This case describes an older adult patient with generalized abdominal pain who was eventually diagnosed with inoperable bowel necrosis. Although she appeared well and had stable vital signs, triage was delayed due to emergency department (ED) crowding, which is usually a result of hospital crowding. She was under-triaged and waited three hours before any diagnostic studies or interventions commenced. Once she was placed on a hallway gurney laboratory and imaging studies proceeded hastily.

A 65-year-old man with metastatic liver disease presented to the hospital with worsening abdominal pain after a partial hepatectomy and development of a large ventral hernia. Imaging studies revealed perforated diverticulitis. A goals-of-care discussion was led by the palliative care service; the patient and his designated decision-makers chose to pursue non-operative management of diverticulitis.

A 61-year-old women with a mechanical aortic valve on chronic warfarin therapy was referred to the emergency department (ED) for urgent computed tomography (CT) imaging of the right leg to rule out an arterial clot. CT imaging revealed two arterial thromboses the right lower extremity and an echocardiogram revealed a thrombus near the prosthetic heart valve. The attending physician ordered discontinuation of warfarin and initiation of a heparin drip.

Diagnostic error has been increasingly recognized as an important and evolving patient safety issue. This Primer applies well-established principles of diagnostic error and improvement of diagnostic accuracy to the topic of COVID-19.

A 71-year-old frail, non-ambulatory woman presented to the emergency department with fever, sweating and dry cough. Her work-up included non-specific evidence of infection but two negative COVID-19 tests. No source of infection was identified, and she was discharged home after three days.