Abstract
Encrustation and the subsequent blockage of indwelling urinary catheters is a common problem. For patients in the community, the resultant urinary bypassing or painful retention, is particularly distressing since professional help is not immediately available. Catheter blockage also places increased demands on nursing time and resources. A prospective longitudinal study of 47 community patients with long-term catheters was conducted. Demographic, dietary and catheter care data were collected. Biochemical and microbiological urinalysis were also conducted. Catheters were changed on three occasions, after six week intervals, and encrustations examined. A model of encrustation in the catheterised bladder was developed, and used to evaluate the effectiveness of bladder washouts in reducing encrustation. The results indicated that patients can be classified as "blockers" and "non-blockers" (Kunin et al., 1987a). "Blockers" produced two or more blocked catheters and were characterised by high urinary pH and ammonium concentration, and by infection with urease-producing micro-organisms, particularly Proteus mirabilis. "Blocker status" was also significantly associated with female sex and with poor mobility, but not with fluid intake and urinary output. "Blockers" were generally managed by "crisis care" in response to leakage or retention, rather than by planned recatheterisations prior to catheter blockage. Recognition of individual patients as "blockers" and the establishment of a "pattern of catheter life", would be useful to planning individualised care. The major components of catheter encrustations leading to blockage, were struvite and calcium phosphate. Calcium oxalate was present on some non-blocked catheters. Acidic bladder washout reagents (Suby G and mandelic acid) effectively reduced encrustation but saline did not. It is suggested that "miniwashouts" of 10-20ml may reduce encrustation and also minimise the potentially detrimental effects of washouts on the bladder mucosa. A number of recommendations for practice are made on the basis of these results.