Lumboperitoneal shunting in pediatric patients and the role of imaging in its evaluation

Abstract

Lumboperitoneal shunting makes it possible to regulate the flow of cerebrospinal fluid by establishing a connection between the thecal sac and the peritoneal cavity. The main indication for lumboperitoneal shunting in children is idiopathic intracranial hypertension, but the technique is also useful in the treatment of postinfectious, posthemorrhagic, and normotensive hydrocephalus, as well as in the treatment of postsurgical pseudomeningocele or leakage of cerebrospinal fluid.

This article reviews nine cases treated at our centre to show the normal imaging findings for lumboperitoneal shunts in children and to provide a succinct review of the possible neurological and abdominal complications associated with this treatment.

Resumen

La derivación lumbo-peritoneal permite regular el flujo de líquido cefalorraquídeo estableciendo una conexión entre el saco tecal y la cavidad peritoneal. Entre las indicaciones en la población pediátrica se encuentra principalmente la hipertensión intracraneal idiopática, siendo también útil en el tratamiento de la hidrocefalia postinfecciosa, posthemorrágica y normotensiva, en el seudomeningocele posquirúrgico o ante una fuga de líquido cefalorraquídeo.

En este artículo, mediante la revisión de 9 casos de nuestro centro, se pretende mostrar la normalidad del dispositivo en las pruebas de imagen y realizar una breve revisión de las posibles complicaciones asociadas, neurológicas y abdominales.

Introduction

A cerebrospinal fluid (CSF) shunt from the central nervous system (CNS) is a drain from the CNS into another body cavity. It has the general objective of regulating CSF drainage when there is an increase in CSF pressure. Depending on the drainage site, there are various types, including ventriculoperitoneal (VPS), lumboperitoneal (LPS), ventriculoatrial, ventriculopleural, ventriculosubgaleal and ventriculocisternal shunts.

An LPS regulates CSF flow by establishing a connection between the thecal sac and the peritoneal cavity. LPS use has been testimonial to date, largely motivated by a high rate of complications (hyperdrainage, tonsillar herniation, etc.).^1,2 However, recent publications have demonstrated a better safety profile for these devices, mostly thanks to advances in placement techniques³ and the use of valve mechanisms in their operation.^4,5 Advantages of this type of shunt include the entirely extracranial nature of the surgical procedure for placement and the need for fewer revisions with the relative shortening of the device in the growing paediatric population.⁴

The LPS device is made up of three parts (Figs. 1 and 2):

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  A lumbar catheter which enters the thecal sac at the lumbar level.

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  A programmable valve in the subcutaneous cellular tissue of the subcostal region.

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  A peritoneal catheter with a paraumbilical inlet.

Figure 1.

Imaging of the normal path of the LPS without a valve. 3D reconstruction of non–contrast-enhanced abdominal and pelvic CT with posterior, lateral and anterior views (a-c) and maximum intensity projection (MIP) on the midsagittal plane (d) showing the arrangement of the different parts of the LPS without a valve. a) Inlet into the spinal canal through the L2-L3 space (thin arrow). b-d) These show the path of the catheter in the subcutaneous cellular tissue of the right flank from back to front (thick arrows). c and d) These show the pelvic and intraspinal ends of the LPS at T10-T11, respectively (dashed arrows). A capsule in the bowel loops is incidentally visualised.

Figure 2.

Imaging of the normal path of the LPS with a valve. Sagittal and coronal MIP reconstruction (a), 3D anterior and posterior oblique reconstruction (b) and transverse multiplanar reconstruction based on MIP imaging (MipPR) (c) of non–contrast-enhanced abdominal and pelvic CT without contrast, showing the arrangement of the different parts of the LPS with a valve. a) Inlet into the spinal canal through the L1-L2 space (thin arrow), with the cable coiled inside the canal and the end at the L4 level (dashed arrow). b and c) These show the lumbar path of the catheter in the subcutaneous cellular tissue of the right flank up to the peritoneal path (thick arrows), with right subcostal internalisation and a coiled intra-abdominal path. Central abdominal end (dashed arrow). Subcutaneous valve device in right flank (*).

