Pediatr Radiol (2013) 43:1009–1016
DOI 10.1007/s00247-013-2627-z
PICTORIAL ESSAY
Fate, complications and MRI implications of retention
anchor suture placed during gastrostomy in children
Surendra Narayanam & Vicente de Oliveira &
Ganesh Krishnamurthy & Elhamy Bekhit &
Madeleine Sertic & Hai-Ling Cheng &
Bairbre L. Connolly
Received: 27 August 2012 / Revised: 15 November 2012 / Accepted: 27 November 2012 / Published online: 17 February 2013
# Springer-Verlag Berlin Heidelberg 2013
Abstract Retrograde radiologic gastrostomy is one of several techniques used for placing a gastrostomy and is a
common technique used in children. The use of a retention
anchor suture (RAS) is an important component of this
procedure. This pictorial essay explores the normal course
and passage of the RAS, as well as abnormal migration,
various complications and the implications of the RAS with
regard to MRI safety.
Keywords T fastener . Retention anchor suture .
Gastrostomy . Pediatrics
Introduction
Although different methods—surgical, endoscopic and radiologic methods— are available for performing gastrostomies in
children, the percutaneous radiologic retrograde gastrostomy
S. Narayanam (*) : V. de Oliveira : M. Sertic : B. L. Connolly
Diagnostic Imaging, Division of Image Guided Therapy,
The Hospital for Sick Children, 555 University Ave,
Toronto, Canada M5G 1X8
e-mail: nrssbabu@gmail.com
G. Krishnamurthy
Department of Radiology, The Children’s Hospital of Philadelphia,
Philadelphia, PA, USA
E. Bekhit
Medical Imaging, RCG Melbourne, Melbourne, Australia
H.-L. Cheng
Diagnostic Imaging, The Hospital for Sick Children,
555 University Ave,
Toronto, Canada M5G 1X8
using a retention anchor suture (RAS) is a technique commonly
employed [1–4]. An alternative term for the RAS is a T fastener. A fundamental component of all methods of gastrostomies is
gastropexy, which refers to the fixation of the anterior wall of
the stomach to the anterior abdominal wall. Single or multiple
gastropexies can be done depending on operator preferences
and institutional practice. In retrograde radiologic gastrostomy,
gastropexy, although not obligatory, is facilitated by a RAS.
One of the RAS commonly used consists of a tiny longitudinal piece of metal with blunt ends, with a thread
attached to its center (Cope Pediatric Gastrointestinal Suture
Anchor Set, Cook, Bloomington, IN). The suture is a braided polytetrafluoroethylene (PTFE) impregnated polyester
fiber. Its metal part is made up of a central metal core with
a metallic wire wrapped around the core. The pediatric RAS
is 1.3 cm in length and 0.025 inches (~0.063 cm) in diameter; the adult RAS is 2.0 cm in length and 0.038 inches
(~0.095 cm) in diameter (Fig. 1). The number of RAS used
during the gastrostomy varies from zero to four, depending on operator preference as well the requirements of
the fixation [2, 5–10]. As the RAS is not expensive (in
the order of $30 Canadian for two) and the potential
advantages significant and complications uncommon, the
risk–benefit balance may be considered in favor of its
use. There are no strict guidelines for when to use a
pediatric versus an adult RAS. The pediatric RAS is
commonly used when performing a gastrostomy procedure in infants and children (e.g., up to approximately
35 kg, 10 years of age, thin abdominal wall), whereas the
adult RAS may be used in older teenagers (e.g., more
than 40 kg, > 12 years of age, thick abdominal wall).
Little is known in the literature about the RAS in terms of
the natural course of its passage, and its normal and
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Pediatr Radiol (2013) 43:1009–1016
Fig. 1 Retention anchor suture
(RAS) used in enterostomy tube
insertion. a Magnified view of
the RAS with thread attached to
its center. b Pediatric (top),
adult (bottom) RAS for
comparison
abnormal appearances. Kim et al. [1] described 25/248
anchor-related complications in their series (breakdown of
string in five, early release of anchor in nine, migration into
peritoneal space in eight, and expulsion from body in three
patients). Although we have had experience using the RAS
in children for years, we paid little attention to it until
recently, as issues or complications related to the RAS are
uncommon.
