Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
2 min synopsisUK scopeSources checked 13 Sept 2026Clinical review pending
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Possible acute shunt failure
A shunted patient with reduced consciousness, pupillary abnormality, seizure, focal deficit, rapidly worsening headache or cardiorespiratory change may have acute intracranial hypertension.
Action: Resuscitate, call neurosurgery immediately, obtain urgent brain imaging when safe, and prepare for specialist CSF diversion; do not delay because ventricles were previously small or manipulate the valve without instruction.
Synopsis
Distinguish life-threatening shunt obstruction or infection from over-drainage, interpret imperfect tests safely, and escalate to definitive neurosurgical source control.
Treat clinical deterioration first: shunt failure is a neurosurgical emergency whose diagnosis integrates examination, device history and comparative imaging.
Blockage can occur proximally, at the valve or distally; symptoms reflect renewed hydrocephalus and may differ from the presentation before insertion.
Infection may be indolent, biofilm-related and culture-sensitive; normal CSF glucose, protein or cell count and a negative Gram stain do not reliably exclude it.
Key red flags
New drowsiness, repeated vomiting, seizure, gaze disturbance, focal deficit or bulging fontanelle can mark obstruction and impending decompensation.
Fever, wound inflammation, discharge, meningism or abdominal tenderness suggests infection, but fever can be absent and presentation may be subtle.
A postural headache, diplopia, new subdural collection or symptoms worse upright suggests over-drainage, yet obstruction and infection must still be considered.
Normal ventricular size, normal routine CSF indices, negative Gram stain or prior-antibiotic negative culture must not independently end the assessment.
Obstruction pattern
Recurrence of the patient's previous pressure symptoms, progressive vomiting, drowsiness, visual change, gait decline or infant head-growth change suggests under-drainage.
Infection pattern
Headache, nausea, lethargy, mental-status change, fever, wound or tract inflammation and abdominal tenderness are compatible; no single symptom is required.
Reasoning priorities
01
CSF culture from an authorised sample
Identify healthcare-associated ventriculitis or shunt infection and determine antimicrobial susceptibility.
Culture is the most important microbiological test. Normal CSF indices, a negative Gram stain and a negative culture after antibiotics do not independently exclude infection; slow-growing organisms may require prolonged incubation, and sampling route is neurosurgical. Arrange urgent neurosurgical and microbiology assessment for suspected shunt infection. Once infection is confirmed, usual treatment combines complete shunt removal, temporary external CSF drainage when needed and intravenous antimicrobial therapy; reimplantation is organism- and culture-guided.
Worked reasoning
Worked caseDrowsy patient with a shunt
A patient develops vomiting and reduced alertness with an implanted VP shunt, regardless of the age of the device.
Context: stabilise airway and circulation, document GCS, pupils, focal signs, fever, wounds, abdominal findings, device type and prior stable neurological and imaging baseline.
Reasoning: contact neurosurgery early and obtain urgent comparative brain imaging; neither small ventricles nor normal valve palpation can safely exclude acute failure.
Outcome: if deterioration continues, prepare for specialist pressure control and CSF diversion while the team distinguishes obstruction, infection, haemorrhage and over-drainage.
Verification: trend examination and observations, confirm imaging and operative findings, and document the revised device plan and future failure signature before discharge.
National guidance is shown before implementation-dependent detail. Apply principles in context and verify current guidance when a decision affects care. Source check completed 13 Sept 2026; clinical approval remains outstanding.
IDSA healthcare-associated ventriculitis and meningitis guidelineIDSA 2017 guideline, recommendations 1–23, 34–36, 62 and 66–81 read 13 September 2026. Covers adults and children with healthcare-associated infection; normal CSF indices or a negative Gram stain do not exclude infection, culture is central, and an infected shunt generally requires complete removal, external drainage and intravenous antimicrobials. US guideline and local microbiology policy still governs empirical drugs. Chapter-specific use: shunt blockage, infection and over-drainage.
Paediatric shunt-malfunction imaging systematic reviewJayanth et al., American Journal of Emergency Medicine 2021, PMID 33067062; abstract and diagnostic meta-analysis scope read 13 September 2026. Applies to patients younger than 21 years and supports that negative CT, MRI, shunt series or optic-nerve-sheath testing cannot independently exclude malfunction; it is not adult validation. Chapter-specific use: shunt blockage, infection and over-drainage.
CNS paediatric shunt-infection prevention guidelineCongress of Neurological Surgeons paediatric hydrocephalus guideline, 2020 update, infection-prevention recommendations read 13 September 2026. Supports perioperative antibiotics and antibiotic-impregnated tubing in children requiring shunts; it does not define adult prophylaxis or local theatre doses. Chapter-specific use: shunt blockage, infection and over-drainage.
NICE NG228 aneurysmal subarachnoid haemorrhageNICE NG228, published 23 November 2022; recommendations 1.3.2–1.3.5 read 13 September 2026. Supports symptom-plus-serial-imaging diagnosis and temporary or permanent CSF diversion only in people with aneurysmal subarachnoid haemorrhage; it is not a universal hydrocephalus algorithm. Chapter-specific use: shunt blockage, infection and over-drainage.