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Year : 2014  |  Volume : 4  |  Issue : 1  |  Page : 31-35

Determination of prostatic volume and characteristics by transrectal ultrasound among patients with lower urinary tract symptoms in Zaria, Nigeria

Department of Surgery, Division of Urology, Ahmadu Bello University, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria

Date of Web Publication14-Jul-2014

Correspondence Address:
Ahmed Mohammed
Department of Surgery, Division of Urology, Ahmadu Bello University Teaching Hospital, Zaria
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2278-9596.136707

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Background: To determine the average volume and ultrasonographic characteristics of the prostate with transrectal ultrasound (TRUS) among adult male patients presenting with lower urinary tract symptoms (LUTS). This is because the size and characteristics of the prostate may suggest the specific pathology and guide the urologist on subsequent investigations and the choice of the most appropriate treatment.
Patients and Methods: All male patients, 30 years or older, presenting with LUTS in the absence of non-prostatic causes of LUTS between 2006 and 2010 were included in the study. Patients with clinical suspicion or confirmed cause of LUTS other than the prostate were excluded from the study. They were all evaluated by TRUS and the findings recorded.
Results: A total number of 602 patients met the inclusion criteria. The mean age of the patients was 62.5 years with a standard deviation (SD) of 13.70. The average prostate volume for all patients was 56.2 (12.5-325) and SD 42.70, while the average prostate volume among patients with suspected benign prostatic hyperplasia (BPH) (317) was 68.7 g and SD 47.52. Diagnosis based on ultrasound features was BPH (52.7%, 317) in majority of the patients, 27.6% (166) suggested carcinoma of the prostate (CaP). The TRUS characteristics of patients with suspected BPH was predominantly mixed echo (51.7%), CaP commonly appeared hypoechoic (70.5%), while prostatitis appeared hyperechoic in most patients (69.4%).
Conclusion: The mean prostate size of 68.7 g among patients with BPH is consistent with most studies among Nigerians, but greater than the mean volume among Caucasians. Thus, open prostatectomy remains relevant in our environment and accurate prostate volume estimation by TRUS is required for proper patient's selection for endoscopic treatment. The predominant ultrasonic features of BPH and CaP are mixed echo and hypoechoic appearance, respectively.

Keywords: BPH, characteristics, LUTS, prostate, TRUS, volume

How to cite this article:
Mohammed A, Bello A, Maitama HY, Ajibola HO, Lawal AT, Isah MJ, Alhassan A, Abubakar BM, Dogo HM, Muhammad SA, Sudi A, Awaisu M. Determination of prostatic volume and characteristics by transrectal ultrasound among patients with lower urinary tract symptoms in Zaria, Nigeria. Arch Int Surg 2014;4:31-5

How to cite this URL:
Mohammed A, Bello A, Maitama HY, Ajibola HO, Lawal AT, Isah MJ, Alhassan A, Abubakar BM, Dogo HM, Muhammad SA, Sudi A, Awaisu M. Determination of prostatic volume and characteristics by transrectal ultrasound among patients with lower urinary tract symptoms in Zaria, Nigeria. Arch Int Surg [serial online] 2014 [cited 2023 Feb 1];4:31-5. Available from:

  Introduction Top

Transrectal ultrasound (TRUS) has become an important modality in the evaluation of prostatic diseases since it was first introduced. In 1963, Takahashi and Ouchi [1] were the first to describe the use of TRUS to evaluate the prostate. [1] Watanabe et al., [2] described the first clinically applicable images of the prostate obtained with TRUS in 1971, they used a 3.5 MHz transducer. Low cost, availability, absence of risk of radiologic contrast, and radiation exposure has made it a very important tool in medical imaging. Today, TRUS is a routine tool in urology and is almost like an extension of the urologist's finger, albeit more sensitive. It should be noted that ultrasonography is operator-dependent, knowledge and experience significantly affects the outcome; thus, the inter- and intraobserver variability are significant, and this marks an important limitation of the procedure. [3],[4],[5],[6],[7]

Prostate gland is afflicted by three disease conditions (benign prostatic hyperplasia (BPH), prostate cancer, and prostatitis). The average size of normal prostate gland in adult is 20-25 g, [3] it normally appears as a homogenous ovoid structure with mixed low-level echoes on ultrasound. [8],[9] An enlarged prostate is the commonest cause of bladder outlet obstruction (BOO)/lower urinary tract symptoms (LUTS) among men 50 years and older and the incidence rises with age. [10] It is an important clinical surrogate of the presence of BPH in addition to LUTS and BOO; however, studies have shown that there is often no direct correlation between prostate size and severity of BOO/LUTS. [11] BPH is rarely ever diagnosed before age 40 and prostate cancer rarely before 45 years; however, prostatitis can afflict males under 40 and they may present with LUTS.

