A 25 yo female presents with abdominal pain and associated mass that has been slowly increasing in size over several months.  She has a history of VP shunt for hydrocephauls as a child.  Physical exam reveals a firm midline mass in her lower abdomen palpated to the level of the umbilicus.  What's the diagnosis?  (scroll down for answer) 

Answer: VP-Shunt associated abdominal pseudocyst

• Ventriculoperitoneal (VP)- associated abdominal pseudocyst is a rare complication of VP shunts
• Cyst wall may develop from focal peritonitis or low-grade infection, however true mechanism of formation not fully delineated
• Pressure from CSF may or may not affect shunt function - some patients may present with signs and symptoms of shunt failure (headache, altered mental status, focal neurologic signs) while others present with abdominal symptoms related to increasing mass (pressure, nausea, decreased appetite, difficulty with urination)
• Treatment is cystectomy and relocation of VP shunt
• Read more on VP shunt associated pseudocyst
• Shunt can be seen marked by yellow arrows below