Huge subcutaneous extraperitoneal pseudocyst after migration of the ventriculoperitoneal shunt catheter

Abstract

The formation of an intraperitoneal pseudocyst as a complication of ventriculoperitoneal shunts is well known. However, the formation of a pseudocyst at the subcutaneous extraperitoneal abdominal space is unusual and likely secondary to the migration of the peritoneal catheter. We present a 53-year-old male who had placement of a ventriculoperitoneal shunt for hydrocephalus secondary to a vestibular schwannoma. Five months later, he presented with an enormously distended abdomen. Investigations showed the peritoneal catheter in the extraperitoneal space within a large right lower quadrant abdominal wall pseudocyst. The patient was taken to the operating theatre, and the shunt was externalised at the original abdominal incision. Approximately 3 L of cerebrospinal fluid were aspirated from the distal peritoneal catheter. After negative cultures, a new peritoneal catheter was placed intraperitoneally at the contralateral lower abdominal quadrant. The contralateral quadrant was utilised to prevent fluid accumulation into the old extraperitoneal cavity.

Background

Ventriculoperitoneal (VP) shunts are used to divert cerebrospinal fluid (CSF) into the peritoneal cavity, where it is absorbed efficiently by the peritoneum. Abdominal complications can arise after the placement of a VP shunt.¹ One of them is the accumulation of CSF around the peritoneal catheter tip, forming an intraperitoneal pseudocyst, sometimes called a CSFoma.^1–4 Usually, they occur secondary to a low-grade inflammatory process.^3–5 However, the formation of a pseudocyst at the subcutaneous extraperitoneal abdominal space is unusual and likely secondary to the migration of the catheter.^6–9 Occasionally, it can occur with inadequate positioning of the peritoneal catheter just beneath the abdominal wall.

Case presentation

A 53-year-old male with hypertension, diabetes mellitus and a body mass index (BMI) of 23.6 kg/m² presented to the emergency department after a head trauma following a motor vehicle accident. He was alert and oriented without focal neurological deficits. He underwent a head CT scan without contrast, which showed a very small brain contusion; however, an incidental left cerebellopontine angle tumour was identified, causing moderate ventriculomegaly. The tumour measured 3.2×2.9×2.9 cm on the brain MRI and was compatible with a vestibular schwannoma. On further questioning, he recalled having difficulty walking in the recent past and decreased hearing on the left ear for more than a year. His ophthalmological evaluation showed visual acuity of 20/50 with no evidence of optic nerve swelling except for mild bilateral epiretinal and preretinal haemorrhages secondary to hypertensive ischaemic changes. On discussion with the patient about the treatment options, he opted for radiosurgery treatment. He was sent home with an appointment for gamma knife radiosurgery evaluation to treat the vestibular schwannoma.

Three weeks later, he started with headaches and disorientation and returned to the emergency department. Although he had no evidence of optic nerve swelling, a Medtronic CSF-flow control medium pressure valve and VP shunt was placed because of the headaches, enlarged ventricles and planned radiosurgery treatment. A postoperative abdominal X-ray film showed an adequately positioned right-sided VP shunt projecting along the right hemiabdomen, extending down to the L5-S1 level and then crossing midline to the left, with the tip projecting at the left lower quadrant at the level of the iliac crest (figure 1). He was discharged home to schedule the radiosurgery treatment of the tumour. Sutures were removed a week later, and no complications were identified.

Figure 1.

Plain abdominal X-ray shows a right-sided ventriculoperitoneal shunt projecting along the right hemiabdomen, reaching down to the L5-S1 level and then crossing midline to the left, with the tip projecting at the left lower quadrant iliac crest level.

Five months later, he was evaluated at the neurosurgery clinic. He stated that he was experiencing fluid retention on the abdomen wall during the last month but thought it would eventually disappear. He denied abdominal discomfort or pain. He was alert and oriented. On the examination, the abdomen was enormously distended related to VP shunt placement area (figure 2). He was sent to the emergency department for further investigations.

Figure 2.

Image of the patient showing the enormously distended abdomen related to the ventriculoperitoneal shunt placement area.

Investigations

Abdominal CT scan demonstrated a right-sided VP shunt, with the distal tip in the extraperitoneal space within a large right lower quadrant abdominal wall fluid collection, which measured 14.8×24.9×16.2 cm compatible with an extraperitoneal pseudocyst (figure 3).

Figure 3.

