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Imaging of Peritoneal
Catheter Tunnel
Infection Using
Positron-Emission
Tomography
Pooja Singh,1,2Reuben E. Last, Michael F. Hartshorne, Karen S.
Servilla,
Antonios H. Tzamaloukas
Imaging by ultrasonography or scintigraphy may
assist in the diagnosis and management of tunnel
infections of the peritoneal dialysis (PD) catheter.
Here, we report a case of tunnel infection in which
imaging with positron-emission tomography (PET)
correctly predicted failure of conservative
management.
A 61-year-old man with diabetic nephropathy
commenced PD in January 2008. He developed
erythema and drainage at the exit site, with
negative cultures in February 2008, and frank
exit-site infection (ESI) with purulent drainage
growing methicillinsensitive Staphylococcus
aureus [MSSA (treated with 3 weeks of oral
dicloxacillin)] in August 2008. Subsequently,
MSSA-growing purulent drainage from the exit
site persisted. Systemic antibiotics were not
administered, but there was gradual
improvement with gentamicin ointment alone. In
November 2008, the patient developed partial
extrusion of the outer cuff of the PD catheter. In
January 2009, a new ESI developed. Despite a
week of treatment with cefazolin and gentamicin,
the patient still developed his first episode of
peritonitis with coagulase-negative
Staphylococcus. He then received intraperitoneal
vancomycin with good response.
Although the ESI appeared to have
responded to the treatment, PET imaging
showed increased fludeoxyglucose (FDG)
activity in the whole abdominal wall portion of the
PD catheter. The patient resisted removal of the
catheter and had no further signs of infection
until June 2009. At that time he presented with
exuberant inflammatory tissue (“proud
1From: 2Renal
Section, Raymond G. Murphy Veterans
Affairs Medical Center (RGM VAMC); 34Surgery
Service, RGN VAMC; Division of Nephrology,
University of New Mexico School of Medicine (UNM
SOM); 5Department of Surgery, UNM SOM; 6Radiology
Service, RGM VAMC; and Department of Radiology,
UNM SOM, Albuquerque, New Mexico, U.S.A.
flesh”) at the exit site. Repeated PET imaging
again showed increased FDG activity along the
abdominal wall portion of the catheter. The PD
catheter was removed and found to be infected.
The patient was placed on temporary
hemodialysis.
This case demonstrates that PET imaging, in
addition to other imaging techniques, may be
useful for diagnosing and managing PD catheter
infections.
Key words Exit-site infection, tunnel infection,
positron-emission tomography, tunnel imaging
Introduction Exit-site infections (ESIs) and
tunnel infections of the peritoneal dialysis (PD)
catheter are ongoing problems. Exit-site
infections are routinely diagnosed by clinical
examination (1). Tunnel infections usually occur
in the presence of ESIs. Staphylococcus aureus
and Pseudomonas aeruginosa ESIs are often
associated with concomitant tunnel infections.
However, tunnel infections may also occur in
the absence of clinically recognized ESIs (2).
The presence and the extent of a tunnel
infection both affect the management of the
infected patient. Peritonitis occurring in a
patient with tunnel infection does not usually
respond to antibiotic therapy without catheter
removal (3). Tunnel infections without
concomitant peritonitis can be treated with
limited surgical intervention and salvage of the
infected catheter (4).
Imaging techniques may be of help in
diagnosing tunnel infections (5). Imaging
procedures address two questions critical for
planning the management of an infection:
• Is a tunnel infection present? • What is the
extent of the tunnel infection along
the length of the portion of the catheter within
the abdominal wall?
Singh et al. 97 Ultrasonography and scintigraphy with labeled
pain, and again visited the outside hospital in his
home town. Blood and PD fluid cultures were
18white blood cells (WBCs) have been used for
obtained at the outside facility, and he was given
imaging tunnel infections. Here, we present a
1 dose of intravenous vancomycin. He was then
case of tunnel infection in which
transferred to our hospital for further care.
positron-emission tomography (PET) with
At presentation, the patient was afebrile with a
F-fluorodeoxyglucose (FDG) was helpful in
blood pressure of 150/82 mmHg and a pulse rate
defining the management goals.
of 81.
Case Report A 61-year-old man with diabetic
nephropathy, who had been on PD for 1 year,
was admitted for treatment of peritonitis in
January 2009. Before this admission and since
PD catheter placement in December 2007, this
patient had had a long history of ESIs. Initially,
the exit site lacked any signs of infection. In
February 2008, the patient developed erythema
and purulent drainage from the exit site. This ESI
was treated with 1 g intravenous vancomycin and
a 7-day course of oral cephalexin. Exit-site
cultures revealed no growth.