Clinical estimation of prostate size using digital rectal examination (DRE) is often inaccurate and fraught with interobserver variability. [10],[11],[12],[13],[14],[15] There are currently a number of imaging modalities available for accurate prostate volume measurement, they include, ultrasound, computed tomography (CT) scan, and magnetic resonance imaging (MRI). Presently, ultrasonography is the preferred imaging technique because of its advantages of being readily available, affordability, and without risk of radiation exposure. [16],[17] Measurement of prostate size using ultrasound can be done either by transabdominal or transrectal (TRUS) routes; however, studies have shown the superiority of TRUS over transabdominal ultrasound both in the measurement of prostate size and evaluation of the characteristics of various prostatic diseases. [18],[19],[20] Thus, this study aims to determine the average volume and characteristic of the prostate among patients with LUTS in our environment using TRUS.

  Patients and Methods Top

This was a prospective study of patients presenting with LUTS and requiring TRUS evaluation between January 2006 and December 2010. Ethical clearance was obtained and all consenting men, 30 years or older, presenting to our facility with LUTS secondary to suspected prostatic disease were enrolled. Suspicion was based on clinical presentation with LUTS and abnormal DRE and prostate-specific antigen (PSA) level. Patients with clinical suspicion or confirmed cause of LUTS other than due to prostate and patients with incidental finding of an enlarged prostate without LUTS were excluded from the study.

They were all evaluated with TRUS using ATL, APOGEE 800-PLUS ultrasound machine with a 7.5-MHz transrectal, multiplanar probe. TRUS was done either by a consultant urologist or a specialist senior registrar in urology. All patients were scanned in the Sims (left lateral) position. Scanning began in the axial plane, and the base of the prostate and seminal vesicles were imaged first, then the rest of the prostate using the bladder as an acoustic window, thus a moderate amount of urine in the bladder facilitated the examination. Prostate size was estimated using the conventional prolate ellipsoid formula (length × height × width × 0.5236 (pi/6)), volumetric or the Simpsons freehand tracing. Only the overall prostate volume was measured, the transition zone volume was not independently measured. Subsequently, the prostate was scanned carefully to determine its echogenic characteristics and identify any suspicious lesion(s).

The eventual diagnosis of BPH, prostatitis, and prostate cancer were strictly on clinical and radiologic evidence, histologic confirmation was not done because not all patients would require a biopsy or surgery. The data obtained were analyzed using Statistical Package for Social Sciences (SPSS) version 11 software.

  Results Top

A total of 602 patients met the inclusion criteria. The mean age of the patients was 62.5 years, range 30-95 years with a standard deviation (SD) of 13.70, majority (34.5%) of the patients were between 60 and 69 years age range as shown in [Figure 1]. The average prostate size for all patients, irrespective of the diagnosis was 56.2 (12.5-325), SD 42.70.
Figure 1: Age distribution of the patients

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Diagnosis based on clinical and ultrasound characteristics were found to be BPH in majority of the patients (52.7%, 317), 27.6% (166) suggested carcinoma of the prostate (CaP), 12% (72) were prostatitis, and the remaining appeared normal [Figure 2].
Figure 2: Suspected diagnosis based on DRE, TRUS findings, and PSA BPH = benign prostatic hyperplasia, CaP = carcinoma of the prostate, DRE = digital rectal examination, TRUS = transrectal ultrasound, PSA = prostate-specific antigen

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The average volume of prostate among patients with BPH was 68.7 cm 3 and SD 47.52. The common TRUS characteristic of BPH was that of mixed echogenic pattern (51.7%) of the adenomas with occasional distinct nodular appearance of the transition zone. Others are as shown in [Table 1].

Hyperechoic in 19.6% and the rest were either isoechoic or hypoechoic. Nodules in the peripheral zone of the prostate suggestive of prostate cancer nodules appeared hypoechoic (70.5%) in the peripheral zone. Other features of prostate cancer were; capsular irregularity with extracapsular extension or seminal vesicle invasion with or without nodules (hypo-, hyper-, or isoechoic) in the peripheral zone. Prostatitis was either acute or chronic, the peripheral zone appeared predominantly hyperechoic (69.4%), and other features were prostatic concretions and abscesses. All patients below 45 year had clinical and ultrasonic features of prostatitis with either a normal or slightly enlarged prostate.
Table 1: TRUS characteristics of prostatic diseases

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  Discussion Top

Clinical evaluation of prostate gland by DRE is inaccurate, fraught with interexaminer variability and often underestimates the prostate size. [14],[15] Thus, TRUS is currently the preferred method of prostate volume estimation. The ultrasonic characteristics of the prostate may suggest the specific prostatic pathology, but prostate volume measurement is largely irrelevant in the management of prostatitis and prostate cancer. Prostate volume is however, important in the evaluation of patients with BPH and significantly influences the choice of treatment modality.

