Few studies with more than 10 patients have been reported.
It is well known in children but uncommon in adults.
The pathogenesis of pseudocysts remains unclear, it is attributed to an inflammatory response, usually the result of infection and nonspecific inflammatory processes.
Diverse predisposing factors have been proposed such as previous abdominal surgeries, multiple VPS revisions, history of necrotizing enterocolitis.
The wall is composed of fibrous tissue without an epithelial lining and is filled with cerebrospinal fluid. Debris is identified in the majority of the fluid collections.
The pseudocyst can either move freely within the peritoneal cavity or adhere to small-bowel loops, the serosal surface of solid organs, the parietal peritoneum, or small-bowel loops. The latter would explain why some bowel loops may become engulfed when the pseudocyst increases in size or why the pseudocyst may be prone to torsion.
Pediatric patients commonly present with symptoms of elevated intracranial pressure and abdominal pain, whereas adults predominantly present with abdominal signs only.
They are seen as a thin-walled cystic mass around the shunt tip. Ultrasonography or CT can indicate the definitive diagnosis.
Ultrasonography proved to be the method of choice in the diagnosis of VPS abdominal complications, especially CSF pseudocyst.
Well defined hypoechoic / anechoic cystic mass with tip of VP shunt within it
Pressure effects on adjacent organs if mass is huge
Multiple septae may form chronically
Debris and internal echoes are seen if the mass is infected
May show a small or massive , loculated cyst like structure in the peritoneal cavity at the distal tip of VP shunt
Measurement of attenuation values with CT characterizes the contents as water attenuation and demonstrates the relationships of portions of the shunt catheter with the pseudocyst.
In case of IH signs, a cerebral CT scan can be performed to evaluate the ventricular distension and to check the shunt position 3).
Possible differential considerations include
Benign cystic teratoma
Cystic spindle cell tumour
Enteric duplication cyst
It may be difficult to differentiate seroma, urinoma, abscess, lymphocele, and cerebrospinal fluid on the basis of imaging findings alone. Fine-needle aspiration with ultrasound or CT guidance has a high diagnostic yield 4).
Gastroenterological surgeons should be aware of this possible complication, and this complication should be considered during differential diagnosis of an acute abdomen complaint 5)
Whenever suspected it should be confirmed by imaging, followed by open exploration and repositioning of the shunt 6).
In case of suspected infection, the VPS is removed and replaced by an external ventricular drain. Antibiotics are started and adjusted to the results of the CSF culture. If there is no direct sign of infection, only the distal catheter is externalized and antibiotics are introduced until infection is treated. Depending on the peritoneal absorption state, the distal catheter is replaced in the abdominal cavity or in the atrium, the pleural space or the gallbladder if there is no suitable place for repositioning. If the peritoneal state allows it, a laparoscopic procedure is recommended to avoid peritoneal adhesion formation increasing the recurrence rate of CSF pseudocyst 7).
Various methods to process the cyst have been described in the medical literature, but the recurrence rate remains elevated (25-100%). Then the probability of an infection without any clinical sign has to be considered.
One hundred thirty-eight patients were treated for hydrocephalus, and 112 patients received a peritoneal catheter during the follow-up. An APC was diagnosed in 14 (12.5%) patients, and 28 revisions were needed for its treatment. The rate of shunt infection in patients with APC was 50%, but bacterial examination of the pseudofluid culture revealed infection in only 3 patients. Age at first surgical procedure, type of first surgical procedure, and etiology of hydrocephalus were not associated with APC diagnosis. APC recurred in 4 patients. These patients had a catheter repositioning directly into the peritoneum as first surgical treatment. No recurrences were observed in patients with shunt externalization or replacement of the peritoneal catheter.
An APC is a major long-term complication after ventriculoperitoneal shunt treatment. Although a sterile inflammatory response cannot be excluded completely, our results favor the hypothesis of low-level shunt infection. In both cases, the surgical consequences are the same. An infected APC should be treated as a shunt infection. Uninfected patients can be treated with shunt externalization and replacement of only the peritoneal catheter 8).
In a retrospective analysis of 4 cases diagnosed to have abdominal pseudo cyst following VP shunt between 2008 and 2013. All the four cases were suspected clinically and diagnosis was confirmed by abdominal ultrasonography.
In three patients, the cyst was multilocular and of varying size. Fourth one had a unilocular cyst at the lower end of VP shunt. All the four patients had features of varying degree raised intracranial pressure and a two patients had abdominal signs also. All the patients needed open exploration. Cyst fluid was drained and partial to complete excision of the cyst was done along with the repositioning of the shunt in abdominal cavity in three patients and exteriorization of shunt in one patient. Patients were followed for any further complication over a period of 1-year 9).