However, after a 4-year-old child presented to our service
when she developed focal pain at her gastrostomy tube
(G-tube) site following an MRI study, we decided to
review the fate of RAS in children following G-tube
placement. Clinical examination revealed the RAS extruding through her stoma. Her pain resolved following
manual removal of the RAS (Fig. 2).
Fig. 2 A 4-year-old girl with a
low-profile button type of
gastrostomy tube (G-tube). a
The orientation of the RAS
(arrow) is in the same axis as
the button. b The girl
complained of a focal pain at
the insertion site. On
examination, the RAS was seen
partially extruded from the
tract. c The RAS was removed
manually using a forceps, with
resolution of symptoms
The aim of this pictorial essay is to review for the diagnostic and interventional radiologist some procedural
aspects of the RAS, various appearances of the RAS, complications and MRI-related implications of the suture.
Historical perspective
The original description of the gastropexy device was the
“Brown/Mueller T fastener” in 1986 [7]. The original device
consisted of a needle with side slot near its tip for keeping
the metal part of the T fastener, with the nylon thread
running along the side of the needle. In the same year, Cope
[11] also introduced a different design of anchor device,
which is the basis of the current RAS commonly used.
Pediatr Radiol (2013) 43:1009–1016
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Technique
The technique described here is just one method of retrograde percutaneous gastrostomy in children and reflects our
practice. Many variations of this technique are possible. The
procedure of gastrostomy tube (G-tube) insertion can be
performed under local anesthetic alone, sedation or general
anesthesia in children. A dilute barium enema may be used
to outline the colon so as to avoid traversing it. The liver and
spleen edges are usually marked with sonography. The
stomach is inflated with air and localized with a combination of sonography and fluoroscopy. A single pediatric
RAS is loaded manually into an 18-G needle (Fig. 3),
which is used to puncture the stomach. We virtually never
use more than one RAS for G-tube, as compared to
cecostomy tubes where we routinely use two RAS. In
situations of high risk for separation of the anterior gastric
wall from the abdominal wall (e.g., patient on peritoneal
dialysis), we may consider using more than one. Once the
intragastric position of the needle is confirmed with a
contrast injection (Fig. 4), a 0.035-inch (~0.089 cm)
straight wire is advanced through the needle, displacing
the RAS into the stomach, while simultaneously maintaining access to the stomach. The needle is removed over the
wire keeping gentle tension on the thread of the RAS.
Dilatation of the track is performed over the wire. External traction on the thread helps to oppose the anterior
gastric wall to the abdominal wall during dilatation. Care
needs to be taken at this point not to exert too much pull
on the thread of the RAS as it may cause the thread to
snap. A pigtail catheter is placed over the wire into the
stomach. The choice of size of the pigtail catheter is at the
discretion of the operator and generally depends on the
size of the child (e.g., 8 Fr in an infant, 10 Fr in a young
child and 12 Fr in an older child or teenager); however,
this will vary from institution to institution and from one
interventionalist to another.
Normally, the RAS attains an orientation either in the
longitudinal or transverse axis, parallel to gastric and abdominal wall. Once the tube is in place, the thread needs to
be secured. The adult RAS comes with a needle attached to
suture it to the skin. The pediatric RAS, on the other hand,
does not have a suturing needle. It may be secured by rolling
the thread of the RAS over a small piece of gauze and the
thread then kept taut with tape; e.g., Steri-Strips (3 M, St.
Paul, MN) to prevent it unraveling. Apposition of the
Fig. 3 Schematic diagram of the RAS preloaded in the hollow of the
access needle with thread passing through the needle and hanging from
its hub
Fig. 4 Schematic diagram of the RAS loaded in the access needle with
syringe filled with contrast agent attached; note the thread of the RAS
is still hanging from the hub. Contrast medium is used to ensure the
position of the tip of the needle is within the stomach; later, the RAS is
deployed into the stomach using a guidewire
stomach to the abdominal wall promotes healing and formation of a short tract (Fig. 5).
