Abstract
In non-azoospermic patients with low semen volume (LSV), looking for partial retrograde ejaculation (PRE) by searching sperm in the postejaculatory urine (PEU) is required. The use of a retro-ejaculatory index (R-ratio) was suggested to define PRE, but none of the studies indicated a specific threshold above which PRE must be considered. Our objective was to propose a threshold value for the R-ratio as indicative of PRE in patients with LSV selected to be devoid of any known causes or risk factors for retrograde ejaculation or LSV. Among our data base (2000–2009) including 632 patients with PEU, 245 male patients from infertile couples who had had a first semen analysis with LSV (< 2mL) and a second semen analysis associated with PEU, were selected on the previous criteria. A prospective control group was randomly constituted (2007–2008) of 162 first consulting male patients from infertile couples, with a normal semen volume (≥ 2mL) on a first semen analysis and who accepted to collect PEU with their usual second semen analysis, selected on the previous criteria. To define an R-ratio threshold indicative of PRE, we used a ROC curve analysis and a regression tree based on a classification and regression tree (CART) algorithm. Of the 245 LSV patients, 146 still presented low semen volume (< 2 mL) on the second semen analysis. From the use of the CART algorithm, two low (1.5% and 2.8%) and two high R-values (7.1% and 8.3%) were defined, according to the lower reference limit for semen volume of 2.0 mL (WHO 1999) or 1.5 mL (WHO 2010) respectively. As only one or no patient with normal semen volume was observed above the two high R-values, we suggest an R-value higher than the range of [7.1–8.3]% as indicative of PRE until confirmation by a prospective multicenter study.
Highlights
Ejaculation is the forceful propulsion of seminal fluid out of the body that consists in the synchronized succession of physiological events with two distinct phases, emission and expulsion.PLOS ONE | DOI:10.1371/journal.pone.0168742 January 6, 2017Low Semen Volume: Is It a Partial Retrograde Ejaculation?Organs involved in the emission phase comprise the distal epididymides, vasa deferentia, deferential ampullas, seminal vesicles, prostate gland and bulbourethral glands
Based on male partners of infertile couples selected to be devoid of any known risk factors for retrograde ejaculation or low semen volume, the main objective of the present study was to define a threshold for the R-ratio as indicative of the presence of an abnormal number of sperm in postejaculatory urine (PEU), i.e. partial retrograde ejaculation (PRE), in non-azoospermic patients presenting with low semen volume
Of the 245 retrospective patients with low semen volume on a former analysis, the second semen analysis performed in our centre demonstrated that 99 had normalized their semen volume (! 2 mL; normalized semen volume (NzedSV) patients) while 146 still presented low semen volume (< 2 mL; LSV patients) (Fig 1)
Summary
Ejaculation is the forceful propulsion of seminal fluid out of the body that consists in the synchronized succession of physiological events with two distinct phases, emission and expulsion.PLOS ONE | DOI:10.1371/journal.pone.0168742 January 6, 2017Low Semen Volume: Is It a Partial Retrograde Ejaculation?Organs involved in the emission phase comprise the distal epididymides, vasa deferentia, deferential ampullas, seminal vesicles, prostate gland and bulbourethral glands. The first step in the emission phase is the closure, by firm contraction, of bladder neck to prevent retrograde flow of the seminal fluid backward into the bladder. This is followed by the ejection of prostatic secretions into the prostatic urethra together with the sperm from the vasa deferentia and deferential ampullas, and the seminal vesicle secretions. Once emission phase is completed, saccadic expulsion of semen through the urethral meatus is caused by synchronized rhythmic contractions of the pelviperineal striated muscles -with a key role for the bulbospongiosus muscle- and intense contractions interrupted by silence periods of the external urethral sphincter. To achieve antegrade semen expulsion, the bladder neck remains closed; whereas the external urethral sphincter is open [1,2,3]
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