Role of Ultrasound in Prostate Diagnosis
Transrectal ultrasound (TRUS) is primarily used for guiding biopsies in suspected prostate cancer cases rather than as a standalone diagnostic tool for prostate issues. 1
Primary Uses of Ultrasound in Prostate Evaluation
- TRUS is the method of choice to evaluate the prostate and guide needle biopsies of suspicious areas when PSA is elevated above locally accepted reference ranges 1
- When residual urine is measured using transabdominal ultrasonography, it simultaneously allows evaluation of prostate shape, size, configuration, and protrusion into the bladder 1
- TRUS-guided biopsy is rated as highly appropriate (rating of 9/9) for clinically suspected prostate cancer in biopsy-naïve patients 1
- TRUS alone without biopsy has limited value (rating of 2/9) for prostate cancer detection due to poor specificity 1, 2
Limitations of TRUS as a Diagnostic Tool
- Conventional grayscale TRUS has poor tumor visualization capabilities with only 11-35% of tumors being sonographically visible 1
- Only 17-57% of hypoechoic lesions detected on TRUS are actually malignant 1
- Studies have shown no statistically significant association between the presence of a hypoechoic lesion and cancer detection 1
- TRUS-guided systematic biopsy has a false-negative rate of 15-46% 1
Comparison with Other Imaging Modalities
- PI-RADS v2 (multiparametric MRI) has been shown to have higher accuracy over systematic TRUS biopsies for prostate cancer diagnosis 1
- MRI is increasingly recommended before TRUS-guided biopsy to identify appropriate targets for sampling using MRI-TRUS fusion technology 1
- MRI-targeted biopsy significantly increases detection rates for clinically significant cancers while decreasing detection of clinically insignificant cancers 1
Specific Clinical Scenarios for Ultrasound Use
- In men with elevated PSA and negative prior TRUS-guided biopsy, MRI is rated higher (8/9) than repeat TRUS-guided biopsy alone 1
- Transabdominal ultrasound can be used to assess prostatic size and shape when planning treatments that depend on anatomical characteristics (e.g., hormonal therapy, thermotherapy, stents) 1
- For hematospermia evaluation, TRUS is considered the first-line imaging modality, with MRI used when TRUS is inconclusive or negative 1
Emerging Applications
- Advanced ultrasound techniques such as Doppler, 3D ultrasound, microbubble contrast-enhanced ultrasound, and elastography show potential for improving TRUS performance but have not yet entered routine practice 1, 2
- Micro-ultrasound, which generates higher resolution images than traditional ultrasound, shows promise for diagnosing prostate cancer and may become a future standard of care 2
- TRUS-guided high-intensity focused ultrasound (HIFU) focal therapy offers a potential treatment option for localized disease with low morbidity 2
Best Practices for TRUS Use
- TRUS should be performed by experienced operators, as the specificity is highly dependent on examiner experience 3
- Computerized analysis of TRUS signal information (C-TRUS) may enhance diagnostic capabilities by detecting cancers missed by multiple systematic biopsies 4
- TRUS-guided biopsy remains a convenient, reliable, and accessible tool for diagnosing prostate cancer, especially in resource-limited settings 5
Cautions and Pitfalls
- TRUS alone should not be used for cancer screening due to its low specificity 1, 3
- Low-echo, cancer-suspicious areas on TRUS may be histologically benign (BPH, vessels, prostatitis) or malignant 3
- TRUS-guided biopsy carries risks of infection and other complications, with transperineal approaches showing lower infection rates but higher urinary retention rates 2, 5