The distal catheter of VPS can migrate into various body parts including abdominal wall, hollow viscous, vagina, mediastinum, bladder, scalp/sub-galeal space, neck, mouth, breast, thoracic cavity, pulmonary artery, intracardiac, and umbilicus . The reported incidence of distal migration of VP shunt is 10%. Migration into the scrotum is a very rare phenomenon that has been reported in nearly 30 case reports in the literature. Patent processus vaginalis can be present up to 30% of infant, and increasing abdominal pressure following shunt insertion contributes to the mechanism of shunt migration . Most of these problems are due to free position of the lower end in the general peritoneal cavity and thus are able to migrate to any site. Many possible mechanisms have been suggested to explain these observations, yet they remain speculative in nature. It could be due to different causes; mechanical factors such as diaphragmatic movement, peritoneal attachments, intestinal peristalsis, and repeated traction of the peritoneal catheter could be attributed for migration or as Rowe et al. pointed out the patent processus vaginalis . The distal catheter enters the scrotum from the patent processus vaginalis which is patent in 30% of children under 1 year of age. Increased abdominal pressure due to cerebrospinal fluid infusion in the smaller peritoneal cavity in pediatric patients through the shunt system may prevent obliteration of the processus vaginalis and facilitates migration of the VP shunt into the scrotum. The involvement of the right-sided scrotum was prevailing, and this can be due to the fact that the right testicle descends later than the left testicle. Primary prevention can be done by searching for a patent processus vaginalis (PPV) at the time of the first VP shunt placement. Laparoscopy can be used to visualize an appropriate window for the VP shunt insertion and to search for a PPV. If a PPV or an occult hernia is found, then hernia repair should be performed primarily in the same sitting.
Most of the VP shunt migration occurs during infancy and within 6 months of implantation, though in our case, it was after 9 months. The average interval from placement of a ventriculoperitoneal shunt to development of clinically evident hernia or hydrocele was 24 h to 6 months as found by Oktem et al. . Only two cases of distal catheter migration into scrotum occurred in adolescent patients as well as two other cases occurred in an adult males. The residual peritoneal cavity volume is linearly correlated with the body surface area (80 ml/m2); pediatric patients have a higher tendency to have VPS distal catheter migrate into the scrotum due to patent processus vaginalis and smaller peritoneal cavity .
Pandey et al. compared the outcome following placement of a VP shunt in the general peritoneal cavity with that in the right suprahepatic space and found that the complication rate with peritoneal placement was 31.43% while with suprahepatic placement it was only 3%. There was no incidence of inguinoscrotal migration of the shunt if its distal end is placed in a right suprahepatic space and suggested an alternative site of peritoneal end placement in the suprahepatic space to reduce abdominal complications with good results .
The issue of the length of peritoneal catheter and complications related to it has been discussed in the literature and suggests that use of full-length peritoneal shunt catheter is not associated with an increase in complications and eliminates the need to lengthen the peritoneal catheter for growth of the child [10, 11].
Scrotal migration of the distal VP shunt can lead to secondary hydrocoele, incarceration of catheter, and shunt malfunction which in turn can cause worsening of the hydrocephalus. A plain radiographic shunt series should be performed to assess integrity of VP shunt. Herniotomy with repositioning of the shunt tube is the treatment of choice .
While our case may not be unique, it highlights the need for reporting of such cases. Despite it being a known complication, primary prevention by primary repair of hernia using laparoscopy for distal end insertion is not being practiced as standard of care especially in pediatric shunts. We hope, by reporting this case, that issues of length of catheter inserted, need for examination of hernia/hydrocele, distal end placement, early recognition of migration, and prompt repair are addressed.