A comparison of how prostate volume obtained using transabominal ultrasound differs to volume obtained using transrectal ultrasound approach

Abstract

Ultrasound is a widely used method for examination of the prostate. This retrospective study compared the prostate volume obtained using transabdominal (TA) ultrasound to the volume of transrectal (TRUS) ultrasound. Over a three year period 42 patients had the volume of the prostate measured using both TA and TRUS methods. Sixteen different sonographers performed the TA measurements and three radiologists the TRUS measurement. Sixty-six percentage of TRUS and 78% of TA measurements were classed as grade 3 prostatomegaly according to the volume obtained. TA measurements were larger than the TRUS measurement in 57% of cases. The findings in this study suggest that TA and TRUS cannot be used interchangeably. K E Y W O R D Sprostate ultrasound, prostate volume, transabdominal ultrasound, transrectal ultrasound, TRUS | INTRODUCTIONUltrasound is widely used for examination of the prostate. 1,2 Clinical indications for its use include changes detected during physical examination of the prostate using digital rectal examination (DRE), elevated prostate-specific antigen (PSA), and surgical evaluation for benign prostatic hyperplasia (BPH). 3 Prostate gland size determined by DRE carries considerable measurement error. 4 The volume can be underestimated by as much as 55%. [4][5][6] This is particularly the case for glands larger than 30 mL. 7,8 Consequently, referring physicians may request an ultrasound to determine a more accurate size of the gland.Transabdominal (TA) ultrasound is a widely accepted method of imaging the prostate, with minimal discomfort to the patient. 1,2,6,9 It is often performed for patients with dysuric symptoms such as frequency, urging needs, or the feeling that their bladder has not completely emptied. 3 Transrectal ultrasound (TRUS) in comparison is invasive with associated discomfort. 10 However, TRUS resolution is superior to TA and is the most widely accepted ultrasound measure for gland size. 1,4,8 The use of TRUS can reduce unnecessary biopsies performed by urologists. 11,12 However, TRUS is not reliable to diagnose carcinoma, with up to 65% of tumors undetected. 3 Gland size determination guides suitability for different types of prostate cancer treatment methods, for example, localized prostate cancer can be treated by brachytherapy. [10][11][12][13] Consequently radiation oncologists require precise measurements. 13 Radiation oncologists deem a patient suitable for brachytherapy if the prostate volume is over 60 cc. 14 This compares to volumes over 80 cc for stereotactic body radiotherapy (SBRT). 14 Assessment of prostate volume can be requested for elevated prostate-specific antigen (PSA). 15,16 PSA is a protein produced by the prostate. The PSA level is used to screen for prostate cancer and monitor treatment of disease. 17 It is closely related to the volume of the prostate and is used as a prescreening tool to determine prostate enlargement. 18,5 A normal range for PSA is less than 4 ng/mL (nanograms per milliliter). 19 However, elevation of PSA is a nonspecific finding, where appro...