Retro-pubic mid-urethral tension free tape (TVT) placement to successfully treat stress urinary incontinence was first described by Ulmsten in 1995.  The procedure describes retropubic infiltration of the cave of Retzius before passing a trocar, to guide needles of the tape retropubically through a mid-urethral vaginal incision.  Commercial kits by various manufacturing groups have been developed to facilitate the technique and provide subjective long term cure rates of 51% – 88% using a ‘bottom to top’ approach. The procedure has an overall 4.5% risk of bladder injury, and <1% risk of bladder mesh erosion.  

TVT can be carried out with or without retropubic infiltration to allow hydrodissection of the bladder away from the pubic bone.  This step is recommended by some manufacturers to facilitate correct placement of the tape insertion trocars and reduce the risk of bladder injury.  The use of local anesthetic with combined adrenaline may provide additional analgesia.  No previous studies have measured the effect of hydrodissection to the retro-pubic space.

Objective

To measure the space between the pubic symphysis and bladder wall before and after hydrodissection to the retro-pubic space prior to TVT trocar placement using abdominal ultrasound.

A prospective study including patients undergoing Trans-Vaginal Tape insertion using Gynecare TVT (Ethicon) was carried out.  41 patients were recruited for ultra sound evaluation.  Following general anesthesia, abdominal ultrasound using a 2D 5mHz probe was performed to measure the space between the pubic symphysis and the bladder.  Hydrodissection was carried out using a total of 120mls of normal saline. 40ml was injected suprapubically to the skin and retro-pubic space on each side of the midline using a spinal needle.  A further 20ml was infiltrated vaginally on each side of the urethra up to the urogenital diaphragm.  Abdominal ultrasound was repeated, measuring the widest space in a sagittal plane between the pubic symphysis and the bladder, before proceeding with trocar and tape insertion.

The average retro-pubic space measurement was 0mm prior to hydrodissection.  Only one patient had a 1.6mm space pre-infiltration. Following infiltration as described, a statistically significant (p<0.00001, Mann Whitney U test) increase in the retropubic space with a mean of 6.7mm [range 3.1mm – 9.9mm] was created with hydrodissection. No intra-operative bladder injury occurred in this group of patients.

Infiltration in the retropubic space to cause hydrodissection creates an operative plane.

This study provides ultrasound evidence of a space produced by hydrodissection that can facilitate trocar passage. Trocars for tape insertion vary in width from 5mm to 2.7mm, this space was generated in up to 70% to 100% patients respectively. This suggests that hydrodissection may reduce bladder injury during the insertion of retropubic mid urethral tapes.