Radiology quiz

FRANK P. MORELLO, MD

aFall 1997

HISTORY: A 16-year-old female with a medical history of meningomyelocele repair at birth presented with headaches, nausea and vomiting. Figure 1 is from the shunt series taken at the time of admission.

FIGURE 1. AP view of the upper abdomen showing the distal end of the shunt tube.

QUESTIONS: What is the significant radiographic finding and the most likely diagnosis? What confirmatory imaging exam would be useful for further evaluation?

FIGURE 2. Left upper quadrant sonogram with shunt tube in the center of a fluid collection.

RADIOGRAPHIC FINDINGS: The distal end of the shunt tube is coiled tightly on itself in the left upper quadrant. A sonogram, Figure 2, identifies a part of the shunt tube (arrow) within a localized fluid collection (arrowheads) in the left upper quadrant.

DIAGNOSIS: CSF pseudocyst.

Discussion

The diversion of cerebrospinal fluid with the use of ventriculoperitoneal shunts is the most frequently used method for the relief of increased intracranial pressure due to hydrocephalus. A few common conditions requiring ventriculoperitoneal shunts include, congenital hydrocephalus, cerebellar tumors, posterior fossa cysts and meningomyelocele.

A child with a ventriculoperitoneal shunt who develops signs or symptoms of increased intracranial pressure must be carefully examined. After clinical evaluation, a CT of the brain to assess change in ventricular size and a shunt survey to exclude extracranial ventriculoperitoneal shunt complications are usually included in the radiographic workup. The shunt survey consists of AP and lateral views of the head and neck plus an AP view of the chest and abdomen. Additional views may be necessary to see segments of the shunt that are not clearly seen on the standard views.

TABLE 1
Complications of Ventriculoperitoneal Shunts

Common
Malfunction
Mechanical—disconnection or kinking
Occlusion*
Infection*
CSF loculation
Visceral perforation
Shunt migration
Uncommon
Intestinal obstruction—not due to adhesion
Metastatic tumor spread

*Not readily diagnosable with standard radiographic examination

A variety of complications have been associated with ventriculoperitoneal shunts. They may be broadly divided into intracranial and extracranial complications. The common and uncommon extracranial complications are listed in Table 1.

Loculated intra-abdominal collections of cerebrospinal fluid are termed CSF pseudocysts or CSF-omas. They may be diagnosed with plain radiographs when bowel loops are displaced or a soft tissue mass is present. A shunt normally drains up to 500 ml. of cerebrospinal fluid per day, so a small amount of fluid in the peritoneal cavity may be normal. However, if adhesions develop around the tip of the shunt tube, eventual encapsulation and obstruction will occur. Sonography can confirm the presence of these collections. When plain-film signs of fluid loculation are not identified, sonography is very sensitive for the detection of smaller but significant collections. The shunt tube has a characteristic sonographic appearance, typically several parallel echogenic lines. When the shunt tube can be seen within or leading to a localized fluid collection, the diagnosis of a CSF pseudocyst can be made with confidence.

FIGURE 3. AP abdomen film of an infant boy whose father noticed the shunt tube protruding from the rectum.

Peritoneal shunt tips may migrate to regions outside the peritoneal cavity, such as the thorax via a diaphragmatic hiatus or into the scrotum through a hernia sac. The shunt may also perforate the bowel or other viscera including gallbladder, liver, vagina, bladder and uterus. In Figure 3, the distal portion of the shunt tube has perforated the colon and follows the course of the colon. This may become clinically obvious if there is extrusion of catheter through the anus. Perforation is presumed to be to secondary to shunt migration and adhesion at the entry site. After eroding into the lumen of the bowel, the shunt is usually propelled distally by the intestinal peristalsis and may disconnect the tube from its proximal connection. Perforation may also be associated with peritonitis and interloop abscess formation, leading to shunt obstruction and ventriculitis.

FOR FURTHER READING:

1. Agha FP, Amendola MA, Shirazi KK, et al: Abdominal complications of ventriculoperitoneal shunts with emphasis on the role of imaging methods. Surg, Gynecol Obstet 1983;153:473–477.

2. Murtagh FR, Quencer RM, and Poole CA: Extracranial complications of cerebrospinal fluid shunt function in childhood hydrocephalus. JR 1980;135:763–766.

3. Lipinski JK, Peacock WJ, Cremin BJ: Ultrasound evaluation of complications in shunted hydrocephalus. Clin Radiol 1984;35:275–279.

4. Agha FP, Amendola MA, Shirazi KK, et al: Unusual complications of ventriculoperitoneal shunts. Radiology 1983;46:323.

5. Gonzalez MG: Extrusion of peritoneal catheter through the anus. Child's Nerv Syst 1987;3:183–184.

6. Post EM: Currently available shunt systems: A review. Surgery 1985;16(2):257–260.

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