Rationale:The spontaneous migration of the peripherally inserted central catheter (PICC) is the displacement of the PICC tip from a satisfactory documented position in the superior vena cava (SVC) into its adjacent veins after several days or months of PICC insertion, and most frequently occurs in the ipsilateral internal jugular vein. However, it is rarely reported to detect migration of PICC tip into the azygos vein in patients who suffered from gastrointestinal dysmotility after abdominal surgery. We report 2 cases of spontaneous malposition of PICC into the azygos vein here and discuss the predisposing factors and processing procedures of this condition.Patient concerns:Two female patients with pancreatic disease were inserted PICCs on the left limbs before the abdominal surgery. After the surgery, 1 patient suffered from gastroparesis, and the other suffered from constipation. The nurses found that blood could not be aspirated from the PICCs while normal saline could be injected through the PICCs smoothly.Diagnoses:We identified the position of the PICC tip step-by-step, using ultrasound, intracavitary electrocardiogram, and chest X-ray, and confirmed that the tip of the PICC migrated into the azygos vein.Interventions:The patients were placed in the semi-reclining position from the supine position, and blood could be easily aspirated from the PICC after flushing with the push-pause flush technique. Intracavitary electrocardiogram displayed the elevated P, indicating that the PICC tip reentered the SVC and was at the lower 1/3 of SVC.Outcomes:The PICCs of the 2 patients functioned well afterward and were removed after the parenteral nutrition support was completed.Lessons:It is critical to assess the function of the PICC before every time of infusion. For patients who undergo abdominal surgery with PICC on the left side, when they had gastrointestinal dysmotility combined with PICC dysfunction, the possibility of spontaneous migration of PICC tip into the azygos vein should be considered.