Intraabdominal Pressure : Is it a Cause of Shunt Dysfunction ? A Pediatric

Ventriculoperitoneal shunting is the most common and most effective method to resolve hydrocephalus. A dysfunctioning shunt is a cold fact and beginning of cascades of various problems for every neurosurgeon. In this article we discussed probable mechanisms of shunt dysfunction due to an abdominopelvic problem which is treated by a basic indwelling urinary catheter in a 14 year old boy.


INTRODUCTION
Since its first utilization in 1898 by Ferguson, usage of ventriculoperitoneal shunts are the most common and most effective method to resolve hydrocephalus (28).These devices work on the basis of Pascal's law and challenge against the laws of entropy.Every man made device is destined to deterioration and breakdown and shunts are not an exception.A dysfunctioning shunt is a cold fact and beginning of cascades of various problems for every neurosurgeon.
In this article we discussed probable mechanisms of shunt dysfunction due to an abdominopelvic problem which is treated by a basic indwelling urinary catheter.

CASE REPORT
A 14 year old boy who had,cerebral palsy, urinary retention and a previous history of V-P shunt operationwas admitted to our institute's emergency department with abdominal pain,abdominal sensitivity including anddecrease in level of consciousness.In his physical examination he had a severe sensitivity in abdomen.He underwent an immediate abdominopelvic ultrasonography scan (USG) and cranial computed tomography scan.(CT).It seen he had a globe vesicale.Additionally ventricles were severely dilated compared to his last follow up visits (Figure 1).Immediate urinary catheter was administered for providing outflow of urine.Two days after on his control abdominopelvic USG bladder size was normal and there was no sign of globe vesicale.Also control cranial CT scan showed significant decrease in ventricular size (Figure 2). 2 days later patient discharged with intermittent urinary catheterization.

DISCUSSION
Since its first usage by Ferguson in 1898, peritoneal cavity is the most common site for cerebrospinal fluid (CSF) absorption.After its popularizationand advent of silicon elastomer, lumboperitoneal shunt systems became widely used (8,16).
We hypothesized two probable cause of abdomen related dysfunctioning of shunt system.Barker et al mentioned, augmentation of bladder, especially in meningomyelocele (MMC) patients would cause distal shunt obstruction due to bladder perforation (9].When all patients investigated in their series this dysfunction is not due to infection since culture of the tip was negative in all.They concluded free urine in the abdominal cavity decreased resorptive ability of the peritoneum due to inflammation and as a result of this process a pseudocyst-type problem develops (7,9).
From this point of view our first hypothesis is resorptive ability of peritoneum is one of the main variables of a "functional shunt system".But is it enough to explain pathophysiology of our case?
Our patient had no free-fluid in USG scans and had no signs, symptoms or findings of a perforation.He experienced a process causing an increase in intraabdominal pressure.In 2011 Al-Hwiesh et al studied on 13 men and 12 women end-stage renal disease patient, for calculating if there is any statistical difference between intraperitoneal pressure (IPP) and intraabdominal pressure (IAP).Their findings indicated there is no statistical difference between IPP and IAP (1).Additionally in 2008 Sahuquillo and Arikan determined a strong relationship between IAP and body mass index (BMI).They found BMI has a positive relationship with IAP (25).Also there are examples of case reports about shunt dysfunction secondary to pregnancy with no signs of shunt obstruction.(22,27,32).In their case report Murakami et al solved the intraabdominal pressure problem by replacing the shunt as ventriculoatrial shunt (22).As a result our more probable hypothesisisthat globe vesicale caused an increase in IAP and IPP respectively.So increasing IPP and IAP decreased resorptive ability of the peritoneum.In addition, increased IAP act like a mechanical barrier and following, increased IAP probably caused an increase in proximal pressure, due to Pascal's law and dilated ventricles.
Controversial issue on this case is we did not perform any radioisotope technique because globe vesicale is an emergent situation and urinary catheter should be applied as soon as possible.

CONCLUSION
Intraabdominal pressure is a neglected element of shunting.While evaluating a shunt dysfunction case not only shunt dependent problems but also abdomen related problems must have considered.This situation is especially important for cases with impaired neurological control of bladder such as myelomeningoceles.

Figure 1 :
Figure 1: Dilated ventricles on first CT scan with globe vesicale.

Figure 2 :
Figure 2: Normal ventricles was observed on the following 2nd day on CT scan.