In our case series, all patients (Table 1) except one had a programmable Strata NSC valve.

Table 1.

Summary table of patients.

	Prior treatment	Date of LPS placement	Age at placement LPS (years)	Indication	Valve complications	Time since LPS placement (months)	Management of complications	Currently functioning?	Model
1	Medical, LP	November 2018	10	IIH	Obstruction (kinking) w/o abnormalities	17	Surgical revision	Yes	Strata NSC
						25
2	Medical, LP, surgical	June 2016	9	IIH	Obstruction	35	Surgical revision	Yes	Strata NSC
3	Medical, LP	March 2015	8	IIH	Disconnection	69	Expectant medical management	No	Strata NSC
4	VPS, ETV	May 2015	6	IIH	Disconnection	72	Replacement with VPS	No	Strata NSC
5	Medical, LP	February 2020	12	IIH	No			Yes	Strata NSC
6	Medical, LP	November 2019	7	IIH	No			Yes	Strata NSC
7	Surgical	November 2016	7	IIH	No			Yes	Strata NSC
8	VPS, ETV	March 2017	9	Postinfective hydrocephalus	hyperdrainage	4	Valve ligation	No	Strata NSC
9	Surgical	February 2012	7	Postoperative pseudomeningocele	Persistence of symptoms (valve w/o abnormalities)	63	LPS valve replacement	Yes	Spetzler, Strata NSC

The objective of this study is to summarise the main indications and surgical technique for LPS implantation, with a special emphasis on its radiological assessment compared to normal findings and its complications.

Indications

One of the main indications for an LPS in the paediatric population is idiopathic intracranial hypertension (IIH). Other indications would be postinfective hydrocephalus (often following meningitis), post-haemorrhagic hydrocephalus in a premature infant, hydrocephalus following subarachnoid haemorrhage, postoperative pseudomeningocele, CSF leakage due to another cause and normal-pressure hydrocephalus (the latter in adults).⁶ In IIH, the normal or decreased size of the lateral ventricles represents a technical difficulty for VPS placement; in this case, LPS placement is easier.⁶

In our case series, IIH was the indication for LPS valve placement in seven of the nine cases. In the other two cases, the indications were the development of postinfective communicating hydrocephalus following superinfection of a dermal sinus and the development of a postoperative pseudomeningocele following resection of a posterior fossa pilocytic astrocytoma.

Idiopathic intracranial hypertension

IIH is a rare disease in paediatrics, characterised by increased intracranial pressure in the absence of parenchymal injury, vascular malformation, CNS infection and hydrocephalus. Its aetiopathogenesis has yet to be elucidated;⁷ however, its hypothetical causal mechanisms have been divided into three groups: increased volume of blood or fluid in the brain, overproduction of CSF and impaired reabsorption of CSF in the arachnoid granulations or venous sinuses.^8,9 For this disease to be diagnosed, multiple clinical and neuroimaging criteria must be met,⁷ and there are differences between prepubertal and postpubertal patients. In postpubertal patients, the behaviour of the disease and the epidemiological characteristics of the patients are similar to those in adult patients with IIH: it is more common in females, overweight is a predominant risk factor and headache is the most common symptom.¹⁰

IIH in prepubertal patients is slightly more common in males, and overweight is not a predominant risk factor.⁸ In this group, strabismus due to sixth cranial nerve palsy is as common or more common than headache^1,8 and irritability may be the sole symptom present.⁷ The natural history of the disease often results in visual impairment; therefore, once it is suspected, an ophthalmological examination should be conducted with a focus on detecting papilloedema.⁷ Paediatrics has traditionally used the modified Rangwala criteria for the diagnosis of this disease and the modified Friedman criteria (Table 2).^11,12

Table 2.

Diagnostic criteria for IIH.

