Is a
Recumbent Plain Abdominal X-ray (Without an Upright Film) Sufficient in the
Evaluation of Patients with Acute Intestinal Obstruction?
A Multicenter Cooperative
Collaborative Action Research Study (MCCCARS)
Centers
that contributed to at least one action-research objective:
Ospital ng Maynila Medical Center
(OMMC); Zamboanga City Medical Center (ZCMC); Manila Doctors Hospital (MDH),
Batangas Regional Hospital (BRH);
Davao Regional Hospital (DRH);
Philippine General Hospital (PGH);
Region 1 Medical Center (R1MC)
MCCCARS Principal Investigators:
Reynaldo Joson, MD (OMMC and MDH);
Alex Cerrillo, MD (ZCMC); Alex Palines, MD (BRH); Alex Tan, MD (DRH); Manuel
Francisco Roxas, MD (PGH); Noneng Monroy, MD (PGH); Roberto Valenzuela, MD
(R1MC)
OMMC Residents: Ana Agoo- Llado, MD; Alfred
Troncales, MD; Marlou Padua, MD; Romero
Dangoy, MD
ZCMC Residents: Giovanni Paolo Gimena, MD;
Rhodora Lo, MD
MDH Resident: Ricardo Naval, MD
Acknowledgement
to other MCCCAR members who participated in the focused group discussion:
Edgardo Penserga, MD; Adrian Yu, MD; Ravel Bartolome, MD; Dionisio Cruz, MD;
Roehl Salvador, MD; and Ricky Torres, MD
·
Plain
Abdomen in Intestinal Obstruction
Is a Recumbent Plain Abdominal X-ray (Without an
Upright Film) Sufficient in the Evaluation of Patients with Acute Intestinal
Obstruction?
A Multicenter Cooperative and Collaborative
Action Research Study (MCCCARS)
·
Plain
Abdomen in Intestinal Obstruction
Plain Abdomen in Intestinal Obstruction 2
Abstract:
A multicenter cooperative and collaborative
action research study (MCCCARS) was conducted to determine if a recumbent plain
abdominal x-ray is sufficient in diagnosing patients with acute intestinal
obstruction. The specific objectives
consisted of the following: 1) to
compare the likelihood ratios of air-fluid level on upright films and
generalized bowel distention with absence of gas in the rectosigmoid on recumbent films; 2) to get a survey among
radiologists on the use and interpretation of plain abdominal x-rays; 3) to
formulate a clinical algorithm using recumbent plain abdominal x-ray only; and
4) to validate the algorithm as to accuracy.
Tools for data gathering included literature search, focused group
discussion, surveys and questionnaires, retrospective chart reviews, and
prospective data accrual. Results showed that the likelihood ratio of air-fluid level
was only 2 whereas that of generalized bowel distention without gas in the
rectosigmoid area was about 70. Most of
the radiologists surveyed considered generalized bowel distention without gas
in the rectosigmoid as the most reliable sign of mechanical intestinal
obstruction. The validation study
without the use of an upright film showed
an overall 94% accuracy rate (87% in one center and 100% in another
center) in diagnosing acute intestinal obstruction. The results of this study will be used as a basis to
institutionalize the practice of omitting an upright film in the evaluation of
patient with acute intestinal obstruction.
Keywords: intestinal obstruction, plain abdominal
x-ray, air-fluid levels
Plain Abdomen in Intestinal Obstruction 3
Introduction:
In the evaluation of patients with
acute intestinal obstruction, after the interview and physical examination, the
usual paraclinical diagnostic procedure being requested by clinicians globally1
including the Philippines (per email communication with members of the
multicenter study group and per survey of radiologists – see appendix) is an
abdominal x-ray in 2 different positions, namely: recumbent and upright or
lateral decubitus position.
In the recumbent x-ray, distention
of bowels, its degree, pattern and distribution, is sought for to aid in the diagnosis of acute intestinal
obstruction and its cause, either mechanical or non-mechanical obstruction. In the upright or decubitus x-ray, an
air-fluid level is sought for.
In the institutions of most of the
authors (except for Hospital C), 2
films corresponding to a recumbent and upright or lateral decubitus positions
have been routinely used in the radiologic examination of the abdomen in
patients with suspected acute intestinal obstruction. Recently, the authors
poised the question whether a recumbent plain abdominal x-ray would be
sufficient. The question aroused from the realization that air-fluid level is
not pathognomonic for mechanical obstruction; that diagnosis of intestinal
obstruction relies primarily on clinical symptoms and signs, and secondarily on
abdominal x-ray; and that a recumbent plain film supplies more diagnostic
information than an upright or lateral decubitus film and may be sufficient as
a paraclinical diagnostic procedure. The experience that air-fluid level is not
pathognomonic for mechanical obstruction is supported by some papers in the
literature2-4 .
