Schwartz-Bartter Syndrome

Classification according to ICD-10
E22.2	Syndrome of inadequate secretion of adiuretin
ICD-10 online (WHO version 2019)

When syndrome of inappropriate antidiuretic hormone secretion or syndrome of inappropriate antidiuretic hormone secretion ( SIADH ) is one, in terms of blood plasma - osmolality , inappropriately high secretion of antidiuretic hormone (ADH, Syn .: Adiuretin, vasopressin). This leads to insufficient fluid excretion via the kidneys with the development of highly concentrated urine. In laboratory tests , the disease is characterized by hypotonic hyperhydration with dilution hyponatremia (serum sodium <135 mmol / l) and an inappropriately high osmolality of the urine(> 100 mOsm / kg). The most common cause is a small cell lung cancer in the sense of a paraneoplastic effect.

Schwartz-Bartter syndrome must be differentiated from Bartter syndrome , a disease of the kidney tubules.

causes

The Schwartz-Bartter syndrome occurs z. B. after traumatic brain injuries , meningitis or encephalitis , aneurysms , severe burns, hypothyroidism or intracranial tumors, pneumonia or tuberculosis. As a paraneoplastic syndrome , it can occur, for example, in lung cancer (especially in undifferentiated small cell carcinoma). It was also observed porphyria and as a side effect of antidepressant drugs of the group of tricyclic antidepressants (eg. As amitriptyline , nortriptyline ), or selective serotonin reuptake inhibitor (z. B. escitalopram ), antipsychotics (such as amisulpride , chlorpromazine , fluphenazine , flupentixol , haloperidol , Trifluoperazine , thioridazine , thiothixene and risperidone ), cytostatics and the antiarrhythmic amiodarone . It is also believed that almost all patients may experience temporary inadequate secretion of ADH after surgery .

Symptoms

It is made up of the symptom complexes of the electrolytes mainly secreted or retained by the kidneys . In the course of this disease, there is a dilution effect due to the inadequate ADH secretion and thus reduced water excretion. In this case one speaks of a hypotonic hyperhydration syndrome. Blood tests show hyponatremia (dilution hyponatremia), hypophosphataemia , as well as hypokalaemia with metabolic hypochloraemic alkalosis, caused by decreased water excretion.

Symptoms of relative hyponatremia depend on how quickly the sodium is diluted. There are headaches , personality changes in terms of increased irritability or lethargy , nausea, vomiting , confusion to delirium and consciousness disorders up to coma possible. Increases in sodium levels should be done slowly to prevent the development of central pontine myelinolysis. In addition to muscle weakness and cramps, myoclonus and epileptic seizures can occur. The reflexes are sometimes weakened or increased. Edema does not occur because the water retention is limited to around three to four liters.

diagnosis

The following examinations and laboratory parameters provide information about the diagnosis:

• Decreased serum osmolality (<270 mosmol / kg)
• Dilution hyponatremia ([Na ⁺ ] <135 mmol / l in serum)
• increased central venous pressure
• no edema or ascites
• low urine volume per time
• inappropriately high urine osmolality / specific gravity of urine
• Inappropriately high concentration of sodium in the urine (> 20 mmol / liter)

Determining the ADH concentration in the blood makes little sense. In practice, it has been shown that the values ​​can be normal or elevated, but by no means have to be elevated. One of the reasons for this is the instability of the ADH molecule. As an alternative, copeptin , a prohormone that is synthesized together with ADH in the hypothalamus , is therefore usually determined.

Differential diagnosis of urinary concentration disorders

	Bartter syndrome	Schwartz-Bartter Syndrome (SIADH)	Diabetes insipidus centralis	Diabetes insipidus renalis
Pathophysiology	Channel defect in the kidney (Na + / K + / 2Cl - -Symporter, ROMK or CLCKB )	inappropriately high ADH secretion	insufficient ADH secretion	ADH type 2 receptor defect or aquaporin 2 defect
etiology	hereditary (autosomal recessive)	paraneoplastic (small cell lung cancer ) secondary to infections, CNS disorders or as a drug side effect (e.g. venlafaxine )	idiopathic (approx. 1/3 of the cases) secondary in tumors, after trauma, in infections	hereditary (X-linked or autosomal recessive) acquired in kidney disease
clinic	Salt appetite, muscle weakness and pain , cramps	CNS symptoms , muscle weakness and pain , cramps	increased amount of urine , increased amount of drink	increased amount of urine , increased amount of drink
laboratory	Serum: Na + ↓, K + ↓, osmolality ↓, pH value ↑	Serum: ADH ↑, copeptin ↑, Na + ↓, K + ↓, osmolality ↓, pH value ↑	Serum: ADH ↓, copeptin ↓, Na + ↑, osmolality ↑	Serum: ADH ↔, copeptin ↑, Na + ↑, osmolality ↑
	Urine: Na + ↑, K + ↑, osmolality ↑	Urine: Na + ↑, osmolality ↑	Urine: Na + ↓, osmolality ↓	Urine: Na + ↓, osmolality ↓
Further diagnostics	Evidence of secondary aldosteronism		Thirst test: ADH ↔ Desmopressin test: urine osmolality ↑	Thirst test: ADH ↑ Desmopressin test: urine osmolality ↔

therapy

The clinical symptoms and the identification and treatment of the cause of SIADH are decisive for the therapy decision. In asymptomatic cases, a drinking quantity restriction is usually sufficient. Action is required, especially when neurological symptoms are present: slow infusion of isotonic (0.9%) or hypertonic (10%) saline solution for substitution. If the saline solution is infused too quickly, there is a risk of pontine myelinolysis , impaired consciousness or seizures. Vaptans for the treatment of SIADH have now also been approved as a new and specific therapy option in Europe . Tolvaptan became the first oral ADH antagonist to be available in Germany since August 2009 . The drug manufactured by Ōtsuka blocks the action of ADH on the kidneys and thus promotes the excretion of electrolyte-free water.

It should also be noted that hyponatremia is often accompanied by hypokalaemia . When potassium is substituted, sodium is released from the cell at the same time. Thus, potassium substitution also helps to compensate for hyponatremia.

Individual evidence

1. ↑ Lothar Thomas : Laboratory and Diagnosis . Frankfurt 1998, p. 314 .
2. ↑ Gerd Herold : Internal Medicine . Cologne 2013, p. 799 .
3. ↑ Olanzapine and hyponatraemia; Nederlands Bijwerkingen Centrum Lareb; September 2006 ( Memento of the original from December 5, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 89 kB). 
4. ↑ Gerd Herold et al .: Internal Medicine , Cologne, 2008 p. 737.
5. ↑ Gerd Herold and colleagues: Internal Medicine 2020. Self-published, Cologne 2020, ISBN 978-3-9814660-9-6 , pp. 633 and 803–805.
6. ↑ ^{a b} List of analyzes | Laboratory crown. Retrieved October 10, 2017 (German). 
7. ↑ Verbalis JG, Goldsmith SR, et al. Hyponatraemia treatment guidelines 2007: expert panel recommendations. Am J Med. 2007; 120 (11A): S1-S21.

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