**2. Patients with a VPS-related abdominal pseudocyst**

 Abdominal pseudocysts receive that name because they are not true cysts. They are produced by adhesion between the intestinal loops with the consequent accumulation of fluid [ 9 – 12 ]. These pseudocysts lack their own wall or capsule. One of the possible theories to explain the physio pathogenesis is that the same material of the valvular catheter produces an inflammatory reaction of the intestinal loops, thus generating this fluid-filled cavity and preventing the catheter from functioning correctly. Another theory is that there is an infection with some germ that generates adhesion between the intestinal loops ( **Tables 1** and **2** ).

#### **Table 1.**

*Management of patients with abdominal Pseudocyst, which cannot wait for the culture results, CFS cerebrospinal fluid, DCI distal catheter insertion, EVD external ventricular drainage, ETV endoscopic third ventriculostomy, US ultrasonography, VAS ventriculoatrial shunt, VPS ventriculoperitoneal shunt. Importantly, Conservative management is not advocated in any clinical scenario.* 

*Abdominal Complications in Patients with a Ventriculoperitoneal Shunt DOI: http://dx.doi.org/10.5772/intechopen.110614*

#### **Table 2.**

 *Management of patients with an abdominal pseudocyst and mild symptoms. CFS cerebrospinal fluid, DCI distal catheter insertion, ETV endoscopic third ventriculostomy, US ultrasonography, VAS ventriculoatrial shunt, VPS ventriculoperitoneal shunt. Importantly, Conservative management is not advocated in any clinical scenario.* 

 This pathology should be suspected in patients who have had a ventriculoperitoneal valve placed and who present with fever, abdominal pain, and symptoms of intracranial hypertension. Since the correct functioning of the shunt may be affected by the presence of the abdominal pseudocyst [ 13 – 19 ], it is mandatory to perform complementary imaging studies to evaluate the shunt system.

 A brain tomography should be performed to assess the size of the ventricles and some indirect signs of intracranial hypertension such as decreased subarachnoid spaces or the presence of periventricular transependymal edema. Radiographs of the system allow evaluation of the indemnity of the valvular system. It is recommended to perform a skull, thorax, and abdomen plate to evaluate the complete path.

 The presence of a pseudocyst should be suspected when two abdominal radiographs show the tip of the catheter in the same position.

 Abdominal ultrasonography is a useful and noninvasive method to confirm the presence of the pseudocyst by imaging. Although it is an operator-dependent method, which means that it requires the skills of the person who performs it, the tip of the distal catheter can be seen in contact with a hypoechogenic cavity.

 In these patients, it should be initially suspected that APC may be associated with a shunt infection by a low-virulence or slow-growing organism [ 2 ]. As described in the literature, in recent years, about 41% of patients with abdominal valves and pseudocysts had an infection at the time of diagnosis [ 20 , 21 ]. Due to this, we recommend ruling out the presence of a nervous system infection before deciding on surgical treatment. In a patient with VPS and an APC, a brain CT scan, radiographs,

#### **Figure 1.**

 *Abdominal ultrasonography shows an anechoic fluid collection measuring 5 x 2 x 2 cm in the left iliac fossa, the region where the patient reported pain, around the tip of the distal catheter.* 

and abdominal ultrasound should be ordered to determine if the APC is causing the ventriculoperitoneal shunt to malfunction [7, 22].

In case of shunt malfunction, suspicion of APC is based on clinical manifestations (headache, fever, abdominal discomfort, etc.), lack of mobility of the distal tip of the catheter on routine x-rays, and is confirmed with abdominal ultrasound (US) (**Figure 1**). The latter study is safe and rapid and should be performed immediately as symptoms of shunt malfunction are already present [1, 4, 6, 7, 20, 23].

