Prognostic impact of hyponatraemia in patients with colorectal cancer

Hyponatraemia is a common in surgical practice, but its clinical impact in patients with colorectal cancer has not been evaluated.

We retrospectively assessed 2944 patients who had been admitted to Chonnam National University Hwasun Hospital, Korea with a diagnosis of colorectal cancer. In order to determine the relationship between the serum sodium level and 3-year mortality, we categorized the patients as having normonatraemia (135-147 mEq/l), or mild (130-134 mEq/l), moderate (125-129 mEq/l) or severe hyponatraemia (< 125 mEq/l).

Hyponatraemia, defined as a serum sodium level of < 135 mEq/l, was evident in 27.6% of patients during hospitalization. Declining serum sodium levels were associated with increasing age, a higher number of comorbidities, a more advanced TNM stage and worsening biochemical parameters. In a multivariate Cox-proportional regression analysis, the mortality risk was correlated with the severity of hyponatraemia [hazard ratio (HR) 1.65, 95% CI 1.38-1.96; HR 2.24, 95% CI 1.69-2.98; HR 2.20, 95% CI 1.25-3.90, for patients with mild, moderate, and severe hyponatraemia, respectively, compared with patients with normonatraemia]. An independent association between hyponatraemia and long-term mortality was sustained among various subpopulations and patients with persistent hyponatraemia had a worse prognosis than those with hyponatraemia that resolved.

A substantial proportion of patients developed hyponatraemia during hospitalization, and the long-term mortality risk increased even in mild cases of hyponatraemia. Hyponatraemia should be considered as an important prognostic factor in colorectal cancer.