Definition:
Diabetes Insipidus (DI) is a disorder caused by a deficiency of antidiuretic hormone (ADH) or the kidneys’ inability to respond to ADH, leading to excessive urine output and dehydration (American Diabetes Association [ADA], 2022).
Types:
- Central (Neurogenic) DI – Caused by damage to the hypothalamus or pituitary gland (e.g., trauma, tumors, surgery, infections) (Hammer & McPhee, 2019).
- Nephrogenic DI – Kidneys do not respond to ADH due to genetic defects, kidney disease, or certain medications (e.g., lithium) (Jameson et al., 2022).
- Gestational DI – Occurs during pregnancy due to placental enzymes breaking down ADH (ADA, 2022).
- Primary Polydipsia – Excessive water intake suppresses ADH release, often associated with psychological disorders (McCance & Huether, 2019).
Signs and Symptoms
- Polyuria (excessive urination, >3 L/day)
- Polydipsia (excessive thirst)
- Nocturia
- Dehydration (hypotension, tachycardia, dry mucous membranes)
- Hypernatremia (due to water loss)
- Dilute urine (low specific gravity <1.005) (Jameson et al., 2022).
Diagnosis
- Water deprivation test – Differentiates between types of DI (McCance & Huether, 2019).
- Serum and urine osmolality
- ADH (vasopressin) levels
Treatment
- Central DI: Desmopressin (DDAVP) to replace ADH (Hammer & McPhee, 2019).
- Nephrogenic DI: Low-sodium diet, thiazide diuretics, NSAIDs (e.g., indomethacin) (Jameson et al., 2022).
- General Management: Monitor hydration, replace fluids, and monitor electrolytes, especially sodium (ADA, 2022).
NCLEX Key Points
✅ Monitor for dehydration and electrolyte imbalances (Hammer & McPhee, 2019).
✅ Encourage fluid intake unless contraindicated.
✅ Educate about medication adherence (e.g., desmopressin for Central DI).
✅ Watch for complications like hypovolemic shock and severe hypernatremia (Jameson et al., 2022).
SIADH vs. Diabetes Insipidus – Comparison Table for NCLEX-RN
| Parameter | SIADH (Syndrome of Inappropriate ADH Secretion) | Diabetes Insipidus (DI) |
|---|---|---|
| ADH Level | ↑ High (excessive release) | ↓ Low (central) or kidneys unresponsive (nephrogenic) |
| Serum Sodium (Na⁺) | ↓ Hyponatremia (<135 mEq/L) | ↑ Hypernatremia (>145 mEq/L) |
| Serum Osmolality | ↓ <275 mOsm/kg | ↑ >295 mOsm/kg |
| Urine Osmolality | ↑ >100 mOsm/kg (concentrated) | ↓ <200 mOsm/kg (diluted) |
| Urine Specific Gravity | ↑ >1.030 (concentrated) | ↓ <1.005 (diluted) |
| Urine Output | ↓ Low (oliguria) | ↑ Polyuria (>3 L/day) |
| Thirst | No intense thirst usually | ↑ Intense thirst (polydipsia) |
| Fluid Balance | Fluid retention (euvolemic/hypervolemic) | Dehydration, fluid loss |
| Treatment | – Fluid restriction – Hypertonic saline (3%) – Demeclocycline, Tolvaptan | – Fluid replacement – Desmopressin (DDAVP) – Treat underlying cause |
| Key Nursing Priorities | – Seizure precautions – Monitor for cerebral edema – Strict I&O | – Monitor for dehydration – Daily weight – Replace fluids and monitor sodium |
References
- American Diabetes Association. (2022). Standards of medical care in diabetes—2022. Diabetes Care, 45(Suppl. 1), S1–S264. https://doi.org/10.2337/dc22-SINT
- Hammer, G. D., & McPhee, S. J. (2019). Pathophysiology of disease: An introduction to clinical medicine (8th ed.). McGraw-Hill.
- Jameson, J. L., Fauci, A. S., Kasper, D. L., Hauser, S. L., Longo, D. L., & Loscalzo, J. (2022). Harrison’s principles of internal medicine (21st ed.). McGraw-Hill.
- McCance, K. L., & Huether, S. E. (2019). Pathophysiology: The biologic basis for disease in adults and children (8th ed.). Elsevier.