DOI:10.2214/AJR.06.1385
AJR 2007; 188:1495-1499
© American Roentgen Ray Society
Stent Collapse as a Delayed Complication of Placement of a Covered Gastroduodenal Stent
Jin Hyoung Kim1,
Ho-Young Song1,
Ji Hoon Shin1,
Eugene Choi1,
Tae Won Kim2,
Sung Koo Lee2 and
Byung Sik Kim3
1 Department of Radiology, Asan Medical Center, 388-1 Pungnap-2dong, Songpa-gu,
Seoul, Seoul, South Korea 138-736.
2 Department of Internal Medicine, Asan Medical Center, Seoul, South Korea
138-736.
3 Department of Surgery, Asan Medical Center, Seoul, South Korea 138-736.
Received October 18, 2006;
accepted after revision January 17, 2007.
Address correspondence to H. Y. Song.
Abstract
OBJECTIVE. The purpose of this study was retrospective evaluation of
the incidence, predictive factors, and interventional management of stent
collapse after placement of a covered metallic stent in patients with
obstruction of the gastric outlet or duodenum due to malignant disease.
MATERIALS AND METHODS. Among 259 patients with symptomatic malignant
gastroduodenal obstruction successfully treated with stent placement, stent
collapse occurred in 12 (4.6%) of the patients 34–270 days (mean, 101.8
days) after stent placement. Multivariate analysis was performed to evaluate
factors predictive of stent collapse. Interventional management of stent
collapse also was evaluated.
RESULTS. Multivariate analysis showed that presence of the stent in
the peripyloric region (odds ratio, 27.745; p = 0.036), longer
survival time (odds ratio, 1.016; p < 0.001), and absence of
chemotherapy after stent placement (odds ratio, 31.661; p = 0.048)
were independent predictors of stent collapse. Eleven patients with stent
collapse were successfully treated with placement of a second bare stent. The
twelfth patient refused further treatment.
CONCLUSION. Stent collapse is an uncommon delayed complication of
placement of covered metallic stents in patients with malignant gastroduodenal
obstruction. Collapse occurs most commonly in the peripyloric region, in
patients with longer survival times, and in patients who do not undergo
chemotherapy after stent placement. Stent collapse can be managed by coaxial
placement of a second bare stent into the collapsed stent.
Keywords: gastrointestinal radiology • interventional radiology • stents
Introduction
Placement of bare or covered self-expanding metallic stents has been a
promising noninvasive palliative method of treatment of patients with
unresectable cancer causing gastric or duodenal obstruction
[1–10].
It has a higher clinical success rate and is associated with a shorter
hospital stay and less morbidity and mortality than palliative surgery
[11,
12]. However, stent
obstruction occurs in approximately 17% of cases of stent placement for
malignant gastroduodenal obstruction and is the most frequent complication
[13]. In bare stents,
obstruction usually is caused by ingrowth of tumor or by tissue hyperplasia
through the wire filaments. In covered stents, it is caused by overgrowth of
tumor or by tissue hyperplasia above or below the ends of the stent.
In theory, stent obstruction can occur from stent collapse due to extrinsic
tumor growth compression. To our knowledge, the only case series
[14] of stent collapses showed
collapse in two (11%) of 18 patients 120 and 256 days after placement of
covered metallic stents for the management of malignant gastroduodenal
obstruction. The authors surmised that stent collapse resulted from
centripetal growth of the tumor or fatigue fracture of the stent wires.
However, because of the small size of the study population, conclusions cannot
be drawn about the true incidence and factors predictive of stent collapse. In
this study, we evaluated cases of stent obstruction due to stent collapse in
patients with malignant gastroduodenal obstruction. We evaluated the incidence
of, predictive factors for, and interventional management of stent
collapse.
Materials and Methods
Informed consent was obtained from each patient, and our institutional
review board approved this retrospective study.
Patient Population
The study population was 259 patients with symptomatic malignant
gastroduodenal obstruction treated with fluoroscopic stent placement. The
inclusion period was September 1998–February 2006. The characteristics
of the patient population are summarized in
Table 1. Because of the
presence of advanced or metastatic disease or a debilitated condition, none of
the 259 patients was considered a candidate for surgery. The diagnosis was
established by means of endoscopic biopsy, percutaneous needle aspiration
biopsy, or forceps biopsy during percutaneous transhepatic or endonasal
biliary drainage. Among 259 patients successfully treated with stent
placement, stent collapse occurred in 12 (4.6%) of the patients 34–270
days (mean, 101.8 days) after stent placement
(Table 2). Nine of the patients
were men, and three were women (mean age, 53.2 years; age range, 27–65
years). Stent collapse was identified because it caused recurrent obstructive
symptoms in all 12 patients.
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Fig. 2A —54-year-old man with stent collapse. Upper gastrointestinal
radiograph after passage of sizing gastric coil catheter over guidewire to
distal part of collapsed stent and injection of water-soluble nonionic
contrast medium through catheter shows collapsed stent in peripyloric
region.
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Fig. 2B —54-year-old man with stent collapse. Upper gastrointestinal
radiograph shows successful insertion of stent delivery system and loading of
0.229-mm-wire inner bare stent (arrowheads) through collapsed
stent.
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Fig. 2C —54-year-old man with stent collapse. Upper gastrointestinal
barium radiograph obtained with water-soluble nonionic contrast medium
immediately after coaxial placement of second bare stent into collapsed stent
shows good downstream passage of contrast medium.
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Placement of the Stent and Follow-Up
Three types of stent were used in this study. A type A stent (Song covered
stent) was knitted from a single thread of 0.2-mm nitinol wire in a tubular
configuration and was fully covered with 12% polyurethane solution
(Chronoflex, Cardiotech International). The stent was 18 mm in diameter, and
both ends of the stent were flared up to 28 mm
(Fig. 1A). The type A stent was
used in 18 patients.
A type B stent consisted of two stents—a bare stent and a fully
covered type A stent—of the same diameter (18 mm). The bare stent was
knitted from a single thread of 0.2-mm nitinol wire in a tubular configuration
(Fig. 1B). These two stents
were designed for placement of the bare stent and then coaxial placement of
the type A stent into the bare stent. The type B stent was used in 38
patients.
A type C stent (Hercules SP Pyloric stent)
[15] consisted of an outer
stent and an inner stent. The outer stent had three parts: a leading bare part
28 mm in diameter, a nylon mesh 18 mm in diameter, and a trailing bare part 28
mm in diameter (Fig. 1C). The
leading and trailing bare parts were knitted from a single thread of 0.22-mm
nitinol wire in a tubular configuration in an interlocking diamond-shaped
pattern. The inner stent was the outer bare part of a type B stent. Like the
type B stent, the type C stent was designed for coaxial placement. The type C
stent was used in 203 patients. The details of stent placement techniques are
described elsewhere [8,
12,
15,
16].
All patients underwent a barium radiographic study and endoscopy 1–3
days after stent placement to confirm the position and patency of the stent. A
barium study and endoscopy were performed 1 month after stent placement to
detect the presence of delayed complications, such as stent migration and
obstruction. The status of oral food intake was monitored at 1-month intervals
on an outpatient basis. Further follow-up barium studies and endoscopy were
performed only for patients with recurrent symptoms.
Patients with recurrent symptoms due to stent collapse were treated with
interventional management. A second bare stent made of 0.229-mm nitinol wire
was chosen for secondary intervention. The technique is shown in Figure
2A,
2B,
2C. For coaxial placement of a
second bare stent into the collapsed first stent, a stiff angled, 260-cm-long,
0.035-inch exchange guidewire (Radifocus M, Terumo) was inserted under
fluoroscopic guidance across the collapsed stent into the third portion of the
duodenum or proximal jejunum. In patients who had difficulty passing the
exchange guidewire through the collapsed stent, use of a sizing gastric coil
catheter (SongLim gastric catheter) helped negotiation. The exchange guidewire
was replaced with a superstiff 260-cm-long guidewire (Medi-tech/Boston
Scientific) with use of a sizing gastric coil catheter (S&G Biotech)
[15]. When it was extremely
difficult to advance the stent delivery system and load the second bare stent
through the collapsed portion of the initial stent, we dilated the tight
collapsed portion with the use of an 8- or 10-mm balloon catheter.
