Multi-parametric MRI findings of granulomatous prostatitis developing after intravesical bacillus calmette-guérin therapy

Interpreting Prostate Multiparametric MRI: Beyond Adenocarcinoma - Anatomical Variations, Mimickers, and Post-Intervention Changes

Prostate magnetic resonance imaging (MRI) is an essential tool in the diagnostic pathway for prostate cancer. However, its accuracy can be confounded by a spectrum of noncancerous entities with similar radiological features, posing a challenge for definitive diagnosis. This review synthesizes current knowledge on the MRI phenotypes of both common and rare benign prostate conditions that may be mistaken for malignancy. The narrative encompasses anatomical variants, other neoplastic processes, inflammatory conditions, and alterations secondary to medical interventions. Furthermore, this review underscores the critical role of MRI quality in diagnostic accuracy and explores the emerging contributions of artificial intelligence in enhancing image interpretation.

Granulomatous prostatitis following Bacillus Calmette-Guérin therapy

Granulomatous prostatitis (GP) is a rare form of chronic prostatitis with reported incidence of 0.65-1.5%. Radiological features of GP overlap with those of prostate adenocarcinoma. The following magnetic resonance imaging characteristics can suggest the diagnosis in an appropriate clinical setting: Diffuse or focal nodular low T2 signal, high signal on diffusion-weighted imaging with corresponding low apparent diffusion coefficient signal, and post-contrast imaging with lesion enhancement or rim-enhancing in the setting of caseous necrosis or abscess formation. Even with suspicion on imaging, the overlapping imaging features with prostate adenocarcinoma necessitate biopsy for confirmatory diagnosis. Here, we report a case of a 70-year-old man with GP in the setting of prior intravesicle bacillus Calmette-Guérin administration.

Negative biopsy histology in men with PI-RADS score 5: is it useful PSMA PET/CT evaluation?

INTRODUCTION

To evaluate the accuracy of PSMA PET/CT in men with mpMRI PI-RADS score 5 negative biopsy histology.

MATERIALS AND METHODS

From January 2011 to January 2023, 180 men with PI-RADS score 5 underwent systematic plus mpMRI/TRUS biopsy; 25/180 (13.9%) patients had absence of cancer and six months from biopsy were submitted to: digital rectal examination, PSA and PSA density exams, mpMRI and 68GaPSMA PET/CT evaluation (standardized uptake value "SUVmax" was reported).

RESULTS

In 24/25 (96%) patients PSA and PSA density significantly decreased, moreover, the PI-RADS score was downgraded resulting < 3; in addition, median SUVmax was 7.5. Only 1/25 (4%) man had an increased PSA value (from 10.5 to 31 ng/ml) with a confirmed PI-RADS score 5, SUVmax of 32 and repeated prostate biopsy demonstrating a Gleason score 9/ISUP Grade Group 5 PCa.

CONCLUSIONS

The strict follow up of men with PI-RADS score 5 and negative histology reduce the risk of missing csPCa especially if PSMA PET/CT evaluation is in agreement with downgrading of mpMRI (PI-RADS score < 3).

Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation

A diverse spectrum of pathologically distinct, nonneoplastic, proliferative conditions of the kidneys and urinary tract demonstrate a expansile growth pattern similar to that of neoplasms. The renal pseudotumors include myriad causes of infections as well as rare noninfectious causes such as sarcoidosis, amyloidosis, and immunoglobulin G4-related disease (IgG4-RD). Rare entities such as cystitis cystica, endometriosis, nephrogenic adenoma, and pseudosarcomatous myofibroblastic proliferation and distinct types of prostatitis comprise tumefactive nontumorous disorders that affect specific segments of the urinary tract. The pseudotumors of the kidneys and urinary tract demonstrate characteristic histopathologic and epidemiologic features, as well as protean clinical manifestations, natural history, and imaging findings. Many patients present with genitourinary tract-specific symptoms or systemic disease. Some cases may be incidentally discovered at imaging. Some entities such as perinephric myxoid pseudotumors, IgG4-RD, fibroepithelial polyp, and nephrogenic adenoma display specific anatomic localization and disease distribution. Imaging features of multisystem disorders such as tuberculosis, sarcoidosis, and IgG4-RD provide supportive evidence that may allow precise diagnosis. Fungal pyelonephritis, xanthogranulomatous pyelonephritis, IgG4-RD, actinomycosis, and endometriosis show markedly low signal intensity on T2-weighted MR images. Although some pseudotumors exhibit characteristic imaging findings that permit correct diagnosis, laboratory correlation and histopathologic confirmation are required for definitive characterization in most cases. A high index of suspicion is a prerequisite for diagnosis. Accurate diagnosis is critical for instituting optimal management while preventing use of inappropriate therapies or interventions. Surveillance CT and MRI are frequently used for monitoring the response of pseudotumors to therapy. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Multiparametric magnetic resonance imaging for the differential diagnosis between granulomatous prostatitis and prostate cancer: a literature review to an intriguing diagnostic challenge

