Differential Diagnosis for Unilateral Cyanosis post Sepsis and UTI without Vasopressors

• Single most likely diagnosis:
  • Pulmonary embolism: This condition is a common cause of unilateral cyanosis, especially in the context of recent sepsis and UTI, which can increase the risk of thromboembolic events. The lack of vasopressor use reduces the likelihood of certain other causes.
• Other Likely diagnoses:
  • Pneumonia: Aspiration or infectious pneumonia can cause unilateral lung involvement leading to cyanosis, particularly if the infection is severe enough to cause significant hypoxia.
  • Atelectasis: Collapse of a lung segment or lobe can lead to decreased oxygenation and unilateral cyanosis, especially in a post-septic patient who may have been immobile or had decreased respiratory effort.
  • Pleural effusion: A significant pleural effusion, possibly as a complication of sepsis or UTI, can cause lung compression and lead to decreased oxygenation on the affected side.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Pulmonary thrombosis or thromboembolism with paradoxical embolism: Although less common, if a patient has a patent foramen ovale, a pulmonary embolism could lead to paradoxical embolism, causing systemic embolization, including to the cerebral or coronary circulation.
  • Acute coronary syndrome: While less directly related to unilateral cyanosis, myocardial infarction can lead to cardiogenic shock and affect oxygenation indirectly. It's crucial to consider in any patient with recent sepsis and signs of hypoxia.
• Rare diagnoses:
  • Anomalous pulmonary venous connection or other congenital heart defects: These conditions can cause cyanosis but are less likely in an adult presenting with new-onset symptoms post-sepsis and UTI.
  • Unilateral diaphragmatic paralysis: This could potentially cause atelectasis or decreased lung expansion on one side, leading to hypoxia and cyanosis, but it's a less common complication of sepsis or UTI.