Application of a sodium alginate hydrogel for clear preoperative endoscopic marking using India ink

Preoperative marking or tattooing is performed in clinical situations using an India ink to identify gastrointestinal lesions. However, diffusion of the carbon particles from the ink results in unclear marking. We observed that subcutaneously injected sodium alginate solutions formed a gel and prevented the diffusion of carbon particles into the tissues of mice. Similar results were observed in resected porcine large intestines. The tattooed area was well correlated with the molecular weight and viscosity of sodium alginate, indicating that an adequately viscous sodium alginate hydrogel is useful for clear marking.