIS). On the other side, VC showed the same tumor lesions identified with the same distribution like CC except for two tiny growths, their sizes were 2.3 and 2.9 mm plus the CIS case (cases number 15, 28 and 64 respectively). Those three cases were not detected by VC. The tumor sizes ranged from 0.23 to 6.4 cm with a mean diameter of 2.7cm (table, 1).

Table (1): Number of bladder growths detected by virtual and conventional cystoscopies according to sizes.

Size of the growth More than 1cm 3 to 10 mm Less than 3 mm
CC (No: 100) 55 (55%) 42 (42%) 3 (1 CIS)
VC (No: 97) 55 (56.7%) 42 (43.3%) 0

Approximate measurements of the lesions’ sizes could be done through CC after calculating the lens magnifying power. Morphologically, the identified tumors were categorized into 4 types; polypoid or papillary in 77 lesions, sessile in 19 lesions, diffuse wall thickening in 3 cases and CIS in one case. In the present study, virtual and conventional cystoscopies were comparable in detection of the tumor growths in the urinary bladder (figures 1-4).

Among the visualized 100 tumor lesions, 32 were located at the posterior wall, 25 at right lateral wall, 20 on the left lateral wall, 10 on the anterior wall, 10 at the bladder base and 3 at the bladder neck. VC showed a sensitivity of (96%) and specificity of (100%) in identification of tumor lesions involving different bladder walls. Nevertheless, sensitivity was as high as 100% if the mass is ≥ 3 mm in size. No growths less than 3mm were detected. The positive and negative predictive values ware 100% and 70% respectively.

Figure (1): Male patient, 62 years old, presented with haematuria. (A) Axial CT scan of the UB with air contrast media reveals large polypoid soft tissue mass arising from posterior wall near bladder neck with nodular surface. (B) VC shows large polypoid mass with lobulated surface. (C) CC shows large papillary mass arising from the posterior bladder wall.  Histopathology: transitional cell carcinoma grade II.


Figure (2): Female patient, 53 years old, presented with haematuria and dysuria. (A) An axial CT scan of the urinary bladder with air contrast media revealed irregular nodular thickening of the left lateral wall. (B) VC showed two large papillary lesions at the left lateral wall. (C) CC shows two papillary tumors involving the left lateral bladder wall.  Histopathology: Squamous cell carcinoma grade II.


Figure (3): Male patient 38 years old, presented with haematuria. (A) Axial CT scan of the urinary bladder with IV contrast media reveals a small filling defect at the left lateral wall. (B) VC: two small papillary growths are seen involving the left lateral wall. (C)  CC: Two small polypoidal tumors involving the left lateral wall.  Histopathology revealed squamous cell carcinoma grade II.

Figure (4): Male patient 57 years old complained of painless haematuria only. Diagnosis: a small papillary tumor arising from left paramedian aspect of posterior wall near the bladder neck. (A) CT, (B) VC, (C) CC & Histology: Papillary transitional cell carcinoma Grade II.

DISCUSSION

Cancer of the urinary bladder is a common disease in Egypt. Many radiological imaging techniques have been in use to evaluate bladder tumors, but none have been found to be fully reliable in detection of bladder cancer. Although invasive, time-consuming, expensive, requires anesthesia, sometimes cause iatrogenic injury and operator dependent, CC remains the gold standard.2,6,15,16 Also, evaluation of lesions located in the base or neck of the bladder or in the diverticulum is difficult because of the limited viewing field of the cystoscope.16-18 Because bladder tumors have a tendency toward multifocality and recurrence, it looks very important to find out diagnostic techniques that are less invasive and in mean time highly sensitive. The recent introduction of virtual endoscopy has enabled evaluation of bladder tumors.

The three dimensional images generated from volumetric data obtained with helical CT imaging ware used for this purpose.2,6,7,16-21 Since the work published by Vining et al.,6 there have been several studies that had discussed the utility of VC for the diagnosis of bladder lesions.1,2,16-18,22 To date, two techniques that use either air or contrast material to fill the bladder have been used for VC.1,2,6,18 The results obtained from cases with IV contrast media were adequately similar to those obtained with air contrast. The IV contrast material filled bladder VC is performed as a part of the routine abdominopelvic IV contrast-enhanced CT examination which is totally non invasive technique.7,16 However, presence of fine faint artifacts within the obtained images when using IV contrast study, make images obtained from air contrast were clearer and sharper.

