Perit Dial Int
29(5):
542-547
2009
© 2009 International Society for Peritoneal Dialysis
RETROPERITONEAL LEAKAGE AS A CAUSE OF ACUTE ULTRAFILTRATION FAILURE: ITS ASSOCIATED RISK FACTORS IN PERITONEAL DIALYSIS
Man Fai Lam1,
Wai Kei Lo2,
Kai Chung Tse1,
Terrence P.S. Yip2,
Sing Leung Lui2,
Tak Mao Chan1 and
Kar Neng Lai1
Nephrology Division,1 Department of Medicine,
Queen Mary Hospital; Nephrology Division,2 Department
of Medicine, Tung Wah Hospital, University of Hong Kong, Hong Kong
Correspondence to: K.N. Lai, Department of Medicine, University of Hong Kong,
Queen Mary Hospital, No. 102, Pokfulam Road, Hong Kong.
knlai{at}hkucc.hku.hk
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ABSTRACT
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Background: Ultrafiltration failure is an important
clinical problem in patients on maintenance peritoneal dialysis (PD) and is
associated with high morbidity and mortality. Acute ultrafiltration failure
(AUFF) is usually secondary to mechanical problems with the peritoneal
catheter or peritoneal leakage. Retroperitoneal leakage (RPL) is an important
cause of AUFF and often poses diagnostic difficulty. Herein we analyze the
incidence of AUFF secondary to RPL in our centers and study its associated
risk factors.
Methods: After excluding causes due to mechanical
problems with the peritoneal catheter, patients complicated by AUFF underwent
computerized tomographic peritoneography (CTP) or magnetic resonance imaging
of the peritoneal cavity (MRP) to determine any RPL. Other patients on
maintenance PD without RPL served as controls for comparison of risk factors.
Demographic and peritoneal membrane characteristics, including history of
hernia and pleuroperitoneal leakage, were analyzed.
Results: During the 5-year study period, 36 patients in
a cohort of 743 patients on maintenance PD developed AUFF. 23 of these 36
patients were found to have RPL, which was confirmed by either CTP (n
= 16) or MRP (n = 7). The duration of PD at the time of RPL and the
dialysate-to-plasma ratio of creatinine at 4 hours were 49.3 ± 24.5
(range 0.5 – 87.9) months and 0.70 ± 0.09 respectively.
Incidences of hernia (52.2%) and pleuroperitoneal communication (34.8%) were
significantly higher than in PD patients without RPL (13% and 7% respectively,
p = 0.001). Logistic regression analysis identified hernia and
pleuroperitoneal communication as the risk factors for RPL. The odds ratios
for RPL with hernia and pleuroperitoneal communication were 6.62 [95%
confidence interval (CI) 2.35 – 18.69, p < 0.001] and 6.23
(95% CI 1.83 – 21.19, p = 0.003) respectively.
Conclusion: RPL was not uncommon in patients with AUFF.
A high index of suspicion for RPL is needed in the management of patients with
history of hernia or pleuroperitoneal communication presenting with
AUFF.
KEY WORDS: Ultrafiltration failure; retroperitoneal leakage; computerized tomographic peritoneography; magnetic resonance peritoneography.
Ultrafiltration (UF) failure is an important clinical problem in patients
on maintenance peritoneal dialysis (PD). It may lead to severe fluid overload
and subsequently congestive heart failure. Fast peritoneal transport
(1), loss of peritoneal surface
membrane, and high lymphatic absorption
(2) are main causes of UF
failure; other anatomical or mechanical etiologies are occasionally seen. A
patient may present with a sudden reduction in UF volume or with acute
ultrafiltration failure (AUFF) in which a mechanical or an anatomical problem
has to be seriously considered. Peritoneal leakage due to a tear of the
peritoneal membrane (3) is a
distinctive clinical entity that can lead to AUFF. These leakages are usually
associated with localized subcutaneous edema although selected conditions,
such as pleuroperitoneal leakage, are difficult to detect clinically. In
addition, AUFF can arise from retroperitoneal leakage (RPL) in patients on PD
(4). Herein we analyze the
incidence of AUFF secondary to RPL in our centers and study its associated
risk factors.
