Indwelling urinary catheters in the elderly. Relation of "catheter life" to formation of encrustations in patients with and without blocked catheters.

In order to define the natural history of indwelling urinary catheters in the elderly, 50 patients aged 65 years or older were followed. Their catheters had been in place for a mean of 33.2 days. When removed, 40.4 percent were blocked or showed poor flow. After the catheters were changed, the 14-day "catheter life" was 78 percent. About half the population had blocked catheters. They had a 14-day "catheter life" of only 31.8 percent (p = less than 0.01). Patients with blocked catheters ("blockers") excreted more alkaline urine, calcium, protein, and mucin than patients without blocked catheters ("nonblockers"), but urea-splitting bacteria were no more frequent. The mortality was not significantly different. Flow of water through catheters was closely related to extent of encrustations. Encrustations formed uniformly throughout the catheter lumen except when the tip was obstructed. The distribution and number of species of microorganisms (three and a half per specimen) were virtually identical in catheter and bladder urine, but the counts in the catheter urine were more frequently greater than 100,000 cfu/ml (p = less than 0.01). Patients with blocked catheters appear to be metabolically different from patients without blocked catheters and should have their catheters changed at seven to 10 days to avoid obstruction.