Kidney Week

Abstract: PO1429

Water Load Test in the Diagnosis of Syndrome of Inappropriate Antidiuresis (SIAD): Results from the Waterline Study

Session Information

• Fluid, Electrolyte, and Acid-Base Disorders: Clinical - 1
  October 22, 2020 | Location: On-Demand
  Abstract Time: 10:00 AM - 12:00 PM

Category: Fluid, Electrolyte, and Acid-Base Disorders

• 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

• Cohen, Raphael Rc, Hopital Europeen Georges-Pompidou Pole Cardio-vasculaire Renal Metabolique, Paris, Île-de-France, France

Raphael Rc Cohen,

• Bouderlique, Elise, U1155 Inserm, Tenon Hospital, Paris, France

Elise Bouderlique,

• Bureau, Côme, Hopital Europeen Georges-Pompidou Pole Cardio-vasculaire Renal Metabolique, Paris, Île-de-France, France

Côme Bureau,

• Seervai, Riyad N. H., Center for Precision Environmental Health, Baylor College of Medicine, Houston, Texas, United States

Riyad N. H. Seervai,

• Blanchard, Anne, Hopital Europeen Georges-Pompidou Pole Cardio-vasculaire Renal Metabolique, Paris, Île-de-France, France

Anne Blanchard,

• Houillier, Pascal, Hopital Europeen Georges-Pompidou Pole Cardio-vasculaire Renal Metabolique, Paris, Île-de-France, France

Pascal Houillier,

• Vrigneaud, Laurence, Hopital Prive La Louviere, Lille, Nord-Pas-de-Calais, France

Laurence Vrigneaud,

• Bertocchio, Jean-philippe, Hopital Europeen Georges-Pompidou Pole Cardio-vasculaire Renal Metabolique, Paris, Île-de-France, France

Jean-philippe Bertocchio,

Group or Team Name

• Waterline study investigators

Background

SIAD is caused by an inadequate kidney reabsorption of water, mainly under the action of antidiuretic hormone. The latest international recommendations stated the diagnosis of SIAD relies on hypotonic hyponatremia with inadequate urine osmolality. Blood volume has to be normal, with adrenal, thyroid, and renal insufficiency excluded. These guidelines ruled out the usefulness of abnormal response to water load test (WLT) due to the lack of published evidence.

Methods

In the Waterline study (NCT04256499), we retrospectively analyzed data from patients who underwent a WLT (oral administration of 20 mL/kg of water) in our department.

Results

From 02/2001 to 10/2019, 173 adults were included. Out of them, 80(46%) had a SIAD and 21(12%) were considered ‘normal’, 72(42%) had hyponatremia of other origin. Among the SIAD patients, 33(41%) had a fasting plasma sodium (PNa) ≥135mM (‘normonatremic SIAD’), 47(59%) had ‘hyponatremic SIAD’: We found no differences in demographic data or medical history between these two groups. During WLT, ‘normonatremic SIAD’ patients behaved specifically by exerting hyponatremia (while normal individuals did not), resembling ‘hyponatremic SIAD’ patients (Figure 1). While their fasting urine osmolality (U-Osm) was initially higher, ‘normonatremic SIAD’ and ‘hyponatremic SIAD’ patients reached the same minimum U-Osm (389±257 vs. 350±202mOsm/kgH₂O, p=0.76). Additionally, they reached a higher minimum value of PNa than ‘hyponatremic SIAD’ patients (132±2 vs. 127±3mM, p<0.0001). These results were confirmed in an independent cohort of 38 WLT where 24 (63%) were ‘normonatremic SIAD’.

Conclusion

We conclude that, without WLT, a diagnosis of SIAD could be missed in 40 to 63% of SIAD patients.

Figure 1. Evolution of PNa during WLT in normal (green), 'hyponatremic SIAD' (red), and 'normonatremic SIAD' (blue) patients.