A 56-year-old man was admitted to the renal unit of the tertiary university hospital with symptoms of polyuria with nocturia, and polydipsia with severe thirst for the past 2 months. Initially, the patient visited a local clinic and was diagnosed as type 2 DM with a fasting blood sugar, 150mg/dL. Despite being controlled hyperglycemia with an oral hypoglycemic agent, he continued drinking daily more than 8 L of cold water (about 10 bottles of refrigerated water, 750 ml capacity) and passed large amounts of urine frequently. He had no specific history including head trauma or mental disorder, and denied any pertinent family history. The patient showed no signs of systemic illness such as fever or arthralgia, or neurologic symptoms involving the central nervous system. He has been working as a gardener with 176 cm in height and 68 kg in weight (71 kg before this event). The physical examination was unremarkable with blood pressure of 132/70 mmHg, pulse rate of 80/min, respiratory rate of 16/min, and temperature of 36.8鈩. In the laboratory findings, his white blood cell count was 9,700/mm3; hemoglobin, 13.4 g/dL; platelet, 376脳103/mm3; sodium, 140 mEq/L; potassium, 3.8 mEq/L; blood urea nitrogen (BUN), 12 mg/dL; creatinine, 1.0 mg/dL and osmolality 295 mOsm/kg water. HbA1c was 7.2% and post-prandial glucose was checked around 180mg/dl with fasting blood sugar of 140 mg/dL. In urine analysis, the urine pH was 6.0; specific gravity 1.006; albumin (-); glucose (-); WBC 0-4/HPF; RBC 0-2/HPF, and osmolality 140mOsm/kg water. Fluid intake and output in 24 hours recorded 9 L in oral water intake from water containers and 11.7 L in urine output. In hormone assays, ACTH was 25.2 pg/mL (reference value, 6.0-76.0 pg/mL), prolactin 8 碌g/L (reference value, 0-15 碌g/L), cortisol 9.8 碌g/dL (referencel value, 5-25 碌g/dL), hGH 2.26 ng/mL (reference value, 0.5-17 ng/mL), and TSH 0.99 碌U/mL (reference value, 0.5-4.7 碌U/mL). Also, angiotensin converting enzyme (ACE) activity was within normal range (reference value, <40 U/L).
On hospital day 5, the patient underwent a water deprivation test according to the method of Miller-Moses test because of persistent polydipsia and polyuria despite blood glucose control. The results are shown in . During dehydration, the patient lost 3kg (4.4% of body weight), and urine osmolality remained hypotonic below 130 mOsm/kg. Basal ADH level was 5.18 pg/dL, and the repeat ADH level following the stimulation by water deprivation was 3.95 pg/dL, which revealed no increment despite the increased serum osmolality up to 300 mOsm/kg from the baseline levels of 285 to 295 mOsm/kg. One puff (5 碌g) of desmopressin nasal spray resulted in the increase of urine osmolality to 266 mOsm/kg (>100% increase from the baseline level, 126 mOsm/kg) and in the marked reduction of urine output from 200-410 ml/hr to 44-60 ml/hr. These results were compatible with CDI,, whose causes would be mostly idiopathic because of normal findings in hypothalamus and hypophysis in magnetic resonance imaging (MRI) scan of sella ().
On discharge (hospital day 9), the dose of desmopressin nasal spray (minirin nasal spray庐) was adjusted to 1 puff per 12 hrs (10 碌g/day), and urine output was markedly reduced to below 2-3 L/day with no more intense thirst. Also, DM was controlled with fasting blood sugar below 115 mg/dL by metformin (novamet GR庐 500mg bid) and American Diabetes Association (ADA) recommended diet.
The formula for computing Cockcroft-Gault is given by CrCl = ((140 - age) * adjusted weight * (gender_coefficient)) / (serum creatinine * 72), where the gender_coefficient is 1 if male, and 0.85 if female. The serum creatinine concentration is in mg/dL.
The patient's gender is male, which means that the gender coefficient is 1.
The patient is 56 years old. 
The concentration of creatinine is 1.0 mg/dL. 
The formula for computing the patient's BMI is (weight)/(height * height), where weight is the patient's weight in kg and height is the patient's height in m.
The patient's height is 176.0 cm, which is 176.0 cm * 1 m / 100 cm = 1.76 m. The patient's weight is 68.0 kg. The patient's bmi is therefore 68.0 kg / (1.76 m * 1.76 m) = 21.952 kg/m^2.The patient's BMI is 22.0, indicating they are normal weight.
Because the patient is normal, we take take minimum of the ideal body weight and the patient's body as the patient's adjusted weight for the Cockroft-Gault Equation. Hence, the adjusted body weight is the minimum of the two giving us an adjusted body weight of 68.0 kg.

Using the Cockcroft-Gault equation:
CrCl = ((140 - age) * adjusted weight * gender_coefficient) / (serum creatinine * 72).
Plugging the patient's values gives us ((140 - 56) * 68.0 * 1) / (1.0 * 72) = 79.333 mL/min. Hence, the patient's creatinine clearance is 79.333 mL/min.