Diabetes & The Body

Polyuria And Polydipsia: Only In Diabetes Mellitus?

Diabetes mellitus is the commonest cause of polyuria and polydipsia. But clinical observation has shown that diabetes insipidus could also be a potential cause of the disease. Precisely because of this reason, it is often said that the physician should bear this in mind when diagnosing polyuria/polydispsia.

This would help in avoiding the delay in detecting the disease as missing the diagnosis can lead to needless suffering by patients and their families. A failure in making a timely diagnosis can result in severe dehydration with irreversible brain damage or even death.

There have been numerous instances of missed diagnosis of polyuria/polydipsia because the physicians didn’t take into account the possibility of diabetes insipidus as a possible cause. This not only increases the suffering of the patient but delays the right treatment and hence cure.

Research into DI is improving day by day and this also helps in understanding the pathogenesis of polyuria/polydipsia. Hence it is important for the doctors to keep in touch with the latest research happening in the field of diabetes research. The bottom line is that it might help in providing the right and modern treatment at the earliest.

Types of DI

The term Diabetes Insipidus refers to an abnormal state of water diuresis (passage of excess urine), as opposed to an abnormal state of osmotic diuresis, as in diabetes mellitus. DI is characterized by a large volume of dilute urine associated with increased fluid intake (polydipsia).

It is now known that there are four types of DI:

1. Neurogenic (or central) DI, where the water diuresis results from a deficiency of the antidiuretic hormone (ADH), often referred to as AVP (arginine vasopressin);
2. Nephrogenic DI, where water diuresis results from an inability of the kidneys to respond to ADH;
3. Primary polydipsic DI (or primary polydipsia) in which the water diuresis is due to suppression of ADH by excessive fluid intake [the high intake can result from abnormal thirst (dipsogenic DI), from psychological or emotional disturbances (psychogenic DI) or from fashionable - but scientifically unproven - beliefs in the benefits of a high fluid intake (iatrongenic DI)];
4. Gestagenic DI, which occurs only during pregnancy and is due to destruction of vasopressin by the placenta.

Factors Causing DI

Given below are the generally observed causes of Diabetes Insipidus:

• Neurogenic: acquired: brain tumors; head trauma; granulomatous diseases; autoimmunity; idiopathic inherited: autosomal dominant or recessive mutation in the vasopressin gene; X-linked recessive mutation in an unknown gene
• Nephrogenic: acquired: hypokalemia; hypercalcemia; lithium inherited: X-linked recessive mutation in vasopressin receptor; autosomal recessive or dominant mutation in water channel
• Polydipsic: acquired: idiopathic (most); chronic meningitis; granulomatous diseases; multiple sclerosis or other diffuse pathology of the brain; psychiatric illness
• Gestagenic: acquired: pregnancy

Urinary frequency, excess urination at night, bedwetting, and frequent or constant thirst should arouse suspicion of DI.

In infants: Inconsolable crying, unusually wet diapers, frequent nursing often accompanied by fever, dry skin with cool extremities suggest the possible presence of DI.

Only a thorough diagnosis based on strict guidelines can rule out the possibility of diabetes mellitus as a cause of polyuria/polydipsia. The simple clinical test to confirm the absence of diabetes mellitus would be to use a Dipstick test in urine.

It is also important to look for the cause of DI. If it began during infancy or childhood or affects other family members, means a lot in the diagnostic process.