CLINICAL QUIZ Taking a multidisciplinary approach to maintaining haemodialysis vascular access: a challenging case in an infant: Answers Rebecca Anderson 1 & Brendan Cusack 1 & Elhamy Bekhit 2 & Bernadita Troncoso Solar 3 & Cathy Quinlan 1,4,5 & Joshua Kausman 1,4,5 Received: 15 July 2020 /Accepted: 24 July 2020 # IPNA 2020 Keywords Child . Haemodialysis . Central venous catheter . Migration . Malfunction . Fibrin sheath Answers 1. A key feature of this patient’s central venous catheter (CVC) malfunction was an inability to aspirate from the catheter despite flushing well. This suggests one of three possible causes of obstruction: catheter tip thrombus, po- sition of the catheter tip against a vessel wall, or a fibrin sheath enveloping the catheter tip. Slow contrast injection through a catheter can differentiate between a catheter tip thrombus (irregularity of the contrast jet as it exits the catheter) and a catheter that is resting against a vessel wall (asymmetric or oblique flow of contrast away from the catheter tip). Neither of these signs was observed in this case. The presence of a fibrin sheath is identified as initial pooling of contrast at the catheter tip in the early phase of the injection followed by tracking of contrast medium back along the length of the catheter on later images. A circumfer- ential but incomplete fibrin sheath will cause the classic subtle sign of narrowing of the contrast jet as it exits the catheter with fanning out of contrast more distally [1]. The presence of a fibrin sheath is often misinterpreted as extravasation due to catheter fracture. In this case, both contrast studies were re- ported as suspicious for line breakage; however, no fracture in the line was identified on inspection of the catheter after re- moval. Despite a lack of clear evidence for a fibrin sheath on imaging studies, this was the most likely diagnosis in this case. 2. Initial management of a blocked central catheter at our institution includes instilling tPA into the catheter lumen for at least 2 h, with repeat dosing within 24 h if necessary. Second-line management options include instillation of HCl into the catheter lumen and consideration of ultra- sound to further evaluate for thrombus [2]. This is consis- tent with the recommended initial treatment of obstruction by a fibrin sheath, which includes infusion of thrombolyt- ic drugs either directly into the catheter lumen or intrave- nously. Unfortunately, thrombolytic treatment is often in- adequate, with a reported success rate of only 19% in a large paediatric population [3]. Subsequent management options involve intraluminal guidewire placement with balloon angioplasty, percutaneous stripping of the fibrin sheath, or catheter replacement via puncture parallel to the fibrin sheath [1]. These techniques avoid resiting a new catheter into the lumen of the fibrin sheath, which can quickly result in occlusion of the line [1]. Stripping of the fibrin sheath was chosen in our case to avoid a further line replacement, having also previously attempted re- puncture adjacent to the presumed sheath tunnel. Using a dis- tal approach via femoral venous access, an interventional ra- diologist used a 10-mm Amplatz Goose Neck snare to remove the fibrin sheath from the permacath without complication (Fig. 1). The CVC remained in situ and functioned well for This refers to the article that can be found at https://doi.org/10.1007/ s00467-020-04726-w. * Joshua Kausman Joshua.Kausman@rch.org.au 1 Department of Nephrology, The Royal Children’s Hospital, Melbourne, Victoria, Australia 2 Department of Medical Imaging, The Royal Children’s Hospital, Melbourne, Victoria, Australia 3 Department of Urology, The Royal Children’s Hospital, Melbourne, Victoria, Australia 4 Department of Paediatrics, University of Melbourne, Melbourne, Australia 5 Murdoch Children’s Research Institute, Melbourne, Australia Pediatric Nephrology https://doi.org/10.1007/s00467-020-04728-8