The thread of the RAS is cut externally after a period of
time (e.g., 1–2 weeks). The optimum time to cut the thread
of the RAS is debatable. Once the thread is cut, the metallic
portion falls into the gastric lumen and in due course it
passes per rectum. However, prompt evacuation of the
RAS does not always happen.
Abnormalities
Angle and alignment
Traction on the thread of pediatric RAS can cause bending
at the center of the metal portion of RAS, which then attains
a V shape with variable angles (Fig. 6). An obtuse angle V
Fig. 5 Image shows one method of securing the thread of the RAS
onto a roll of gauze with traction maintained using tape around the
thread. This plays an important role in maintaining apposition of the
stomach to the abdominal wall and formation of the short tract. During
the healing phase it helps minimize leakage into the peritoneal cavity
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Fig. 6 Image shows bending
and obtuse angle. a Image in a
3-year-old boy with
gastrostojejunostomy tube
placed with RAS (arrow)
shows a bend at its center. b
When there is traction on the
thread of the RAS, there is a
tendency for the RAS to bend at
its center where the thread is
attached into the shape of a V.
Often, it forms an obtuse angle
of the RAS is very common. If the angle of the V is very
acute, it may slip in retrogradely into the tract and thus not
serve its intended purpose. If the RAS lodges in the tract, it
may cause symptoms such as focal pain, irritability and
infection. Sometimes, it may get embedded in the gastric
wall or stuck in the tract. At this point, fluoroscopy assessment combined with high-frequency sonography provides
valuable information. Sonography easily identifies the gut
signature, abdominal wall layers, and the location and shape
of the RAS (Fig. 7), as well as any collection that may have
formed around the RAS in the tract (Fig. 8). The RAS can
orient itself parallel to the long axis of the G-tube, in which
case it is liable to be extruded spontaneously out from the
tract. It may be a cause of focal pain and occasionally
require manual removal with forceps as shown in Fig. 2.
Timing of passage
After cutting the thread, within a few weeks the RAS will be
passed in the stools. However, the speed with which it
passes is quite variable. The passage can be delayed for
Fig. 7 A 2-year-old girl with G-tube with high-resolution US shows a
V-shaped RAS (arrow) within the stomach abutting the anterior
gastric wall
months, even years, or may fail to pass entirely, if stuck in
the tract or embedded in the gastric wall. As routine postprocedure imaging is not always performed, the exact rate of
passage is uncertain. Preliminary review of data shows that
in approximately 90–93% patients, the RAS had passed by
week 5.
Position and passage
Occasionally, the thread of the RAS may snap during deployment or dilatation if excessive traction is used. As a
result, the RAS may fall into the gastric lumen or be pulled
into the peritoneal cavity (Fig. 9). Normally after cutting the
thread, the RAS passes per rectum in the stools. Incidental
abdominal radiographs in the subsequent weeks following a
G-tube insertion may show the RAS in various locations
during its passage: free in the stomach cavity, in the
duodenum (Fig. 10), in the small bowel, colon or rectum
(Fig. 10). CT imaging may be helpful for evaluation of
atypical locations of the RAS: examples show the RAS
Fig. 8 An 8-year-old boy who underwent G-tube insertion 10 days
prior presents with tenderness at the site of insertion; high-resolution
US shows the access site in the anterior gastric wall (thick arrow) and a
collection anterior to the stomach in which the RAS (thin arrow)
is noted
Pediatr Radiol (2013) 43:1009–1016
Fig. 9 A 9-year-old boy during a G-tube insertion procedure: The
thread of the RAS snapped and resulted in intraperitoneal placement of
the RAS (arrow). Another needle puncture (preloaded with a second
RAS) was required, as shown. Contrast medium injection shows the
position of the tip of the needle in the stomach
outside the anterior gastric wall (Fig. 11) or deep to the
posterior gastric wall in the lesser sac with a pseudocyst
formation (Fig. 11).