Multiparametric magnetic resonance imaging (mpMRI) is currently the most effective diagnostic tool for detecting prostate cancer (PCa) and evaluating adenocarcinoma-mimicking lesions of the prostate gland, among which granulomatous prostatitis (GP) represents the most interesting diagnostic challenge. GP consists of a heterogeneous group of chronic inflammatory lesions that can be differentiated into four types: idiopathic, infective, iatrogenic, and associated with systemic granulomatous disease. The incidence of GP is growing due to the increase in endourological surgical interventions and the adoption of intravesical instillation of Bacillus Calmette-Guerin in patients with non-muscle invasive bladder cancer; therefore, the difficulty lies in identifying specific features of GP on mpMRI to avoid the use of transrectal prostate biopsy as much as possible.

Granulomatous prostatitis after bacille Calmette-Guérin instillation resembles prostate carcinoma: A case report and review of the literature

BACKGROUND

Bacille Calmette-Guérin (BCG) instillation is recommended in patients with non-muscle-invasive bladder cancer who have intermediate-risk and high-risk tumors. However, granulomatous prostatitis is a rare complication induced by BCG instillation, which can easily be misdiagnosed as prostate cancer. Here, we report a case of granulomatous prostatitis that resembled prostate cancer.

CASE SUMMARY

A 64-year-old Chinese man with bladder cancer received BCG instillation. Three days later, he stopped BCG instillation and received anti-infective therapy due to the urinary tract infection. Three months after BCG restart, he had rising total prostate-specific antigen (PSA) (9.14 ng/mL) and decreasing free PSA/total PSA (0.09). T2-weighted images of magnetic resonance imaging (MRI) showed a 28 mm × 20 mm diffuse low signal abnormality in the right peripheral zone, which was markedly hyperintense on high b-value diffusion-weighted MRI and hypointense on apparent diffusion coefficient map images. Considering Prostate Imaging Reporting and Data System score of 5 and possibility of prostate cancer, a prostate biopsy was conducted. Histopathology showed typical features of granulomatous prostatitis. The nucleic acid test for tuberculosis was positive. He was finally diagnosed with BCG-induced granulomatous prostatitis. Thereafter, he stopped BCG instillation and received anti-tuberculosis treatment. During 10 mo follow-up, he had no evidence of tumor recurrence or symptoms of tuberculosis.

CONCLUSION

Temporarily elevated PSA and high followed by low signal abnormality on diffusion-weighted MRI are important indicators of BCG-induced granulomatous prostatitis.

Imaging Patterns of Bacillus Calmette-Guérin-Related Granulomatous Prostatitis Based on Multiparametric MRI

Objective

To categorize multiparametric MRI features of Bacillus Calmette–Guérin (BCG)-related granulomatous prostatitis (GP) and discover potential manifestations for its differential diagnosis from prostate cancer

Materials and Methods

The cases of BCG-related GP in 24 male (mean age ± standard deviation, 66.0 ± 9.4 years; range, 50–88 years) pathologically confirmed between January 2011 and April 2019 were retrospectively reviewed. All patients underwent intravesical BCG therapy followed by a MRI scan. Additional follow-up MRI scans, including diffusion-weighted imaging (DWI), were performed in 19 patients. The BCG-related GP cases were categorized into three: A, B, or C. The lesions with diffusion restriction and homogeneous enhancement were classified as type A. The lesions with diffusion restriction and a poorly enhancing component were classified as type B. A low signal intensity on high b-value DWI (b = 1000 s/mm²) was considered characteristic of type C. Two radiologists independently interpreted the MRI scans before making a consensus about the types.