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METHODS AND PATIENTS
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We studied our patients on long-term PD who were complicated by fluid
overload or UF failure between October 2002 and September 2007. Recent history
of peritonitis or any abdominal pathology during the onset of UF failure was
assessed and any subcutaneous edema or pericatheter leakage was examined.
Following confirmation of reduction in UF volume by reviewing PD exchange
records, radiological imaging was performed to exclude any malposition of the
peritoneal catheter. Acute UF failure was defined as a 50% reduction in UF
volume compared with the patient's own usual PD regime (within 1 week using
same exchange volume and dialysis concentration) with no mechanical
obstruction or catheter malposition. When other causes of fluid overload or
reduction in UF volume, including changes in peritoneal membrane transport
characteristics identified from the latest results of peritoneal equilibration
testing (PET), were also excluded, these patients would then undergo
computerized tomographic peritoneography (CTP) or magnetic resonance
peritoneography (MRP) to look for RPL.
The CTP was usually performed within 2 weeks following the onset of AUFF: 2
L PD fluid containing 1 mL/kg (patient body weight) nonionic contrast
(Omnipaque 300 mg/mL; GE Healthcare, Princeton, NJ, USA) was instilled into
the peritoneal cavity 1 hour before the radiological examination
(5,6);
the patient was asked to walk, strain, and bend for 30 minutes following the
instillation. After the scanning, the peritoneal fluid was drained out
completely. The MRP was performed as imaging sequences of the abdomen and
pelvis using axial FSPRG T1W and FSE T2W imaging with fat saturation, and
coronal FSE T2W imaging with fat saturation. Peritoneal dialysis fluid without
contrast was used as the contrast medium to visualize any abnormality in the
peritoneal cavity (7).
When hernia or peritoneal leakage was diagnosed, patients were first
treated by twice weekly intermittent peritoneal dialysis (IPD), 2 L in hourly
cycles, for a total duration of 8 weeks. During the IPD period, the abdomens
of these patients were kept dry to allow the leakage sites to heal. In
addition, these patients were suggested to adopt, if possible, a supine
position during IPD. They were also advised to avoid coughing, constipation,
and other precipitating factors that may suddenly increase intra-abdominal
pressure. Temporary hemodialysis was performed only when IPD failed or the
patient had extensive leakage. At the end of 8 weeks of IPD, patients had a
second CTP or MRP to assess healing of RPL.
Patients' demographic characteristics, including age, gender, body mass
index, body surface area, mode of PD, underlying renal disease, and history of
hernia (including incisional hernia) and leakage at other sites (exit
site/tunnel tract, pleuroperitoneal leakage), were recorded. Comparison was
made between patients with RPL, patients with leakage at other sites, and
patients with no UF problems.
STATISTICAL ANALYSIS
All data are expressed as mean ± standard deviation unless otherwise
specified. Statistical difference was analyzed with Student's t-test,
Mann–Whitney (nonparametric) test, and chi-square test, as appropriate.
Logistic regression and multivariate analyses were also performed to determine
any risk factor associated with the development of RPL. A p value of
0.05 was taken as the level of statistical significance. Statistical
calculation was performed with SPSS 14.0 software (SPSS Inc., Chicago, IL,
USA).
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RESULTS
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During the 5-year study period, 743 patients were treated with maintenance
PD at our two dialysis centers for a total of 22280 patient dialysis months.
There were 132 episodes (in 108 patients) of fluid overload requiring
hospitalization and temporary IPD (rapid exchanges) for fluid removal. Due to
our limited hemodialysis facility, almost all patients were put on rapid
exchanges of PD for fluid removal except those complicated by blockage of the
peritoneal catheter; these patients were excluded from this analysis. The
causes of fluid overload are depicted in
Table 1; fluid noncompliance
was the major cause.
Further investigations were arranged for patients that had inappropriate
reduction in UF volume. Patients with AUFF (50% reduction in UF volume;
n = 36) or suspected of having RPL underwent CTP or MRP; 23 of these
36 patients (7 females) were confirmed to have RPL by either CTP (n =
16) (Figure 1) or MRP
(n = 7) (Figure
2).
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Figure 1 — A computerized tomographic peritoneography (CTP) from a patient
with retroperitoneal leakage (upper panel). Repeat CTP in the same patient
shows disappearance of the leakage after treatment (lower panel).