In children with dilated, flaccid, poorly peristalsing bowel, the RAS may fail to pass. Intervention may be required
(Fig. 12). Occasionally, the thread of the RAS entangles in
the loop of the G-tube itself and, despite cutting the thread, it
will not pass. Opening the G-tube pigtail and rotating the
pigtail may be needed to release the RAS (Fig. 13).
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Fig. 11 CT of G-tube and RAS. a A 12-year-old girl with G-tube
placed 4 weeks prior. a Axial CT image shows G-tube and RAS. The
position of the RAS (white arrow) is incidentally found to be outside
the anterior gastric wall due to migration. b A 15-year-old boy with Gtube placed 4 weeks prior in an outside institution. He presented to us
with abdominal pain, tenderness and fever. Axial CT image shows the
position of the RAS (thin black arrow) posterior to the posterior gastric
wall and with pseudocyst formation (thick white arrow). There is small
sleeve of collection around the G-tube anterior to the anterior gastric
wall (thin white arrow)
A low-profile balloon button-type G-tube (MIC‐KEY
Low Profile Gastrostomy Feeding Tube, Kimberly
Clark, Mississauga, ON), which is usually placed after
6–8 weeks following a primary insertion, has a radioopaque stripe that can mimic a RAS (Fig. 14). It is not
metallic and does not pose a problem for MRI. Some
pigtail tubes contain a metallic strip in their hub (e.g.,
Mac-Loc Dawson-Mueller tube; Cook, Bloomington,
Fig. 10 A 10-year-old boy with G-tube. The RAS thread had been cut
externally 2 weeks earlier. a Radiograph shows the position of the RAS
still in the duodenum (arrow). b Another child with G-tube placed
6 weeks prior. The RAS thread had been cut externally 4 weeks earlier.
The pelvic radiograph shows the rectal position of the RAS (arrow)
before it was evacuated in the stool
Mimics of RAS
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Fig. 12 A 3-year-old boy with duodenal atresia postsurgical repair, Gtube placed 10 weeks prior. The thread had been cut externally 8 weeks
earlier. Intermittent imaging showed the RAS alternating between the
stomach and duodenum without distal propagation. a, b Snaring and
removal of the RAS was performed using a gooseneck snare. c The
RAS (white arrow) seen caught in the snare before it is taken out
IN) that also mimics a RAS, if the hub portion is
projected in the image (Fig. 15). Surgical staples can
look like a RAS (Fig. 15); the latter are usually nonferromagnetic; but occasionally, it is difficult to distinguish multiple surgical clips from a RAS unless several
views are taken.
Recognition of the RAS is important when reviewing
imaging studies from both a patient safety perspective as
well as for optimal MR image quality. The RAS is
made of ferromagnetic material. We tested the adult
and pediatric RAS on the 1.5- and 3-T MRI scanner.
Both showed similar and strong magnetic attraction
(displacement force > 45° to an almost 90° angle). To
investigate if displacement occurred when the RAS
was embedded in tissue, we also tested it in water
(nonviscous), honey (viscous), and tofu (soft solid) as
different tissue-mimicking media. The RAS aligned with
the magnetic field in water and honey, but no movement
was observed in tofu, thus demonstrating that motion
was not an issue when the RAS was embedded in solid
tissue. With respect to heating, the risk of heating is low
because although the RAS is made of a coiled wire
around a central metal core, the adult suture is only 2
cm long, 0.038 inches (0.095 cm) diameter and the
pediatric is only 1.3 cm long and 0.025 inches (0.063 cm)
diameter. These dimensions are much smaller than those at
Fig. 13 A 6-year-old girl came for her G-tube change as it was
blocked. a Fluoroscopic image shows the RAS (white arrow) in the
loop of the G-tube, even though the thread had been cut externally
5 weeks earlier. It was speculated that the thread of the RAS was
entangled in the loop of G-tube. b, c During the tube change, the
RAS was pushed away from the G-tube loop using the guidewire and
the loop of the new tube was successfully formed away from the RAS
(white arrow)
MR imaging
Pediatr Radiol (2013) 43:1009–1016
Fig. 14 A 12-year-old boy with a low profile button-type G-tube shows a
linear radio-opaque stipe (thick black arrow), which mimics the RAS. The
original RAS with obtuse V shape (thin black arrow) is seen in the left
hypochondrium region just above the button, most likely in the stomach
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which resonance or high currents are established (i.e. loop
circumference between 6 cm and 12 cm, and implant length
between 12 cm and 24 cm), limits that essentially define when
significant implant-related heating will occur.
In children, the RAS can cause pain probably due to
movement, as exemplified by the index case. It will
also cause compromise to the image quality due to
susceptibility artifact during MRI studies of the abdomen (Fig. 16). The most common indication for G-tube
in children is neurological disorders, many of which
require MRI of the central nervous system [12]. Given
the ferromagnetic properties of the RAS, one approach
is to ensure the RAS has passed before a child undergoes an MRI by reviewing any available relevant imaging on PACS and if necessary performing fluoroscopic
screening. Additionally, in those children requiring both
an MRI and a G-tube, all attempts can be made to
perform the MRI prior to the G-tube placement; or
Fig. 15 A 14-year-old boy with lateral view of the abdominal radiograph (a) shows a linear radio-opaque line due to the metal within the
hub of the Mac-Loc Dawson-Mueller G-tube, this mimics the RAS
(thin arrow) as it is usually secured on the abdominal wall. Hence, it
may be seen in the expected positions of the RAS as it passes normally
through the bowel. Normal RAS (thick arrow) was seen near the loop
of the G-tube. b A 12-year-old boy underwent surgical resection of
Wilm tumor with G-tube insertion. Flouroscopic image AP view shows
multiple surgical staples mimic RAS (arrow); lateral view (not shown)
of the same child separated the RAS anteriorly from the surgical staples
posteriorly in the retroperitonium
Fig. 16 A 12-year-old boy with G-tube insertion. a CT image in bone
window shows RAS in the stomach (arrow). b Axial MRI at the same
level shows susceptibility artifacts degrading the image quality. c
Coronal MR image shows similar artifacts. d Image shows the attraction of the freely hanging RAS toward a magnet, highlighting the
hazard of potential movement of a RAS in the magnetic field
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Pediatr Radiol (2013) 43:1009–1016
Fig. 17 A 6-year-old boy who presented with accidental dislodgement
of the G-tube on fourth day post insertion. a Attempt to access the
immature tract using a guidewire (white arrow) shows the wire in the
subcutaneous plane in a false tract. Black arrow indicates RAS. b As
the external thread of the RAS was still present rolled around the
gauze, it provided a potential route to the gastric cavity. The thread
was unrolled and used to regain access into the stomach by advancing
an intravenous cannula over the thread. Once within the stomach, a
guidewire was advanced alongside the thread. The cannula was removed and the new G-tube was advanced over the wire
failing that to recommend deferring the MRI if clinically
permissible, until it is shown the child has passed the
RAS.
References
Access through immature stoma
The RAS can be used to advantage. In the event of accidental tube dislodgement when the tract is very new, there may
be difficulty in passing a wire or catheter through an immature stoma. In such cases, the thread of the RAS can be
employed to access the stomach. By unwinding the thread
from the gauze roll and advancing it through an intravenous
cannula or a dilator, one can then advance the cannula over
the thread through the tract, thus enabling access to be
regained into the stomach (Fig. 17). From there, a new Gtube can be replaced.
Conclusion
RAS is an important component of the retrograde percutaneous radiologic gastrostomy procedure. It has a
varied fate and may be retained in the patient and
potentially cause the patient symptoms. It causes MR
image degradation and also potentially pulls or moves
during MR imaging. It behooves the diagnostic and
interventional radiologist to be aware of these issues
in interpreting images and understanding a patient’s
symptoms.
Conflicts of interest None
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