Best answer: cholelithiasis (symptomatic gallstones). Sickle cell disease predisposes to black pigment stones, and recurrent similar episodes of RUQ pain radiating to the shoulder with no fever and normal vital signs fit symptomatic gallstones. However, the sources define biliary colic as lasting < 6 hours, while pain lasting > 6 hours points to acute cholecystitis, and this pain has lasted 3 days. The stem therefore partly fits acute cholecystitis (C), although that would usually come with fever and a Murphy sign.