To the Editor:

We read with great interest the article by Ojeda et al. that was recently published in Nefrología.1 In this study, the authors identified the presence of dehydration prior to admission as a risk factor for incomplete recovery of renal function during a follow-up on children with haemolytic uraemic syndrome associated with diarrhoea (D + HUS).

We previously reported that the presence of dehydration at diagnosis in children with D + HUS increases the likelihood that they will require dialysis in the acute stage. Additionally, we observed that the aforementioned patients had a significantly longer oligoanuric and dialysis phase than patients with normal hydration; nevertheless, our study focussed exclusively on the acute phase of the disease.2 By contrast, the present study aimed to identify whether certain clinical variables prior to hospitalisation allowed long-term renal involvement to be predicted. Although the authors found the only predictor of non-recovery of renal function to be the presence of dehydration at diagnosis, in the study discussion they maintained that their patients with long-term renal injury had a “more severe degree of acute deterioration” than patients without long-term renal involvement. Bearing in mind that the best predictor of non-recovery in patients with D+ HUS is the length of the oligoanuric period,3 we believe that reporting the duration of the latter in groups with and without long-term renal involvement, along with the statistical significance of this comparison, would allow for a more comprehensive explanation of the study. Likewise, the authors reported that patients with incomplete recovery of renal function required dialysis more often (12 out of 13 patients; 92.3%) than those with recovery (9 out of 23 patients; 39.1%), but the difference was not statistically significant (P=.2052). We were struck by the percentage difference between both groups (92.3% compared with 39.1%) and we re-calculated this comparison and obtained a P value of .0039 (Fisher’s exact test) with an odds ratio of 18.66, 95% confidence interval (2.05-169.34), which would mean, if our estimation is correct, that patients with long-term renal involvement required dialysis significantly more often. As a result, in the event that both the oligoanuric period and the requirement for dialysis were significantly greater in patients with long-term renal damage, we must ask the question whether the real predictor of non-recovery is initial dehydration or more severe renal dysfunction in the acute phase (possibly aggravated by concomitant volume depletion in dehydrated patients).

From our point of view, although not necessarily correct, dehydration determines greater renal injury in the acute phase and its severity, which is deduced by the dialysis requirement and the duration of the oligoanuric period, ultimately increases the risk of long-term renal involvement. We do not believe it is sufficient to associate dehydration on admission with the development of long-term renal damage without considering the acute phase of the disease. Nevertheless, we agree with the authors that, in order to obtain definitive conclusions in this regard, prospective studies should be conducted on a higher number of patients; in the meantime, we would like to highlight the importance of preventing volume depletion in patients at risk of developing D+ HUS.

Conflicts of interest

The authors declare that they have no conflicts of interest related to the contents of this article.