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The age of the patients with RPL was 55.3 ± 15.2 years and the onset
time of RPL after entering the renal replacement program was 49.3 ±
24.5 (range 0.5 – 87.9) months. Demographics and peritoneal membrane
characteristics of the patients with RPL are shown in
Table 2. The greatest volume of
daily peritoneal dialysate effluent and UF volume during the PETs were 2428
± 145 mL and 2375 ± 164 mL respectively. Mean peritoneal solute
transport determined by the dialysate-to-plasma ratio of creatinine at 4 hours
(D/P Cr) was 0.70 ± 0.09. Only 1 patient received temporary
hemodialysis due to extensive RPL extending to the inguinal region and pleural
space. Of these 23 patients, only 3 had recurrence of RPL, which was
successfully treated with IPD in 2 and 1 had to switch to long-term
hemodialysis permanently.
To identify any predicating factor for RPL, comparison was made between
patients with RPL, patients with leakage at other sites, and patients with no
UF problems (Table 3). There
was no difference in patients' demographic characteristics, body mass or size,
peritoneal membrane characteristics, or dialysate effluent volume among the
groups. Compared to unselected patients on PD without UF complications, the
only significant differences were residual renal function and urine
volume.
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TABLE 3 Comparison of Peritoneal Transport Characteristics and Ultrafiltration
Volume Between Patients With (RPL) and Patients Without (Non-RPL)
Retroperitoneal Leakage
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The incidences of hernia (n = 12, 52.2%) and pleuroperitoneal
leakage (n = 8, 34.8%) were significantly higher in patients with RPL
than in those without RPL [hernia: n = 15 (13%); pleuroperitoneal
leakage: n = 8 (7%); p = 0.001 for both). Logistic
regression analysis identified residual renal function and urine volume,
hernia, and pleuroperitoneal leakage rather than age, body mass, or body size
as significant risk factors for RPL (Table
4). In multivariate analysis, hernia and pleuroperitoneal leakage
were found to be statistically significant. The odds ratios for RPL with
history of hernia and pleuroperitoneal leakage were 6.62 [95% confidence
interval (CI) 2.35 – 18.69, p < 0.001) and 6.23 (95% CI 1.83
– 21.19, p = 0.003) respectively.
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DISCUSSION
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Extraperitoneal leaks are common in patients on PD and usually occur in the
anterior abdominal wall or the pelvis, with localized edema in the abdominal
wall, perineum, or genitalia
(3). It has been reported that
leakage of dialysate through the peritoneal catheter exit site,
pleuroperitoneal communication, patent processus vaginalis, or an abdominal
hernia occurs in more than 5% of patients undergoing continuous ambulatory
peritoneal dialysis (CAPD) (8).
These are easily detected clinically and do not require special imaging to
confirm the diagnosis.
In the present study, we reported 23 (3%) patients complicated by RPL among
743 CAPD patients. Retroperitoneal leakage turned out to be the second most
common cause of UF problems requiring hospitalization. In addition, the
frequency of RPL appears to be similar to that of leakages at other sites in
PD, namely, hernia, exit site, and pleuroperitoneal communication. Previously,
there was only one paper describing this complication, which was detected by
MRP (9). The actual incidence
of RPL is probably unknown. With a higher index of suspicion and suitable
imaging techniques, incidence may appear to increase.
Clinical diagnosis of RPL is difficult as there is no localizing sign in
the systemic examination. The only clue is a sudden reduction in UF volume:
usually >50% of normal daily UF volume as illustrated by our patients.
Therefore, an accurate measurement of UF volume is essential for diagnostic
accuracy in detecting AUFF in PD patients. McCafferty and Fan
(10) showed that the
calculation of overfill volume during PD exchanges might affect the diagnosis
of UF failure. They found that almost all dialysis units made this
overestimation in calculating daily UF volume. In their study, 73% of patients
with daily UF volume < 750 mL were not diagnosed as having inadequate daily
UF volume. Similarly, 73% of patients with potential UF failure during the PET
(4-hour UF < 100 mL) were missed if the overfill volume was misrepresented
as UF volume. They recommended standardization of weighing drain bags and the
importance of excluding any overfill volume in calculations of UF volume.