Definition and Analysis of Data
Stent collapse was defined as delayed luminal narrowing of a fully expanded
stent owing to extrinsic compression from tumor growth. Univariate analysis
was performed to compare variables between the group with stent collapse and
the group without stent collapse. The Mann-Whitney U test was used to
compare continuous variables, and the Fisher's exact test was used for
categoric variables.
A multivariate logistic regression model with forward stepwise selection
was planned for finding independent predictive factors associated with stent
collapse. Only variables with p < 0.2 at univariate analysis
(Mann-Whitney U test or Fisher's exact test) were entered into the
multivariate logistic regression model. This lenient p value was
chosen to avoid rejection of a variable that might have contributed to
prediction of outcome (stent collapse) in the multivariable analysis. Model
fit was evaluated by means of the Hosmer-Lemeshow goodness-of-fit test
[17]. Two-sided p
< 0.05 was considered to indicate statistical significance. All statistical
analysis was performed with the SPSS program (version 11.5, SPSS). After
interventional management for stent collapse, clinical outcome was evaluated
retrospectively.
Results
Predictive Factors of Stent Collapse
All episodes of stent collapse occurred in the barrel portion of type C
stents (Fig. 3A,
3B,
3C) but not in type A or type B
stents, which were covered with polyurethane membrane. Univariate analysis
showed stent collapse was associated with younger age (53.2 ± 14.2 vs
61.8 ± 11.5 years for patients without stent collapse, p =
0.01), location in the peripyloric region (p = 0.033), and longer
survival time (141.3 ± 62.8 vs 75.5 ± 74.1 days for patients
without stent collapse, p < 0.001)
(Table 2). Other variables
showed no significant difference between the group with and the group without
stent collapse.
The following variables of p < 0.2 at univariate analysis were
entered into the multiple logistic regression model: age, site of obstruction,
covering membrane, chemotherapy after stent placement, and survival time.
Multivariate analysis confirmed that peripyloric region (odds ratio [OR],
27.745; 95% CI, 1.251–615.551; p = 0.036), longer survival time
(OR, 1.016; 95% CI, 1.008–1.024; p < 0.001), and absence of
chemotherapy after stent placement (OR, 31.661; 95% CI, 1.033–970.213;
p = 0.048) were independent predictors of stent collapse
(Table 3). The Hosmer-Lemeshow
goodness-of-fit test showed a nonsignificant p value (0.998) for the
model, which indicated good fitness of the model.
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TABLE 3: Results of Multivariate Logistic Regression Analysis for Evaluation of
Factors Predictive of Stent Collapse
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Interventional Management for Stent Collapse
Eleven of the 12 patients with stent collapse underwent interventional
management. One patient refused further treatment and underwent total
parenteral nutrition until death. Before secondary stent placement, dilation
of the collapsed portion with an 8- or 10-mm balloon catheter was needed in
all 11 patients. In two patients, a sizing gastric coil catheter was needed
for negotiation of an exchange guidewire through the collapsed stent. All 11
patients had relief of recurrent obstructive symptoms after placement of the
second bare stent and had no complications. After management of stent
collapse, the 11 patients maintained oral intake until death or the end of the
follow-up period (mean, 46.4 days; range, 10–104 days) without
recurrence of obstructive symptoms.
Discussion
The results showed the rarity of stent collapse, which occurred with a
frequency of 4.6% (12/259) and which tended toward late occurrence (mean,
101.8 days after placement; range, 34–270 days). In our multiple
logistic regression analysis, stent placement in the peripyloric region (OR,
27.745; p =0.036), long survival time (OR, 1.016; p
<0.001), and absence of chemotherapy after stent placement (OR, 31.661;
p = 0.048) were significant predictors of stent collapse. Therefore,
we can predict this uncommon complication after placement of covered metallic
stents in patients with malignant peripyloric gastroduodenal obstruction,
longer survival times, and no chemotherapy after stent placement.
