Incorrect. The stomach is located to the left, an ulcer is likely to cause upper left quadrant pain not right side pain.

Incorrect. Diaphragm hernia are often non-painful, and if there were diaphragm irritation it would typically refer to the shoulder girdle (the diaphragm is innervated by C3,4,5 via the phrenic nerve, levels that also innervate the shoulder, thus referring pain to that area). Additionally, due to the solid mass of the liver most diaphragmatic hernias occur around the esophageal hiatus and towards the left.    

Incorrect. While artery obstruction could cause ischemic injury, the inferior epigastric artery anastomoses with the superior epigastric artery such that a blockage of the interior is completely compensated for by supply from the superior. Thus, this blockage generates no symptoms.

Correct!  This would be a high suspicion given that the individual engaged in physical activities involving torso twisting in close proximity to the onset of the flank pain. The pain becoming worse in the afternoon is typical of muscle use during the day exasperating the injury, similarly the reduction in pain with rest/stillness when the muscle is not contracted is consistent.

Incorrect. Classic heart attack pain refers to the left shoulder or the epigastrium (T6 dermatome at the lower chest/upper abdomen). Heart attack would not be felt as pain on the right abdominal flank.

Incorrect. Rectus abdominal muscle strain would be felt towards the midline where the muscle is located. Also, the action of rectus abdominis is superior to inferior following the axis of the muscle (e.g. 'sit-ups'), while the patient reports stronger pain with torsional motion.

Incorrect. Pain to the right abdomen is always a suspicion for appendicitis. In this case the history of the weekend work implies possible muscle strain, similarly the relief of symptoms when the individual rests suggests a strain. Appendicitis wouldn't be expected to typically stop hurting with sitting/rest as the patient describes.