Multidetector computed tomography evaluation of bladder lesions

Abstract

Background

Urinary bladder tumors are the most common type of tumors detected in patients with gross hematuria. Multidetector computed tomography (MDCT) is an accurate method for detecting bladder lesions. This review aims to describe the features of MDCT and the possible values for distinguishing these lesions in the bladder.

Main body

In this review, we discuss the role of MDCT in the evaluation of patients with bladder cancer and describe a broad spectrum of bladder lesions, including malignant bladder lesions beyond bladder cancer, benign bladder lesions, and diffuse bladder wall thickening.

Short conclusion

Familiarity with the clinical presentations and imaging features of bladder lesions can lead to more accurate diagnosis and appropriate management.

Background

Urinary bladder lesions account for approximately 20% of all causes of hematuria and bladder tumors and are the most common types of tumors detected in patients with hematuria [1,2,3]. Multidetector computed tomography (MDCT) is an accurate examination for bladder lesion detection, with the sensitivity and positive predictive value of MDCT being 94% and 96%, respectively [1, 2]. The advantages of MDCT over conventional cystoscopy are patient tolerance and the ability to allow evaluation of the entire urinary tract and surrounding structures, as well as the bladder [1, 2]. MDCT can provide high accuracy and reliability comparable to conventional cystoscopy for bladder lesion detection and can be used as the primary diagnostic tool in patients with hematuria [1,2,3,4]. There is gap of knowledge in literature and limitations of MDCT in evaluation of bladder lesions.

In this review, we discuss the role of MDCT in the evaluation of bladder lesions and discuss broad spectrum bladder lesions ranging from benign to malignant.

Main text

MDCT for the detection of bladder lesions

Bladder CT scans were classified as conventional CT, CT cystography, and virtual cystoscopy [1].

On conventional CT, urothelial-phased scan (arterial or early portal phase) or delayed excretory-phased scans were used. Currently, both urothelial (portal) and excretory (delayed) phase CT scans are used to evaluate bladder lesions to improve sensitivity [1, 2]. Because most bladder cancers show early enhancement (with maximal enhancement at 60–80 s after contrast administration), a 70-s delayed urothelial phase has been found to show satisfactory contrast between a bladder tumor and the rest of the bladder wall and the highest diagnostic accuracy. Bladder lesions are usually revealed as intraluminal hyper-enhanced lesions or hyper-enhanced wall thickening compared with the normal bladder wall on urothelial phase images or filling defects on excretory phase images (Figs. 1, 2) [1, 2]. CT can also be useful for monitoring in patients who have been previously treated for bladder cancers (Fig. 2). Furthermore, MDCT enables high-quality multiplanar reformation (MPR) owing to thinner collimation and faster scanning, thereby greatly improving scan resolution, and allowing reconstruction in any desired plane, leading to better sensitivity for the detection of small bladder lesions (Fig. 3) [1].

Fig. 1

Urothelial (portal) and excretory (delayed) phase scans of CT urography in two patients of urothelial carcinoma. a Axial urothelial phase CT image of a 63-year-old man obtained at 70 s after bolus intravenous contrast material injection shows a small hyper-enhancing polypoid mass (arrow) that enhances more than normal bladder mucosa. b Axial excretory phase CT image shows the enhancing bladder lesion (arrow) but is less pronounced compared to the urothelial phase. c The nodule was also identified using conventional cystoscopy. d Axial urothelial phase CT image of a 74-year-old man shows an intraluminal hyper-enhancing mass (arrow) on the left wall of the bladder. e Axial excretory phase CT reveals the mass as a filling defect (arrow) within the bladder lumen. f The nodule was also detected using conventional cystoscopy

Fig. 2

Urothelial and excretory phase scans of CT urography in initial and recurred urothelial carcinomas. a Axial urothelial phase CT image of a 70-year-old man shows a small hyper-enhancing polypoid mass (arrow) that enhances more than normal bladder mucosa. b Axial excretory phase CT image shows the enhancing bladder lesion (arrow) but is less pronounced compared to the urothelial phase. c The nodule was also identified using conventional cystoscopy. Taken at the 6-month follow-up after transurethral resection of the bladder tumor, this axial urothelial phase CT image d shows an intraluminal hyper-enhancing mass (arrow) on the posterior wall of the bladder, the same as the initial tumor site. e Axial excretory phase CT of the patient shows that the mass is a filling defect (arrow) within the bladder lumen. f The nodule was detected using conventional cystoscopy

