Lactulose may help prevent urinary tract infections

BMJ 2001; 323 doi: http://dx.doi.org/10.1136/bmj.323.7318.936 (Published 20 October 2001) Cite this as: BMJ 2001;323:936
  1. M Battle, specialist registrar,
  2. T Martin, preregistration house officer,
  3. J Fulton (jamie.fulton{at}phnt.swest.nhs.uk), consultant physician
  1. Department of Health Care of the Elderly, Derriford Hospital, Plymouth PL6 8DH

    EDITOR—The study by Kontiokari et al did not show a significant reduction in the prevalence of urinary tract infection in women using a lactobacillus drink, but it did show a benefit of cranberry-lingonberry juice.1 They concluded that this lack of benefit may have been because they were unable to induce periurethral colonisation with lactobacilli.

    Most urinary tract infections are caused by autoinfection, the pathogenic organisms originating from the host's own colonic flora. Previous studies have shown a reduction in the prevalence of urinary tract infections by using lactulose. 2 3 This synthetic disaccharide is predominantly used as an osmotic laxative and in managing portosystemic encephalopathy. It is neither absorbed nor metabolised in its transit through the upper gastrointestinal tract, but it is degraded by the bacterial flora of the proximal colon to organic acids. These acidify the proximal colon and result in a dose dependent catharsis.

    Lactulose also has several additional properties, including an anti-endotoxin effect and alteration of faecal floral patterns. 4 5 This quantitative alteration in faecal floral patterns, with an increase in faecal Lactobacillus acidophilus and a reduction in both coliforms and bacteroides, has been confirmed in our own unpublished work.

    We believe that this alteration in faecal floral patterns is responsible for the observed reduction in urinary tract infections. We suggest that a composite effect of the relative increase in lactobacilli associated with the relative reduction in coliforms and other organisms potentially pathogenic to the urinary tract achieves the reduction in urinary tract infections as distinct from pure lactobacillus loading. There may also be a qualitative alteration in bacterial pathogenicity that is relevant to the development of urinary tract infections from using lactulose as an alternative substrate. Manipulation of the faecal floral content using lactulose may prove to be an effective means of preventing urinary tract infections.


    • Competing interests None declared.


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