Four unique cases of abdominal pseudocyst formation. The first patient initially presented with a right upper quadrant pseudocyst. Shunt was externalized and the distal end was revised with placement of catheter on the opposite side. He developed another pseudocyst within 5 months of shunt revision and developed another shunt failure.
The second patient had a history of shunt revisions and a known pseudocyst, presented with small bowel obstruction, and underwent laparotomy for the lysis of adhesions with improvement in his symptoms. After multiple readmissions for the same problem, it was thought that the pseudocyst was causing gastric outlet obstruction and his VP shunt was converted into a ventriculopleural shunt followed by percutaneous drainage of his pseudocyst.
The third patient developed hydrocephalus secondary to cryptococcal meningitis. He developed abdominal pain secondary to an abdominal pseudocyst, which was drained percutaneously with relief of symptoms.
The fourth patient had a history of multiple shunt revisions and a previous percutaneous pseudocyst drainage that recurred with cellulitis and abscess secondary to hardware infection.
Abdominal pseudocysts are a rare but important complication of VP shunt placement. Treatment depends on etiology, patient presentation, and clinical manifestations. Techniques for revision include distal repositioning of peritoneal catheter, revision of catheter into pleural space or right atrium, or removal of the shunt completely 10).
A 31-year-old female, in which a large abdominal pseudocyst was developed 1 year after insertion of a ventriculoperitoneal shunt for hydrocephalus. The abdominal CT scan and the ultrasonographical evaluation of the abdomen showed a well defined, cystic mass lesion with a volume of 50 cm3, in the recessus hepato-renal. The peritoneal tip of the shunt was located within the mass lesion. A distal externalization of the peritoneal catheter without excision of the pseudocyst was performed. Cerebrospinal fluid culture demonstrated a Staphylococcus epidermidis infection and adequate antibiotic treatment was administrated. The previous symptoms improved 4 weeks later and a new catheter was placed intraperitoneally in a different quadrant. The postoperative course was uneventful. They suggest that chronic inflammation or subclinical peritonitis is a predisposing factor for this complication 11).
64 cases of APC were found in 36 patients. The records were then reviewed for the presence of infection, history of necrotizing enterocolitis, prior abdominal surgery, and treatment performed. Of the cases of APC, 46 were primary and 18 were recurrent. A history of prior abdominal surgery other than shunt revision was found in 47% of patients and a history of necrotizing enterocolitis was found in 19% of patients. The average number of prior shunt revisions was 4.1 per patient. Shunt infection as defined by positive cultures of either cerebrospinal fluid or abdominal fluid was present in only 23% of cases of APC. A history of prior shunt infection was present in 30% of patients. Infection was treated by shunt removal, external ventricular drainage, and appropriate antibiotics. After the infection was cleared or if no infection was present, treatment consisted of: (1) repositioning the distal catheter into the peritoneum, (2) repositioning the distal catheter into the pleural space, the atrium, or the gallbladder, (3) exploratory laparotomy with lysis of adhesions and repositioning the peritoneal catheter, (4) APC aspiration only, or (5) shunt removal or disconnection. Because of the complexity of APC management, we analyzed the outcomes of our cases and outlined an algorithm to simplify this process 12).
Rainov et al., report on 14 cases of sonographically diagnosed abdominal pseudocysts, an incidence of pseudocyst formation of 4.5%. The most common presentation of the paediatric patients is with symptoms of elevated intracranial pressure and abdominal pain, whereas the adults have predominantly local abdominal signs. Diagnosis is readily made with ultrasonography. Predisposing factors for pseudocyst formation are multiple shunt revisions and infection. Microscopically, the pseudocysts consist of fibrous tissue without epithelial lining. The treatment involves surgical removal of the catheter with or without excision of the pseudocyst wall and placement of a new catheter intraperitoneally in a different quadrant or an intra-atrial shunt. Recurrences are rare, especially under appropriate medical treatment of infection. In this series, microbiologically proven infection was present in 30% of the cases 13).
Five cases of children with abdominal complications of VP shunts (four pseudocysts and one umbilical granuloma with spontaneous drainage of CSF) 14).
