Evaluation of risk factors for obstruction of the intraventricular catheter after ventriculoperitoneal shunting in dogs with congenital internal hydrocephalus

Anna Katarzyna Siwicka^1,2*Daniela Farke^1,3Kathrin Büttner^4,5Andreas Moritz^1,6Martin Jürgen Schmidt^1,3

• ¹Justus-Liebig-Universitat Giessen Veterinar-Klinikum, Giessen, Germany
• ²Small Animal Clinic, Department of Radiology, Gießen, Germany
• ³Small Animal Clinic, Department of Neurology and Neurosurgery, Gießen, Germany
• ⁴Justus-Liebig-Universitat Giessen, Giessen, Germany
• ⁵Institut of Biomathematics, Gießen, Germany
• ⁶Small Animal Clinic, Department of Internal Medicine, Gießen, Germany

Background: Ventriculoperitoneal shunting (VPS) is the standard treatment for congenital internal hydrocephalus in dogs, but obstruction of the ventricular catheter is a frequent and serious complication. In human medicine, several predictors of catheter obstruction have been identified, while corresponding risk factors in veterinary patients remain largely unknown. Objectives: The aim of this study was to identify potential risk factors for ventricular catheter obstruction after VPS implantation in dogs with congenital internal hydrocephalus. Methods: A retrospective cohort study was conducted, including 100 client-owned dogs diagnosed with congenital internal hydrocephalus and treated by VPS implantation between 2001 and 2022. Medical records and magnetic resonance imaging (MRI) data were reviewed for age, sex, breed, body weight, ventricular size, ventricular catheter position, and preoperative medical treatments. Cerebrospinal fluid (CSF) samples were analyzed for cell count, red blood cell count, protein concentration, and cytology before and after surgery. Single logistic regression and chi-square tests were applied to evaluate associations with ventricular catheter obstruction. Results: Obstruction occurred in 9 of 100 dogs (9%; 95% confidence interval 3– 15%), with onset ranging from 8 to 210 days after VPS surgery (median 38 days). No significant associations were found between demographic factors, ventricle–brain ratio, ventricular catheter position, preoperative medical treatment, or CSF parameters and the occurrence of obstruction. Cerebrospinal fluid analysis revealed marked postoperative increases in cell counts, protein concentration, and red blood cell counts, peaking within the first week after surgery and gradually returning toward reference ranges at the 3-month follow-up. Histological examination of obstructed catheters in three dogs demonstrated intraluminal blockage caused by inflammatory infiltrates, fibrin, and choroid plexus cells. Conclusion: Obstruction of the ventricular catheter remains a clinically important complication after VPS implantation in dogs with internal hydrocephalus. No definitive risk factors could be identified in this study. The observed postoperative CSF changes appear to reflect inflammatory and surgical responses rather than predictors of obstruction. Further investigations with larger case numbers and detailed immunological analyses are required to clarify the underlying mechanisms and to improve prevention strategies.