AJR 2004; 182:1493-1496
© American Roentgen Ray Society
CT of Nontraumatic Abdominal Fluid Collections After Initial Fluid Resuscitation of Patients with Major Burns
Vernon M. Chapman1,
James T. Rhea,
Richard Sacknoff and
Robert A. Novelline
1 All authors: Department of Radiology, FND 216, Division of Emergency
Radiology, Massachusetts General Hospital, PO Box 9657, 55 Fruit St., Boston,
MA 02114.
Received October 31, 2003;
accepted after revision November 20, 2003.
Address correspondence to V. M. Chapman.
Abstract
OBJECTIVE. The purpose of this study was to describe the presence
and CT distribution of nontraumatic fluid collections and edema in the abdomen
and pelvis after initial fluid resuscitation of patients with major (
25%
total body surface area) thermal burns.
CONCLUSION. Awareness of the presence and expected CT distribution
of nontraumatic fluid after initial fluid resuscitation in patients with major
burns can assist the radiologist in differentiating such collections from
those caused by mechanical trauma.
Introduction
In the United States, approximately 2.4 million burn injuries are reported
per year, of which 75,000 require hospitalization. Of those patients who
require hospitalization, 20,000 have major burns, defined as burns involving
at least 25% of the total body surface. Approximately 12% of major burn
patients die as a result of their injuries
[1]. With advances in medical
care and the advent of aggressive fluid resuscitation in the 1960s and 1970s,
irreversible shock has been replaced by wound sepsis as the most common cause
of death in patients who have suffered major burns
[2].
Fluid resuscitation of the burn patient is primarily accomplished with
large volumes of crystalloid fluid, totaling between 10 and 20 L in the first
24 hr for most adults, depending on body mass and percentage of total body
surface area burned. Such large fluid volumes are required to maintain
intravascular volume and tissue perfusion because these patients experience
evaporative losses from their burns as well as intra- to extravascular fluid
shifts caused by hypoalbuminemia and other metabolic derangements.
Extravascular fluid shifts result in significant soft-tissue edema, including
the brain, lungs, airways, and subcutaneous tissues
[3,
4].
We report the presence and distribution of nontraumatic fluid in the
abdomen and pelvis in eight patients who presented to our hospital 24 hr after
initiation of fluid resuscitation after severe thermal injury resulting in
major burns.
Materials and Methods
Patients
Eight patients (four men and four women; age range, 21–44 years; mean
age, 33 years) with major thermal burns and mechanical trauma were transferred
to our hospital approximately 24 hr after injury. All patients were victims of
the same event and were evaluated by MDCT of the abdomen and pelvis as part of
an evaluation for mechanical trauma. Examination of the patients' medical
records and imaging for the purposes of our study was approved by our
hospital's institutional review board.
CT
CT scans were obtained with an MDCT scanner (LightSpeed Plus, General
Electric Medical Systems). Patients were given 200–300 mL of a 2.5%
dilution of diatrizoate meglumine and diatrizoate sodium solution
(Gastrografin, Mallinckrodt) via a nasogastric tube before scanning. In all
patients, the entire abdomen and pelvis were scanned from the dome of the
diaphragm to the ischial tuberosities using the following parameters:
high-speed mode, pitch of 6, 5-mm slice thickness and 5-mm image spacing.
Scanning was performed 75 sec after injection of 120 mL of nonionic IV
contrast material (iopromide, Ultravist 300, Berlex Laboratories) using an
Envision CT injector (Medrad).
Image Analysis
The CT scans were retrospectively reviewed in consensus by two
radiologists. Scans were evaluated for the presence of abnormal
intraperitoneal fluid, which included any fluid in men and fluid extending
beyond the pelvic cul-de-sac in premenopausal women. The presence and
distribution (but not the volume) of soft-tissue edema were determined and
categorized as subcutaneous, mesenteric, perirenal, anterior pararenal, or
posterior pararenal. Scans were also assessed for the presence of intrahepatic
periportal edema. All images were reviewed using soft-tissue window settings
(window level, 40 H; window width, 400 H) on a PACS (picture archiving and
communications system, Agfa).
Results
All eight patients examined showed evidence of soft-tissue edema or
intraperitoneal fluid collections measuring less than 20 H. No CT evidence of
traumatic injuries involving the abdomen or pelvis was present. Clinical,
laboratory, and radiographic follow-up during the 4 weeks after CT showed no
evidence of mechanical trauma involving the abdomen or pelvis.
