A peritoneal CSF pseudocyst is a rare complication of ventriculoperitoneal shunt catheter placement. The time from the last shunting procedure to the development of an abdominal pseudocyst ranges from 3 weeks to 5 years.
The wall is composed of fibrous tissue without an epithelial lining and is filled with CSF (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.
Cerebrospinal fluid pseudocysts are seen as a thin-walled cystic mass around the shunt tip. Ultrasonography or CT can indicate the definitive diagnosis.
This is the method of choice in the evaluation of the pseudocyst and other complications at the distal end of the ventriculoperitoneal shunt.
- well defined hypoechoic / anechoic cystic mass with tip of VP shunt within it
- pressure effects on adjacent organs if mass is huge
- multiple septa 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.
Treatment and prognosis
Excision or repositioning of the shunt tip with minimally invasive laparoscopic techniques is usually performed. This technique in the setting of a non-infected pseudocyst has proved to be safe, with results comparable to those of a conventional open surgical technique.
If infection is present, the pseudocyst wall should be excised and the peritoneal shunt tube removed. Percutaneous drainage of the pseudocyst can be both diagnostic and therapeutic.
Possible differential considerations include
- mesenteric abscess
- cystic lymphangioma
- cystic mesothelioma
- mesenteric cyst
- benign cystic teratoma
- cystic spindle cell tumor
- pancreatic pseudocyst
- enteric duplication cyst
- omental 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.
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