Indwelling catheters (urethral or supra-pubic) are often used to manage bladder emptying following spinal cord injury (SCI). A regime of catheter clamping has been proposed as a technique to maintain bladder capacity, prevent or reduce complications such as catheter blockages and reduce bladder pain. However, the existing evidence supporting this view is limited. The aim of this study was to undertake an audit of the urodynamic findings of a cohort of SCI patients with an SPC who either follow a clamping regime or rely on free drainage.

A total of 243 urodynamic reports of SCI patients were sorted to identify those who had an SPC. 43 patients with an SPC were identified, of which 22 were on a clamping regime and the remaining 21 were using free drainage (FD). When these patients were identified, a urodynamics report 5 years earlier was also reviewed.  The results for maximum detrusor pressure (MDP), maximum cystometric capacity (MCC) and bladder compliance were analysed. Additionally, the change in bladder capacity over the period between the two urodynamic reports was analysed. Statistical comparisons between the clamped and FD groups for each parameter were based on two-tailed chi squared and Students t test with p<0.05 indicating a significant difference. Standard deviation and upper and lower quartiles were also calculated to aid with analysis.

There were 28 males and 15 females with age range of 22 to 85 years old. There was statistical significance (p = 0.03) between the male and female distribution in the cohort.  There were varying levels of injury, with 63% sustaining a cervical level injury, 31% with a thoracic level injury, 3% with a lumbar level injury and 3% with either spina bifida or cauda equina syndrome.

The median value for maximum cystometric capacity (MCC) for FD and clamped patients was 125 mL and 240 mL respectively on the most recent urodynamics report, this was statistically significant (p = 0.001) (Figure A). The MDP ranged between 0 – 60 cmH₂O, with median value of 32 cmH₂O for FD and 21 cmH₂O for clamped patients which was not statistically significant (p = 0.28). 6 patients on FD leaked during the CMG compared to 0 clamped patients which was statistically significant (p = 0.007). Additionally, 64% of clamped patients had a reduced compliance compared to 70% of FD patients which was not statistically different (p = 0.21). When comparing the change in bladder capacity over a 5 year period, there was a significant difference (p<0.02) between the change in MCC between the clamped and free drainage group (Figure B).

The results of this retrospective review of investigations showed that the patients who followed a clamping regime had a significantly greater bladder capacity (MCC) than the patients who had their catheter on free drainage. However, further study is required to identify if clamping is the cause of the results.

Sheriff MK et al. Long-term supra-pubic catheterisation: clinical outcome and satisfaction survey. 1998. Spinal Cord. 36(3);171-6
Pannek J et al. To clamp or not to clamp? Bladder management by supra-pubic catheterisation in patients with neurogenic bladder dysfunction.  2010. World J Urol 28(5):637-41