Intraperitonal encapsulated CSF collection containing distal ventriculoperitoneal shunt catheter

Clinical History

A 55-year-old man presented with a three-week history of progressive abdominal distension, pain, nausea and headaches. There were no signs or symptoms of raised intracranial pressure or neurological deficit. He had been diagnosed with hydrocephalus eleven years before and a ventriculoperitoneal shunt had been inserted.

Imaging Findings

An abdominal and pelvic CT was performed after the administration of intravenous contrast with a delay of seventy seconds. The CT demonstrated a 27 x 21 x 15 cm (CC x AP x TR) fluid collection in the right upper quadrant, which was compressing the liver and deviating it to the left. The cystic collection contained the ventriculoperitoneal shunt within it. Four litres of fluid were drained from the collection and the patient's abdominal symptoms were completely relieved. The VP shunt was then successfully re-sited.

Discussion

Ventriculoperitoneal shunt is the treatment of choice for obstructed hydrocephalus and is used to divert the excess cerebrospinal fluid (CSF) from the ventricular system to the peritoneal cavity. A number of complications have been commonly reported in the literature including infection, blockage, disconnection, migration of the shunt tip, CSF overdrainage leading to subdural haematoma and collections as well as bowel perforation and obstruction [1, 2]. It is extremely rare for blockage of a VP shunt not to cause hydrocephalus and to cause a large abdominal CSF collection. The exact cause of such abdominal CSF collections is still widely debated, however, predisposing risk factors include chronic inflammation, low-grade shunt infection, raised CSF protein, sub-clinical peritonitis and multiple shunt revisions [1, 2]. The wall is composed of fibrous tissue without an epithelial lining and is filled with CSF with the majority of fluid collections containing debris. The most common intra-abdominal response to infection is re-sheathing of the distal catheter. Intraperitoneal encapsulated collections occur as a result of CSF draining into these sheaths [3]. Presenting features include progressive abdominal distension, palpable abdominal mass, features of shunt or intestinal obstruction with or without signs of raised intracranial pressure [4, 5]. Ultrasound or CT can indicate the definitive diagnosis. US may show a well-defined hypoechoic or anechoic cystic mass with the catheter tip of the VP shunt within it. If the mass is large, pressure effects on adjacent organs may be seen and if infected, debris and internal echoes may be visualised. CT is helpful in identifying other intrabdominal cystic masses which form important differential diagnoses including abdominal ascites, abscesses and cysts of the mesentery and omentum [3, 5]. Infected intraperitoneal collections usually resolve with antibiotics and surgical management. Treatment involves an explorative laparotomy and drainage of the encapsulated collection with or without excision of the walls. The shunt catheter is surgically removed and repositioned in the peritoneal cavity at a different site [6].
In patients who present with progressive abdominal distension and a past medical history of hydrochephalus with VP shunt insertion, intraperitoneal CSF collections should be considered as an important differential diagnosis.

Differential Diagnosis List

Final Diagnosis

Right subphrenic intraperitonal encapsulated CSF collection containing the distal ventriculoperitoneal shunt catheter.

URL:	https://eurorad.org/case/12090
DOI:	10.1594/EURORAD/CASE.12090
ISSN:	1563-4086