Application of Urethral Contrast Computed Tomography Three-Dimensional Imaging in the Postoperative Assessment of Prostate Hyperplasia

Abstract

This study assesses the morphological effectiveness of benign prostatic hyperplasia (BPH) surgery using multislice spiral computed tomography three-dimensional imaging (CT3D) with urethral contrast. Twenty-five male patients with BPH and bladder outlet obstruction (BOO) who underwent bipolar transurethral resection of the prostate were selected. Preoperative and postoperative CT3D indicators of retrograde and voiding cystourethrography, including bladder neck diameter, length of the posterior urethra, and degree of prostate protrusion into the bladder and upper and lower diameter of the prostate were used to assess bladder neck and posterior urethra morphology and BOO severity. In addition, preoperative and postoperative International Prostate Symptom Scores and maximum urine flow rates were compared. Postoperative CT3D was used to evaluate changes following obstruction relief postsurgery. Preoperative CT3D indicated significant BOO, whereas postoperative imaging showed improved patency but with irregular posterior urethral lumens and varying degrees of residual glandular tissue. Comparative analysis of preoperative and postoperative bladder outlet metrics revealed significant changes (p < 0.05). Urethral contrast CT3D effectively visualizes the prostate, bladder neck, and prostatic urethra. It quantifies changes in the urethral lumen postsurgery, correlating the extent of posterior urethral lumen spaciousness with urinary flow rates.

Introduction

Benign prostatic hyperplasia (BPH) is a common urination disorder in middle-aged and elderly men. This disorder can cause bladder outlet obstruction (BOO), leading to significant lower urinary tract symptoms (LUTSs), hydronephrosis, and even renal dysfunction, severely impacting patients’ quality of life and health status. The literature reports that the incidence of BPH in men aged 60 years is over 50%, increasing to 83% by the age of 80 years (Gu et al., 1994). BPH is characterized by anatomical prostate enlargement and BOO in urodynamics. Transurethral resection of the prostate (TURP) is an effective method to alleviate BPH obstruction (Zhang et al., 2023). Clinically, urinary flow rate and the International Prostate Symptom Score (IPSS) are commonly used to assess surgical outcomes. Although urinary flow rate measurement is objective and clear, it requires specialized equipment and good patient cooperation; inaccurate results may occur with inadequate bladder filling (e.g., <100 ml). Although comprehensive, IPSS assessment depends on precise patient descriptions and is subject to significant subjective variation.

Morphological assessment methods for BPH include ultrasound and magnetic resonance imaging (MRI; Gabr et al., 2022; Han et al., 2023). Ultrasound allows for real-time imaging but demands high operator skill and produces less visual clarity. Despite its widespread use, transrectal ultrasound lacks uniformity in operation and has significant measurement variability (David et al., 2020; Pate et al., 2020). Neither ultrasound nor MRI can provide a comprehensive view of the urethral lumen. Multislice spiral computed tomography (CT) excretory urography has been reported to be advantageous in diagnosing traumatic urethral strictures, offering a complete and intuitive depiction of urethral lumen changes (Su et al., 2018). In the diagnosis and treatment of urethral strictures, urethral contrast CT three-dimensional (3D) imaging has provided clear urethral stereoscopic images, suggesting its potential in studying preoperative and postoperative multidimensional changes in the posterior urethral lumen in BPH, assessing the effectiveness of surgery in relieving BOO and analyzing causes of poor postoperative urination, thereby aiding in improving surgical outcomes.

This study selected 25 patients with BPH and BOO scheduled for surgery. Urethral contrast CT3D imaging was used to observe and measure the morphological changes of the bladder neck and posterior urethra before and after surgery, exploring its value in evaluating postoperative effectiveness in BPH.

