The Relationship Between Morphological Features Of Urethral Submucosal Vascular Plexus And Urethral Pressure Distribution In Female Canines

Aims:To Describe and study the morphological features of the urethral submucosal vascular plexus and its relationship with the characteristics of urethral pressure distribution in female canines.Methods:Totally 6 healthy female canines were used for this study,aged 2 years and weighed 8.5±0.6Kg.All procedures were performed under an intraperitoneal injection of2%sodium pentobarbital?40 mg/Kg?.The urethral pressure profile at 6 o'clock and 12o'clock was first recorded,and the maximum urethral closure pressure?MUCP?and functional urethral length?FUL?were calculated respectively.Then a midline abdominal incision was made and the urethra,bladder,abdominal aorta and inferior vena cava were exposed.Cystectomy was made and the bladder was half-filled with saline.Abdominal aorta puncture was performed and ink-dextran solution was perfused in vivo.When the urethra,bladder,skin and finally the whole body gradually became dark,the abdominal aorta and inferior cava were ligated.The animals were killed by overdose anesthesia.Then the bladder,urethra,vagina and surrounding tissues were taken en block and were fixed.Tissue blocks were embedded and serial frozen sections were prepared.The morphology of urethra and its submucosal vascular plexus were observed and photographed under stereoscopic microscope.Vascular density of the urethral submucosal vascular plexus and bladder wall was measured by the ImageJ software.Results:The UPP recording and ink-dextran perfusion were performed successfully in all six female dogs.The MUCP at 12 o'clock and 6 o'clock were?37.71±9.96?cmH₂O and?20.36±5.62?cmH₂O,and the FUL at 12 o'clock and 6 o'clock were?5.77±1.25?cm and?7.56±1.56?cm,respectively,the MUCP at 12 o'clock and the FUL at 6 o'clock was significantly greater than in the other direction?p<0.01?.Observing the gross specimens,the bladder and urethra were significantly stained,and the coloration was uniform,suggesting that the result of ink perfusion was good.Under the stereoscopic microscope,the vascular structure in the urethra and bladder wall was clearly visible,and no ink spilled through the blood vessels.The characteristics of vascular morphology in different segments and different zones of urethral submucosa vascular plexus and bladder wall were as follows:large areas of the cavernous sinus are widely distributed in the submucosal wall of the distal urethra;dense large cystic vessels can be seen in the anterior wall of the distal urethra.And large size cystic vascular sinusoids were observed in sub-distal urethral segment and middle urethral segment,mainly in anterior urethral wall.The size of vascular sinusoid became smaller in the proximal urethral wall and almost without polarized distribution.The vessels in the bladder wall are mostly thin and reticular,with no polarized distribution.Compared with the distal,middle and proximal urethral segments,the vascular density of the submucosal vascular plexus was the highest in the distal urethra?p<0.01?.The vascular density in the anterior wall of distal,subdistal and middle urethral submucosa was significantly higher than that in the posterior wall?p<0.01?,but there was no significant difference between the anterior and posterior wall of proximal urethral submucosa?p>0.05?.The MUCP and maximal vascular density of submucosal vascular plexus appeared in the subdistal urethra.The directional variation of MUCP at 6 o'clock and 12 o'clock corresponded to the polar distribution of vascular density of urethral submucosal vascular plexus in the anterior and posterior wall of urethra.Conclusion:Ink perfusion in vivo is proved being an effective method for visualizing the submucosal microvascular structure of the urethra.The morphology and distribution characteristics of the urethral submucosal vascular plexus in female canines were obtained for the first time.The morphological features of urethral submucosal vascular plexus were related with urethral pressure distribution in female canines,which provides a basis for further exploration of the relationship between the urethral submucosal vascular plexus and urinary continence.