PURPOSE: We investigated the effect of preoperative urodynamic detrusor underactivity on the transurethral surgery outcomes of benign prostatic hyperplasia. MATERIALS AND METHODS: We systematically searched the online PubMed®, Embase® and Cochrane Library databases for articles published between January 1989 and June 2017. RESULTS: A total of 10 articles met the eligibility criteria for this systematic review. The eligible studies included a total of 1,113 patients with a median of 73 per study (range 40 to 382). Five of the 10 studies involved conventional transurethral prostatectomy and 5 described laser surgery. In patients with detrusor underactivity the pooled mean difference was significant for the poorer I-PSS (International Prostate Symptom Score) (pooled mean difference -3.73, 95% CI -5.65--1.80 for 9 studies and 936 participants) and maximal flow rate improvement (pooled mean difference -3.92, 95% CI -4.85--3.00 for 8 studies and 951 participants) but not for quality of life score (pooled mean difference -0.15, 95% CI -0.56-0.25 for 7 studies and 858 participants) or post-void residual volume (pooled mean difference -5.57, 95% CI -20.65-9.50 for 9 studies and 971 participants). Some comparisons showed interstudy heterogeneity despite strict selection criteria for the included studies. However, there was no clear evidence of publication bias in this meta-analysis. CONCLUSIONS: Our meta-analysis results showed that preoperative detrusor underactivity correlated with poorer I-PSS and maximal flow rate improvement. Preoperative urodynamic detrusor underactivity is a valuable finding for excluding patients who are inappropriate candidates for transurethral surgery.