Essa M. Abdulla ( Essa’s Laboratory and Blood Bank, North Nazimabad, Karachi. )
Physicians often recommend that patients with UTI increase their fluid intake. This practice has continued for years largely unchallenged because it is so logical: a water diuresis would serve to “flush” the urinary tract of infecting organisms and the increased frequency of voiding would reduce bacterial multiplication in the bladder. However, since dilution of urine affects both the osmolality of the renal medulla and the action of urinary inhibitory substances that participate in natural host defense mechanisms1, it is of interest to re-examine fairly the evidence supporting this common treatment advice. Andriole, in a controlled animal study showed that enterococcal pyelonephritis in rats could be cured by a sustained water diuresis for 7-14 days without antimicrobial therapy2. It was postulated that reduction of hypertonicity of the renal medulla and infiltration of PMNs improved host response to bacterial infection. In 1971, an uncontrolled study of nursing home residents with bacteriuria who were not necessarily symptomatic suggested that hydration and frequent voiding reduced urine bacterial load3. These studies possibly provided the historical rationale for increasing oral fluid intake in patients with TJTI and yet there is an apparent deficiency of additional reports in the literature evaluating the use of hydration alone or as an adjunct to antibiotic therapy in the treatment of TJTI. Although it is clearly important to avoid dehydration, it is essential to consider the potential hazards of forcing fluids, as well as reasons that it may not be necessary. Antibiotherapy is an important component of a treatment regimen for symptomatic UTI. Many antibiotics are satisfactorily concentrated in the urinary tract and, if undisturbed, are effective in eradicating sensitive organisms. Forced-water diuresis could theoretically impair the effect of some antibiotics because their concentration in the urine is substantially reduced with aggressive hydration4. Indeed, other treatment protocol such as making the urine alkaline (citrate, bicarbonate) alleviates dysuria and potentiates the activity of sulphonamides5 but may significantly reduce the action of most quinolones, currently the preferred urinary drugs, which function only poorly at alkaline pH6,7. Besides, urine with a pH below 5.5, in contrast, tends to be antibacterial and many substances that can acidify urine (ascorbic acid, ammonium chloride, methionine and mandelic acid) can produce antibacterial activity8. Also, forcing oral or intravenous fluids can cause clinically significant hyponatremia, especially in the elderly and the chronically ill, because of their diminished renal tubular function and inability to clear free water9,10. In individuals with diabetes, intervention with diuretics to reduce hypertension is associated with excess mortality11. Indeed, the authors have concluded that until there is a clinical trial showing a beneficial effect of diuresis in diabetic patients, there is an urgent need to reconsider its usage in this population. In conclusion, it is considered important to treat symptomatic UTI promptly with appropriate antibiotics or urinary antiseptics and to maintain clinically normal fluid status. Overzealous hydration, especially in the elderly, may not be beneficial and can be harmful, while in the average, patient it may dilute the antibiotic and “hurry” it through the very tract where it was intended to exert its effect.
1. Kaye, 0. Host defense mechanisms in the urinary tract. Urol. din. North Am., 1975;2:407-22.
2. Andriole, V. Effect of water diuresis on chronic pyelonephritis. 7. Lab. dim. Med., 1968;71:1-16.
3. Friedman, S.A. and Gladstone, J.L. The effects of hydration and bladder incubation time on urine colony counts.). Urol., 1971;105:428-32.
4. Whelton, A, and Walker, W.G. An approach to the interpretation of drug concentrations in the kidney. Johns Hopkins Med. J., 1978; 142:8-14.
5. Benn, R.A.V. Aids to microbiology and infectious diseases. N.Y., church ill Livingstone, 1958, p-168.
6. Almeida, A.F. Antibiotics in clinical practice. Basel, Recom. Publishers, 1991, pp. 71-76.
7. Andriole, VT. The quinolones, N.Y. Academic Press, 1988, p-87.
8. Tierney, L.M. Current medical diagnosis and treatment. London, Appleton and Lange-Prentice Hall, 1993, p. 1210.
9. Nunez, 3P.M. and Cameron, J.S. Renal function and disease in the elderly. London, Butterworths, 1987, pp. 84-85.
10. Lorrergan, E.T. Aging and the kidney: adjusting treatment to physiological change. Geriatrics, 1988;43:23-33.
11. Warren, J.J. Excess mortality associated with diuretic therapy in diabetes mellitus. Arch. Intern. Med., 1991;151:1350-35.