Results

The median lesion size was 22 mm with the interquartile range (IQR) of 18–26 mm as measured using the initial MRI scans. The lesion types were A, B, and C in 7, 15, and 2 patients, respectively. Cohen’s kappa value for the inter-reader agreement for the interpretation of the lesion types was 0.837. On the last follow-up MRI scans of 19 patients, the size decreased (median, 5.8 mm; IQR, 3.4–8.5 mm), and the type changed from A or B to C in 11 patients. The lesions resolved in four patients. In five patients who underwent prostatectomy, caseous necrosis on histopathology matched with the non-enhancing components of type B lesions and the entire type C lesions.

Conclusion

BCG-related GP demonstrated three imaging patterns on multiparametric MRI. Contrast-enhanced T1-weighted imaging and DWI may play a role in its differential diagnosis from prostate cancer.

Analysis of risk factors for post-bacillus Calmette-Guerin-induced prostatitis in patients with non-muscle invasive bladder cancer

The objective of this study was to evaluate risk factors for bacillus Calmette–Guerin-induced prostatitis in patients with non-muscle invasive bladder cancer following bacillus Calmette–Guerin therapy. Clinical findings from patients with non-muscle invasive bladder cancer who underwent multi-parametric magnetic resonance imaging before transurethral resection of bladder tumor and post-bacillus Calmette–Guerin therapy from March 2004 to August 2018 were evaluated. The population was grouped into patients with or without newly developed lesions on multi-parametric magnetic resonance imaging performed 3 months after bacillus Calmette–Guerin instillation. Patients with prostate-specific antigen levels ≥ 4 ng/mL or prostate cancer were excluded. Univariable and multivariable analyses were performed to determine the predictors of prostate lesions in patients with prior bacillus Calmette–Guerin exposure. Post bacillus Calmette–Guerin-induced prostatitis was found in 50 of the 194 patients (25.8%). No significant differences were observed between the groups except for prostate volumes (33.8 mL vs. 30.8 mL, P = 0.012) and body mass index (25.2 kg/m² vs. 24.1 kg/m², P = 0.044). After bacillus Calmette–Guerin exposure, no significant differences in prostate-specific antigen levels, international prostate symptom scores, or post-voiding residual volume were noted. Multivariable regression analysis showed that body mass index (odds ratio, OR = 1.115, P = 0.038) and prostate volume (OR = 3.080, P = 0.012) were significant predictors of post-bacillus Calmette–Guerin prostate lesions. Body mass index and prostate volume may be clinical predictors of prostate lesions after bacillus Calmette–Guerin exposure. Awareness of potential risk factors for this entity should contribute to the clinical decision-making process for patients following bacillus Calmette–Guerin therapy.

Negative Biopsy Histology in Men With PI-RADS Score 5 in Daily Clinical Practice: Incidence of Granulomatous Prostatitis

INTRODUCTION

The purpose of this study was to evaluate the biopsy histology of men who underwent transperineal multi-parametric magnetic resonance imaging (mpMRI)/transrectal ultrasound fusion biopsy for Prostate Imaging Reporting and Data System (PI-RADS) score 5 lesions.

PATIENTS AND METHODS

From January 2016 to June 2019, 105 men with PI-RADS score 5 underwent mpMRI/transrectal ultrasound fusion biopsy combined with systematic prostate biopsy. All the patients underwent a 3.0 Tesla pelvic mpMRI for the first time before prostate biopsy. In detail, the detection rate for clinically significant prostate cancer (PCa) and the follow-up of the patients without proven diagnosis of PCa has been reported.

