Safe hepatectomy in patients with constitutional indocyanine green excretory defect: two case reports highlighting multimodal functional assessment.

Introduction and importance: Constitutional indocyanine green (ICG) excretory defect is a rare condition characterized by markedly impaired ICG clearance despite preserved conventional liver function. This discrepancy makes the preoperative assessment of hepatic functional reserve difficult. We report two patients with hepatocellular carcinoma (HCC) and constitutional ICG excretory defect who underwent hepatectomy based on multimodal functional assessment. Case presentation: Case 1 was a 71-year-old man with a 40-mm HCC involving segments 5 and 8. The indocyanine green retention rate at 15 minutes (ICGR15) was 94.3%, whereas other liver function tests were preserved. Galactosyl human serum albumin (GSA) scintigraphy and fibrosis-related markers supported adequate hepatic reserve, and right anterior sectionectomy was safely performed. Case 2 was an 80-year-old man with a 30-mm recurrent HCC in segment 4, contacting the middle hepatic vein. Although ICGR15 was markedly elevated at 80.0%, conventional liver function tests and GSA scintigraphy suggested acceptable hepatic reserve. Extended left hepatectomy was performed without postoperative liver failure. Clinical discussion: These cases illustrate that markedly elevated ICGR15 does not necessarily indicate impaired hepatic functional reserve in patients with a constitutional ICG excretory defect. When ICGR15 is disproportionately elevated relative to conventional liver function, alternative assessment methods are required. GSA scintigraphy may help guide surgical decision-making in this rare condition. Conclusion: A constitutional ICG excretory defect should be suspected when ICGR15 is markedly elevated despite preserved liver function. In selected patients, hepatectomy may be feasible when the surgical indication is determined using multimodal functional assessment, particularly GSA scintigraphy.