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We read with great interest the case report, ‘Unusual complication of ventriculoperitoneal shuts: Anal extrusion’ published in MJAFI 2007; 63(1): 82-4.
Anal extrusion of the abdominal end of a shunt catheter is a very rare complication but has significant scope for serious and life threatening sequelae, as very well brought out in the paper. The most common clinical presentation is meningitis, which occurs in about 43% of these cases. Fewer than 25% of such cases may present with peritonitis . Various mechanisms have been suggested with regard to the pathogenesis of the perforation viz. foreign body reaction, pressure necrosis of intestinal wall by the tube, and silicon tube allergy. The catheter most commonly associated with perforations, is the Ralmondi spring coiled catheter. The introduction of softer, more flexible silastic tubing has reduced, but not totally eliminated the incidence of bowel perforation .
However, a few points in the paper need to be clarified. Standard teaching recommends a different approach to such cases. A small incision is given over the shunt catheter over the abdomen (previous abdominal insertion site could also be chosen), the catheter is located, amputated and exteriorised. The anal protruding distal segment is then pulled out from the anal opening, pre empting any chance of peritoneal or subcutaneous track contamination with luminal microorganisms. Sequential cerebrospinal fluid (CSF) analysis is done daily from the exteriorised catheter and when infection has been conclusively ruled out, revision into a fresh abdominal site can be done . However, some surgeons believe such an anally extruded shunt to be a potentially contaminated system in spite of normal CSF reports and prefer to remove the whole shunt assembly and place a fresh shunt on the contra lateral site.
This thinking is actually reflected in the algorithm described by the authors (Fig. 3) and we fail to understand why the same algorithm was not applied in Case 2. The authors have described removal of lower end of an anal extruded shunt catheter through a neck incision. The procedure of pulling out the entire distal catheter through a neck incision potentially causes contamination of not only the peritoneal cavity but also the subcutaneous track up to the neck incision. As CSF analysis showed no evidence of infection, replacement with a fresh distal catheter was done at the same sitting. Leaving behind and using the original ventricular catheter and tunnelling a fresh abdominal catheter through such a potentially contaminated track at the same sitting in spite of normal CSF reports is fraught with danger. This is clearly reflected in the complications and morbidity that followed in Case 2.
It is amazing how a recurrent extrusion could take place within 48 hours (Case 2). As described elegantly in the pathophysiology by the authors, the process of bowel penetration is slow and takes place over a period of time. This repeat extrusion within 48 hours could probably be explained by inadvertent intra luminal placement of abdominal catheter during the repeat procedure .