We studied a total of 602 patients out of which 317 (52.7%) had features suggestive of BPH. Diagnosis of BPH was based on the presence of clinical and laboratory surrogates (LUTS, enlarged prostate on DRE/TRUS and PSA). The mean age of the patients was 62.5 years, which is consistent with the peak age incidence of BPH (7 th decade) as observed in several population-based studies. [21],[22] Similar results were obtained in hospital-based studies among Nigerians; Ibinaiye et al., [23] and Badmus et al., [24] found mean ages of 64.1 and 64.4 years, respectively. The mean prostate volume for all patients (602) irrespective of their diagnosis was 56.2 (12.5-325) cm 3 , however this has no significant clinical value, thus we selectively measured the more relevant and clinically applicable mean prostate volume among patients with BPH (317), which was found to be 68.7 cm 3 . The measurement of total prostate volume without discrimination of the zones is one of the limitations of our study. The transition zone of the prostate is the predominant site of BPH in over 75% of cases; thus, the volume will be a better surrogate of BPH and has been shown to correlate better with LUTS/BOO. [25],[26] Similar studies by other workers among Nigerians show wide disparities in mean prostate volumes obtained among symptomatic men [Table 2]. The lowest mean volume reported by these studies was 42.62 cm 3 and the highest was 214 cm 3 . It is difficult to proffer a reason for the observed wide variation; however, operator experience, ultrasound route (TRUS/transabdominal), and inadequate sample sizes might be responsible. While all the previous studies had smaller sample sizes (average of 100), the sample size of this study (317) is at least three times larger; therefore the mean prostate volume in this study might be closer to the actual mean. Resected specimen at prostatectomy can be correlated with the preoperative estimated volume, though the non-inclusion of the peripheral zone and occasional incomplete resections or enucleations may account for a difference, it has been used by some studies to validate the sensitivity of ultrasound. In a study by Alhasan et al., [28] among 502 men with BPH in northwestern Nigeria, they found a mean volume of resected prostate chips of 59.8 cm 3 following TURS, though the mean volume they obtained is close to that of this study, larger multicenter studies are required to establish a more accurate value.
Table 2: Studies of prostate volume among Nigerians

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Racial differences in prostate size among patients with BPH has been observed, Blacks tend to have larger prostates compared to Whites and Asians, Asians generally have smaller prostates compared to both Blacks and Caucasians. [29],[30] The volume of the prostate influences the choice of treatment for BPH, generally sizes greater than 60 cm 3 are amenable to endoscopic or minimally invasive therapies and larger prostates (> 60 cm) are treated by open prostatectomy, although experienced urologists are still able to treat them endoscopically. Most studies among Nigerians show a mean prostate volume greater than 60 cm 3 [Table 2], which is similar to our finding of 68.7 cm 3 . Thus, open prostatectomy remains an important treatment modality in this region, as endoscopic treatment for larger glands requires more experience.

The TRUS characteristic of BPH often appear as homogeneous low to medium level mixed echo in the transition zone and occasionally the central zone of the prostate, the nodules may be evident with a clear distinction from the relatively hyperechoic peripheral zone, in BPH this is compressed to form the surgical capsule. [8],[31] In this study, 51.7% of BPH appeared as homogeneous mixed level echoes in the transition zone, 19.6% were hyperechoic, and the rest were either iso- or hypoechoic. CaP usually appear as hypoechoic (71%), but may be isoechoeic (28%) or hyperechoeic (1%). [32] The diagnosis of prostate cancer in this study was based on clinical, biochemical, and radiologic suspicion; though the absence of histologic confirmation is a limitation, our emphasis was on the presence of LUTS and prostatic disease. Secondly, only patients with suspicion of prostate cancer and those that had prostatectomy would have had histologic diagnosis, majority of our patients (those with prostatitis and those with BPH treated with medically) would have been excluded. In this study, prostate cancer nodules appeared hypoechoic in 70.5% of cases, other features were capsular irregularities, capsular breach, and tumor extension into contiguous tissue and seminal vesicles. Prostatitis was either acute or chronic and the predominant ultrasonic feature was diffuse hyperechoic peripheral zone (69.4%), prostatic concretions, and prostatic abscesses. All patients below 45 years had clinical and ultrasonic features of prostatitis with either a normal or slightly enlarged prostate and BPH was not observed below 40 years.

However, it must be borne in mind that an important limitation of this study is the absence of histologic diagnosis; prostate cancer has been demonstrated in young patients with a low to normal PSA and normal DRE and TRUS findings. TRUS findings are nonspecific with a low positive predictive value for prostate cancer, though a combination with clinical findings, DRE and PSA significantly improves the specificity, a histologic diagnosis remains the most reliable.

  Conclusion Top

The mean prostate size of 68.7 g among patients with BPH is consistent with most studies among Nigerians, but greater than the mean volume among Caucasians and Asians. Thus, open prostatectomy remains relevant in our environment and accurate prostate volume estimation by TRUS is required for proper patient's selection for endoscopic treatment. The predominant ultrasonic features of BPH and CaP are mixed echo and hypoechoic appearance respectively.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2]

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