The tendency of indwelling catheters to cause urinary tract infection was evaluated in a randomised clinical study of 223 patients. A Foley catheter coated with silver alloy on both inner and outer surfaces was used in 60 patients; 60 others received a Teflonised latex Foley's catheter and the remaining 103 patients were excluded because of antibiotic treatment, diabetes, etc. There was a statistically significant difference in the incidence of catheter-associated bacteriuria (greater than 10(5) organisms/ml) in the 2 groups after 6 days' catheterisation: 6 patients with the silver coated catheter developed bacteriuria compared with 22 who had the Teflonised latex catheter. This suggests that the silver impregnated urethral catheters reduce the incidence of catheter-associated urinary tract infection.

The toxicity of silver-coated urinary catheters was assessed using a cell culture technique. The inhibitory effect of catheter extracts on the uptake of 3H-labelled thymidine by mouse fibroblasts was measured. The results show that silver-coating had no toxic effect whereas silvernitrate and silversulphate coating did have a toxic effect.

Interstitial cystitis (IC) is a painful condition in the urinary bladder of unknown aetiology and pathogenesis. To assess the contribution of the nervous system to IC a biopsy was taken from 6 patients with IC and from a control group of 6 patients with non-ulcerative IC. Mast cells were counted and histamine measured in bladder washings from all patients. There were significantly more nerve fibres within the sub-urothelium and detrusor muscle in chronic IC than there were in non-ulcerative IC. The bladder washings from all patients with IC contained mast cells and histamine, while only occasional mast cells and traces of histamine were found in washings from patients with non-ulcerative IC. There was a good correlation between the number of nerve fibres and number of mast cells as well as between the number of nerve fibres and the amount of histamine.