Hyponatremia secondary to reset osmostat in a child with a central nervous system midline defect and a chromosomal abnormality

Case report: Twice-daily tolvaptan dosing regimen in a challenging case of hyponatremia due to SIAD

Background

Syndrome of inappropriate antidiuresis (SIAD) is one of the most frequent causes of euvolemic hyponatremia (serum sodium levels < 135 mEq/L) and it represents more than 35% of hyponatremia cases in hospitalized patients. It is characterized by an inappropriate vasopressin (AVP)/antidiuretic hormone (ADH) secretion, which occurs independently from effective serum osmolality or circulating volume, leading to water retention via its action on type 2 vasopressin receptor in the distal renal tubules. Corpus callosum agenesis (CCA) is one of the most common congenital brain defects, which can be associated to alterations in serum sodium levels. This report presents a rare case of chronic hyponatremia associated with SIAD in a woman with CCA, whose correction of serum sodium levels only occurred following twice-daily tolvaptan administration.

Case presentation

A 30-year-old female was admitted to our hospital for non-acute hyponatremia with dizziness, headache, distal tremors, and concentration deficits. She had profound hyponatremia (Na 121 mmol/L) with measured plasma hypo-osmolality (259 mOsm/Kg) and urinary osmolality greater than 100 mOsm/Kg (517 mOsm/Kg). She presented clinically as normovolemic. After the exclusion of other causes of normovolemic hyponatremia, such as hypothyroidism and adrenal insufficiency, a diagnosis of SIAD was established. We have ruled out paraneoplastic, inflammatory, and infectious causes, as well as ischemic events. Her medical history showed a CCA and frontal teratoma. We administered tolvaptan initially at a low dosage (15 mg once a day) with persistence of hyponatremia. Therefore, the dosage was first doubled (30 mg once a day) and then increased to 45 mg once a day with an initial improvement in serum sodium levels, although not long-lasting. We therefore tried dividing the 45 mg tolvaptan administration into two doses of 30 mg and 15 mg respectively, using an off-label treatment schedule, thus achieving long-lasting serum sodium levels in the low-normal range associated with a general clinical improvement.

Conclusions

This report underlines the importance of the correct diagnosis, management and treatment of SIAD, as well as the need for further studies about the pharmacokinetics and pharmacodynamics of vasopressin receptor antagonists.

Differential diagnosis between syndrome of inappropriate antidiuretic hormone secretion and cerebral/renal salt wasting syndrome in children over 1 year: proposal for a simple algorithm

Hyponatremia, especially if acute and severe, can be a life-threatening condition. Several conditions can trigger hyponatremia. In this review, we will discuss two conditions that can determine euvolemic hyponatremia: the cerebral/renal salt wasting (CRSW) syndrome and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), including the two subtypes: reset osmostat (RO) and nephrogenic syndrome of inappropriate antidiuresis (NSIAD) and their differential diagnoses. Despite the passage of over 70 years since its first description, to date, the true etiopathogenesis of CRSW syndrome, a rare cause of hypovolemic/euvolemic hyponatremia, is almost unknown. SIADH, including RO and NSIAD, is sometimes difficult to differentiate from CRSW syndrome; in its differential diagnosis, the clinical approach based on the evaluation of the extracellular volume (ECV) was proven insufficient. We therefore suggest a simple diagnostic algorithm based on the assessment of the degree of hyponatremia, urinary osmolality, and the assessment of the fraction of urate excretion (FEUa) in conditions of hyponatremia and after serum sodium correction, to be applied in children over 1 year of life.

Chronic Hyponatremia Due to the Syndrome of Inappropriate Antidiuresis (SIAD) in an Adult Woman with Corpus Callosum Agenesis (CCA)

BACKGROUND Corpus callosum agenesis (CCA) is one of the most common congenital brain abnormalities, and is associated with neurodevelopmental and neuropsychiatric disorders. In CCA, defects in osmoregulation have been reported. This report presents a rare case of chronic hyponatremia associated with the syndrome of inappropriate antidiuresis (SIAD) in a woman with CCA. CASE REPORT A 41-year-old woman presented to the renal unit with symptomatic hyponatremia. In her past medical history, she had a four-year history of systemic arterial hypertension and Sjögren's syndrome, and a three-year history of systemic lupus erythematosus (SLE), which was treated with cyclophosphamide. She had CCA but with irregular neurological follow-up. During the previous eight years, her plasma sodium levels ranged from between 118-134 mEq/L. On this hospital admission, she had plasma hypo-osmolality, measured in milli-osmoles per kilogram of H2O (mOsm/kg H2O), of 251 mOsm/Kg H2O, and a urinary hyper-osmolality of 545 mOsm/Kg H2O, and increased level of plasma antidiuretic hormone (ADH) (1.8 pg/ml). Bone densitometry was consistent with osteoporosis. The patient remained asymptomatic during her hospital stay. Chronic hyponatremia associated with the SIAD was diagnosed. Water restriction and increased protein intake resulted in a partial improvement in the serum sodium level (128-134 mEq/L). The patient was discharged from the hospital with outpatient follow-up. CONCLUSIONS A rare case of chronic hyponatremia due to the SIAD associated with CCA is reported that demonstrates the importance of correct diagnosis, management, and clinical follow-up of the SIAD, including bone densitometry.

Evaluation and management of hyponatraemia in children

AIM

Paediatric hyponatraemia is usually caused by an excess of antidiuretic hormone and may lead to serious neurological complications. It is challenging for clinicians to differentiate between conditions causing excess water and salt loss. This review analyses individual causes of hyponatraemia and focuses on optimal diagnostic algorithms and treatment strategies.

CONCLUSION

Correct evaluation of hyponatraemia requires proper understanding of the aetiology and appropriate management calls for a detailed history, physical examination and specific laboratory investigations.

Oral urea for the treatment of chronic syndrome of inappropriate antidiuresis in children

We report the successful use of oral urea in the management of children with chronic syndrome of inappropriate antidiuretic hormone secretion (SIAD). We performed a retrospective review of four children with chronic SIAD. After initial attempts at management with fluid restriction, each was started on a 30% to 50% oral urea solution, and the dose was titrated until normal serum sodium was achieved. Fluid intake was liberalized after serum sodium normalization. All four children normalized their serum sodium. No side effects or toxicities were experienced. Oral urea is a safe, effective treatment for chronic SIAD in children.