APC does not always cause the full spectrum of symptoms of intracranial hypertension syndrome [21]. It is recommended to collect CSF for culture, to rule out infection. The sample could be taken by lumbar puncture (LP), but sampling from the shunt is recommended because LP is not always possible, for example in patients with spinal dysraphism. Furthermore, in obstructive hydrocephalus, the lumbar cistern may not be in communication with the ventricular space [24, 25]. Some of the organisms responsible for this type of complication are slow growing. Therefore, it is recommended that the minimum reading time of the culture fluid be approximately one week (five to seven days).

It must also be taken into account that some microorganisms produce biofilm. Therefore, its recovery in cultures will be greater in prostheses, in this case, the ventriculoperitoneal valve.

After evaluating the CT scan, the severity of the symptoms of intracranial hypertension, and the degree of abdominal pain, we can classify patients as oligosymptomatic or asymptomatic. The treatment will be different according to the presence or not of severe symptoms.

In patients with an abdominal pseudocyst and symptoms of intracranial hypertension and/or ventricular enlargement on computed tomography or abdominal pain that is difficult to manage clinically with medication, it is recommended to remove the distal peritoneal catheter. The externalization of the distal catheter, that is to say, the removal of the system from the abdomen and its connection to a collecting system abroad should be carried out while awaiting the results of the culture [7]. To define the site where the outsourcing will take place, the patient's anatomy must be considered.

We found the thoracic site the easiest and safest to outsource the shunt since it is easy to palpate in this region. If this is not the case, x-rays can be used to locate it in the operating room. However other sites may be considered. It is recommended to attempt to evacuate the APC by aspiration through the proximal end of the severed distal catheter before removing it from the abdominal cavity. It is important to consider that some catheters have a non-return mechanism at the tip that prevents aspiration of the cyst. Some authors consider the possibility of performing an abdominal tomography and aspiration puncture of the pseudocyst. We do not consider it necessary, since it is not a true cyst, only the withdrawal of the catheter allows the absorption of the liquid.

If a microorganism is isolated from the CSF culture collected from the reservoir, it is an infection associated with the ventriculoperitoneal valve. In this case, the system should be removed and an external ventricular drain (EVD) placed. Long-term treatment consists of reinsertion of the shunt. Ultrasound- or laparoscopy-guided repositioning into the peritoneum may be considered. Placement of a ventriculoatrial shunt (VAS) may also be considered [5]. The decision should be made after an evaluation together with the general surgeon. If the ventricular anatomy is favorable and the endoscopic third ventriculostomy (ETV) success score is high, then ETV can be considered [26].

#### *Abdominal Complications in Patients with a Ventriculoperitoneal Shunt DOI: http://dx.doi.org/10.5772/intechopen.110614*

In patients with an abdominal pseudocyst without shunt malfunction or with mild symptoms of intracranial hypertension and/or mild abdominal pain, the result of the CSF sample can be awaited without externalizing the shunt system. CSF reading is recommended for approximately one week (five to seven days) to rule out lowvirulence and slow-growing pathogens. If no germs are present, a new distal catheter can be inserted at another location in the abdomen. Ultrasound or laparoscopy can be used as a guide. Reinsertion into the abdomen can also be avoided by diverting it to the cardiac atrium. In candidate patients, endoscopic treatment of hydrocephalus should be considered; ETV is another option.

In the case of a central nervous system infection, the shunt system should be removed and an EVD placed temporarily until the infection resolves. Once the infection is resolved, a new shunt system should be placed taking into account the same aspects as in patients with negative cultures.

The two main theories about the pathophysiology of APCs are that it originates from an infection and the other that APC is caused by an allergic reaction. Therefore, shunt infection should always be ruled out. In case the patient has mild symptoms or no symptoms and can wait for the final result of the CSF culture, it is recommended to change the distal catheter with a new one in another location or to perform an endoscopy.

There is no high-grade evidence to support the exteriorization of a system in oligosymptomatic patients without infection in the nervous system. We propose not to carry out the exteriorization in a systematic way, since surgery and/or superinfection of the valve can be avoided when exteriorizing it.