Modified Rangwala criteria (combining clinical findings and imaging tests)

Prepubertal patient

Signs and symptoms of IIH or papilloedema

Documented increase in intracranial pressure

Normal CSF composition

Imaging tests (MRI of the head with and without intravenous contrast) with no evidence of hydrocephalus, masses, structural abnormalities or intracranial vascular abnormalities

Cranial nerve palsies may be seen if there is no other identifiable cause and if there is improvement with reduction of intracranial pressure

There should be no other identifiable cause of IIH

Modified Friedman criteria (in the absence of papilloedema and sixth cranial nerve palsy, imaging findings take on a more important role)

Posterior flattening of the sclera

Optic nerve sheath distension

Partially empty sella turcica

Stenosis of the transverse venous sinuses

Complementary tests include MRI of the head with and without contrast in order to rule out other causes of intracranial hypertension such as hydrocephalus, parenchymal lesions, vascular malformations, venous thrombosis and meningeal enhancement suggestive of meningitis.⁷ MRI may also detect signs indicative of intracranial hypertension, such as those compiled by Albakr et al.⁷ and Degnan and Levy:¹³

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  Posterior flattening of the sclera.

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  Optic nerve signs: protrusion or enhancement of the nerve head, distension of the sheath or vertical tortuosity of the intraconal segment of the optic nerve.

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  Partially empty sella turcica.

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  Stenosis of the transverse venous sinuses.

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  Tonsillar herniation.

Scleral flattening, sellar changes and transverse venous sinus stenosis are less common in prepubertal patients than in adolescents.¹⁴ In the absence of papilloedema and sixth cranial nerve palsy, imaging takes on a more important role.

The management of these patients requires a multidisciplinary team (from paediatrics, ophthalmology, neurosurgery, neurology, endocrinology and radiology) and initially includes close ophthalmological follow-up,^10,15 lifestyle changes (such as weight loss), drug treatment (carbonic anhydrase inhibitors such as acetazolamide, diuretics or corticosteroids) or repeated lumbar CSF drainage,^7,9,10,15 intended to decrease intracranial pressure and papilloedema.

Surgical treatment is reserved for cases refractory to medical treatment and includes VPS and LPS valves, which achieve symptomatic relief and improvement in visual function in most cases.^7,9,15 Other occasionally used surgical techniques are endoscopic optic nerve decompression (EOND), which consists of optic nerve sheath fenestration,^9,15 and transverse sinus stenting.⁹

Slit ventricle syndrome

Slit ventricle syndrome is a syndrome of valvular hyperdrainage that develops in patients with VPS placement in which ventricular collapse occurs due to CSF hyperdrainage.^16,17 The classic triad in this syndrome consists of intermittent headache, small ventricles on imaging tests and a slow refilling shunt reservoir. Radiologically, the slit ventricle can be defined as a ratio of fronto-occipital horns (mean of the sum of maximum diameters at the frontal and occipital horns of the lateral ventricles divided by the largest biparietal diameter times two) ≤0.2, at any point during follow-up. Radiological findings indicative of hyperdrainage appear in 10%–85% of patients with a ventricular shunt, but only some of those patients will develop symptomatic hyperdrainage requiring treatment. The management of these patients consists of conservative treatment (posture changes and medication) initially, and surgical treatment in cases of treatment failure. Surgery consists of counteracting the siphon effect and, secondly, possibly replacing the VPS catheter. When refractory symptoms persist, the VPS is removed and another option for a CSF shunt is pursued, such as placement of an LPS. This entails greater technical difficulty given the small ventricular size. Endoscopic third ventriculostomy (ETV) can be performed¹⁶; failing that, cranial expansion is a last resort. There is a subtype of slit ventricle syndrome, likely corresponding to normal-volume hydrocephalus as described by Engel et al., with pathophysiology similar to that of IIH: difficulty in terminal reabsorption of CSF with no restriction of CSF flow between the ventricles and subarachnoid space, with hypertension in the subarachnoid space transmitted in a retrograde direction to the ventricular system, thus hindering its expansion. An LPS would be the type of shunt indicated in this case, since it fosters the establishment of a favourable pressure gradient through the cortical mantle.¹⁷

Surgical technique

The surgical technique for LPS placement used at our centre is the following: the patient is placed in left lateral decubitus with their legs flexed. Access to the thecal sac is gained at L4-L5 through an epidural needle. After CSF outflow upon application of pressure is confirmed, the lumbar catheter is inserted in the spinal canal in a cranial direction. Next, an incision is made in the subcutaneous cellular tissue of the right flank to create a bed for the shunt valve, and the lumbar catheter is tunnelled towards it. The peritoneal catheter is then tunnelled through the abdominal wall to an incision previously made in the abdomen and inserted into the peritoneal cavity through a mini-laparotomy. Finally, the two catheters are connected to the valve.

