Teaching Case

A 73-year-old male patient presented to the emergency department with macroscopic haematuria lasting for two weeks and urinary obstructive symptoms.  
On digital rectal examination there were no suspicious findings for malignancy. Laboratory tests revealed an elevated serous prostate-specific antigen (PSA) of 12.26 ng/mL.

Pelvic ultrasound (US) showed a markedly enlarged prostate, with an estimated volume of 520cc (Fig. 1). A slight and diffuse thickening of the bladder wall and a bladder stone were also noted (Fig. 2). Kidney US was unremarkable.
Prostatic magnetic resonance imaging (MRI) followed, confirming prostatomegaly of 439cc. PSA density (PSAD) was within the normal range (0.03 ng/mL/cc).
On MRI there was notorious enlargement of the transitional zone, containing multiple nodules with mixed signal intensity in T2-weighted images (Fig. 3b), without significant diffusion restriction and with some contrast enhancement (Fig. 3c), in keeping with benign prostate hyperplasia (BPH). A laminar peripheral zone was seen, and both the central zone and the anterior fibromuscular stroma showed no abnormalities. There was no evidence of suspicious findings for clinically significant prostate cancer (PI-RADS 2 examination).
The bladder showed a dome-like indentation along the base due to the enlarged prostate, and a 14 mm bladder stone (Fig. 3d).

Prostatomegaly is used to describe prostate enlargement, regardless of its cause [1]. The maximum volume reported in literature was of 734cc [2].

The most frequent aetiology of prostatomegaly is BPH, a common condition in older men, with a prevalence that reaches 50%–60% by the age of 60 [3]. It is characterised by enlargement of the transition zone and formation of multiple large nodules, secondary to hyperplasia of the prostatic stromal and epithelial cells [1, 4].
Although the size of the prostate does not necessarily correlate with the voiding symptoms, some patients with BPH will present with lower urinary tract symptoms (LUTS), including storage and voiding disability, and nocturia. Complications of untreated BPH include bladder stones and diverticula, recurrent urinary tract infection, gross haematuria, bilateral symmetric hydronephrosis and even renal failure [1, 3].

Prostatic volume is most commonly calculated in US or MRI, using the ellipsoid formula (width x height x length x 0.52), being abnormal when it exceeds 30cc (Fig. 4). MRI-based calculations are more accurate, with better correlation with gross specimen weight [5], and therefore, increase the utility of PSAD. PSAD is calculated by dividing PSA by the prostate volume (PSA/prostate volume) and in combination with multiparametric MRI, improves the negative predictive value of PI-RADS scoring, preventing unnecessary biopsies in approximately 20% [6]. The normal value is up to 0.15-0.20 ng/mL/cc [6].
On MRI, BPH is seen as heterogeneous transition zone on T2-weighted images, with multiple nodules that can be hypo, iso, or hyperintense, depending on the amount of glandular and stromal tissue [1]. Glandular elements tend to be hyperintense, whilst mixed/stromal BPH nodules are hypointense, have restriction to diffusion and early enhancement, mimicking transition zone malignant tumours [3]. Generally, BPH nodules tend to be well defined, distinguishing them from transition zone cancer [1, 3]

Prostatitis, prostatic abscesses and rare tumours besides prostate adenocarcinoma can cause prostatomegaly [7, 8]. Prostate sarcomas and prostatic stromal tumours are usually solid, with heterogeneous T2 signal intensity and diffuse low-contrast enhancement [7, 8, 9].

In our case, although PSA level was elevated (12.26ng/mL) since BPH tissue produces PSA, PSAD was normal (0.03 ng/mL/cc). At the Urology multidisciplinary team meeting it was assumed that there was no indication for biopsy and transurethral resection of the prostate (TURP) was proposed as treatment. On pathology TURP specimen showed benign prostatic hyperplasia.

As a take home point, the value of PSAD should be underlined, namely assisting biopsy decisions. According to PI-RADS v2.1 orientations, PSAD should be included in the prostate MRI report [10].

Written informed patient consent for publication has been obtained.