Methods

Research Design

This study targeted patients with BPH requiring surgery who were admitted to Tongling City People’s Hospital between April 2015 and August 2021. With patient consent, urethral contrast CT3D imaging was conducted. The inclusion criteria were as follows: male patients (a) diagnosed with BPH based on digital rectal examination, prostate ultrasound, or MRI; (b) aged between 54 and 82 years (median age = 71); and (c) presenting with symptoms such as difficulty urinating, urinary retention, or overflow incontinence. The exclusion criteria included (a) concurrent neurological diseases or neurogenic bladder; (b) detrusor weakness; (c) small bladder capacity (<100 ml); (d) prostate cancer; and (e) contraindications to urethral contrast CT examination. This study was approved by the Ethics Committee of anonymized for Tongling People’s Hospital (approval number: 2024.10). All participants signed the written informed consent form.

Equipment and Examination Method

Urethral contrast CT3D imaging was performed at hospitalization and at discharge following surgery. A Philips balance 256-slice spiral CT scanner was used. The scan parameters were as follows: slice thickness = 1 mm, reconstruction interval = 0.5 mm, tube voltage = 120 kV, tube current = 100 mAs, and field of view = 356 mm. The scanning range included the bladder above the pubis to the posterior and most of the anterior urethra.

For the retrograde urography, the patients were positioned laterally or supine. A F10–F12 dual-lumen balloon catheter was then inserted 3–4 cm into the urethra, with 1–3 ml of water inflating the balloon at the navicular fossa. The catheter was connected to an infuser containing contrast medium (3%–12% iopamidol or iodixanol). Contrast medium was injected under pressure into the urethra and bladder, synchronized with spiral CT scanning, capturing images of the urethral bladder neck.

In terms of voiding cystourethrography (following retrograde filling of the bladder), the patients were positioned laterally or semi-sitting, holding a urine collector at the urethral meatus. They were instructed to urinate voluntarily, with CT scanning synchronized to capture images of the urethral bladder neck as urine continuously entered the collector. Multiple scans were performed to ensure clear urethral cavity imaging.

All scanned volumetric data were imported into a workstation and reconstructed using computer software to obtain multiplanar reconstruction and 3D volumetric images of the urethra, including sagittal and curved-plane images.

Image Analysis

The largest cross-sectional and volumetric images of the posterior urethra were selected for analysis. Preoperatively, the morphology of the prostate and its protrusion into the bladder and the degree of compression deformation of the bladder neck and prostatic urethra segment (excluding patients with urinary retention and indwelling catheters) were observed. Postoperatively, after the removal of the catheter and during spontaneous urination by the patients, changes in the prostate, bladder neck, and posterior urethra (e.g., prostate protrusion into the bladder, diameter of the bladder neck, and length of the prostatic urethra segment) were observed and measured. In addition, the IPSS and maximum urine flow rate were assessed before and after surgery. The study compared changes in the bladder neck and posterior urethral lumen before and after surgery, as presented in Table 1.

Table 1.

Comparisons of Preoperative and Postoperative Parameters

Project	Before surgery	After relief of obstruction	p
Bladder neck diameter (mm, M±SD)	14.16 ± 2.2	32.19 ± 3.1	<0.05
Length of the posterior urethra (mm, M±SD)	50.2 ± 0.53	34.25 ± 4.1	<0.05
Degree of prostate protrusion into the bladder (mm, M±SD)	18.37 ± 0.15	6.0 ± 0.2	<0.05
Upper and lower diameter of the prostate (mm, M±SD)	46 ± 16	34 ± 4	<0.05
International prostate symptom scores (M±SD)	24 ± 4	12 ± 5	<0.05
Maximum urine flow rate (ml/s, M±SD)	8.38 ± 0.5	15.92 ± 2.5	<0.05

Note. SD = standard deviation.

Statistical Methods

Data in this study were processed using SPSS (version 11.5) software. Quantitative data were presented as mean ± standard deviation. A p < 0.05 was considered statistically significant.

