Missed retro-arterial (eparterial) bronchus in automated 3D modelling during robotic left upper lobectomy.

Pre-operative planning is crucial before minimally invasive lung resection. 3D reconstruction software has become an essential tool to identify anatomical variations and anticipate surgical difficulties. Nevertheless, a misinterpretation can make surgery more challenging, especially in the presence of anatomical anomalies such as a cleft left upper lobe. A 74-year-old woman was treated for an adenocarcinoma in the left upper lobe. Multidisciplinary discussion recommended robotic assisted left upper lobectomy. At first, pre-operative 3D reconstruction showed no anomalies. Intra-operatively, dissection revealed an unusual culmen bronchus (B1+3) arising posterior to the pulmonary artery trunk, so-called "cleft" left upper lobe or "eparterial" bronchus. This lesser-known variant had not been identified pre-operatively by automated software, creating temporary intra-operative uncertainty. The dissection was adapted, and lobectomy was successfully completed. A retrospective analysis of the 3D model made it possible to understand the error and to better appreciate the anatomical relationships of this bronchus. The post-operative course was uneventful and at 8-month follow-up the patient remained recurrence-free. This case highlights the importance of pre-operative imaging analysis, the limitations of automated 3D reconstruction, and the need for surgeon awareness of rare bronchial variants to ensure efficiency during minimally invasive surgery.