The patient with a V-P shunt (VPS)

Introduction

patients with a Ventriculo-Peritoneal shunt in situ have additional clinical issues which need to be considered
in patients presenting with symptoms of shunt malfunction, infection should always be suspected since shunt infection is a serious complication with a great potential for severe morbidity and mortality

SUSPECT POSSIBLE COMPLICATIONS EARLY if headache, irritability, seizures, lethargy, nausea, vomiting or fever occur
some of these may be emergently life threatening and clinicians should consider discussing with neurosurgical colleagues as soon as they are suspected, and even prior to imaging if the patient is unwell, particularly if any of the following are present:
- decreased mental state (GCS not 15)
- bradycardia
- hypertension
- sun setting eyes
- papilloedema

this is the most common complication and early recognition is important
the most common site of obstruction sited in most studies is the proximal catheter however it may also obstruct at the valve or in the distal catheter
clinical features include:
- headache
- lethargy
- nausea
- vomiting
diagnosis:
- combination of CT (enlarged ventricles), shunt series, and shunt tapping (poor CSF flow during a shunt tap had a 93% positive predictive value of proximal shunt obstruction) or lumbar puncture (increased opening pressure) may be needed.
- due to the risk of introducing bacteria into the shunt during the tap, many believe that tapping of the shunt should be performed only if less invasive studies, such as imaging, do not reveal the source of malfunction

infection is the 2nd most common cause of shunt malfunction, affecting some 8-15% of patients
most occur within the first few weeks to several months after VPS placement
most common causative organisms isolated from infected shunts in order of frequency are Staph epidermidis, Staph aureus, and gram negative rods
late infections have been traced to instances of peritonitis, abdominal pseudocyst, bowel perforation and haematogenous inoculation
risk factors include:
- young age, especially premature infants (under-developed immune system)
- post-operative CSF leak
- glove holes during shunt handling
- past shunt infection
clinical features:
- as for obstruction but with fever as well
diagnosis:
- Ix as for suspected obstruction + LP micro and culture
- shunt tapping appears to have a much higher sensitivity for detecting infection than blood culture or lumbar puncture
- presence of fever and > 10% neutrophils in the ventricular fluid had a specificity of 99%, a positive predictive value of 93%, and a positive test probability of 92% for predicting shunt infection¹⁾

pseudocysts are collections of fluid that accumulate around the tip of the distal catheter and are surrounded by a wall of fibrous tissue lacking an epithelium
a rare complication of VPS with a reported frequency among patients ranging from 1 to 4.5%
most cases occurring a year or more after VPS placement or revision
even more rarely, hepatic pseudocysts, which may occur when the distal catheter tubing migrates to the surface of the liver and induces chronic irritation and inflammation
clinical features:
- abdominal pain and distention associated with a palpable mass
- occasionally neurological symptoms may be present as well
- if a hepatic pseudocyst occurs, RUQ pain worse after meals,abdominal distension +/- elevated liver function tests (LFTs)
diagnosis:
- abdominal USS

a rare complication of VPS placement that is estimated to occur with a rate of between 0.1 and 0.7%
most occur in children perhaps due to thinner bowel walls
most commonly reported presentation is protrusion of the tip of the distal catheter through the anus

CSF overdrainage may result in subdural collections and subdural haematomas
most of collections are asymptomatic and resolved spontaneously although some require surgical drainage

¹⁾