Results

Preoperative mid-sagittal and curved-plane CT3D retrograde urography revealed prostate protrusion into the bladder, with the prostatic urethra segment appearing compressed, deformed, twisted, narrow, and even indistinct (Figure 1). Voiding cystourethrography showed a narrowed bladder neck opening, prostate protrusion into the bladder and a slender, constricted prostatic urethra (Figure 2). Postoperatively, following bipolar TURP, the mid-sagittal and curved-plane CT3D retrograde urography revealed that the majority of the gland protruding into the bladder had been excised and had disappeared. The prostatic urethra segment became shorter and significantly wider, and the bladder neck opened wider at the top and was narrower at the bottom, forming a funnel shape (Figure 3). Similarly, voiding cystourethrography clearly showed a significantly widened and open bladder neck, with the protruding gland into the bladder disappearing and the prostatic urethra segment well visualized (Figure 4), appearing as a funnel shape with a wider top and narrower bottom. The urethral lumen was not smooth, with varying degrees of residual glandular tissue (Figures 3B and 5).

Figure 1.

Prostate Segment Urethra Compressed, Distorted, Slender, Narrow, and Even Indistinct

Figure 2.

Prostate Urethral Stricture

Figure 3.

The Bladder Neck Expands and Presents a Funnel-Shaped Shape With a Wide Top and Narrow Bottom

Figure 4.

The Glands Protruding into the Bladder Disappear, and the Prostate Urethra Is Well Visualized

Figure 5.

The Urethral Cavity Is Not Smooth and There Are Varying Degrees of Residual Glandular Tissue

Discussion

Following TURP, some patients continue to exhibit minimal improvement in LUTS, which may be attributed to a variety of factors (Chapple & Osman, 2022; Chen et al., 2019; Khavari et al., 2019; Sagen et al., 2020; Spivak et al., 2021). In some cases, LUTS may not be solely caused by BOO, making preoperative confirmation of BOO necessary. Traditional assessments of prostatic hyperplasia-induced BOO using ultrasound and MRI present various limitations (Chapple & Osman, 2022; Garg et al., 2019; Vredeveld et al., 2022; Yu et al., 2019), lacking direct visualization. Urologists have long sought an intuitive and visual method to assess the obstruction caused by prostatic hyperplasia and the changes in the posterior urethra following surgery. The pathophysiological basis of urinary difficulties caused by prostatic hyperplasia obstruction is urethral deformation, involving the elongation of the prostatic urethra, luminal narrowing, and a narrowed bladder neck opening. Multislice spiral CT urethrography can detect changes caused by BOO, but quantifying the degree of obstruction and stenosis in the bladder neck and posterior urethral lumen, as well as changes in urethral patency postprostatectomy, is rarely reported in clinical practice (Ishii et al., 2019; Kwon et al., 2019; Minagawa et al., 2019; Su et al., 2018; Wongwaisayawan et al., 2021).

In the diagnosis and treatment of urethral strictures, we utilized CT3D imaging urethrography technology to rapidly and comprehensively display the urethral lumen containing contrast agents and the 3D image of the penile corpus cavernosum. We further used CT3D to analyze changes in the bladder neck diameter, posterior urethra length, and the degree of prostate protrusion into the bladder before and after prostate hyperplasia surgery. Through CT3D imaging technology, we obtained the required multiplanar and multiphase images, quantifying multiparameter changes in the prostatic urethral lumen and bladder neck, achieving the goal of intuitively judging surgical outcomes.

This study utilized retrograde plus voiding urethrography to overcome the limitations faced by some patients who could not complete urethrography because of an inability to urinate. Through CT3D analysis of the radiological manifestations of BPH with BOO (Garg et al., 2019; Reddy & Shaik, 2019; Tan et al., 2022), we not only observed the 3D morphology of the prostate but also provided 3D images of posterior urethral deformation and measured various data pertaining to posterior urethral deformation (narrowing of the bladder neck opening, elongation, and compression narrowing of the posterior urethra) and the degree of prostate protrusion into the bladder, providing direct evidence for the diagnosis of BOO. Following transurethral prostatectomy, the gland tissue protruding into the bladder disappeared or was significantly reduced, the bladder neck was widely opened in a funnel shape, and the posterior urethral lumen became spacious (Figures 3 and 4), vividly and intuitively displaying the surgical outcomes. We observed that the degree of bladder neck opening correlated positively with the maximum urinary flow rate; inadequate opening of the bladder neck and posterior urethra might explain poor surgical outcomes.

