=====SIADH=====
(Syndrome of Inappropriate ADH secretion)
  *Most common = secondary to other disease process.
  *Hereditary SIADH, (nephrogenic SIADH) - mutation in vasopressin 2 (V2) receptors in the kidneys
  *variously caused by excessive Vasopressin (exogenous or ectopic) or increased sensitivity to Vasopressin as well as unknown mechanisms.

^  Secondary causes of SIADH  ||
^Respiratory |• pneumonia commonly causes SIADH by unknown mechanism\\ • asthma, atelectasis and pneumothorax |
^CNS |• any CNS condition including stroke, malignancy, psychosis, infection\\ • trauma |
^Malignancy |• Small cell CA lung is the most common malig causing ectopic ADH production\\ • GIT and other malignancies are also associated with SIADH |
^Endocrine |• hypopituitarism and hypothyroidism |
^Surgery |• not uncommon after surgery. Possibly pain mediated mechanism |
^Drugs |• Most common: carbamazepine, oxcarbazepine, chlorpropamide, cyclophosphamide & SSRIs. |
^Other |• almost any other condition - HIV, automimmune diseases and inflammatory processes |

==Bartter and Schwartz criteria for SIADH:==
  *various versions which include different lab values, but essential elements:
  -Hyponatremia with hypo-osmolality
  -Continued renal excretion of sodium
  -Urine less than maximally dilute
  -Absence of clinical evidence of volume depletion
  -Correction of hyponatremia by fluid restriction

===Manifestation===
  *hyponatraemia and hypo-osmolality
  *may be asymptomatic depending on chronicity of development and causative background
  *severe cases:
    *Confusion, disorientation, delirium
    *Generalized muscle weakness, myoclonus, tremor, asterixis
    *hypo-reflexia, ataxia, dysarthria
    *Cheyne-Stokes respiration, pathologic reflexes
    *Generalized seizures, coma 

===Management===
  *depends on acuity of presentation
  *asymptomatic patients can usually be assumed to be chronic development and Mx includes fluid (water) restriction and diuretics. V2 antagonists occasionally
  *when development is acute and patient unwell, rate of correction of osmolality is critical
    *generally accepted, in most settings, correction of seNa+ at rate ≤1mmol/hr to avoid [[wiki:neurology:centralpontinemyelinolysis|Central Pontine Myelinolysis]]
    *hypertonic saline - usually 3%
    *water restriction
    *diuretics and V2 antagonists

==References include:==
[[https://www.ncbi.nlm.nih.gov/books/NBK507777/|SIADH review]]\\ 
[[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3183532/|SIADH review2]]\\ 
[[https://emedicine.medscape.com/article/246650-overview#a1|Emed SIADH]]\\