Fig. 3

CT detection of small and flat bladder lesions multiplanar reformation (MPR) in three patients of urothelial carcinoma. Axial (a) and sagittal (b) urothelial phase CT images of a 73-year-old woman showing an enhanced area of focal wall bladder thickening (arrows). Axial (c) and sagittal (d) urothelial phase CT images of a 58-year-old woman showing two tiny enhancing lesions (arrows) on the anterior wall of the bladder. Axial urothelial (e) and excretory (f) phase CT images of a 71-year-old woman showing subtle diffuse or segmental mucosal enhancement of the bladder without filling defects. The patient was diagnosed with urothelial carcinoma in situ on histopathological examination. Small or flat lesions are more difficult to detect with CT

However, a false-negative diagnosis of bladder cancer can be made using MDCT. Small and flat lesions, such as carcinoma in situ, may not present as filling defects and show only a little or no focal bladder wall thickening or abnormal enhancement (Fig. 3). Furthermore, bladder lesions located near the bladder base may be difficult or impossible to differentiate from an enlarged prostate or periurethral tissue. Causes of false-positive results include prostate enlargement, post-treatment, or inflammatory changes, trabeculated bladder, and blood clots [5, 6].

The MDCT protocol at our institution for evaluating patients with suspected bladder lesion includes an unenhanced scan, urothelial-phase scan, delayed excretory-phase scan and coronal maximal intensity projection view during the excretory-phase. A 64-slice CT scanner (including Brilliance 64; Philips Health Systems, Cleveland, OH, USA) was used. Patients were instructed not to void for at least one hour before the examination to obtain adequate bladder distension. During unenhanced scanning, adequate bladder distension was assessed. After unenhanced CT images were obtained, intravenous contrast agent (Iobrix® 300, Iohexol; Taejoon Pharm, Seoul, Korea) was administered by a power injector at 2 mL/kg of body weight and 3 mL/s. The urothelial-phase scan covered the entire bladder at the 70-s scanning delay. The parameters for the urothelial-phase scan were as follows: X-ray tube voltage: 100–120 kV; tube current: 130–250 mAs; beam collimation: 64 × 1.25 mm; gantry rotation time:0.33 s; matrix: 512 × 512; field of view: 320–400 mm; effective section thickness: 2–3 mm; reconstruction interval: 2 mm. The data were automatically reconstructed with iDose reconstruction technique, level 5 (Philips Healthcare).

CT cystography and virtual cystoscopy

CT cystography and virtual CT cystoscopy are invasive procedures that require the Foley catheterization and active bladder distension [1, 2]. Moreover, it offers little advantage over performing flexible cystoscopy. Nevertheless, the sensitivities are not impressively better than those obtained in evaluating bladder CT [1].

CT cystography should be considered in patients with suspected bladder injury after initial CT scan of the abdomen and pelvis [7]. To obtain an optimal CT cystography scan, drain urine via catheter to remove unopacified urine from the bladder prior to instilling contrast material. Typically, commercially available prediluted contrast or admixed ionic/nonionic intravenous contrast diluted at a 1:10 ratio with normal saline (approximately 3–5% iodinated solution) is instilled via gravity-drip infusion. A container of contrast is hanged 40 cm above bladder to generate adequate pressure and connected to the catheter. The bladder is filled with contrast until flow of contrast stops, bladder distension is uncomfortable to patient, or 350 mL of contrast has been instilled. Image acquisition with thin section imaging allows for isotropic voxel acquisition and optimal multiplanar reformats. Added coronal and sagittal reconstructions have shown improved detection of bladder injuries, that could potentially be missed on axial images [7]. Delayed post drainage reimaging is generally not performed.