Merkle et al.1 was the first to report that VC of the contrast material-filled bladder is a non-invasive, safe, comfortable, and easy technique. VC with IV contrast material-filled bladders may be limited by a risk of contrast-induced reactions and nephrotoxicity.7 Additionally, the examination time takes longer times.7,22 With regard to the size of the bladder growths, researchers17 identified all lesions >10mm, and they reported an up to 100% detection rate.  Narumi et al18 identified 77% of lesions smaller than 10mm. Others reported a 90.9% detection rate for bladder tumors overall and a 100% detection rate for tumors 1cm or larger in diameter.21 However, these studies retrospectively evaluated bladder lesions that had been confirmed on CC. The present study was a prospective trial designed to evaluate the usefulness of VC for detection of bladder tumors.

Song et al2 reported a detection rate of 60% for lesions <5 mm using surface rendering algorithms while; Yazgan et al16 identified a detection rate of 43% for either polypoid or sessile lesions. Single-detector helical CT and the surface-rendering algorithm were used in both studies, which were different from the one used in this study (multi detector CT scanner with volume rendering algorithm). Sensitivity and specificity of CT VC has been reported since 1995 to be as high as 95% and 87% respectively for identifying bladder tumors, and 95% and 93% respectively for identifying abnormal bladder mucosa due to all causes.4 In addition, for polypoid and sessile lesions <10 mm, the detection rate was 86%. Kim et al7 detected 88% of polypoid lesions <5 mm using multi-section CT and the volume-rendering algorithm. Tsampoulas et al23 showed that a combined evaluation of axial, multi-planar reformat (MPR) and virtual images should be used to increase the performance of the technique, especially in the detection of smaller tumors. The thin slice CT sections (1mm) technique is quite suitable for detection of such minute growths. The present results demonstrated that VC is a feasible technique for the detection of polypoid bladder lesions down to 3mm.

CT virtual cystoscopy (CT-VC) gives no information about the color and texture of the bladder mucosa; therefore, it cannot be used to detect carcinomas in situ. This method is also unable to distinguish between stage Ta and T1 tumors because it does not produce tissue for histological examination.23 For these reasons, VC is not a substitute method that can completely replace CC. Nonetheless, VC provides many advantages like accurate lesion localization especially at areas of the urinary bladder that are difficult to assess with CC because of its wide field of view (360°) and multi-planar capability.

Also it measures tumor size reliably and can depict anatomic landmarks outside the bladder. Moreover, in situations where CC cannot be applied or is contraindicated as in case with severe urethral strictures or in the presence of active bleeding,2,16,18 VC can provide excellent intraluminal information. Additionally, combining evaluated virtual images with axial and MPR images could provide valuable information for extraluminal disease, such as extravesical invasion, distal ureteral obstruction, lymphadenopathy and pressure of the neighboring organs. VC of the contrast-filled bladder is a non-invasive method that should be applied to patients as a routine component of the abdominopelvic CT examination in the diagnostic algorithm for macroscopic haematuria.23,24

The present study has shown several limitations about VC. First, the radiation dose is relatively high with thin section thickness slices. Second, in patients who cannot easily change positions, the image quality of VC is suboptimal due to inadequate mixing of the contrast material and urine. Next, no samples are provided for histological evaluation, so, the technique is not sufficient to differentiate tumors from inflammatory lesions. Moreover, helical CT machine is unable to depict flat lesions (CIS) and small lesions <3 mm with a major disadvantage of the urologist inability to manage any lesion found immediately, for example by fulguration.

CONCLUSIONS

Considering the fact that CT is crucial for the staging of bladder tumor, VC holds no extra-burden over the health system. VC using air filled or IV contrast material-filled bladder is a minimally invasive method which is very useful for detection and evaluation of bladder tumors, especially those larger than 3mm. Even with thin slice section imaging (1mm), the detection rate for flat and less than 3mm lesions is still inadequate. In addition, VC provides reliable information on the size of the lesion, localization, shape, and number which will make an excellent guide for the urologist on planning the following resection step. Besides this, it is possible to obtain the image information in a short time, and the data can be stored for re-examination when needed.  It is an excellent advisable step prior to operative cystoscopy for the bladder tumor diagnosis and management or also can be used alone in the follow up after TURT for observation of recurrence. High cost, radiation hazards and long waiting list might be obstacles to such technology to be routine in use. Accumulating experience and rising learning curve will be soon available for different types of bladder lesions from correlation of VC data and histopathology.

REFERENCES

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