Plain Abdomen in
Intestinal Obstruction 4
As a result of this question, an
action research study was conducted with the general objective of determining
whether a recumbent plain abdominal x-ray would be sufficient without having to
request for an upright or lateral decubitus film in the evaluation of patients
with acute intestinal obstruction.
Objectives:
The
specific objectives consisted of the following:
1. To determine the sensitivity,
specificity, and likelihood ratios of
radiologic air-fluid level on upright or lateral decubitus position in
patients with acute intestinal obstruction.
2. To determine the sensitivity,
specificity, and likelihood ratios of generalized bowel distention with absence
of gas in the rectosigmoid area on recumbent plain x-ray of the abdomen in
patients with acute intestinal obstruction.
3. To get a survey among radiologists
on the use and interpretation of plain films of the abdomen in patients with
possible intestinal obstruction.
4. To formulate an algorithm that
utilizes data obtainable from history, physical examination, and recumbent
plain abdominal x-ray only in evaluating patients with acute intestinal
obstruction.
5. To validate the algorithm as to
accuracy.
Methods:
General Methodology:
Plain Abdomen in Intestinal Obstruction 5
The concept and methodology of an
action research5-6 was
utilized, namely: analysis of the problems, research designs on how to solve
the problems, implementation of the
action plan; and evaluation of results of implementation. Multicenter cooperation
and collaboration was tapped for data gathering, patient accrual, and validity
testing of proposed solution.
Multicenter cooperation and collaboration does not necessarily mean that
all centers were accomplishing the same thing at the same time and all the
time. Cooperation and collaboration was
utilized when some centers could not, because of logistic and technical
problems, accomplish certain research objectives while some centers could. Tools for data gathering included literature
search using evidence-based approach, focused group discussion among the
members of the multicenter cooperative collaborative action research study
(MCCCARS) group, surveys and questionnaires, retrospective chart reviews, and
prospective data accrual. Focused group
discussion done mainly through email was the tool used for consensus gathering,
problem-solving and decision-making. Appropriate statistics, both descriptive
and analytical, were used as needed.
Literature search using an
evidence-based approach, focused group discussion among the members of the
MCCCARS group, surveys and questionnaires, retrospective chart reviews, and
prospective data accrual were used to gather data for objectives 1 and 2.
A retrospective chart review
conducted in hospital A included 81 adult
patients operated on for acute intestinal obstruction from January, 1996 to
December, 2000. The age ranged from 18
to 75 years old with a mean age of 44 years old. The sex distribution was 58 males and 23 females. The sensitivity, specificity, and likelihood
ratios of air-fluid levels were computed using the operative findings as gold
standards.
Plain Abdomen in Intestinal Obstruction 6
A prospective study conducted in
hospital B included 29 adult patients evaluated for acute intestinal obstruction
from January, 2002 to June, 2002. The
age ranged from 16-89 years
old
with a mean age of 51 years old. The
sex distribution was 14 males and 15 females.
The sensitivity, specificity,
and likelihood ratios of air-fluid level and generalized distention of bowels
associated with absence of gas in the rectosigmoid were computed using
operative findings and observation as gold standards for operated and
non-operated patients respectively.
Radiologists from 5 different
centers were requested to answer a questionnaire that was formulated to bring
out their use and interpretation of the plain films of the abdomen in patients
with possible acute intestinal obstruction.
A total of 19 radiologists from 5 institutions submitted answers to the
questionnaire.
Focused group discussion and
consensus gathering was done and based on the results of objectives 1 to3, an
algorithm was formulated.
Prospective data gathering was done
to validate the algorithm formulated in objective 4. From January, 2002 to September, 2002, the algorithm without an
upright film was used in the evaluation of patients with possible
obstruction. A total of forty-nine patients
were accrued from two centers, one in Luzon (Manila) and one in Mindanao, with
age ranging from 14 to 73 years old and a sex distribution of 24 males and 25
females. The diagnostic accuracy rate
was determined using the operative findings and observation as gold standards
for operated and non-operated patients respectively. An error in diagnosis was considered to be present in those
observed who were sent home with a diagnosis of a non-surgical abdomen and who
came back in a week’s time needing an operation.