In this study, we also observed that during prostatic hyperplasia obstruction, CT3D imaging showed a narrow bladder neck opening (Figure 1A), with the neck opening either not moving downward or only slightly open (Figures 1B and 2), displaying the position and degree of prostate protrusion into the bladder (Figure 1A), and compression and twisting deformation of the prostatic segment of the urethra (or poor visualization of the posterior urethra and bladder neck; Figure 1C). This provided a vivid and intuitive reflection of the degree of BOO, consistent with the morphological changes in the posterior urethra observed endoscopically by Su Zexuan in patients with BPH complicated by BOO. Postbipolar TURP, CT3D imaging showed good opening and downward movement of the bladder neck (Figures 3 and 4), with most of the gland tissue protruding into the bladder disappearing (Figure 5), and the posterior urethral lumen becoming clear, vividly demonstrating the effective resolution of BOO and the intuitive visualization of the surgical outcomes.

Postoperatively, if CT3D imaging shows insufficient opening or continued narrowing of the bladder neck, patients are likely to experience recurrent urinary difficulties or retention. In this study, two patients experienced significant difficulty in urination shortly after transurethral prostatectomy (2 months to 1 year). The CT3D urethrography showed a still narrow and unopened bladder neck, with IPSSs of 26 and 23, as well as maximum urine flow rates of 6.5 and 9.2 ml/s. This vividly highlighted the cause of the recurrent urinary difficulties. Further cystoscopic examination indicated bladder neck contracture, and following bladder neck incision and scar excision, the patients urinated smoothly. Follow-up CT3D showed significantly better opening and downward movement of the bladder neck and enlargement of the prostatic urethra (Figure 3B), vividly demonstrating the effects of surgery in relieving obstruction. This may also suggest that short-term urinary difficulties postprostatectomy are not solely caused by residual gland tissue; ineffective opening of the bladder neck during surgery or postoperative bladder neck contracture can directly affect surgical outcomes.

We observed that in many patients, both preoperatively and postoperatively, CT3D consistently showed the membranous urethra as slender and narrow or poorly visualized (Figure 4), indicating good contraction function of the external urethral sphincter. This also indicates that even if patients experience urinary incontinence postoperatively, it is likely to be temporary and recoverable, and there is no concern regarding permanent incontinence.

Postbipolar TURP, varying degrees of glandular tissue residue were present; however, provided the CT3D imaging showed good downward movement and opening of the bladder neck, even if the posterior urethral lumen was not smooth and the transverse diameter of the prostate did not decrease (Figure 5), patients still urinated smoothly postoperatively (compared with preoperatively). This indicates that provided the bladder neck is not significantly obstructed, a small amount of residual glandular tissue does not significantly impact urination. However, this suggests that clinicians must be more patient and meticulous during surgery, should excise as much gland tissue as possible to minimize residue and should maintain a smooth urethral lumen to achieve better surgical outcomes.

This study inevitably involves radiation exposure, and the procedure is not particularly convenient. Currently, the sample size is small, and the objectivity of the evaluation indicators may not be sufficient. In the future, we plan to increase the sample size to overcome these limitations.

Conclusion

In summary, using urethral contrast CT3D, we can intuitively judge the presence and degree of BOO accompanying prostatic hyperplasia. Following transurethral prostatectomy, CT3D examination can more effectively display changes in the posterior urethra and bladder neck, vividly and intuitively reflecting the outcomes of surgery in relieving obstruction.