Modified versions of the technique have been reported. For example, Yang et al.³ performed the technique with the patient first in prone decubitus and then in supine decubitus, and Singh and Vajpeyi¹⁸ carried out the procedure through the left side, all for purposes of reducing complications.

LPS implantation is contraindicated in obstructive hydrocephalus, provided that an alternative pathway for CSF circulation (e.g. through an ETV) has not been created.⁵ Compromise of the foramen magnum (as in, for example, Chiari II malformation) and the absence of an accessible spinal arachnoid space also represent contraindications.¹⁶

Imaging of normal LPS

Precautions in the magnetic field

The LPS valves implanted at present (at our centre, adjustable Strata valves) are compatible with magnetic fields up to 3 T.¹⁹ However, since the magnetic field of the MRI system can alter the pressure setting, it must be adjusted after MRI is complete.

Pre-implantation precautions

Paediatric patients, unlike the adult population, need not undergo imaging assessment of the lumbar spine prior to LPS implantation, given that these patients do not present degenerative bone or disc disease or spinal canal stenosis.³

Follow-up

Following a successful LPS, the clinical staging of the patient improves and a change in ventricular size can be seen on successive imaging studies. A non-decrease or increase in ventricular size, along with clinical deterioration or a lack of clinical improvement, are indicative of shunt malfunction.⁴ Both lumbar and peritoneal catheters are radiopaque;⁴ therefore, XRs can be taken to verify that the catheters are properly positioned and deployed, with all parts connected.²⁰

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  Plain XR. In general, only the anteroposterior (AP) view of the abdomen is needed. A lateral (L) view of the thoracolumbar spine could be included should it be necessary to more accurately locate the lumbar catheter (Fig. 3).

  
  

  Figure 3.

  Imaging of LPS on XR. AP XRs in supine decubitus and lateral XRs with the patient standing of the abdomen in two different patients (a and b). Short arrow: lumbar end of valve; long arrow: abdominal end of valve; dashed arrow: reservoir. The VPS was recently placed and the sutures corresponding to the spinal canal inlet and subcutaneous reservoir placement are identified (b).
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  CT. Potential mechanical complications of the device (disconnection, migration, kinking, etc.) are assessed by means of non–contrast-enhanced CT of the pelvis, extended to the mid-inferior thoracic region. This identifies the end of the abdominal catheter in the pelvis and locates the end of the catheter in the spinal canal (which, in the event of disconnection, might have migrated to the upper thoracic region). With this volumetric acquisition, it is possible to then perform multiplanar reconstructions and 3D reconstructions to best evaluate the valve ends (Figs. 1 and 2).

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  MRI. MRI identifies and locates the lumbar catheter in the spinal canal. A sagittal T2-weighted sequence of the thoracic and lumbosacral spine is recommended, since this sequence would best identify the catheter; coronal sequences of the spinal canal are also useful (Fig. 4). T1-weighted sequences of this same region can also be acquired, as they would identify bleeding or another type of complication. MRI of the head is performed using a non–contrast-enhanced protocol according to the standard sequences acquired at each centre. Our centre adds a T2-weighted 3D turbo spin echo (TSE) sequence (voxel size in mm: 0.3 × 0.3 × 0.6; repetition time: 1400 ms; echo time: 185 ms; acquisition of 16 slices on the sagittal plane centred on the midline, with a duration of 4:44 min). The spine is examined without contrast in the lumbar region, and the thoracic region if necessary, in general through sagittal T1-weighted TSE, T2-weighted TSE and coronal angulated T2-weighted TSE sequences to visualise the spinal canal, and transverse T1-weighted TSE sequences to locate the valve.

  
  

  Figure 4.

  Imaging of LPS on MRI. Sagittal imaging at two adjacent levels in a T2-weighted SE sequence (a) and coronal posterior and anterior imaging in a T1-weighted SE sequence (b). Path of the LPS catheter from inside the lumbar spinal canal with the end at the L4-L5 level, exiting between L2 and L3 (arrows) (a) to the posterior subcutaneous path (arrows) and entering the peritoneum in a right paraumbilical location (dashed arrow) (b). Note the panniculus as these patients are usually overweight. The LPS has low signal intensity on all sequences.

During a shunt revision, to facilitate this process, the intra-abdominal portion of the dysfunctional catheter is sometimes left as a remnant. This is known as an orphaned or abandoned catheter. Abandoned catheters are vulnerable to the same complications as intact catheters, except that there is no risk of ascending infection thereof when they are no longer in contact with the CSF.²¹

LPS patency can be evaluated by means of cisternography with a radionuclide (technetium-99 m diethylene-triamine-pentaacetate [Tc-99 m DTPA]) instilled in the subarachnoid space through lumbar puncture (LP). Although recent studies have shown this technique in combination with CT to have greater sensitivity, it has a low positive predictive value in paediatric patients.^3,20 None of our patients underwent assessment of LPS patency using nuclear medicine techniques; in all cases in which symptoms persisted, surgical assessment was pursued.

To the best of our knowledge, imaging follow-up of these patients is not standardised. At our centre, an AP XR of the abdomen and an L XR of the thoracolumbar spine are taken following valve placement to have a baseline imaging study available should it be needed later on in the event of a suspected mechanical valve complication. If the patient is asymptomatic, imaging follow-up is not performed. A targeted imaging study (MRI of the head or MRI/CT of the spine) is performed if symptoms recur or a complication that could be attributed to the valve is suspected.

Imaging of pathological LPS

Neurological complications

LPS implantation is entirely extracranial,⁴ which minimises the risks associated with VPS placement.²² In addition, the use of programmable valves significantly decreases complications resulting from hyperdrainage.⁴

As mentioned above, clinical deterioration or a lack of clinical improvement, as well as a non-decrease or increase in ventricular size, are indicative of shunt malfunction.⁴

The neurological complications reported in the literature have seen a very significant decrease with technical improvements in the procedure, to the point that none occurred in our case series. The literature features reports of complications including tonsillar ectopia, hydrosyringomyelia, subdural collections, parenchymal and subarachnoid haemorrhage following LPS placement, infection, spinal epidural haematoma following lumbar puncture, and traumatic CSF leakage; all these complications are very uncommon.^23–28

Mechanical complications are more typical, presenting in the form of valve disconnection, system misalignment, kinking, catheter fracture or valve system migration. Disconnection usually occurs early, presenting as a loss of continuity between the valve and one of the catheters or loss of alignment of the catheter–valve–catheter system (Fig. 5). In catheter fracture, usually a late complication, there is a lack of continuity along the tube, not at the valve–catheter junction, with or without migration of the detached fragment. Proximal or lumbar catheter migration is less common than distal or abdominal catheter migration. It usually occurs as a result of poor securing of the components of the shunt. The migrated lumbar catheter usually remains within the spinal cord and is treated with conservative management, repositioning or surgical replacement. Intracranial migration is very rare.²⁹

Figure 5.

Imaging of LPS disconnection. Abdominal CT, sagittal MIP (a), 3D posterior and lateral oblique (b) and anteroposterior (c) reconstructions. a) An LPS is seen inside the spinal canal with the upper end at T7; note that the end has a millimetric tip with a higher density (black arrow) and observe the disconnected end inside the spinal canal between S1 and S2, with no higher-density tip (white arrow). The lumbar valve path has migrated into the spinal canal. b) The images show the absence of the lumbar path of the LPS from the posterior midline to the valve and the patency of the path from the valve to the peritoneal inlet in a paraumbilical location. c) Path of the intra-abdominal LPS with its end at the midline (dashed arrow).

