Diabetes insipidus is a condition characterized by the excretion of large amounts of dilute, low-specific-gravity urine due to a deficiency of antidiuretic hormone (ADH) or the kidneys' inability to respond to ADH. This disorder can be divided into two main categories: central diabetes insipidus and nephrogenic diabetes insipidus. Central diabetes insipidus is caused by a deficiency of ADH and can be further classified as primary or secondary. The cause of primary diabetes insipidus is unknown, though a small number of cases may be hereditary. Secondary diabetes insipidus can result from intracranial tumors (such as craniopharyngioma), skull base fractures, intracranial surgery, radiation therapy, histiocytosis X, or central nervous system infections. Nephrogenic diabetes insipidus may occur due to congenital unresponsiveness of renal medullary adenylate cyclase to ADH or various conditions affecting the renal medulla and collecting ducts, such as hypokalemia, hypercalcemia, obstructive nephropathy, or the use of certain medications (e.g., lithium, outdated tetracycline, amphotericin B).

bubble_chart Clinical Manifestations

The urine output increases, with little daily variation, and children may exhibit enuresis. Along with increased urine output, there is polydipsia and excessive drinking. In infancy, if water intake is insufficient, fever, dysphoria, dehydration, and even spasms may occur. Secondary cases may also show manifestations of the primary disease.

bubble_chart Auxiliary Examination

1. Blood and urine tests Blood osmolality is normal or increased, urine osmolality <200mOsm/L，比重常在1.001～1.005，在限水情況下一般也不超過1.010
2. Water deprivation test Generally used for older children, it can differentiate between psychogenic polydipsia and true diabetes insipidus. After 6–12 hours of water deprivation, if urine output decreases and specific gravity increases, it indicates psychogenic polydipsia. If urine output fails to decrease, urine osmolality does not exceed 300 mOsm/L (specific gravity approximately 1.010), or body weight decreases by more than 3%, it indicates true diabetes insipidus. If dysphoria, dehydration, or a weight loss of more than 3% occurs during the test, it should be promptly discontinued.
3. Vasopressin treatment test Used to differentiate between central and nephrogenic diabetes insipidus. Intramuscular injection of water-soluble vasopressin at 0.1 U/kg is administered. If urine output decreases and specific gravity reaches 1.015, it indicates central diabetes insipidus. If there is no change after injection, it indicates nephrogenic diabetes insipidus.
4. Other tests For secondary cases, investigate the underlying cause, such as fundus and visual field examinations, lateral and anteroposterior X-rays of the sella turcica, and cranial CT scans.

bubble_chart Treatment Measures

(1) Central diabetes insipidus

1. Replacement therapy: Injectable vasopressin tannate (long-acting diabetes insipidus stop) 1-2U/dose can maintain efficacy for 24-72 hours, so it can be injected once every 2-3 days. DDAVP <1-脫氨-8-右旋精氨酸)鼻腔滴入，每次1.25～10μg，能維持效力12～24小時。或吸入垂體後葉素粉劑15～25mg/次(鼻腔吸入)。近年也有人應用彌凝(minimin )，口服，取得較好效果。
2. Non-hormonal adjuvant therapy: Chlorpropamide 150-250mg/(kg·d) orally divided into 2 doses; Hydrochlorothiazide 1-2mg/(kg·d) orally; or Clofibrate 50mg/(kg·d) divided into 2-3 doses.

(2) Nephrogenic diabetes insipidus

In addition to treating the primary disease, hydrochlorothiazide can be given orally. Pay attention to providing a low-salt diet and avoid excessive protein intake. Children with diabetes insipidus should be provided with adequate water.

bubble_chart Differentiation

After confirming diabetes insipidus, further water deprivation and vasopressin tests are conducted to differentiate between true diabetes insipidus or psychogenic polydipsia, central diabetes insipidus or nephrogenic diabetes insipidus. Medical history, physical examinations, or other necessary tests are also referenced to identify any underlying primary conditions causing diabetes insipidus.