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Background Refractory chylothorax after fenestrated total cavopulmonary connection (TCPC) is a serious complication in children with single ventricle physiology. Precise localisation of thoracic duct anatomy and site of disruption is essential when targeted intervention is required. Conventional intranodal contrast lymphangiography is invasive, technically demanding in small children, and typically requires general anaesthesia.Methods We reviewed two 6-year-old children with persistent high-output chylothorax after fenestrated TCPC. Both had drain losses >10–20 mL/kg/day despite conservative management including low-fat diet, nil by mouth, total parenteral nutrition, octreotide and/or aggressive diuresis. Awake non-contrast MR lymphangiography was performed on a 1.5T Siemens Sola using heavily T2-weighted lymphangiographic imaging of the thoracic venolymphatic spaces and 3D whole-heart imaging. Imaging was completed without sedation or contrast using audio-visual support and play therapist facilitation. Scan time was <20 minutes.Results Both scans were fully diagnostic without significant motion artefact. MR lymphangiography demonstrated thoracic duct laterality and precisely identified the site of leak in both children. Findings directly guided surgical thoracic duct ligation. In one child, this enabled successful re-intervention after failed non-targeted thoracic duct ligation and pleurectomy. In both patients, drain output became serosanguineous immediately after surgery, fell to <5 mL/kg/day within one week, drains were removed within 10 days, and both patients were discharged within 2 weeks (figures 1–4).Conclusion Awake non-contrast MR lymphangiography is a feasible and clinically valuable technique for young children with refractory chylothorax after TCPC. It provides actionable anatomical information to guide successful surgery while avoiding contrast administration, radiation, interventional lymph node cannulation, and general anaesthesia. Question:Why was non-contrast MR lymphangiography favoured over intranodal contrast lymphangiography in this early experience of refractory chylothorax after fenestrated TCPC?A. Non-contrast MR lymphangiography is always therapeutically superior to surgeryB. Intranodal contrast lymphangiography does not show thoracic duct anatomyC. Contrast lymphangiography was resource-intensive, required general anaesthesia and specialist procedural support, and had previously been technically unsuccessfulD. Non-contrast MR lymphangiography can only be performed after failed surgeryE. Contrast lymphangiography is contraindicated in all children after TCPCCorrect answer:C. Contrast lymphangiography was resource-intensive, required general anaesthesia and specialist procedural support, and had previously been technically unsuccessfulExplanation:Abstract 30 Figure 4Abstract 30 Figure 3Abstract 30 Figure 2Abstract 30 Figure 1In our two cases, awake non-contrast MR lymphangiography provided diagnostic delineation of thoracic duct anatomy and leak site without contrast administration or sedation. This avoided the substantial practical limitations of intranodal contrast lymphangiography in young children, including the need for general anaesthesia, anaesthetic staffing, interventional radiology support, and technically challenging lymph node cannulation.