SIADH + DI

Question 1

What causes SIADH?

Answer 1

Excess production/release of ADH, most commonly from a tumor secreting ectopic ADH.

Question 2

What does ADH do in SIADH?

Answer 2

Promotes water retention, increasing fluid volume and diluting sodium.

Question 3

What electrolyte imbalance occurs in SIADH?

Answer 3

Hyponatremia (↓ Na) – hypotonic, water accumulates in cells, altering function.

Question 4

What is the pathophysiology of SIADH?

Answer 4

Excess ADH → water retention → ↑ intracellular fluid → diluted Na → hypotonic hyponatremia

Question 5

Clinical manifestations of mild SIADH?

Answer 5

• Decreased urine output (concentrated)
• Anorexia, nausea, vomiting
• Headache, irritability, disorientation, cramps, weakness

Question 6

Severe symptoms of SIADH (Na <110 mEq/L)?

Answer 6

Psychosis, gait disturbances, seizures, coma

Question 7

Diagnostic criteria for SIADH?

Answer 7

• Serum Na <135 mEq/L
• Plasma osmolality <280 mOsm/kg
• Decreased urine volume
• Concentrated urine with high sodium
• Absence of renal, adrenal, or thyroid abnormalities

Question 8

Mild SIADH treatment?

Answer 8

Water restriction: 800–1000 mL/day

Question 9

Severe SIADH treatment?

Answer 9

IV isotonic or hypertonic (3% NaCl) fluids

Question 10

Pharmacologic treatments for SIADH?

Answer 10

• Diuretics to remove excess fluid
• Demeclocycline – reduces kidney response to ADH (long-term therapy)

Question 11

Goal of treatment for SIADH?

Answer 11

Remove underlying cause and correct water/electrolyte imbalance.

Question 12

What is Diabetes Insipidus?

Answer 12

Disorder caused by insufficient ADH or kidney resistance to ADH, leading to inability to concentrate or retain water.

Question 13

What happens in DI?

Answer 13

Water cannot be retained → polyuria, dehydration, hypernatremia.

Question 14

What are the 4 major types of DI?

Answer 14

1. Central DI – low ADH production; 2. Nephrogenic DI – kidneys resistant to ADH; 3. Dipsogenic DI – excessive water intake; 4. Gestational DI – placental enzyme breaks down ADH during pregnancy

Question 15

Central DI causes?

Answer 15

Brain surgery, head trauma, tumor affecting pituitary gland.

Question 16

Nephrogenic DI causes?

Answer 16

Kidney disease, medications (e.g., lithium), genetic disorders.

Question 17

Dipsogenic DI causes?

Answer 17

Excessive water drinking, behavioral or psychiatric disorders.

Question 18

Gestational DI causes?

Answer 18

Placental enzyme breaks down ADH; usually resolves after delivery.

Question 19

Common signs of DI?

Answer 19

Polyuria, polydipsia, nocturia.

Question 20

Other symptoms of DI?

Answer 20

Signs of dehydration (dry mucous membranes, low BP) and hypernatremia (confusion, weakness).

Question 21

How is DI diagnosed?

Answer 21

History, physical exam, lab tests.

Question 22

Key lab findings for DI

Answer 22

• ↑ Serum Na
• ↓ Urine-specific gravity
• ↓ Urine osmolality

Question 23

what additional history for DI do you need to know?

Answer 23

Recent cranial surgery, trauma, pituitary tumor.

Question 24

First step in treatment for Central DI?

Answer 24

Treat underlying cause if possible.

Question 25

Fluid management for Central DI?

Answer 25

Oral hydration if possible; IV hypotonic fluids if needed.

Question 26

Medication for central DI

Answer 26

Desmopressin (DDAVP) – synthetic ADH analog. May be lifelong.

Question 27

Diet adjustments for nephrogenic DI

Answer 27

Low salt and low protein diet.

Question 28

Medications for Nephrogenic DI

Answer 28

Thiazide diuretics to reduce urine output.

Question 29

Treatment Approach for Dipsogenic DI?

Answer 29

Behavioral therapy to reduce excessive water intake.

Question 30

Additional support for Dipsogenic DI

Answer 30

May involve mental health professionals.

Question 31

Treatment for Gestational DI

Answer 31

Desmopressin (DDAVP).

Question 32

Prognosis for Gestational DI

Answer 32

Usually resolves after delivery.