C H A P T E R

8

Diagnosis and

Surgical Treatment

of Patients with

Hydrocephalus or

Pseudotumor

Ann Marie Flannery

HYDROCEPHALUS

CEREBROSPINAL FLUID PHYSIOLOGY

Cerebrospinal fluid (CSF) surrounds the brain and fills the
ventricles within it. Normally, CSF is produced at a rate of
0.3 mm per minute, or approximately 500 cm

3

per day.

Approximately 50 to 70 percent of the CSF is secreted by
the choroid plexus; the remainder is a venous transudate. At
the time of production, CSF reflects its origin, containing
approximately the same amount of sodium, chloride, and
potassium as plasma. Other normal constituents of cerebro-
spinal fluid include: glucose, approximately two-thirds of
the amount being found in plasma; small amounts of protein,
mainly albumin; and a few white cells—all lymphocytes.

1

Most CSF is produced in the lateral ventricles. From

there, it moves by bulk flow, propelled by the pulsation of
the cardiac output and by respiration. Propelled CSF exits
from the lateral ventricles through the paired foramina of
Monro, into the third ventricle, exiting through the aqueduct
of Sylvius, a narrow channel of 1 to 2 mm, in the midbrain.
From the aqueduct, CSF flows into the fourth ventricle, then
into the subarachnoid space through the paired lateral fora-
mina of Luschka and medial foramen of Magendie to enter
the basal cisterns. Once in the basal cisterns, some fluid
flows along the spinal cord, while the remainder is pumped
slowly over the convexity of the brain to the arachnoid
granulations and villi, where most is reabsorbed.

1

This simple, yet effective, system may be disrupted at

many points. Disturbances in flow may result in hydroceph-
alus, which has numerous causes. The pathophysiology
usually occurs in one of three ways. First, excessive quanti-
ties of CSF may be produced. This cause of hydrocephalus

is the least common. It is, most likely, the result of a tumor,
the choroid plexus papilloma, which secretes excessive
amounts of CSF. Second, CSF production may be normal in
amounts, but its circulation may be blocked—most com-
monly where the pathway is narrowest, at the aqueduct of
Sylvius, but also at the foramen of Monro, the third or fourth
ventricles, or in the subarachnoid spaces. Finally, the path-
ways may be open, but the reabsorptive mechanism may
malfunction, usually the result of hemorrhage or an inflam-
matory process. The result of any of these pathological
events is hydrocephalus. Imaging ultrasound, computerized
tomography (CT), or magnetic resonance imaging (MRI)
reveal enlarged ventricles.

SIGNS AND SYMPTOMS OF
HYDROCEPHALUS

The diagnosis of hydrocephalus may be made when ventri-
culomegaly is noted in association with signs or symptoms
consistent with increased intracranial pressure. Table 8-1
lists the symptoms and signs of hydrocephalus.

CLASSIFICATION OF

HYDROCEPHALUS

Hydrocephalus may be classified by its pathophysiology or
etiology. The pathophysiology, as listed previously, may
include excessive production, obstruction, or failure of reab-
sorption. Excess production is seen only from an uncommon
tumor, the choroid plexus papilloma. Hydrocephalus caused

134

CHAPTER8

Table 8-1

HYDROCEPHALUS IN CHILDREN AND

ADULTS

Symptoms

Emesis
Neck pain

Developmental delay
Developmental regression
Personality changes
Intellectual decline

Irritability

Lethargy
Headache

Signs

In Adults

Vlth nerve palsy

Ataxia

Gait disturbance
Dementia
Incontinence
Paresis of upward gaze

(Parinaud's syndrome)

Hypertension
Bradycardia
Apnea
Coma

In Infants

Increasing head circumference
Full fontanel
Split sutures

by obstruction above the spinal cord is called noncommuni-
cating hydrocephalus. Obstruction may be due to tumors,
blood clots, congenital malformations, or arachnoiditis.
When the CSF pathways are open, but reabsorption fails,
communicating hydrocephalus results. Causes of communi-

cating hydrocephalus include intraventricular hemorrhage,

subarachnoid hemorrhage, and meningitis. Details will be
given in the following sections.

When hydrocephalus is classified by etiology, a division

is made between congenital hydrocephalus and acquired
hydrocephalus. Congenital hydrocephalus is present from
birth and is the result of a central nervous system malforma-
tion. Acquired hydrocephalus, secondary to a postnatal oc-

currence, is caused by infection, trauma, or tumor.

