The bacteria most often responsible for shunt infection are coagulase-negative staphylococci, with Staphylococcus epidermidis the most often reported causative organism (60–70 %) followed by Staphylococcus aureus (20–30 %), particularly in patients with concomitant skin infections [11, 19, 22]. After adhesion to the inner surfaces of the shunt tubing, the coagulase-negative staphylococci produce an extracellular mucoid biofilm (slime) embedding the bacteria and protecting them from the immune system and antibiotics [24, 27].

Anaerobic organisms such as Propionibacterium acnes and Corynebacterium diphtheriae account for less than 10 % of infections [19, 35]. The other causative microorganisms that may be found are Gram-negative bacteria (especially Escherichia coli, Pseudomonas, and Enterobacter) and are usually associated with corresponding abdominal and bladder pathology. Less frequently, other Gram-positive cocci (Streptococcus, Micrococcus, and Enterococcus) were isolated. In some cases, no pathogen could be identified. On the contrary, polymicrobial infections account for up to 20 % of infections and are often associated with an abdominal origin, a contaminated head wound, or a systemic coinfection [33]. Non-bacterial shunt infections are rare and most commonly fungal infections (Candida albicans), usually in premature infants or immunocompromised patients [3, 24].

The clinical presentation can vary greatly depending on the site of infection, the age of the patient, and the timing of infection (acute or chronic).

Early infection occurs days to weeks after the placement of the shunt. A high index of suspicion and proximity to a recent shunt manipulation makes this infective complication more likely. The patient is usually febrile (>38.5 °C). Staphylococcus aureus infections often present with erythema along the shunt track and may have a purulent drainage from the wound or visible shunt components (Fig. 9.1a) [21]. On the contrary, chronic shunt infections occur weeks to months after the shunt has been placed. In those cases, the most common presentation is that of repeated malfunctions (headache, irritability, nausea, vomiting, and lethargy) with or without fever [19, 22]. It is clear that the absence of fever does not rule out an infection.

Neonates may manifest apneic episodes, anemia, hepatosplenomegaly, and stiff neck [11]. Less commonly, patients may present with signs of meningeal irritation or seizures. Infected ventriculoatrial shunts may present with subacute bacterial endocarditis and “shunt nephritis”—an immune complex disorder that resembles acute glomerulonephritis (hepatosplenomegaly, hematuria, proteinuria and hypertension)—this rare condition is secondary to persistent stimulation of the immune system due to chronic infection, especially by Staphylococcus epidermidis [13]. Abdominal pain, gastrointestinal symptoms, and signs of intra-abdominal infection were seen with ventriculoperitoneal shunt infection. Ventriculopleural shunt infections may present with respiratory symptoms such as shortness of breath or a pleuritic chest pain.

CSF cultures are the most definitive method of diagnosis, although other laboratory values and imaging studies may point to an infection. Administration of antibiotics to a patient with suspected shunt infection before obtaining CSF culture reduces the likelihood of obtaining a positive culture.

In cases with high suspicion of shunt infection, a shunt tap should be performed and CSF sent for laboratory analysis. Studies should include CSF glucose, protein, cell counts, culture (bacterial and fungal), and sensitivities. Some advocate sending both aerobic and anaerobic cultures with the initial CSF tap [4]. Although a lumbar puncture is also possible (caution in obstructive hydrocephalus with a nonfunctioning shunt), CSF obtained this way is often sterile, even in patients who are later proven to have a ventricular shunt infection [11, 34].

Classically, CSF often shows a mild to moderate white blood cell count elevation (with predominantly polymorphonuclear cells), pleocytosis, low glucose level (a glucose ratio (CSF glucose/serum glucose) of <0.4), and elevated protein. For McClinton and colleagues, the combination of fever history and ventricular fluid neutrophils >10 % had a 99 % specificity for shunt infection and 93 positive predictive value [20]. Recurrent shunt malfunctions in a short time period can be indicative of infection, even with sterile CSF cultures, so the surgeon should have a high index of suspicion. In some doubtful situations, it is often helpful to re-tap the shunt to differentiate between a contaminant and true indolent infection [4]. A recent study showed that CSF vascular endothelial growth factor (VEGF) levels were associated with the subsequent development of shunt infection [18].

Routine blood tests often show a peripheral leukocytosis (75 %) and erythrocyte sedimentation rate is rarely normal. Blood cultures are positive in less than one-third of cases [11]. Elevated C-reactive protein (CRP) levels may also be observed in nearly three-fourths of cases [36]. In addition, any apparent sites of infection (especially open wounds) should be cultured.

Imaging studies of the patient with a suspected shunt infection include plain radiographies of the shunt system to establish continuity of the shunt hardware. Brain CT-scan and/or MRI were used to evaluate shunt configuration and location as well as the size of the ventricles and possible etiology. After contrast or gadolinium administration, patients may exhibit signs of infection: meningeal enhancement, ventriculitis (ependymal enhancement), and brain abscess. When a distal infection is suspected or there is evidence of distal malfunction, an abdominal ultrasound or CT-scan should be performed to detect a pseudocyst, the exact localization of the distal shunt catheter (Fig. 9.1), or possible pathological abdominal complications. For Kariyattil and colleagues, it is important to distinguish between CSF pseudocyst and CSF ascites (failure to absorb CSF) [14]. However, the presence of an abdominal pseudocyst is usually suggestive of infection until proven otherwise [11]. In patients with a ventriculoatrial shunt, an echocardiography must be used to look for vegetations if shunt infection is suspected.

Multiples studies have been performed to find the best strategy to manage CSF shunt infections [1, 11, 16, 19, 30, 33, 37]. The following are some gold questions: