Functional ventriculoatrial shunt obstruction in the setting of increased intra-abdominal pressure: illustrative case.

BACKGROUND: Functional ventriculoatrial (VA) shunt failure due to unfavorable distal pressure dynamics is a recognized but poorly characterized complication, with no prior case documenting intra-abdominal pressure (IAP) as the precipitating mechanism. OBSERVATIONS: A 44-year-old paraplegic male with post-infectious hydrocephalus and a VA shunt presented with progressive somnolence and bilateral upper extremity weakness. Four serial shunt taps over 2 days yielded variable opening pressures (3-18 cm H2O) with only transient neurological improvement after each. Serial frontal horn measurements demonstrated dynamic ventricular caliber changes (hospital day [HD] 1, 49 mm; HD 3, 47 mm; HD 7, 51 mm; HD 9, 44 mm), consistent with fluctuating CSF drainage rather than fixed obstruction. Intraoperative shunt exploration confirmed complete mechanical patency via transesophageal echocardiography. The patient had concomitant severe abdominal distension from fecal impaction. His neurological status improved completely following bowel regimen escalation, without neurosurgical revision. LESSONS: This case illustrates functional VA shunt failure secondary to increased IAP. The authors hypothesized that elevated IAP was transmitted to the thoracic cavity, increasing central venous pressure and functionally obstructing the otherwise patent VA shunt. This report highlights the importance of considering extracranial causes of shunt failure and assessing the distal drainage site's pressure environment in the diagnostic algorithm. https://thejns.org/doi/10.3171/CASE26556.