CONGENITAL HYDROCEPHALUS

The majority of cases of congenital hydrocephalus are cate-

gorized as idiopathic; that is, no known cause can be found.
Some are diagnosed prenatally. Although prenatal therapy
has been advocated, intrauterine CSF shunts are rarely per-

formed at present. Children with idiopathic hydrocephalus

may have a good prognosis. Normal intelligence is possible,
and it is likely if anomalies are minimized and the hydro-
cephalus is not severe.

2

Congenital hydrocephalus is usually

noncommunicating. This anomaly in many cases includes
obstruction to CSF flow at some point in the pathway.
Aqueductal stenosis is accompanied by enlargement of the
lateral and third ventricles and a normal-sized fourth ventri-
cle. (See Fig. 8-1.) Some, but not all, cases of aqueductal

stenosis are X-linked disorders. Hydrocephalus associated
with a myelomeningocele is usually noncommunicating. The

hypothesized obstruction to flow is in or around the fourth

ventricle; however, the absorptive mechanisms may also be
developmentally abnormal. Hydrocephalus occurs in up to

95 percent of children with myelomeningoceles. With ade-

quate treatment, 80 percent of these children will have an
intelligence quotient (IQ) above 80.

3

A unique variant of congenital hydrocephalus is the

Dandy-Walker syndrome. Characterized by a large posterior

fossa cyst, with or without dilitation of the lateral ventricles,
the Dandy-Walker syndrome is thought to be a congenital
atresia of the outflow of the fourth ventricle, the foramina of
Luschka and Magendie. Midline cerebellar hypoplasia is
characteristically seen. (See Fig. 8-2.) Seizures, develop-
mental delay, and agenesis of the corpus callosum are often
associated.

4

-

5

ACQUIRED HYDROCEPHALUS

While most cases of congenital hydrocephalus are due to
obstruction, acquired hydrocephalus may be communicating
or noncommunicating. Increased survival of premature in-
fants has resulted in a number of infants with intraventricu-
lar hemorrhage. Neonates, born between 28 and 32 weeks of

gestation, have a layer of subependymal tissue, the germinal

matrix, which is richly supplied with blood vessels. It has
been hypothesized that, as a result of respiratory distress
from immature lungs along with episodes of hypoxemia,
vessels in the germinal matrix of these infants have a ten-

dency to rupture and hemorrhage into the ventricles.

6

Most

of the hemorrhages are asymptomatic and resolve without
therapy. A small number of the most severe type (grades III
to IV) cause communicating hydrocephalus, probably be-
cause of the effects of the red blood cells on the immature
arachnoid villi. Many of these children can be managed by
maneuvers which temporarily drain CSF, such as serial
lumbar punctures. Although some children require a ventri-
culoperitoneal shunt, the overall outlook for these infants is
relatively good, but up to 25 percent will be more severely
affected with major motor dysfunction and/or developmental
delay.

7

-

8

(See Fig. 8-3.)

Any event resulting in red blood cells in the CSF, such as

head trauma, subarachnoid hemorrhage from a ruptured an-
eurysm, or arteriovenous malformation may result in com-
municating hydrocephalus. The mechanism is similar to that
postulated as causing hydrocephalus secondary to intraven-

tricular hemorrhage. Occasionally, this hydrocephalus is

temporary and resolves spontaneously or with temporary
drainage. Intracranial pressure may be controlled by drain-
age of the CSF by lumbar puncture or by an external
ventricular drainage system. Permanent shunting will be
necessary if the hydrocephalus persists.

The inflammatory responses incited by meningitis may

also affect the ability of the arachnoid villi and granulations
to absorb CSF. Communicating hydrocephalus is most com-
monly seen after bacterial meningitis.

9

Tuberculous menin-

gitis has a unique tendency to cause dense inflammatory

adhesions of the basilar meninges.

10

(See Fig. 8-4.) This

DIAGNOSIS AND SURGICAL TREATMENT OF PATIENTS WITH HYDROCEPHALUS OR PSEUDOTUMOR

135

Figure 8-1 Aqueductal stenosis. A.
Axial MRI. B. Sagittal MRI. Note the
lack of signal flow void in the aqueduct
of Sylvius.

intense inflammatory response may bring about obstructive

hydrocephalus, which can be treated temporarily by external
ventricular drainage or permanently by placement of a ven-
triculoperitoneal (VP) shunt. Intraventricular brain
tumors—especially those in or around the aqueduct of Syl-

vius and the fourth ventricle—may also cause acquired hy-
drocephalus.

