What is the appropriate diagnosis and treatment for a patient presenting with polydipsia, polyuria, insomnia, anxiety, back pain, and loss of balance?

Diagnostic Approach to Polydipsia, Polyuria, Insomnia, Anxiety, Back Pain, and Loss of Balance

This constellation of symptoms requires immediate evaluation for endocrine emergencies, particularly diabetes mellitus with possible diabetic ketoacidosis, hypercalcemia, or diabetes insipidus, as polydipsia and polyuria are red flags that demand urgent laboratory assessment. 1

Initial Urgent Laboratory Evaluation

The first priority is to rule out life-threatening metabolic derangements:

• Check serum glucose immediately to identify uncontrolled diabetes mellitus, as hyperglycemia with glucosuria is the most common cause of solute diuresis presenting with polydipsia and polyuria 1
• Obtain serum sodium, calcium, and potassium since hypercalcemia and electrolyte abnormalities can cause polyuria, back pain (from nephrolithiasis or bone disease), and neurologic symptoms including loss of balance 1
• Measure serum and urine osmolality to differentiate between solute diuresis and water diuresis 2
• Check renal function (creatinine, BUN) and urinalysis for proteinuria, hematuria, and glucosuria 1

Quantifying Polyuria

Complete a 3-day frequency-volume chart to document total 24-hour urine output and determine if nocturnal polyuria is present (>33% of 24-hour output occurring at night) 3, 1, 4. This objective measurement is essential before pursuing further diagnostic workup 3.

Differential Diagnosis Framework

If Hyperglycemia is Present:

• Diabetic ketoacidosis or hyperglycemic hyperosmolar state requires immediate insulin therapy, as polyuria is secondary to osmotic diuresis 1
• The anxiety, insomnia, and neurologic symptoms (loss of balance) may represent metabolic encephalopathy from severe hyperglycemia 3

If Hypercalcemia is Present:

• Back pain may indicate bone metastases, multiple myeloma, or primary hyperparathyroidism 1
• Hypercalcemia causes polyuria through tubular injury and can produce anxiety, insomnia, and ataxia 2

If Osmolality Studies Suggest Diabetes Insipidus:

• Perform water deprivation test to differentiate central from nephrogenic diabetes insipidus 2, 5
• Genetic testing for AVPR2 and AQP2 genes should be obtained early if nephrogenic diabetes insipidus is suspected 1
• Consider MRI of the pituitary if central diabetes insipidus is suspected, particularly if back pain suggests metastatic disease 3

If Primary Polydipsia is Suspected:

• Psychiatric patients with schizophrenia or anxiety disorders commonly develop polydipsia, which can progress to hyponatremia with confusion, lethargy, and seizures 6, 7
• Check serum sodium urgently as hyponatremia from water intoxication can cause the neurologic symptoms (loss of balance) and psychiatric symptoms (anxiety, insomnia) 6, 7
• More than 20% of chronic psychiatric inpatients may have polydipsia, with up to 5% experiencing water intoxication 7

Systematic Medical History Review (SCREeN Framework)

The European Association of Urology recommends assessing for conditions that commonly cause polyuria 3:

• Sleep disorders: Obstructive sleep apnea can cause nocturia and contributes to insomnia, anxiety, and daytime dysfunction 3. Ask: "Have you been told you gasp or stop breathing at night?" 3
• Cardiovascular: Congestive heart failure causes nocturnal polyuria from fluid redistribution. Ask: "Do you experience ankle swelling or shortness of breath when walking?" 3
• Renal: Chronic kidney disease impairs concentrating ability. Check for proteinuria and declining GFR 1
• Endocrine: Beyond diabetes mellitus, consider hyperthyroidism (causes anxiety, insomnia, polyuria), hypothyroidism (can cause balance problems), and testosterone deficiency 3
• Neurologic: Most neurologic diseases can cause nocturia and balance problems. Back pain with loss of balance raises concern for spinal cord compression 3

Medication Review

Review all medications that can cause polyuria: diuretics, calcium channel blockers, lithium, and NSAIDs 3, 1. Lithium specifically causes nephrogenic diabetes insipidus and can produce neurologic symptoms 2.

Red Flags Requiring Immediate Action

• Severe hyponatremia (sodium <120 mEq/L) from water intoxication can cause seizures and death 6, 7
• Diabetic ketoacidosis presenting with polyuria, polydipsia, nausea, and altered mental status requires ICU admission 3
• Back pain with loss of balance may indicate spinal cord compression requiring urgent MRI 3
• Hypercalcemia >14 mg/dL requires aggressive IV hydration and treatment of underlying cause 1

When to Refer

• Endocrinology consultation is recommended for confirmed or suspected diabetes insipidus, hypophysitis, thyroid disorders, or type 1 diabetes mellitus 3
• Nephrology referral if proteinuria, hypertension, or declining GFR is present 1
• Neurology referral if loss of balance persists after metabolic derangements are corrected 3

Critical Pitfalls to Avoid

• Do not assume diagnosis based on symptoms alone, as polyuria and polydipsia occur in both diabetes mellitus and diabetes insipidus 1
• Do not give desmopressin without confirming central diabetes insipidus, as it is ineffective and potentially harmful in nephrogenic diabetes insipidus or primary polydipsia 1
• Do not overlook psychiatric polydipsia in patients with anxiety, as this can progress to life-threatening hyponatremia 6, 7
• Do not dismiss insomnia as purely psychiatric until sleep apnea is excluded, as it commonly coexists with polyuria 3