Aim: We hypothesized that the quality of the assessment of abnormal laboratory data in the emergency department (ED) could affect the hospital-attending physicians' decision-making after a patient's hospitalization. To test this hypothesis, we investigated how patients with a positive D-dimer result were reported by ED physicians in electronic medical records, and measured whether lower extremity venous ultrasonography examination was undertaken during hospitalization by the hospital-attending physicians. Methods: In an urban tertiary acute care general hospital in Japan, between January 2012 and December 2013, we included patients hospitalized after a positive D-dimer measurement (≥1.0 µg/mL) that was taken in the emergency department. We retrospectively measured the quality of ED physician assessments. Then we examined whether that affected the decisions of attending physicians to order lower extremity venous ultrasonography examinations during hospitalization. The exposure variable was the quality of the ED physicians' assessment of patients with positive D-dimer results. The outcome was whether a lower extremity venous ultrasonography examination was ordered by the attending physician during hospitalization. Results: When assessments were described by ED physicians for patients with positive D-dimer results, the attending physicians frequently ordered lower extremity venous ultrasonography (odds ratio, 10.74; 95% confidence interval, 5.92-19.50), even if the assessments only contained "copied and pasted" laboratory data (odds ratio, 1.68; 95% confidence interval, 2.10-2.40). Conclusions: Better documentation by ED physicians, regarding patients with positive D-dimer results, strongly affected the decisions made by attending physicians to order lower extremity venous ultrasonography examination.