Caudal Lumbar Splanchnic Nerves Provide Primary Control of the Porcine Bladder Neck

Abstract

BackgroundFunctional infertility caused by retrograde ejaculation (RE) is the most significant postoperative complication following surgery for advanced stage testis cancer. This occurs because of iatrogenic injury to the sympathetic nerves of the aortic‐ and superior hypogastric plexuses in control of internal urethral sphincter (IUS) contraction, thus impairing bladder neck closure.Despite recent advancements in our anatomical understanding of these plexuses to inform nerve‐sparing surgical technique, complete preservation of all nerves is not always possible due to the extent of some cancers. As such, the most effective approach would spare only the nerves required to prevent RE (i.e., the sympathetic innervation to the bladder neck). However, the relative contribution of the nerves comprising the the aortic plexus — the intermesenteric nerves (IMN) and caudal‐most lumbar splanchnic nerves (LSN) — in control of bladder neck closure remain unknown, thus directed nerve‐sparing cannot be yet be achieved.AimTo investigate the contribution of the IMNs and LSNs in bladder neck closure.MethodUsing a translational porcine model that has been shown to have homology to the human aortic plexus, the first objective evaluated the role of the contributing nerves (the IMN & LSN) in IUS contraction compared to the hypogastric nerves (HN; homologous to the human superior hypogastric plexus). For the second objective, we determined the arrangement of the fibers supplying the IUS within the ipsilateral and contralateral HNs.To achieve this, we measured IUS contraction following electrostimulation [10Hz, 30mA, 1ms pulse width, 200V, 30s] of the (1) HN, (2) LSN, and (3) IMN in an intact state (Obj #1) and following an ipsilateral HN lesion to test if relevant axons decussate proximal to the HNs (Obj #2) in three boars (85.6 ± 6.4 kg). Direct electrostimulation was performed using a bipolar electrode, and the resultant contraction was monitored using a pressure‐sensing balloon catheter.ResultsImportantly, the average IUS contraction following LSN stimulation was approximately 3.5 fold greater (157.3 ± 79.7 mmHg□s) than the ipsilateral IMN stimulation (44.0 ± 70.2 mmHg□s; p<0.05). Moreover, ipsilateral LSN stimulation produced an average IUS contraction integral that rivaled the maximal response generated by ipsilateral HN stimulation (82.1% of total; 193.4 ± 107.9 mmHg□s; p>0.05). Lastly, a lesion to the ipsilateral HN significantly reduced (in some cases, abolished) the response (87.2% reduction; 13.8 ± 14.2 mmHg□s; p<0.05) indicating minimal decussation of fibers at the level of the aortic plexus.ConclusionThese data demonstrate that the most caudal LSNs provide the majority of sympathetic innervation to the IUS in comparison to the IMNs. In addition, few fibers within the LSNs pass contralaterally, but rather continue through an ipsilateral HN to supply the bladder neck. These findings position the LSNs as major contributors to the maintenance of normal bladder neck function in the boar. Future studies seek to test this hypothesis in retrospective clinical studies to verify the translatability to humans.Support or Funding InformationCIHR; LRCP Catalyst; Lawson IRFThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.