A 72-year-old man comes to the physician for vague lower right quadrant pain for 3 months and foul-smelling urine. There is mild tenderness of the lower right quadrant. Hematocrit is 30%. Urinalysis shows 100 WBC/hpf and 4+ bacteria. Urine culture shows mixed flora. Test of stool is positive for occult blood. He has darkening of the skin of the forearms. Serum potassium is 5.4 mEq/L. Which of the following is the most likely diagnosis?
Addison disease
Amebiasis
Diverticulitis
Neoplasia
Ulcerative colitis