In August 2008, purulent drainage from the
exit site recurred. Cultures from the site grew
methicillinsensitive Staphylococcus aureus
(MSSA). The patient did not have any evidence
of peritonitis at that time. He was treated with
dicloxacillin for a total of 3 weeks. After
completion of the course of dicloxacillin, the exit
site continued to be erythematous, with open
bleeding areas around the site and continuous
purulent drainage. New cultures from the exit site
again grew MSSA. At that time, antibiotics were
not restarted, but continued care of the exit site
with gentamicin ointment was maintained.
In a follow-up visit 1 month later, the exit site
appeared to be healing, with improvement in
erythema. In November 2008, mild protrusion of
the external cuff was noted. The exit site
appeared dry and without signs of infection at that
time.
In January 2009, the patient was admitted
with his first episode of peritonitis. Seven days
before the admission, he reported erythema
around the exit site. Intraperitoneal cefazolin and
gentamicin were started at an outside hospital.
Exit-site cultures from the outside hospital grew
MSSA. On the last day of treatment for the ESI,
the patient noted cloudy PD fluid and abdominal
His abdomen was soft, non-distended, with
normoactive bowel sounds and mild tenderness
to palpation of the right upper and lower
quadrants. The exit site was erythematous and
indurated, but without drainage. Of 3 blood
cultures from the outside hospital, 2
cultures—and the PD fluid culture—grew
coagulasenegative Staphylococcus. Repeat
blood cultures at our hospital were negative. The
patient was subsequently started on
intraperitoneal vancomycin and was treated for 2
weeks.
An FDG PET scan of the patient’s abdomen
disclosed increased FDG activity along the length
of the PD catheter tunnel, including both cuffs
[Figure 1(A)]. No evidence of peritonitis was
present, but the patient had already received
several doses of antibiotics at the time that the
imaging study was performed.
Removal of the PD catheter was advised.
However, the patient, who lives far away from the
dialysis unit, declined to consent to catheter
removal. Together, the patient and the
nephrology team determined that the catheter
would continue to be used for PD, but that it
would have to be removed if the patient
developed another episode of overt
catheter-related infection. At a subsequent follow
up, that patient showed no signs of ESI or
peritonitis.
In March 2009, no drainage or erythema was
observed around the exit site. Furthermore, the
outer cuff no longer appeared to be exposed.
In May 2009, pus was expressed from the
patient’s exit site during a routine PD clinic visit.
Cultures from the PD fluid were negative, but the
exit-site culture grew MSSA. Thus, the patient
was treated with oral cephalexin for 2 weeks. The
ESI subsequently resolved after completion of
antibiotics.
In June 2009, the patient reported cloudy fluid
draining from his PD catheter. The exit site was
noted to be indurated and erythematous; it also
had evidence of new exuberant tissue (“proud
flesh”) growth, indicating a chronic infection.
The outer cuff was also fully exposed. The
patient was readmitted and started on
intravenous vancomycin. The exit site grew
MSSA, and the PD fluid contained WBCs (205
cells/mL), but did not grow any organism.
Repeated FDG PET imaging showed recurrent
or persistent tunnel infection and areas of
inflammation through the abdominal wall at
each end of the tunnel [Figure 1(B)]. The PD
catheter was removed and, on inspection,
found to be grossly infected. The patient was
treated for 3 weeks with intravenous
vancomycin and put on hemodialysis. A
98
Imaging of PD Catheter Tunnel Infection
1 Positron-emission tomography images showing increased activity along the abdominal wall portion of the
peritoneal dialysis catheter. Arrows point to inner cuff. (A) January 2009. (B) June 2009.
FIGURE
Tunnel infections produce widening and loss of
clarity of the circumferential rim. This area
new PD catheter was placed in November 2009
becomes hypoechogenic, showing fluid
after complete healing of the infected abdominal
collection (10,11). Abscesses can produce
wound.
larger areas of reduced echotexture. These
areas may be similar to those seen with
Discussion The management of PD catheter
cellulitis, but by compression with the
infections involves one of three methods:
ultrasound transducer, an abscess will be
deformable and compressible (2).