RESULTS

In 91 (86.7%) of 105 patients, a stage T1c PCa was diagnosed, and 89 (84.5%) of 105 of them were classified as clinically significant PCa. Among the 16 (15.5%) of 105 patients with absence of cancer, 5 (31.5%) of 16 had an aspecific granulomatous prostatitis, 1 (6.2%) of 16 had a specific granulomatous prostatitis secondary to prostatic Mycobacterium Tubercolosis, and 10 (62.3%) of 16 had a diagnosis of normal parenchyma. The 6 patients with granulomatous prostatitis underwent specific antibiotic therapy followed by laboratory (ie, semen and urine cultures) and clinical evaluation. Six months from prostate biopsy, none of the 16 patients underwent repeat prostate biopsy because prostate-specific antigen (PSA) (15/16 cases) plus PSA density significantly decreased; in addition, in all the cases the initial PI-RADS score 5 was downgraded at mpMRI revaluation to PI-RADS score ≤ 3.

CONCLUSION

The reduction of PSA plus PSA density values and the downgrading of PI-RADS score to ≤ 3 allow avoiding a repeated prostate biopsy in men with initial mpMRI PI-RADS score 5 lesion and negative biopsy histology.

Multiparametric MRI appearances of primary granulomatous prostatitis

OBJECTIVE

Radiological features of granulomatous prostatitis (GP) overlap with those of prostate adenocarcinoma. Identification of specific GP features may aid diagnosis. We aimed to evaluate the multiparametric MRI (mpMRI) features of GP.

METHODS

We retrospectively reviewed 16 patients from a cohort undergoing mpMRI and transperineal sector-guided prostate biopsies between July 2012 and May 2017. Images were analysed for lesion location, shape, size, extracapsular extension, signal intensity (SI), apparent diffusion coefficient (ADC) values, dynamic contrast enhancement (DCE) pattern and PI-RADS (Prostate Imaging - Reporting and Data System) v2 score.

RESULTS

Histology revealed 13 cases of nonspecific GP and 3 cases of xanthogranulomatous prostatitis. GP lesions were diffuse involving > 50% of the prostate ( n = 13) or nodular ( n = 3). Signal intensity on T ₂ weighted imaging was low and high on diffusion-weighted imaging. ADC values were low (mean 702 ± 79 × 10^-6 mm/s² ). Five patients had DCE imaging with all cases 'positive' as per PI-RADS scoring, with two cases displaying further ring enhancement consistent with abscess formation. Overall PI-RADS score for all cases was 5, indicating high suspicion of prostate cancer.

CONCLUSION

GP is difficult to differentiate from prostate cancer, but typically gives diffuse changes involving > 50% of the gland on mpMRI, with extracapsular extension and rim-enhancing areas. It should be considered a differential diagnosis in patients with recent urinary tract infection (UTI) or prior Bacillus Calmette-Guerin (BCG) treatment.

ADVANCES IN KNOWLEDGE

Prostate MRI imaging features including diffuse changes, extracapsular extension and rim-enhancing areas, in patients with recent UTI or BCG treatment may help identify granulomatous prostatitis cases.

The distribution of BCG prostatitis: A clue for pathogenetic processes?

BACKGROUND

We observed in cystoprostatectomy specimens that Bacillus Calmette-Guérin (BCG) granulomatous prostatitis tended preferentially to affect the peripheral zone (PZ) and aimed to study the matter, postulating that assessment of its distribution might contribute to understanding pathogenetic processes.

METHODS

Entire prostate glands from 27 men (47-83 years; mean = 69 years), who had previously received intravesical BCG therapy for non-muscle-invasive urothelial carcinoma of the bladder, were studied as whole-mount sections to determine the anatomical distribution and histopathological characteristics of BCG prostatitis.

RESULTS

Twenty-two (81.5%) showed BCG-type granulomatous inflammation. It often radiated from close to the prostatic urethra toward to the gland periphery as a wedge-shaped area related to one or more duct systems. Twenty-one of these prostate glands (95.5%) showed predominantly or exclusively PZ involvement. Eighteen (81.8%) involved only the PZ, while three cases (13.6%) also showed involvement of the transitional zone (TZ). One case (4.5%) involved only the TZ. No granulomas were seen in the central zone or anterior fibromuscular septum.

CONCLUSIONS

Our observations imply the microanatomical arrangement of prostatic ducts is a factor in the pathogenesis of BCG prostatitis. PZ ducts enter the urethra at less obtuse angles than those from other zones and are likely to be more prone to urine reflux and damage from suspended BCG. We speculate that prostatic duct microanatomy could also play a role in the pathogenesis of other prostatic diseases, including conventional prostatitis and adenocarcinoma.