Teaching Case

A 5-year-old child presented with abdominal pain after falling down 6 hours before. On examination the patient had swelling and tenderness at the right hypochondrial region. A V-P shunt was placed 4 years before to treat obstructive hydrocephalus.

The patient was referred to ultrasound unit where a large hepatic subcapsular fluid collection was detected which indented the hepatic surface (Fig. 1a). High resolution Ultrasonography tracked the VP shunt tube and found it to lie in subcapsular position (Fig. 1b).
Non contrast CT axial cuts demonstrated the subcapsular fluid to be of low attenuation (average 6 HU in density) that excluded subcapsular haematoma (Fig 2a) and the shunt tip was seen within the fluid beneath hepatic capsule (Fig. 2b). Free ascites was also noted (Fig. 2c). The course of the shunt tube is illustrated in the MIP image (Fig. 3), it descended along the subcutaneous tissue of the left anterior chest wall and left anterior abdominal wall and then at level of L2 vertebra it penetrated the anterior abdominal wall muscles and directed superiorly and to the right side forming a loop (Fig. 3) and ended in right hypondrium.

The VP shunt has been widely used in treatment of obstructive hydrocephalus since 1908 as the peritoneal cavity is an effective way for absorption of CSF. Many complications occur either at the ventricular end e.g. obstruction or at abdominal end e.g. infection, obstruction of the distal tuba, peritoneal pseudo cyst formation, abnormal migration of the tube e.g. to the scrotal sac and bowel obstruction [1, 2].
Radiological evaluation of patients with VP shunt placement is important if there is suspicion of shunt malfunction or newly developed manifestations e.g. headache, vomiting, fever, abdominal swelling or increased head circumference [1]. Ultrasound and CT are the primary methods of evaluation of VP shunt and its possible abdominal complications while Tc99m DTPA is used to detect tubal obstruction [2].
In this case of abnormal location of the VP shunt tube, the tip of the shunt tube dissects the hepatic capsule and lies beneath it. The rest of the tube, with its side holes, is extra-hepatic in location which results in slow pouring of CSF in subcapsular space through the tip while most of CSF is drained via the side holes to the peritoneal cavity and hence responsible for the delayed discovery of this subcapsular collection.
Shunt tube revision follow by CT is the appropriate management.