TREATMENT OF HYDROCEPHALUS

The treatment goals of hydrocephalus include control of

increased intracranial pressure and avoidance of infection.

Achieving these allows the preservation of maximal intellec-

Figure 8-2 The Dandy-Walker syndrome.

Characteristic features include a large
posterior fossa cyst.

tual function and minimizes neurological deficits. Many of
the congenital forms of hydrocephalus are associated with an
overall good outcome. The definitive therapy for hydroceph-

alus is shunting the CSF from the lateral ventricles to

another region where it can be absorbed. The VP shunt, first
available in the 1950s, but improved after silastic tubing
became available, is now the standard of therapy. Cerebro-
spinal fluid may be shunted to other locations, including the
right atrium and pleura. Historically, CSF has been diverted

to other areas, including the gall bladder, stomach, fallopian

tube, and ureter.

Placement of the VP shunt, under general anesthesia, is

usually well-tolerated, even in the youngest individuals.
Risks of the ventriculoperitoneal shunt do include infection,
malfunction, and hemorrhage into the brain or ventricles, but
these complications are uncommon. The expected rate of
infection is 3 to 5 percent.

11

SURGERY

A VP shunt is placed by making a cranial incision and an
abdominal incision and tunneling a valve and silastic tube
between the two incisions.

The ventricular catheter is introduced frontally, anterior to

the coronal suture in the midpupillary line. The alternative

standard introduction is posterior parietal-occipital, inferior
and posterior to the parietal boss and well away from the
sensorimotor cortex, with the tip being directed toward the
frontal horn. After shaving, the patient is placed with the

neck extended and the head turned away from the side to be
shunted. Shunts are usually placed on the right side to avoid
the dominant hemisphere areas.

The scalp incision is made through skin and galea and a

C-shaped flap is centered on the chosen burr hole site. The

scalp is held open by a self-retaining retractor.

The abdominal incision may be located below the costal

edge, below the xyphoid, or along the lateral border of the

(A)

( B )

136

CHAPTER 8

Figure 8-3 A. Grade IV intraventric-

ular hemorrhage seen in a 26-week infant.
B. Same patient as A, following
placement of a ventriculoperitoneal shunt.

rectus sheath near the level of umbilicus. The skin is incised
and sharp and blunt dissection divides the subcutaneous fat

to the external oblique fascia. A tunneling device is used to

create a subcutaneous tunnel between the cranial and ab-

dominal incisions. (See Fig. 8-5A.) The chosen shunt is
passed into the subcutaneous tunnel and the tunneler is
removed.

At the cranial incision, the pericranium is incised. A small

burr hole, 3 to 8 mm in diameter, penetrates the skull. The
dura is incised. A ventricular catheter is passed into the
lateral ventricle. Catheters which start from a posterior bun-
hole are directed into the frontal horn of the ventricle by
aiming toward the medial canthus of the eye* on the ipsila-

teral side. This landmark may vary with the configuration of
the lateral ventricles.

Good flow of CSF confirms appropriate placement. CSF

pressure is checked by a manometer connected to the ven-

tricular catheter. CSF is collected for cell count, Gram's

stain, protein, and glucose. The ventricular catheter is cut to

an appropriate length and connected to the distal valve and

tubing. CSF flow is checked at the distal end.

The layers of the abdominal wall are opened by muscle

splitting or penetrated by a blunt trocar. If a trocar is used,
the bladder must be emptied by preoperative catheterization.
During passage of the catheter through the abdominal wall,

the anesthesiologist should increase the intra-abdominal

Figure 8-4 A. Hydrocephalus

secondary to tuberculosis. B. Note
enhancing basilar meninges.

(A)

DIAGNOSIS AND SURGICAL TREATMENT OF PATIENTS WITH HYDROCEPHALUS OR PSEUDOTUMOR

137

Figure 8-5 A. Placement of the ventriculoperitoneal shunt. Note
incisions and the placement of subcutaneous tunneling device.

