For inpatients younger than 66 years, knowledge of the validity of hyponatraemia diagnoses is limited to a study performed in a single hospital in the Netherlands using ICD-9 codes for hyponatraemia. 12 The sensitivity of hyponatraemia coding was found to be as low as 7%. This Canadian study was restricted to patients 66 years of age or older with serum sodium values at the time of emergency department contact or at hospital admission. Until now, only one study has investigated the validity of the International Classification of Diseases, 10th revision (ICD-10) codes for hyponatraemia. 9 10 Thus, use of only inpatient discharge diagnoses of hyponatraemia in epidemiological studies may cause bias that can affect the validity of study results. However, as symptoms of mild and moderate hyponatraemia may be vague, and concealed by or construed as symptoms of an underlying disease, it is likely that the condition will not be reported. The Danish population-based medical registries may offer a unique opportunity for studies of the epidemiology of hyponatraemia, if data are valid. 3–8 However, key aspects of the aetiology and prognosis of hyponatraemia remain unknown. 2 Results of recent studies have indicated that even a mild-to-moderate level of hyponatraemia may be an important predictor of poor prognosis in patients with cardiovascular disease, kidney and liver disease and cancer. 1 It can be caused by a large variety of conditions, such as heart failure, kidney failure, cirrhosis, syndrome of an inappropriate antidiuretic hormone, vomiting and diarrhoea, and can also be a side effect of several medications.

Hyponatraemia, defined as a serum sodium value <135 mmol/L, is the most common electrolyte abnormality encountered in clinical practice.

Icd 10 code for hyponatremia