Ultrafiltration failure secondary to peritoneal membrane dysfunction is the
most frequent transport abnormality in long-term PD and is one of the main
reasons for discontinuation of PD. The underlying cause of increased small
solute transport is an increase in effective peritoneal vascular surface area
(11), as reflected by a high
D/P Cr, or a loss of peritoneal membrane surface due to prolonged PD or severe
peritonitis, as reflected by a low D/P Cr. Studying these membrane parameters
helps to define the causes of AUFF. As we perform PET for our patients
annually and the latest results are usually within a year prior to the onset
of AUFF, we are able to exclude membrane dysfunction as the cause of AUFF in
our patients. The values of D/P Cr (0.70 ± 0.09) for our patients with
RPL, which are similar to patients without RPL, suggest that our patients are
average transporters. Although reduction in UF volume is unlikely due to
peritoneal membrane dysfunction, it is recommended to perform a PET or a
standard peritoneal permeability analysis when a patient is complicated by
AUFF and the membrane characteristics are unknown.
As clinical diagnosis of RPL is difficult because there is no localizing
sign in the systemic examination, further investigation to look for RPL should
be warranted, after excluding mechanical obstruction, malposition of the
peritoneal catheter, or other extraperitoneal causes, for patients developing
AUFF. Radiological imaging using either CTP or MRP is frequently employed.
Magnetic resonance imaging is preferred over CT because PD fluid can be used
as contrast medium, whereas CT requires administration of ionic contrast
medium into the peritoneal cavity. Moreover, MRP is more sensitive and a small
amount of leakage may be detected earlier. The diagnostic value of
radioisotope peritoneal scintigraphy [previously useful in detecting
peritoneal leakage (12)] to
detect RPL remains unknown.
Retroperitoneal leakage is likely to arise from a tear or a gap in the
peritoneum precipitated by an increase in intra-abdominal pressure associated
with walking, coughing, straining, or using a high instilled volume (2.5 L or
3 L). We believe the underlying pathogenesis of development of RPL is similar
to the development of an inguinal hernia. First, it is likely that there is a
defect in the peritoneal lining over the retroperitoneal area. Second, with
the increased intra-abdominal pressure, mechanical strain would push PD fluid
leak into the retroperitoneal space. Precipitating factors, such as chronic
cough and straining, for hernia formation are related to increased
intra-abdominal pressure. These risk factors are likely to operate in the
formation of RPL. This pathogenetic mechanism is supported by our logistic
regression and multivariate analyses, which demonstrate associated risk
factors, including pleuroperitoneal communication and hernia, in the presence
of RPL. However, we did not find any association between RPL and age, sex, or
body weight in accord with the few reported series on dialysate leakage
(5).
One may speculate that the instilled volume could be a precipitating factor
for peritoneal leakage. A larger instilled volume (2.5 L) resulting in an even
higher intraabdominal pressure compared to a standard instilled volume (2 L)
could be an additional cause. Nevertheless, all of our patients, with or
without RPL, were using 2 L as the instilled volume, with the largest
dialysate effluent averaging 2.5 L. Whether a larger instilled volume (2.5 L
or 3 L) could predispose the development of RPL is unknown. We recommend a
high index of suspicion for RPL when managing patients with AUFF who have a
history of hernia or pleuroperitoneal leakage.
Temporary interruption of PD and the introduction of intermittent cycling
PD achieve a curative treatment for most patients with RPL. A surgical
approach is difficult in the management of RPL as the exact site of leakage
might not be localized precisely. Moreover, surgical risk and associated
complications may prevent patients from returning to long-term PD treatment.
Avoidance of acts associated with increased intra-abdominal pressure, such as
straining, constipation, and cough, and use of smaller dialysate volume if
adequacy allows seem to reduce the risk of recurrence.
In conclusion, retroperitoneal leakage is not uncommon in patients with UF
problems and should be considered when managing patients with acute
ultrafiltration failure, especially in those patients with a history of hernia
or pleuroperitoneal communication.
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DISCLOSURE
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The authors declare no conflict of interest.
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ACKNOWLEDGMENTS
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The authors thank the nursing staffs of the dialysis centers, Queen Mary
Hospital, and Tung Wah Hospital, and also Dr. Ferdinand S.K. Chu and Dr.
Stephen C.W. Cheung from the Department of Diagnostic Radiology for performing
CTPs and MRPs respectively.
Received 3 September 2008;
accepted 29 October 2008.
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ABSTRACT
METHODS AND PATIENTS