B. Ventriculoperitoneal shunt. Ventricular subcutaneous and

peritoneal catheters in final position. This figure illustrates the

parietal occipital approach.

pressure of the patient by inflating the patient's lungs and
delaying expiration (Valsalva's maneuver). Each incision is

then closed. (See Fig. 8-5S.)

VENTRICULOPERITONEAL (VP)

SHUNT INFECTIONS

The VP shunt may become infected, with shunt infecjjon

manifesting as acute or chronic. Although the treatment is

similar for both presentations, the clinical presentation is
different for each and is important to discuss.

Acute shunt infection occurs days to weeks after the

placement of the shunt. The patient is usually febrile. The

wound often, but not always, demonstrates erythema and
may have a purulent drainage. The subcutaneous tract of the
shunt can also become erythematous. The peripheral blood
count will demonstrate an elevated white count with a left
shift. If the shunt is percutaneously tapped, the CSF will

generally have an increased number of white cells and

positive cultures. The CSF Gram's stain may also be posi-
tive. An infected shunt will usually malfunction, and the

resultant increased intracranial pressure combined with the

infection will cause the patient to appear very ill.

Chronic shunt infections occur weeks to months after the

shunt has been placed. The most common presentation for a

chronic shunt infection is that of repeated malfunctions.

Systemic signs such as fever and elevated peripheral white

COunt may or may not be present. If the shunt is tapped, the
CSF white count may be only slightly elevated, the Gram's

stain may be negative, but the culture will usually be posi-

tive. Occasionally, infection can be diagnosed only when the
shunt device is cultured.

Treatment of a shunt infection, whether acute or chronic,

is accomplished by removing the entire system. Particular

attention must be paid to extracting all foreign bodies from
the ventricular system. An external ventricular drain is then

placed to control CSF flow. Appropriate antibiotics are

started after cultures of CSF and removal of the shunt

hardware. Duration and dosage of antibiotics are determined
by the organism infecting the shunt. The draining CSF

should be cultured daily to monitor the effectiveness of the
chosen antibiotic and to detect suprainfections, which may
occur. When the culture shows that the infection has been

eradicated, a new shunt system is installed.

Alternative therapeutic plans to treat shunt infections may

be effective. The treatment should include high-dose intra-
venous antibiotics, plus installation of antibiotics into the

shunt via percutaneous puncture, with or without preplace-
ment of the system. Other plans use the externalization of

the existing system via an incision at the cervical, thoracic,

or abdominal tract of the shunt, draining the CSF and
antibiotic administrations. The system is then replaced after
an appropriate period of antibiotic therapy.

Organisms which commonly infect the shunt include

Staphylococcus epidermidis (SE) and Staphylococcus

aureus. SE is the most common infecting organism. Less-

common infections are caused by anaerobic diphtheroids,

Escherichia coli (seen most commonly in premature and

term infants), as well as organisms known to cause meningi-
tis. Treatment duration is usually 10 to 14 days after the
culture becomes negative. The treatment for virulent or

highly resistant organisms may be longer.

138

CHAPTER8

If treated promptly and vigorously, shunt infections

usually resolve without sequelae. Complications, however,
can include cerebritis with cortical damage, polycystic ven-

tricles, brain abscess, and peritoneal CSF malabsorption.

Developmental delay has been associated with severe shunt
infections with E. coli occurring in the neonatal period.

PSEUDOTUMOR CEREBRI

Intracranial pressure may be increased without ventricular
enlargement. This disorder is termed benign intracranial

hypertension, or pseudotumor cerebri. Affected individuals

present with papilledema, or, in infants, bulging fontanels.

The primary symptom is headache. Other symptoms include
dizziness, nausea, vomiting, paresthesia, diplopia, tinnitus,
and blurred vision. Signs include abducens and facial nerve

palsy, especially in children.

13

The most serious symptom is

visual loss, which can be abrupt and irreversible.

14

Affected

individuals may demonstrate hemianopia, quadrantanopia,

and, following prolonged visual loss, optic atrophy.

13

Imaging studies will usually include a CT to screen for

overt hydrocephalus. An MRI with gadolinium enhancement

should be performed to evaluate the patient for tumor and

vascular occlusions. Lumbar puncture will demonstrate in-
tracranial pressure, which is significantly above normal

(greater than 200 mm of water.)