CT virtual cystoscopy can be of great value as a complementary tool when conventional cystoscopy is not feasible. The creation of virtual cystoscopy can be obtained via 3D volume rendering technique. The procedure involves bladder distension, usually using air insufflation technique prior to CT scan. A three-way Foley catheter is inserted into the bladder to achieve complete voiding. The bladder is then distended by insufflating 350–500 cc of room air with syringes, according to the patient’s tolerance. Helical CT scans are obtained with patients in both the supine and prone position to prevent possible residual fluid obscuring small mural lesions. Post-processing CT data obtained are transferred to a workstation equipped with software for interactive intraluminal navigation with a surface-rendering algorithm. Navigation inside the bladder can be performed at 360 degrees from different directions to assess the bladder wall and lumen. If any abnormal lesion is detected, it should be fully evaluated in all projections. Virtual cystoscopy is a minimally invasive technique that allows visualization of the entire bladder within the lumen, even in areas inaccessible with conventional cystoscopy. Limitations of virtual cystoscopy include its inability to detect color changes of the mucosa and obtain tissue biopsy [2, 4].

Malignant bladder lesions

Bladder cancer

According to the 2022 World Health Organization (WHO) classification of the urinary and male genital tumors [8], bladder cancers are mainly classified as invasive urothelial carcinoma, squamous cell carcinoma, adenocarcinoma and urachal carcinoma (Table 1). Mesenchymal, hematolymphoid, neuroendocrine, metastatic and genetic syndrome–related tumors are splitted by tumor lineages of differentiation that may occur in different urinary tract locations. Invasive urothelial carcinoma, also known as transitional cell carcinoma, is the most common urinary tract cancer, accounting for 95% of bladder cancer cases, and has a propensity to be multicentric (up to 40% of cases). Bladder cancers have a variety of different CT appearances, such as intraluminal papillary or nodular mass, asymmetric or focal wall thickening, small filling defects (Figs. 1, 2), and less frequently diffuse wall thickening (Fig. 3) [5]. Diffuse bladder wall thickening is usually caused by benign abnormalities, including cystitis, bladder outlet obstruction, overactive bladder, and neurogenic bladder [5, 9]. Incidentally detected bladder wall thickening on CT can be suggestive of bladder malignancy (Fig. 3), particularly focal bladder wall thickening rather than diffuse. Therefore, further workup, including cystoscopy and urine cytology, should be performed to assess bladder malignancy [9].

Table 1 The 2022 WHO classification of urinary tract tumors

Nonetheless, squamous cell carcinoma tends to be sessile rather than papillary, compared with urothelial carcinoma (Fig. 4). Furthermore, nonurachal adenocarcinoma tends to show diffuse bladder wall thickening, perivesical fat stranding (Fig. 4), lymphadenopathy, and invasion of adjacent organs. Urachal adenocarcinoma is characteristically located at the midline of the bladder dome, and an infraumbilical soft tissue mass with calcification strongly suggests urachal adenocarcinoma [10].

Fig. 4

Two cases of bladder cancer. a Axial urothelial phase CT image of a 67-year-old female patient with bladder squamous cell carcinoma shows an enhancing sessile or nodular mass (arrow) in the anterior wall of the bladder. b, c Axial contrast-enhanced CT images of a 68-year-old male patient with bladder adenocarcinoma show diffuse bladder wall thickening (arrow) along the anterior wall of the bladder and a large irregular enhancing intramural mass within the bladder. There is irregular soft tissue stranding (small arrow) from tumor invasion into the perivesical fat

It is difficult to distinguish superficial bladder cancer (T1) from muscle-invasive bladder cancer (T2) using MDCT. Magnetic resonance imaging (MRI) can distinguish muscle-invasive from non-muscle-invasive tumors with accurate local staging. Vesical Imaging-Reporting and Data System (VI-RADS) score is a new diagnostic modality used for the prediction of tumor aggressiveness and therapeutic response [2]. Furthermore, the detection of microscopic perivesical tumor invasion (stage T3a disease) using MDCT can be challenging. The diagnosis of stage T3b disease (macroscopic perivesical tissue invasion) can also be challenging because perivesical soft tissue stranding is a nonspecific finding and can be due to tumor extension or merely reactive change or edema [5].

Leiomyosarcoma

Leiomyosarcoma is the most common malignant mesenchymal tumor originating in the bladder in adults. It accounts for less than 1% of all bladder malignancies, and its risk factors include systemic chemotherapy with cyclophosphamide and radiation therapy [10].