Thoracoabdominal complications

In the literature, abdominal complications are primarily reported in patients with VPS placement; however, assuming that the behaviour of the abdominal catheter component of a VPS is similar to that of an LPS, it is worthwhile to mention some of these complications. They include:

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  Shunt infection: This is one of the most common complications. It can lead to secondary peritonitis, abscesses or catheter obstruction.

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  Pseudocyst: This rare complication commonly occurs months or years after shunt placement. In most cases, it results from infection; encapsulation of the peritoneal catheter and difficulty in reabsorption of the CSF that accumulates along with waste products are thought to be involved in its development. They can become large³⁰ and exert a secondary mass effect on neighbouring structures. On CT, they are fluid collections with thin walls and possible inner areas of higher density due to waste products. The distal portion of the peritoneal catheter is typically identified inside the pseudocyst.²¹

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  Haematoma: An early complication following LPS placement, usually in the abdominal wall. On CT, they are collections with a higher density than liquid, whose attenuation decreases over time with progression; bleeding at different points in time and liquid–liquid levels due to the haematocrit effect may be seen.³⁰

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  Calcification: This rare complication occurs in long-term catheters; the outer surface of the catheter calcifies and becomes stiff and brittle, rendering it vulnerable to mechanical complications such as fracture. On both conventional XR and CT, the calcified portion of the catheter will be denser and thicker than the non-calcified portion.³⁰

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  Obstruction: This is described in the section on neurological complications. CSF leakage and accumulation occur in disconnection and fracture of the segment that runs through the abdominal wall.

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  Distal migration: Paediatric patients are at higher risk of distal catheter migration due to the redundancy thereof to adjust to the child's growth. If the tube retracts from the abdominal cavity into the subcutaneous cellular tissue, a subcutaneous collection may form, and if the tube enters an encapsulated organ such as the liver or spleen, a subcapsular collection may form. The catheter can also migrate into the genitourinary tract or perforate the gastrointestinal tract, with significant morbidity in part due to ascending CNS infection²⁵; it can even surround the bowel, resulting in mechanical obstruction. Much rarer is intrathoracic migration of the catheter through the oesophageal hiatus or diaphragm, due to either a birth defect or diaphragmatic rupture. Intrathoracic migration may lead to CSF hydrothorax, pneumothorax, pneumonia or bronchial perforation.

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  Ascites and hydrothorax: Ascites is a rare complication,³⁰ though it is more common in adults. It can be attributed to ineffective peritoneal CSF absorption. Ascites can occur weeks, months, or even years after catheter placement. Some 15% of paediatric patients with CSF ascites will develop an inguinal hernia or hydrocele; the incidence is higher if the shunt is placed before the patient reaches two years of age.

No abdominal complications occurred in our case series.

Conclusion

An LPS is a type of CSF shunt, used in paediatrics in a testimonial manner to date, that in certain contexts carries advantages over the traditional VPS system, and also represents a treatment alternative in cases of hyperdrainage refractory to said system. Added to the above, the safety profile of LPS has improved in recent times, and therefore its use will probably become more widespread. For this reason, radiologists would do well to familiarise themselves with the main indications for its placement, the surgical technique for its implantation and the radiological evaluation thereof, both under normal circumstances and in the event of complications.

Authorship

• 1

  Responsible for study integrity: MML, BFG and MPB.

• 2

  Study concept: MML.

• 3

  Study design: MML, BFG and MPB.

• 4

  Data collection: MPB.

• 5

  Data analysis and interpretation: MML, BFG and MPB.

• 6

  Statistical processing: N/A.

• 7

  Literature search: BFG and MPB.

• 8

  Drafting of the article: BFG and MPB.

• 9

  Critical review of the manuscript with intellectually significant contributions: MML and SI.

• 10

  Approval of the final version: MML, BFG, MPB and SI.

Conflicts of interest

The authors declare that they have no conflicts of interest.