14

Multiple etiologies have been proposed as the cause of

pseudotumor. The most commonly affected individual is an
obese young woman, often with menstrual irregularities.
Usually, no clear anatomical or endocrinological abnormal-
ity is found in this group of patients who have idiopathic
pseudotumor.

Pseudotumor cerebri has been found in association with

numerous lesions or agents. The leading cause in the prean-

tibiotic era was mastoiditis. Other proposed etiologies in-
clude: antibiotics, especially tetracycline; steroids; oral con-

Figure 8-6 A. Idiopathic hydrocephalus
with marked ventriculomegaly prior to
placement of a shunt. B. Same child, age
3, with excellent ventricular decompression.
Development is so far normal.

traceptives; excesses and deficiencies ot vitamin A;
hypothyroidism; anemia; polycythemia vera; head injury;
and infection, including Lyme disease; as well as autoim-

mune disorders, including discoid lupus erythematosis.

13

Treatment of pseudotumor includes detecting and correct-

ing the underlying problem. For idiopathic pseudotumor,
medical management may include exogenous corticosteroids
and diuretics, such as furosemide (Lasix) or acetazolamide.
If symptoms continue or visual acuity worsens, lumbar

puncture, sometimes once or serially, is often effective. If

the need for serial lumbar punctures persists and the symp-
toms persist or worsen despite therapy, a permanent diver-

sion of CSF via shunt, usually lumbar subarachnoid-periton-

eal, is indicated.

NORMAL PRESSURE

HYDROCEPHALUS "

Normal pressure hydrocephalus is one of the few treatable
causes of dementia. First described by Hakim and then by
Adams in 1965, this disorder is characterized by the clinical
triad of dementia, gait ataxia, and urinary incontinence.
Additional features include usually normal intracranial pres-
sure and enlarged ventricles.

15

Some patients who present with normal pressure hydro-

cephalus have a known or probable cause, including trauma,
meningitis, subarachnoid hemorrhage, or tumors. The deci-
sion to treat is often straightforward, and the outcome is
usually quite satisfactory in this group.

Idiopathic normal pressure hydrocephalus can be difficult

to treat. Those patients who are most likely to benefit have a
significant gait disturbance and a limited degree of dementia.
A radionuclide cisternogram may provide useful objective

data of altered CSF dynamics. Some reports favor the use of

lumbar puncture to assess improvement and pressure prior to
shunting.

16

(See Fig. 8-6.)

(A)

(B)

DIAGNOSIS AND SURGICAL TREATMENT OF PATIENTS WITH HYDROCEPHALUS OR PSEUDOTUMOR

Placement of a shunt in these patients is similar to the

procedure described above. Technical difficulties include the

selection of the correct valve pressure to achieve maximum

benefit with minimum risk. The most significant risk is that
of extra-axial fluid collections of CSF or blood due to
overshunting. These collections may be asymptomatic, but

often the patient presents with headache, a diminished level

of consciousness, or new neurological deficits. When the

clinical situation warrants, additional surgery to drain the

subdural collection, adjust the shunt pressure, or remove the

shunt completely may be necessary.

REFERENCES

1. Rowland LP: Blood brain barrier, cerebrospinal fluid, brain

edema, and hydrocephalus, in Kandel ER, Schwartz JH (eds):
Principles of Neural Science, 2d ed. Amsterdam, Elsevier,

1985, pp 837-844.

2. Hudgins R et al: History of fetal ventriculomegaly. Pediatrics

82:692-697, 1988.

3. McLone DG, Nardic TP: Myelomeningocele: Outcome and

late complications, in McLaurin RL et al (cds): Pediatric

Neurosurgery. Philadelphia, Saunders, 1989, chap 4, pp 53-70.

4. Raimondi AJ, Sato K, Shimoji T: The Dandy Walker Syn-

drome. Basel, S Karger, 1984.

5. Pasueal-Castroviejo I et al: Dandy Walker malformation: Anal-

ysis of 38 cases. Child's Nervous System. 7:88-97, 1991.

6. Hill A, Shackelford GD, Volpe JJ: A potential mechanism of

pathogcncsis for early post-hemorrhagic hydrocephalus in the

premature, newborn. Pediatrics 73:19-21, 1984.

7. Palmer P, Dobowitz LMS, Levene MT, et al: Developmental

and neurological progress of preterm infants with intraventri-
cular hemorrhage and ventricular dilation. Arch Dis Child
57:748-753, 1982.