Abdominal axial CT scan shows a large right lower quadrant abdominal wall fluid collection measuring 14.8×24.9x16.2 cm with the distal tip of the ventriculoperitoneal shunt in the extraperitoneal space, compatible with an extraperitoneal pseudocyst.

Treatment

The patient was taken to the operating theatre, and the shunt was externalised at the original abdominal incision. The peritoneal catheter was cut, leaving the distal portion of the peritoneal catheter inside the abdominal wall where approximately 3 L of xanthochromic CSF were aspirated, followed by the removal of the catheter. The peritoneal catheter’s proximal end drained crystal clear CSF spontaneously and was connected to a ventriculostomy drainage collecting bag (figure 4). The initial CSF laboratory results from the pseudocyst had protein of 342 mg/dL and glucose of 64 mg/dL. He was started on antibiotic treatment but stopped after the culture results from the abdominal pseudocyst and the proximal shunt were negative. Postexternalisation abdominal CT scan showed significant improvement of the abdominal fluid collection (figure 5).

Figure 4.

Intraoperative image of the patient showing the abdomen after the shunt was externalised and the pseudocyst aspirated.

Figure 5.

Abdominal axial CT scan after the pseudocyst was aspirated, showing only a small amount of residual fluid at the right lower abdominal flank.

Outcome and follow-up

Two weeks later, the VP shunt was revised by removing the old peritoneal catheter and placing a new peritoneal catheter. The peritoneal catheter was tunnelled subcutaneously to the contralateral left lower abdominal quadrant. A purse-string suture was placed at the peritoneum around the catheter, and the left rectus fascia was closed with 3–0 vicryl interrupted sutures. He was evaluated at the clinic a week later, and the wounds were healing adequately. Two months later, he was re-evaluated and showed no complications from the procedure.

Discussion

Extraperitoneal pseudocysts are typically related to the migration of the peritoneal catheter into the subcutaneous tissue.1 7 8 10 Infection of the CSF is rarely identified in cases of catheter migration. Bolster et al noticed in their study that all 11 patients with an extraperitoneal pseudocyst who had migration of their VP catheter tip were obese with an average BMI of 40.2 kg/m².¹ However, our patient had a BMI of 23.6 kg/m². Obese patients have significantly increased intra-abdominal pressure, which can lead to catheter migration and extrusion of the catheter from the peritoneal cavity.^{1 7 8} Most subcutaneous pseudocysts are small; however, larger collections have been reported. A patient with an improper peritoneal shunt placement developed an acute intestinal obstruction secondary to the massive size of the pseudocyst.¹¹

In our patient, intraperitoneal placement of the catheter during the initial surgery was confirmed by a plain abdominal X-ray showing the catheter inside the peritoneal cavity without coiling at the anterior abdominal wall. In obese patients, this abdominal X-ray is important to confirm proper placement and prevent future complications. An extraperitoneal fluid pseudocyst can easily be mistaken as ascites; however, in our case, it was mostly localised to the right side. As the extraperitoneal cavity can enlarge significantly, symptoms of acute hydrocephalus secondary to distal shunt malfunction are rarely presented.

Imaging studies using plain abdominal X-ray and abdominal CT scan can be used to establish the correct diagnosis.^{1 2 12} The initial treatment of the pseudocyst consists of externalisation of the peritoneal catheter with drainage of the contents, followed by reconstruction of the shunt system. In our patient, a distal externalisation of the peritoneal catheter was initially performed, and a new peritoneal catheter was placed intraperitoneally using the contralateral left lower abdominal quadrant after negative cultures. The contralateral lower abdominal quadrant was utilised to prevent the CSF accumulation into the old extraperitoneal cavity.

To avoid complications in obese patients, placing the peritoneal catheter beneath the abdominal fat pad just over the rectus abdominis muscle and closing the peritoneum has been recommended.⁸ Laparoscopic-assisted shunt placement has been associated with fewer distal shunt failures.^13–17 Its use ensures adequate placement of the distal catheter inside the peritoneal cavity under direct vision.^{14 15 18} However, no review has evaluated its effectiveness in avoiding catheter migration. Tight closure of the fascia layer and a purse-string suture at the peritoneum placed around the catheter may decrease the chance for migration of the catheter outside the peritoneal cavity.

Learning points.

• A subcutaneous extraperitoneal pseudocyst can develop after migration of the peritoneal catheter outside of the peritoneal cavity.

• Imaging studies using plain abdominal X-ray and abdominal CT scan help to diagnose an extraperitoneal pseudocyst.

• A new peritoneal catheter can be repositioned intraperitoneally after the pseudocyst fluid culture result is negative.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).