The distribution of nontraumatic fluid in the abdomen and pelvis is
depicted in Table 1. All eight
patients showed intrahepatic periportal edema of varying degree, as shown in
Figure 1. All eight patients
showed patchy subcutaneous edema, which was diffusely distributed and often
remote from the site of the patient's burns, as shown in
Figure 2. Six patients had
edema in the anterior pararenal space, predominantly surrounding the pancreas
and porta hepatis, as shown in Figure
3A,
3B. Four patients had edema in
the perirenal space. All these patients had a small amount of edema near the
lower pole of the kidneys, as shown in
Figure 4. Two patients had
mesenteric edema, as shown in Figure
5. No patients had edema in the posterior pararenal space. Three
patients showed intraperitoneal fluid that was considered abnormal by virtue
of its presence (any fluid in men) or volume (fluid extending beyond the
pelvic cul-de-sac in premenopausal women).
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Fig. 3A. —Transverse CT scans obtained with oral and IV contrast media
in 33-year-old woman with major burns. CT scan shows fluid and edema in
anterior pararenal space (arrows), particularly surrounding
pancreas.
|
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Fig. 5. —Transverse CT scan obtained with oral and IV contrast media
in 33-year-old woman with major burns shows fluid and edema in small-bowel
mesentery, predominantly at root of mesentery (arrow). Prominent
enhancement of bowel mucosa, likely caused by hypoperfusion, is also
present.
|
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The significance of peripancreatic edema was evaluated by comparison with
amylase and lipase values in the 2 weeks after CT. Two (33%) of the six
patients with peripancreatic edema and one (50%) of the two patients without
peripancreatic edema developed an elevated level of amylase. Five (83%) of the
six patients with peripancreatic edema and one (50%) of the two patients
without peripancreatic edema developed an elevated level of lipase. Using
chi-square analysis, we saw no statistically significant difference in the
incidence of pancreatic enzyme elevation between the two groups.
Discussion
Over the past 40 years, tremendous advances in medical technology and our
understanding of the physiology of patients who have experienced major burns
have led to the development of aggressive fluid resuscitation regimens and
significantly reduced the mortality caused by shock in the early postburn
period. Such resuscitation regimens result in the infusion of as much as
10–20 L of fluid in the first 24 hr after the injury. Soft-tissue edema
and related complications of resuscitation in the burn patient have been
described, such as airway, pulmonary, and cerebral edema, as well as
compartment syndromes in the extremities
[3]. Our study shows the
presence and distribution of nontraumatic fluid on abdominal or pelvic CT
after initial fluid resuscitation of patients with major burns.
The patchy subcutaneous edema observed in all eight patients examined is
not surprising because this has been previously described in burn patients and
attributed to decreased plasma osmotic pressure after fluid resuscitation
[4]. Similarly, the finding of
intrahepatic periportal edema in all eight patients is predictable because
this phenomenon has been previously reported in trauma patients during IV
resuscitation [5]. The proposed
mechanism is elevated central venous pressure caused by rapid expansion of
intravascular volume, and this mechanism likely applies to the patients
examined in this study.
Patients with major burns are at significantly increased risk of developing
postburn pancreatitis, with 40% developing laboratory evidence of pancreatitis
[6]. Though most patients in
the current study developed edema in the anterior pararenal space,
particularly surrounding the pancreas and porta hepatis, no statistically
significant increase in pancreatic enzyme levels in patients with
peripancreatic edema was seen.
According to this study, perirenal fluid collections in patients with major
burns are not rare. Delayed imaging and assessing attenuation values may
assist in differentiating such collections from urine extravasation or
hemorrhage, respectively.
Most patients in this study did not have mesenteric edema or
intraperitoneal fluid. Therefore, patients presenting with such a collection
after a major burn injury should be carefully evaluated and followed up
closely to exclude mechanical trauma, including injury to the bowel, urinary
bladder, and gallbladder.
Lack of involvement of the posterior pararenal space is not surprising
because this space is rarely involved in processes affecting the
retroperitoneal soft tissues. Any fluid collection in the posterior pararenal
space after a major burn should be considered the result of mechanical
trauma.
In conclusion, fluid resuscitation of patients with majors burns leads to
multicompartmental edema and fluid in the abdomen and pelvis, which is well
shown on CT. Patients with major burns uniformly develop subcutaneous and
periportal edema and frequently develop edema in the anterior pararenal space,
particularly surrounding the pancreas and porta hepatis. Peripancreatic
collections in such patients are not predictive of subsequent pancreatic
enzyme elevation. Intraperitoneal or mesenteric collections in patients with
major burns should raise suspicion of mechanical trauma, and collections in
the posterior pararenal space are the result of mechanical trauma until proven
otherwise. Awareness of the expected CT distribution of fluid and edema should
assist in discriminating between traumatic and nontraumatic fluid collections
in patients with major thermal burns who have undergone initial fluid
resuscitation.
References
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Abstract
Introduction