8. Paplie LA, Munsick Bmno G, Schaefer A: Relationship of

cerebral intraventricular hemorrhage and early childhood: Neu-
rological handicaps. J Pediatr 103:273-276, 1983.

9. Handler LC, Wright MGE: Post

infancy. Neumradiology 16:31-35, 1978.

10. Adams RD, Victor M: Principles of Neurology, 3d ed. New

York, McGraw-Hill, 1985, chap 31, pp 510-544.

11. McLaurin RL: Ventricular shunts: Complications and results,

in McLaurin RL et al (eds): Pediatric Neurosurgery. Philadel-
phia, Saunders, 1989, chap 15, p 223.

12. Chutorian AM, Gold AP, Braum CW: Benign intracranial

hypertension and Bell's palsy. N Engl J Med 296:1214-1215,

1977.

13. Gree M: Pseudotumor cerebri, in Youmans J (ed): Neurologi-

cal Surgery. Philadelphia, Saunders, chap 122, pp 3514-3530.

14. Jefferson A, Clark J: Treatment of benign intracranial hyper-

tension by dehydrating agents with particular reference to mea-

suring the blend spot area as a means of recording improve-

ment. ./ Neural Neurosurg Psychiatry 39:627-639, 1976.

15. Adams RD et al: Symptomatic occult hydrocephalus with

"normal" cerebrospinal fluid pressure. A treatable syndrome.

AT Eng/7 Med 273:117-126, 1965.

16. Wood JH et al: Normal pressure hydrocephalus: Diagnosis and

patient selection for shunt surgery. Neurology 24:517-526,

1974.

STUDY QUESTIONS

I. A newborn was referred because of a large head. Delivery

had been by C section because the head did not engage.
Pregnancy had been normal.

1. What diagnoses might be entertained? 2. How could

they be differentiated? 3. What respective treatments might
b& instituted? 4. What accompanying conditions might influ-
ence the intellectual outcome? 5. What might be the anatom-
ical causes of hydrocephalus?

II. The patient described in question I above has hydroceph-
alus and is treated by a ventriculoperitoneal shunt. Four days
later the patient begins running a fever, vomiting, and devel-
oping a tight fontanel. There is erythema about the incision
over the cranium.

1. What is the most likely complication of the shunt?

2. How should it be treated? 3. What is the most likely
offending organism? 4. For how long should the shunt be
externalized? 5. How might this complication influence the
eventual outcome?

III. A 45-year-old male with a previous history of a
ruptured aneurysm treated successfully 10 years earlier is
referred because of an increasingly ataxic gait and deterior-
ating intellect. Detailed history reveals that the patient has
also been experiencing urinary incontinence in recent
months. The patient denies headaches. A CT scan reveals
enlarged ventricles and the sulci are almost completely
obliterated.

1. What is the most likely diagnosis in this patient?

2. What therapies might be considered? 3. What is the
likelihood of recovery of the described deficits? 4. What is

139

140

CHAPTER8

the explanation for the hydrocephalus? 5. What tests might

be used to confirm a diagnosis of malabsorption?

IV. A 24-year-old overweight female is referred because of
headaches and decreasing visual acuity. The headaches have
been present for 3 months, but the loss in vision has been
noticed during the last week. The patient has severe papille-
dema. Menstrual periods have been irregular for several
months.

1. What is the most likely diagnosis? 2. What imaging

examinations would be helpful in confirming the diagnosis'?
3. Assuming that a diagnosis of "pseudotumor" is con-
firmed, what type of shunting device will be most efficiently
applied? 4. What is the most feared complication of "pseu-
dotumor"? 5. What is the most likely eventual outcome

assuming a shunt were implanted and headache relieved?

V. A child of 6 years who had a VP shunt implanted shortly

after birth is admitted with severe headache, nausea, vomit-
ing and papilledema. A CT shows moderately enlarged
ventricles.

1. What are the diagnoses that should be entertained?

2. What studies should be obtained? 3. Assuming plain
x-rays showed a disconnection of the distal catheter from the
valve, what treatment should be administered? When?
4. Assuming the cranial catheter to be connected by the tip
lying at the region of the trigone and the distal shunt intact,

what etiology of shunt obstruction should be entertained?

How might the diagnosis be confirmed before surgery?
5. What surgical procedure should be performed assuming
the proximal catheter cannot be removed easily?