Imaging findings of leiomyosarcoma can mimic those of benign leiomyoma, and it can be difficult to distinguish leiomyoma from leiomyosarcoma even with MRI [10]. However, if the mass is large, heterogeneous signal intensity on T2-weighted images is seen in leiomyosarcoma due to necrosis. Furthermore, poorly circumscribed margins and invasion of adjacent structures can also be observed (Fig. 5) [10].

Fig. 5

A 67-year-old male patient with bladder leiomyosarcoma. Axial (a), coronal (b), and sagittal (c) contrast-enhanced CT images showing a large, poorly circumscribed, heterogeneously enhancing mass (arrows) on the dome of the bladder wall

Rhabdomyosarcoma

Rhabdomyosarcoma is the most common bladder tumor in children and generally occurs before the age of 10 years. It affects boys more than girls in a 3:1 ratio [10].

Rhabdomyosarcoma typically shows large, nodular filling defects or masses in polypoid or grape-like shapes, often referred to as ‘sarcoma botryoides.’ These tumors often involve the bladder base, are associated with urinary tract obstruction, and may become difficult to distinguish from a prostate tumor. Grape-like intraluminal masses of the bladder on imaging in pediatric patients strongly suggest rhabdomyosarcoma [10].

Lymphoma

As no lymphoid tissue is normally found in the bladder, primary bladder lymphoma is extremely rare, but secondary involvement of the bladder can occur in 10–25% of patients with systemic lymphoma and leukemia [10, 11]. Primary lymphoma of the bladder is either the low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) or diffuse large B-cell lymphoma (DLBCL) [10, 11]. Typically affecting adults aged > 60 years, 75% are females with associated chronic cystitis, and the initial symptoms include hematuria, dysuria, and abdominal or back pain [11].

The imaging features are nonspecific and include solitary bladder masses (70%), multiple masses (20%), and diffuse bladder wall thickening (10%) (Fig. 6) [2, 10, 11].

Fig. 6

A 60-year-old male patient with bladder lymphoma. Axial contrast-enhanced CT image showing marked circumferential wall thickening of the bladder (arrow)

Benign bladder lesions

Benign bladder lesions can be classified as epithelial tumors, mesenchymal tumors, and non-tumorous bladder lesions. Benign bladder neoplasms represent less than 1% of bladder tumors. There is a significant overlap in the clinical features and radiologic findings of benign bladder neoplasms, which often require a biopsy for diagnosis.

Leiomyoma

Leiomyoma is the most common mesenchymal tumor of the bladder and is mainly found in the trigone of the bladder. Nevertheless, bladder leiomyoma is a rare, benign tumor with an incidence rate lower than 0.5% among all types of bladder tumors [10, 12]. The incidence of bladder leiomyoma in females is twice that in males. Furthermore, patients aged approximately 50 years have the highest risk [12]. Bladder leiomyomas can be intravesical (60%), intramural (10%), or extravesical (30%) [10]. Among these three types of bladder leiomyomas, the intravesical forms are most likely to cause irritation, obstruction, or bleeding symptoms because they protrude into the lumen of the bladder.

Imaging findings include well-delineated, smooth, and uniform solid masses of the bladder wall, similar to those of the uterine counterpart (Fig. 7) [10]. Bladder leiomyoma can also manifest as a cystic component, indicating degeneration.

Fig. 7

A 57-year-old female patient with bladder leiomyoma. Axial non-contrast a and contrast-enhanced b CT images showing a smooth homogenous enhancing solid mural mass of the bladder (arrow), similar in appearance to uterine leiomyoma

Papilloma and papillary urothelial neoplasms of low malignant potential (PUNLMP)

Papillary lesions of the bladder urothelium include papilloma, inverted papilloma, PUNLMP, and papillary urothelial carcinoma [10].

PUNLMP is a low-grade, small, solitary neoplasm with no invasion or metastasis, and it can be difficult and subjective to distinguish it from low-grade carcinoma (Fig. 8) [10]. Surveillance is required because the recurrence rate of PUNLMP is approximately 35% and progresses at approximately 10% [13].