A 30-year-old woman with abdominal distension, vomiting and confusion caused by her developing an abdominal CSF pseudocyst, 13 years after her last shunt revision 15)
In 1999, a 50-year-old woman underwent ventriculoperitoneal (VP) shunt surgery for hydrocephalus after subarachnoid hemorrhage. She was hospitalized for fever and recurrent systemic seizures in November 2006. Head computed tomography (CT) showed only old changes. The seizures and fever were controlled by medicinal therapy. However, in December, her consciousness level suddenly decreased, and she showed progressive lower abdominal distension. Head CT showed marked ventriculomegaly, and abdominal CT showed a giant cystic mass at the shunt-tube tip in the lower abdominal cavity. Because thick pus was aspirated from the intra-abdominal mass, we diagnosed the patient with acute obstructive hydrocephalus due to an infected abdominal pseudocyst. Laparotomy and direct cyst drainage were performed, and antibiotic therapy against Streptococcus, the causative pathogen, was administered. The VP shunt tube was replaced. The postoperative course was uneventful, and postoperative CT showed hydrocephalus improvement and no pseudocyst recurrence. Abdominal pseudocysts, which are rare after VP shunt surgeries, usually occur after the subacute postoperative course in younger cerebral hemorrhagic cases. The case was quite rare because the cyst developed in the chronic phase in an older patient and was caused by streptococcal infection. The cyst components should be examined before cyst drainage when choosing surgical strategies 16)
A 14-year-old patient, known to have a VPS as intraventricular hemorrhage treatment, presenting cephalalgia, vomiting, apathy, and an indurate abdominal mass without fever. The first abdominal CSF pseudocyst diagnosis had been established 3 months earlier. Abdominal ultrasounds confirmed a large homogeneous cyst with the shunt tip within the pseudocyst. Cerebral CT revealed an increased ventricular size. An exploratory laparotomy with cyst aspiration, lysis of adhesions, excision of cystic walls, and repositioning of the peritoneal catheter was performed.
No antibiotics were initiated given that the cultures were negative 17).
A case of a 4-month-old girl with shunted hydrocephalus who presented with shunt failure from a suspected abdominal pseudocyst that was found to be a fetal ovarian cyst is reported 18).
Chick JF, Chauhan NR, Mullen KM, Kamdar NV, Khurana B. Teaching NeuroImages: massive abdominal CSFoma. Neurology. 2013 Mar 26;80(13):e146. doi: 10.1212/WNL.0b013e318289705e. PubMed PMID: 23530158 19).
A 22-year-old man who was admitted because of diffuse abdominal distention. A VPS was placed 21 years earlier to treat hydrocephalus secondary to spina bifida. Abdominal computed tomography (CT) revealed a homogeneous low-density fluid collection adjacent to the VPS catheter tip, causing stomach obstruction. Thus a peritoneal pseudocyst around VPS was suspected and emergency laparotomy was performed. The large mass was localized in the left upper abdomen between the stomach and mesentery of the transverse colon, exactly at the omental bursa. The cystic mass was opened and 1500 ml of clear fluid was drained; the distal end of the VPS was repositioned outside the mass. Thus, an abdominal cerebrospinal fluid pseudocyst as a complication of VPS was diagnosed 20).
A nineteen year-old female with a VP shunt who presented with only abdominal distension suggestive of a full-term pregnancy. Abdominal CT studies subsequently established a diagnosis of APC. A total of 12.7L of fluid was drained laparoscopically, and the VP shunt was eventually revised into a ventriculo-atrial shunt. Because adult patients often present years after their VP shunt procedures with only abdominal complaints, the diagnosis of APC relies on detailed history taking and a strong clinical suspicion 21).
A 13-year-old girl with a VP shunt presented with progressive abdominal distention, pain and vomiting. The shunt was inserted at infancy for congenital hydrocephalus. A shunt infection was treated with externalization of the shunt, antibiotics and subsequent shunt replacement. At the age of four, the shunt was revised for a distal malfunction. Nine years later, abdominal CT and ultrasound demonstrated large multiseptated cysts. The shunt was externalized and 1.8 L of sterile, xanthochromic peritoneal fluid was drained. The cerebrospinal fluid was clear, colorless, acellular and sterile with normal protein and glucose levels. Two days later, the distal portion of the shunt was replaced back into the pleural cavity. Five months later a pleural effusion formed. Thoracentesis was performed and there was no evidence of infection. The shunt was subsequently converted to a ventriculoatrial system. The patient has remained well for over 3.5 years 22).
Pernas JC, Catala J. Case 72: Pseudocyst around ventriculoperitoneal shunt. Radiology. 2004 Jul;232(1):239-43. PubMed PMID: 15220507. 23).