Catheterized patients with heavy bacteriuria and short catheter life received a short-course of antimicrobial therapy and then were allocated at random to double-blind treatment for 5 months with methenamine hippurate (MH), 1 g three times daily, or placebo 1 g 3 times daily. MH treatment reduced the number of catheter blockages and instances of spontaneous removal of the catheter, and doubled catheter life (p less than 0.001). It is suggested that the doubled catheter life was due to the reduced bacteriuria and lowering of urinary pH.

The pH of the urine within a blocked indwelling catheter was significantly higher than the pH of the first urine portion from the new catheter. This observation suggests that the urinary pH was changed in an alkaline direction within the indwelling catheter, probably due to the production of ammonia induced by urease from Proteus strains. This pH gradient could only be demonstrated under conditions where the circadian pH variations of the urine within the individual could be neglected.