Fig. 8

Two cases of bladder papilloma and papillary urothelial neoplasm of low malignant potential (PUNLMP). Axial urothelial phase a CT image of a 60-year-old male patient with bladder papilloma showing a tiny enhancing lesion (arrow) on the trigone of the bladder and also demonstrating a filling defect (arrow) on the excretory phase (b) CT image. Axial urothelial phase c of a 19-year-old male patient with PUNLMP and excretory phase (d) CT images showing an irregular polypoid enhancing lesion and filling defect (arrows) in the bladder mimicking bladder cancer

Cystitis cystica and cystitis glandularis

Cystitis cystica and cystitis glandularis are chronic inflammatory disorders associated with metaplasia caused by chronic irritation or infection. The urothelium proliferates into the lamina propria, forms a solid nest called Brunn’s nest, and then degenerates into cystic deposits, resulting in cystitis cystica or differentiation into the mucin-secreting glandular structure of cystitis glandularis [14]. They predominantly occur in the bladder neck, and trigone region of the bladder [15]. They may occur at any age, and there is a slight male predominance [15]. Some authors have reported that these masses can progress to adenocarcinoma of the bladder; however, this remains contentious [15].

Cystitis cystica and cystitis glandularis manifest as single or multiple masses that vary in number and size, which may result in a cobblestone pattern, mimicking bladder cancer on imaging (Fig. 9) [14].

Fig. 9

A 49-year-old male patient with cystitis glandularis. Axial urothelial (a) and excretory (b) phase CT images showing multiple polypoid intramural enhancing and filling defect lesions (arrows) in the bladder. c Cystoscopy showing a cobblestone appearance of the mucosa with polypoid masses

Endometriosis

Bladder endometriosis is uncommon. However, the bladder is the most common site for endometriosis within the urinary tract. Bladder endometriosis has only been reported in premenopausal women [14]. Bladder implants typically occur in the posterior wall of the bladder, including the dome, trigone, or vesicouterine pouch.

Imaging findings typically show a submucosal mass located posteriorly in the bladder, with variable protrusion into the bladder lumen, producing an obtuse bulge (Fig. 10). They are rarely isolated, and other endometriosis foci in the pelvis help to correct the diagnosis [14].

Fig. 10

A 37-year-old female patient with bladder endometriosis. Axial (a) and coronal (b) urothelial phase CT images showing a solid, well-marginated enhancing mass at the dome of the bladder. Note the obtuse angle of the mass from the bladder wall (arrow)

Paraganglioma

Paraganglioma of the bladder is an exceedingly rare pheochromocytoma arising outside the adrenal gland, which rarely develops in the bladder [10]. It constitutes less than 6% of all paragangliomas and 0.06% of all primary bladder tumors [16, 17]. It has a predilection age of 30–50 years, with no sex differences [17]. A characteristic ‘micturition attack,’ such as elevated blood pressure, headache, or syncope during micturition, occurs in 50% of patients due to catecholamine release. Functional paraganglioma should be considered when the tumor is > 3 cm [16]. Most are sporadic but can also occur due to hereditary syndromes such as neurofibromatosis, von Hippel–Lindau syndrome, and Sturge–Weber syndrome [10].

A bladder paraganglioma is usually a well-marginated, submucosal, solid solitary mass (Fig. 11) and can occur anywhere in the bladder, but most commonly in the dome or trigone [16]. It often attaches to the bladder wall with a broad base. It may be pathologically based on its tendency to infiltrate and grow along the muscularis [17]. Marked enhancement, peripheral ring calcification, and high signal intensity on T2-weighted images are key imaging features of bladder paragangliomas (Fig. 11) [10].

Fig. 11

Two cases of bladder paraganglioma. Axial pre-contrast (a) and post-contrast (b) CT images of a 38-year-old female woman showing a well-circumscribed, avidly enhancing nodular lesion at the anterior wall of the bladder. c Axial contrast-enhanced CT image of a 48-year-old man showing a lobulated intraluminal mass with heterogeneous early enhancement. d Axial T2-weighted MRI showing heterogeneous high signal intensity in the mass with a peripheral hypointense rim representing the calcification component

Inflammatory myoblastic tumor

An inflammatory myoblastic tumor (IMT) is a spectrum of nonneoplastic myofibroblastic proliferation with inflammatory infiltrates and myxoid components [14, 18]. IMTs of the urinary system are relatively rare, and the bladder and prostate are the most common sites of their occurrence [18]. Bladder IMTs typically occur in younger individuals, particularly females, but rarely in children [19]. The clinical symptoms of bladder IMT include hematuria, frequent micturition, and painful urination [18]. Moreover, in some studies, urinary system IMTs were associated with a history of pelvic surgery [19].

