Review Question - QID 213543

A 57-year-old man is sent to the emergency department by his primary care physician for hypertension. He was at a general health maintenance appointment when his blood pressure was found to be 180/115 mmHg; thus, prompting his primary doctor to send him to the emergency room. The patient is otherwise currently asymptomatic and states that he feels well. The patient has no other medical problems other than his hypertension and his labs that were drawn last week were within normal limits. His temperature is 98.3°F (36.8°C), blood pressure is 197/105 mmHg, pulse is 88/min, respirations are 14/min, and oxygen saturation is 99% on room air. Physical exam is unremarkable. Laboratory values are redrawn at this visit and shown below.

Hemoglobin: 15 g/dL
Hematocrit: 46%
Leukocyte count: 3,400/mm^3 with normal differential
Platelet count: 177,000/mm^3

Serum:
Na+: 139 mEq/L
Cl-: 102 mEq/L
K+: 4.0 mEq/L
HCO3-: 24 mEq/L
BUN: 29 mg/dL
Glucose: 139 mg/dL
Creatinine: 2.3 mg/dL
Ca2+: 10.2 mg/dL

Which of the following is the most likely diagnosis?