A 67-year-old man in good health reported numbness and weakness of his lower legs in June 2010. He presented to the clinic due to the spread of the symptoms to his upper limbs. Magnetic resonance imaging revealed multiple lacuna infarctions. Laboratory analysis revealed anemia (hemoglobin [Hb], 9.8 g/dL) and renal dysfunction (creatine, 2.7 mg/dL). He was admitted to a nearby hospital for further examination and was diagnosed with hypertension and multiple mononeuropathy. In addition, laboratory findings revealed increased levels of C-reactive protein (CRP, 16.82 mg/dL). After 8 days in the hospital, severe right-flank pain suddenly occurred, and anemia worsened (Hb, 6.8 g/dL). Abdominal computed tomography (CT) without enhancement revealed a right perirenal hematoma. He was then transferred to our hospital for investigation and treatment.
On admission, his height was 156.0 cm, and his weight was 54.5 kg (approximately 2-kg loss over months). His blood pressure was 192/114 mm Hg; pulse, 98 bpm; and body temperature, 37.1 ℃. On physical examination, palpebral conjunctiva was pallid, and he had severe right-flank pain with muscular defense. No skin rush was evident in the extremities, although hypesthesia was detected by neurologic examination. Laboratory findings on admission are presented in Table . The results of the urine tests were as follows: protein levels, 2.4 g/g⋅Cr; occult blood 3+ by dipstick test; red blood cells ≧ 100/high-power field; and sediment contained granular cast 2+ . The results of serum examinations were as follows: white blood count, 13,610/µL (with 74.0% neutrophils and 16.0% eosinophils); hemoglobin, 6.2 g/dL; platelet count, 32.1 × 104/µL; alkaline phosphatase, 1,867 IU/L; γ-glutamyl transpeptidase (γ-GTP), 360 IU/L; blood urea nitrogen, 39 mg/dL; Cr, 1.3 mg/dL; erythrocyte sedimentation rate, 156 mm; C-reactive protein, 11.5 mg/dL; immunoglobulin (Ig) G, 2533 mg/dL; IgA, 306 mg/dL; IgM, 106 mg/dL; C3, 83 mg/dL; C4, 15 mg/dL; and CH50, 48 U/mL. ANA, PR3-ANCA, MPO-ANCA, anti-GBM antibody, and HBs-antigenemia were not detected. Contrast-enhanced CT revealed bilateral pleural effusion, right small renal infarction, and right perirenal hematoma. CT angiography revealed multiple small aneurysmal dilatations in the intrarenal branches of the bilateral renal arteries and the intrasplenic branches of the splenic artery (Fig. a–c). Emergency selective coil embolization was conducted to the right renal artery aneurysm, which was responsible for the bleeding (Fig. ). To obtain a definitive diagnosis, we performed a left sural nerve biopsy (Fig. ). We confirmed a small arterial occlusion with inflammatory cell infiltration in the sural nerve tissue, although a histological examination did not reveal fibrinoid necrosis or granuloma. Collectively, and based on his clinical and radiographic findings, we diagnosed polyarteritis nodosa.
On the fifth hospital day, we started oral prednisolone therapy at 40 mg/day. On the 8th and 15th hospital days, intravenous methylprednisolone pulse (500 mg/day) therapy was started for 3 consecutive days. Although these therapies suppressed the disease activity, including inflammatory response, urine protein, and pleural effusion, the patient failed to achieve remission. Intravenous pulse cyclophosphamide therapy was, therefore, given on the 30th day. Clinical symptoms such as numbness and weakness of limbs gradually diminished, and laboratory findings dramatically improved. Moreover, contrast-enhanced CT revealed the disappearance of pleural effusion and the decreased size of perirenal hematoma concomitant with aneurysms. The patient was then transferred to another hospital for rehabilitation training (Fig. ).
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 67 years old. 
The concentration of creatinine is 2.7 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 156.0 cm, which is 156.0 cm * 1 m / 100 cm = 1.56 m. The patient's weight is 54.5 kg. The patient's bmi is therefore 54.5 kg / (1.56 m * 1.56 m) = 22.395 kg/m^2.The patient's BMI is 22.4, 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 53.259 kg.

Using the Cockcroft-Gault equation:
CrCl = ((140 - age) * adjusted weight * gender_coefficient) / (serum creatinine * 72).
Plugging the patient's values gives us ((140 - 67) * 53.259 * 1) / (2.7 * 72) = 20.0 mL/min. Hence, the patient's creatinine clearance is 20.0 mL/min.