Prostatic stromal inflammation is associated with bladder outlet obstruction in patients with benign prostatic hyperplasia

BACKGROUND: Benign prostatic hyperplasia (BPH) is a common urologic disease in older men. Prostatic inflammation research has focused on the magnitude of inflammation; its location has received little attention. We investigated whether the anatomic location of prostatic inflammation is related to the severity of lower urinary tract symptoms (LUTS), measured subjectively and objectively. METHODS: We retrospectively analyzed hematoxylin+eosin-stained tissue specimens from 179 BPH patients who underwent transurethral resection of the prostate (TURP) or holmium laser enucleation of the prostate (HoLEP). Chronic prostatic inflammation was assessed by the grade (lymphocyte density), extent (lymphocyte distribution), and location of inflammation. Each inflammation-finding type was evaluated in relation to these clinical parameters: age, prostate volume, prostate-specific antigen (PSA) value, body mass index (BMI), the frequency of acute urinary retention (AUR) episodes, the international prostatic symptom score (IPSS), and urodynamic study results. RESULTS: The magnitude and extent of inflammation were not associated with any clinical parameters. We classified the BPH patients into stromal (n = 72) versus non-stromal (n = 105) groups based on their inflammation's dominant location. The stromal group's prostatic volume was significantly larger than the non-stromal group's (63.8 vs 53.8 mL; P = 0.032). AUR episodes were more significantly frequent in the stromal group (36.1% vs 11.4%; P = 0.006). Between-group differences in storage parameters (ie, maximum cystometric capacity) in the urodynamic study were not significantly different. Voiding parameters differed significantly between the stromal and non-stromal groups: maximum detrusor pressure (maxPdet) (116.8 vs 94.5 cmH2 O, P = 0.014), Pdet at the maximum flow rate (Qmax) (95.8 vs 75.4 cmH2 O, P = 0.014), and the bladder outlet obstruction index (BOOI) (78.5 vs 56.3, P = 0.014). The stromal group's Qmax was significantly lower than the non-stromal group's (7.3 vs 9.8 mL/s, P = 0.004). CONCLUSIONS: The location of inflammation in the prostate might be an important factor affecting the severity of LUTS, especially voiding dysfunction.