A 34-year-old man was admitted for evaluation of worsening pedal edema. He was apparently healthy until four years back, when he developed edema of both feet and nonpruritic macular skin rash involving both lower limbs. Subsequently, he was detected to have hypertension, proteinuria and mild renal failure (6 months ago). He had no history of arthralgia, Raynaud's phenomenon, paraesthesia or gastrointestinal hemorrhage.
Six weeks prior to admission in our centre, he developed weakness of left upper and lower limbs with slurring of speech and was hospitalized elsewhere. A computerized tomographic scan of head had revealed an infarct in the right middle cerebral artery territory and he was treated with aspirin, statins, and antihypertensives. He made a complete recovery but was detected to have renal failure and was referred to us for further evaluation.
He weighed 74 kg and had a height of 174 cm. He had pallor and bilateral pitting pedal edema. There was no skin rash or lymphadenopathy. Blood pressure was 140/90 mmHg. Examination of cardiovascular system, respiratory system, and abdomen was normal. There were no neurological deficits.
Investigations revealed hemoglobin of 8.79 gm/dL, platelet count of 112000/mm3, total WBC count of 7960/mm3 - with a normal differential count, ESR of 40 mm at end of first hour. Urinalysis showed protein ++++, 6-8 RBCs/HPF; and 24 hour urine protein was 4420 mg. Blood urea was 72 mg/dL and serum creatinine was 3.1 mg/dL with normal serum levels of electrolytes. Liver function tests, PT and aPTT were normal. Serum albumin was 3.6 gm%, serum globulin 3.8 g/dL and serum cholesterol 240 mg/dL. Serum protein electrophoresis was normal. Blood and urine cultures were sterile. HBsAg, antihepatitis C virus (HCV) and HIV antibodies were negative VDRL, cANCA, pANCA, antiphospholipid antibodies, ANA, antids DNA were negative. Serum homocysteine [12 碌mol/L] was normal and serum complement levels were reduced (C3:70 mg/dL, C4:18 mg/dL). Serum cryoglobulin assay was positive. On PAGE electrophoresis, the mobility was suggestive of mixed cryoglobulins. HCV RNA was negative in serum [polymerase chain reaction (PCR)]. Qualitative analysis for HCV RNA [by reverse transcriptase-PCR (RT-PCR)] in the cryoprecipitate was negative []. Doppler study of extra cranial carotid and vertebral vessels was normal. Ultra sonogram of abdomen, ECG, and echocardiogram were normal. Bone marrow examination was normal. X-rays of chest, skull spine, and pelvis were normal. Kidney biopsy showed lobular accentuation of glomeruli with mesangial proliferation, mild endocapillary proliferation, and double contour of glomerular basement membrane on light microscopy. Intracapillary eosinophilic PAS positive hyaline deposits were noted []. Interstitium showed mononuclear infiltrates. Immunofluorescence showed mesangial and capillary granular positivity for C3 IgG and IgM.

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 34 years old. 
The concentration of creatinine is 3.1 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 174.0 cm, which is 174.0 cm * 1 m / 100 cm = 1.74 m. The patient's weight is 74.0 kg. The patient's bmi is therefore 74.0 kg / (1.74 m * 1.74 m) = 24.442 kg/m^2.The patient's BMI is 24.4, 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 69.559 kg.

Using the Cockcroft-Gault equation:
CrCl = ((140 - age) * adjusted weight * gender_coefficient) / (serum creatinine * 72).
Plugging the patient's values gives us ((140 - 34) * 69.559 * 1) / (3.1 * 72) = 33.034 mL/min. Hence, the patient's creatinine clearance is 33.034 mL/min.