• conservative management with antibiotics
Scintigrams using WBCs labeled either with
alone, • management with antibiotics plus
In111 oxine (12) or with Tc-99m exametazime
minimal surgical
(13) have also been used to image infected PD
intervention (for example, shaving the outer
catheter tunnels. The use of scintigraphy
cuff) aimed at saving the catheter, or
• management with antibiotics and removal of the confirmed that previously reported failures in
saving infected PD catheters by shaving the
catheter.
outer cuff (14) were routinely associated with
To decide on the appropriate management, infection of the inner cuff (15).
any question about the presence or the extent of Imaging by FDG PET has been extensively
used in diagnosing and staging tumors. Its
tunnel infection should be cleared. Imaging
second widespread use is in the diagnosis of
should be considered if there is uncertainty
deep-seated infections. Imaging by FDG PET
about either of these two issues.
has proved to helpful in the diagnosis of
infected foreign material in the body (such as
Ultrasonography has been the imaging modality prosthetic cardiac valves, pacemaker wires,
most commonly employed for diagnosis of PD
prosthetic joints, aortic grafts, and central
catheter infections (6–9). A low-echo
venous catheters) and of occult infections in
circumferential rim is seen around the catheter
hemodialysis
under normal circumstances (5).
Singh et al. 99 vascular access (16). The case presented here illustrates
tunnel infections was around 70%; the specificity
was 100% (18). In another report, a labeled WBC
the use of FDG PET imaging in PD catheter
scan had a sensitivity of 83% and a specificity of
infections. In the presence of several imaging
75% in diagnosing PD catheter infection (13). An
methods for PD
advantage of labeled WBC scans is that they
catheter infections, the choice of method is
determine the extent of infection along the length
routinely based on 5 criteria:
of the catheter with accuracy, and they are
• Availability •
helpful in the decision to remove the PD catheter
Local expertise •
(15).
Risks •
Performance •
Costs
The differences between the three
techniques are small for the first 3 criteria.
Ultrasonography is, in general, available to
many institutions at which PD patients are
followed. Scintigraphy and FDG PET imaging
are less available. A well-trained radiologist and
a radiology department with expertise in the
relevant technique are indispensable for
avoiding diagnostic errors regardless of the
technique used. Ultrasonography has no
recognizable risks ; scintigraphy and FDG PET
imaging both have a small risk from exposure to
radiation.
The three imaging methods differ substantially
in the two last criteria mentioned, however.
Despite the larger number of reported studies, the
accuracy of ultrasonography in diagnosing PD
catheter infections has not been adequately
studied. Looking at studies of ultrasonography in
other deep-seated infections, it appears that the
accuracy of the procedure is not great. For
example, one report indicated that the sensitivity
of ultrasound in detecting abdominal abscess in
patients after colorectal surgery was only 43%;
the specificity was 100%, and the overall
accuracy was 65% (17). In addition to its low
sensitivity, ultrasonography is poor in detecting
the extent of deep infections.
Labeled WBC scintigrams may show
collections of pus deep in the catheter tunnel in
cases in which ultrasonography fails to
demonstrate any abnormality around the
peritoneal catheter (18). In that report, the
sensitivity of In-111 WBC scans in detecting deep
Although the accuracy of FDG PET in diagnosing recommendations. Perit Dial Bull 1987;7:130–8.
tunnel infections of the PD catheter will need to be
evaluated in future studies, the procedure has
been shown to have a high diagnostic accuracy
for deep abscesses. In one study of 165 infections
in 148 of 248 patients with multiple myeloma,
FDG PET identified the site of the infection in 46
episodes in which other imaging methods failed
(19). In a meta-analysis of infections in prosthetic
joints, the pooled sensitivity of FDG PET in
diagnosing those infections was 82.1%; the
specificity was 86.6% (20). In the case reported
here, FDG PET imaging was accurate both in
diagnosing the tunnel infection and in determining
its extent.
The costs of imaging procedures vary by
geographic area in the United States. In New
Mexico, Medicare pays $121.24 for
ultrasonography, $1065.54 for WBC scans, and
$1350.82 for FDG PET scans with computed
tomograms. Thus the choice of imaging technique
for a tunnel infection of the PD catheter appears
to be between a cheaper but relatively inaccurate
method (ultrasonography) and one of two
accurate but expensive methods (scintigraphy,
FDG PET).
Conclusions Imaging by FDG PET is an
expensive but accurate method of diagnosing
deep-seated infection and seems to be useful in
tunnel infections of the PD catheter. The case
presented here demonstrates that FDG PET
imaging can be used to diagnose the presence
and extent of PD catheter-related tunnel infections
and to guide their treatment.
Acknowledgments This work was supported by
the Raymond G. Murphy VA Medical Center. The
authors thank Mr. James Jannis of the Department
of the Medical Media at that institution for his
invaluable assistance.
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Corresponding author: Pooja Singh, MD, 1
University of New Mexico, MSC 10-5550,
Albuquerque, NM 87131 U.S.A. E-mail:
psingh@salud.unm.edu