Monday, May 6, 2013

Topic Discussion: Plain water intake and CKD

A recent article published in the Am J of Nephrology raises an interesting question- does drinking more plain water benefit CKD or renal disease? This was a study of analysis of the NHANES database.
Over 3000 patients reviewed and 13% had CKD and 18% had cardiovascular disease.
CKD turned out to be the highest amongst the lowest plain water drinkers( <2 liters/day) and lowest in the highest water drinkers( >4.5L/day).

The authors suggest a protective effect of plain water intake.  Unclear what the mechanism of this might be.  Two years ago, the Australians had shown a similar finding. In their study, they showed that increased fluid intake was protective for CKD. Increased urine volume might be protective for progression of CKD.  Even the lay press in NYTimes took notice of these findings and had a blog post on this very topic.

What is the mechanism for this? Any thoughts, could this be ADH related? or flow related?


  1. These are observational studies, therefore hypothesis generating only. I usually tell my patients to drink water when they are thirsty as is the common thought that water will flush their kidneys. I only see drinking water as an advantage in ADPCKD with relatively preserved GFR so it supresses ADH which will increase cAMP and cyst growth. Otherwise, I see many people who develop hyponatremia from this habit.

  2. I agree with the above. At this point, I don't buy it. This is association only, not cause and effect. Strongest data for increased water intake is in ADPKD and stone prevention and of course dehydration (evident by hypernatremia); the more advanced the CKD, the more the impairment of diluting and concentrating ability ("isosthenuria") and the more likely the risk of hyponatremia - especially if the CKD pts would consume 4.5L/d as this paper suggests. I tend to go by the rule of thumb according to this paper:

  3. Agreed regarding the point that this is an observational study this does not prove any causality. For instance, how about thinking about this the other way around.. and wondering if as CKD worsens there is a decrease in thirst and thus was water intake? Often CKD is associated with volume overload.. which can lead to less activation of ADH and the RAAS cascade (and thus less thirst). Thus it might look like less fluid intake might be harming the kidneys, but it might be that bad kidneys are leading to less fluid intake --- Dommu, M.D.

  4. This is why observational studies are only hypothesis generating.


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