Mr. W is a 63-year-old male, who visited his family physician with a one-month history of increased urination which wakes him up several times at night and frequently drinking water.  Four months prior to this visit, he was involved in a motor vehicle accident (MVA) and admitted to the hospital in a post-concussion state due to head trauma. A week after, he completely recovered and was discharged. He had never smoked and is occasionally a social drinker. His family medical history is insignificant.

On examination:

• Height: 182 cm, Weight: 78 Kg, BMI: 23.5
• B/P: 124/70 mmHg, Heart rate: 96/min, Respiratory rate: 16/min, Temperature: 36.8⁰C, O₂SAT: 96%

Which of the following statements is correct regarding urine osmolarity?

Mr. W laboratory tests showed:

• Blood analysis:
  • CBC:
    • RBCs: 6.0 x 10¹²/L, Hemoglobin: 150.5 g/L, Hematocrit: 0.60,
    • MCV: 89 fL, MCH: 31 pg, RDW: 12.0%, Reticulocytes: 1%, ESR: 11 mm/hour
    • WBC: 6.5 x 10⁹/L, (Neutrophils: 3.1 x 10⁹/L, Lymphocytes: 3.2 x 10⁹/L, Basophils: 0.07 x 10⁹/L, Eosinophils: 0.31 x 10⁹/L, Monocytes: 0.7 x 10⁹/L)
    • Platelet counts: 206 x 10⁹/L
  • Na: 152 mmol/L, K: 5.0 mmol/L, Cl: 111 mmol/L, Ca (total): 2.4 mmol/L, Ca (ionized): 1.2 mmol/L
  • Glucose: 6.0 mmol/L, HbA1c: 5.7%, BUN: 8.9 mmol/L, Creatinine: 120.0 µmol/L, Uric acid: 320 mmol/L
  • Triglycerides: 2.0 mmol/L, Cholesterol: 5.1 mmol/L, HDL: 1.0 mmol/L, LDL: 2.1 mmol/L
  • Bilirubin: 16 mmol/L, Albumin: 38 g / L, AST: 22 U/35L, ALT: 34 U/L
  • TSH: 1.2 µU/mL, Total T₄: 80.2 nmol/L, Free T₄: 11 pmol/L, Total T₃: 2.1 nmol/L, Free T₃: 5.0 pmol/L
  • Serum cortisol (8 am): 327 nmol/L, Aldosterone (recumbent): 0.13 nmol/L, Renin activity: 1.3 ug/L/hr
  • Plasma Arginine Vasopressin: 0.46 pmol/L
  • Plasma osmolarity: 320 mOsmol/kg
• Urinalysis:
  • Color: clear watery, pH: 7.1, Specific gravity: 1002, Osmolarity: 112 mOsmol/kg; Glucose, Ketones, Albumin, Bilirubin: negative, WBCs and RBCs: 1 and 2/HPF, Epithelial cells, Casts, Bacteria, Yeast: negative

How can you interpret Mr. W.’s plasma and urine osmolarity?

Water deprivation test was conducted. The following are readings of body weight, plasma osmolarity, and urine osmolarity prior to the test and 6 hours after cessation of fluid intake:

	Baseline Time	6 hours
Weight (kg)	78	76.3
Plasma osmolarity (mOsmol/kg)	319	325
Urine osmolarity (mOsmol/kg)	112	115

According to the test results, what is the most likely diagnosis of Mr. W’s condition?

Two µg of desmopressin (DDAVP) were injected intramuscularly and urine was collected for 4 hours. Urine osmolarity became 738 mmol/Kg This test result indicates that Mr. W. has cranial diabetes insipidus:

_____________ is responsible for the reabsorption of water in the distal renal tubules and the collecting ducts and synthesized by the _____________. (Fill in the blanks)

What are the complications of diabetes insipidus? (select all that apply)