On imaging evaluation, IMT usually appears as a single intraluminal or exophytic bladder mass, which may be ulcerated or show ring enhancement (Fig. 12). IMTs mainly occur in the superior or front wall of the bladder [19]. The pathognomonic feature of ring-like enhancement is produced by necrosis in the central region and spindle cells, myxoid components, vessels, and inflammatory cells in the periphery. The observation that polypoid nodules on the bladder walls show ring enhancement may be valuable in the diagnostic imaging of bladder IMTs [14, 19].

Fig. 12

A 40-year-old male patient with an inflammatory myoblastic tumor of the bladder. Axial pre-contrast (a) and post-contrast (b) CT images showing a single poorly marginated intraluminal polypoid mass with avid ring enhancement (arrow)

Solitary fibrous tumor

Solitary fibrous tumors are extremely rare mesenchymal neoplasms with fibroblast differentiation. They are more common in males and those aged 42–67 years [10].

On CT and MRI, solitary fibrous tumors appear as well-demarcated, solid, polypoid intraluminal or submucosal enhancing masses (Fig. 13). The presence of prominent feeding vessels or a vascular pedicle, although not specific, is a useful distinguishing feature [10].

Fig. 13

A 49-year-old male patient with a solitary fibrous tumor of the bladder. Axial pre-contrast (a) and post-contrast (b) CT images showing a large well-circumscribed solid enhancing mass (arrow) in the bladder

Acute bacterial cystitis

Acute bacterial cystitis is more common in females and is usually caused by Escherichia coli. Patients with acute uncomplicated bacterial cystitis are readily diagnosed by history, clinical examination, and laboratory findings without the need for secondary CT [7].

Patients with acute bacterial cystitis often have normal CT findings but may show diffuse bladder wall thickening, mucosal irregularity, enhancement, and mural hypertrophy due to severe mucosal edema and fold thickening (Fig. 14) [2, 7, 20]. Furthermore, pseudotumors and focal protrusions can sometimes be observed. If severe infection and inflammation progress chronically, bladder volume may be reduced owing to fibrosis or contraction of the bladder wall [7, 20].

Fig. 14

A 62-year-old female patient with acute bacterial cystitis. Axial pre-contrast (a) and contrast-enhanced (b) CT images showing diffuse enhancement of the mucosal surface with wall thickening of the bladder

However, CT offers a more comprehensive anatomical and functional assessment of the upper and lower urogenital tract, a detailed assessment of renal function and excretion, and increased sensitivity for calculi and early gas-forming infections [7].

Eosinophilic cystitis

Eosinophilic cystitis is a rare chronic inflammatory disease of the bladder. It is characterized by an extensive local infiltrate of eosinophils into all layers of the bladder wall and is associated with variable degrees of fibrosis and muscle necrosis [14, 21]. The mean age at diagnosis has been reported to be 41.6 years, with equal distribution in both sexes [21].

The imaging findings are nonspecific, with focal or diffuse thickening of the bladder wall (Fig. 15), which can be difficult to differentiate from other types of cystitis and sometimes bladder cancer [14, 21].

Fig. 15

A 65-year-old male patient with eosinophilic cystitis. Axial pre-contrast (a) and contrast-enhanced (b) CT images showing diffuse mural thickening of the bladder wall, which is nonspecific and difficult to distinguish from other cystitis or tumors

Conclusions

MDCT plays a large role in the evaluation of patients with known and suspected bladder cancer. MDCT can be used as an initial bladder examination in such patients and can replace cystoscopy. A summary of the MDCT findings for bladder lesions is provided in Tables 2 and 3. The role of the radiologist is to ensure that broad spectrum bladder lesions are detected and diagnosed preoperatively if possible.

Table 2 Summary of the clinical and CT features of malignant bladder lesions

Table 3 Summary of the clinical and CT features of benign bladder lesions