To our knowledge, there have been no reports of studies of stent collapse
after placement of covered stents in the esophagus or colorectal area
[18–23],
but there have been a few reports
[14] of this complication in
the gastroduodenal area. There are several explanations for the lack of
reporting of this complication. First, in cases of polyurethane-covered
stents, not stent collapse but tumor ingrowth through the disruption of the
covering membrane occurs [16,
20]. In our study, stent
collapse occurred only in the type C stents covered with nylon mesh, which may
be more durable than polyurethane membrane. Both the outer and inner
components of type B stents had a framework made of 0.2-mm nitinol wire. On
the other hand, the barrel portion of type C stents was weaker than that of
type B stents because the outer, partially covered component of a type C stent
does not have a framework in the nylon mesh between the proximal and distal
stent bodies. We speculate that this structural weakness caused collapse of
the type C stents alone. Second, given the rarity and delayed presentation of
this complication in this study, stent collapse may be difficult to detect,
especially in patients with short-term survival and follow-up periods. Third,
stent collapse appears to have a preferable location. In our study and that of
Jeong et al. [14], almost all
cases of collapse occurred in the peripyloric region.
The observation that peripyloric lesions are related to the incidence of
stent collapse can be explained by the presence of the pyloric channel, which
is a physiologic stenotic and resistant structure. The pyloric channel is
formed by duplication of mucous membrane and an abundant muscle layer
[24]. Therefore, stents in
this area can be subjected to high levels of stress, which causes collapse,
especially with peristaltic movement in the area around the stent. We found
that absence of chemotherapy after stent placement was a risk factor for stent
collapse. Chemotherapy, by reducing the tumor burden, might have decreased the
risk of stent collapse due to compression from tumor growth.
Jeong et al. [14]
successfully managed a case of stent collapse by placing a second covered
stent through the collapsed portion of the initial covered stent. Although
they obtained positive clinical outcome in the one case, coaxial placement of
a covered stent because of stent collapse seemed inappropriate for the
following reasons: Placement of the covered stent through the collapsed
portion can be difficult because of the requirement for a rigid 6-mm delivery
system, and an inner covered stent is at high risk of migration
[16].
In all 11 patients who underwent placement of a second bare stent,
recurrent obstructive symptoms were relieved and new symptoms did not occur.
Hoop strength, a parameter that describes the ability of a stent to withstand
external forces, is directly influenced by stent wire thickness
[25]. Because of its greater
hoop strength, a 0.229-mm-wire inner bare stent as opposed to a 0.2-mm-wire
inner bare stent was used in all 11 patients. The 0.2-mm-wire inner bare stent
appeared to be too weak in patients with bulky masses. Although stent collapse
was uncommon after placement of type C stents, which had 0.2-mm-wire inner
bare stents, the incidence of stent collapse is more likely to decrease when a
0.229-mm-wire inner bare stent is used initially. The optimal hoop strength
value, however, remains unclear. A stent with high hoop strength may have the
potential for increasing the perforation rate or decreasing stent flexibility.
Further study regarding the optimal hoop strength of gastroduodenal stents is
needed.
The principal limitation of this study was its nonrandomized and
retrospective design, which inherently decreased the statistical strength.
Another limitation was the small number of patients who underwent placement of
polyurethane-covered (types A and B) stents compared with the number who
underwent placement of nylon-mesh-covered (type C) stents.
In summary, stent collapse is an uncommon delayed complication of placement
of covered metallic stents in patients with malignant gastroduodenal
obstruction. Factors predictive of stent collapse are the presence of the
stent in the peripyloric region, longer survival time, and absence of
chemotherapy after stent placement. Stent collapse can be managed by coaxial
placement of a second bare stent into the collapsed stent.
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Abstract
Introduction