The conceptual framework of this
action research is illustrated in Fig. 1.
Plain Abdomen in Intestinal Obstruction 7
Results:
The sensitivity and specificity rates of air-fluid levels
in acute intestinal obstruction ranged from 52 to 73% and 40 to 71%
respectively (Table 1). The likelihood
positive ratios ranged from 1.21 to 2.1.
No paper in the literature was found
that could give the sensitivity, specificity, and likelihood ratios of the
radiologic signs of intestinal obstruction on recumbent plain abdominal
x-ray. The rates were computed from the
local studies.
The sensitivity and specificity of diffuse
bowel distention with absence of gas in
the rectosigmoid area were 70% and 100% respectively (Table 2A). The positive predictive value was 100% and
the positive likelihood ratio was ~70.
In the absence of diffuse bowel
distention on recumbent film, non-diffuse or segmental bowel distention may be
seen in patients with acute intestinal obstruction, either with or without gas
in the rectosigmoid area. A computation
of the sensitivity and specificity of non-diffuse bowel distention with absence of gas in the rectosigmoid area was
33% and 62% (Table 2B). The positive
likelihood ratio was 0.49.
A total of 19
radiologist-respondents from 6 different institutions answered the
questionnaire formulated to survey on
their use and interpretation of plain films of the abdomen in patients with
possible intestinal obstruction. Based on their answers (Table 3), most of
them agreed that a lot of physicians
still request 2 views of the abdomen whenever they are entertaining a case of an acute intestinal obstruction. Though most of the respondents said that
Plain Abdomen in Intestinal Obstruction 8
air
fluid level is not pathognomonic of mechanical obstruction and that they see
bowel distention
more
often than air fluid level, majority of them still believe that 2 views are
still necessary and is the basic requirement in diagnosing acute intestinal
obstruction. However, for most of the
radiologists, diffuse bowel distention with no presacral or rectosigmoid gas is
the most reliable sign of mechanical obstruction, while diffuse bowel
distention with presacral or rectosigmoid gas is most likely non-mechanical
obstruction.
After
considering all the evidences gathered in objectives 1 to 3, in a focused group
discussion and consensus gathering, with some support from the literature7,
a clinical algorithm was formulated utilizing data obtainable from history,
physical examination, and recumbent plain abdominal x-ray in evaluating
patients with acute intestinal obstruction (Fig 2).
The clinical algorithm was validated
in terms of accuracy. A total of
49 patients were accrued.from two centers. One center accrued 23 patients and another
26 patients. The accuracy rate of one center was 87% and the other center,
100%. The overall accuracy rate was 94%
(Table 4).
Plain
Abdomen in Intestinal Obstruction 9
Discussion:
Looking at the conceptual framework
of this research (Fig.1), the
diagnostic track records and values of recumbent and upright abdominal films,
the result of the survey from the
radiologists,
and the validation results on the clinical algorithm all supported the
non-inclusion of an upright film anymore.
In the diagnostic track records and
values of the two x-ray films, the likelihood ratio of air-fluid level in an
upright film is low at 2 for mechanical intestinal obstruction whereas the
likelihood
ratio of a diffuse bowel distention with absence of gas in the rectosigmoid
area on a recumbent film is high at almost 70.
This difference in likelihood ratio is enough to favor a recumbent film
over an upright film. Furthermore, the
low likelihood ratio of an air-fluid level is
enough
to recommend that it is no longer necessary to request for an upright film
after a recumbent film is done because it will not significantly affect the
pretest-probability.
These arguments can be illustrated by some clinical
examples.
If after history and physical
examination, the pre-test probability is about 60%, 70% or even 80%, and there
is a need for a paraclinical diagnostic procedure that will be chosen from
either a recumbent or an upright plain abdominal x-ray, what should be
recommended? The recumbent plain
abdomen is usually the initial x-ray to request because right away, the x-ray
can tell whether bowel distention is present or not, and if present, the degree
of distention, whether diffuse or non-diffuse (segmental). Gas in the rectosigmoid area can also be
studied. If a generalized bowel
distention with absence of gas in the rectosigmoid is seen, with the likelihood
ratio of 70, the recumbent plain abdomen will be able to increase the pre-test
probability to a
Plain Abdomen in Intestinal Obstruction 10
post-test
probability as high as 98-99% not needing an upright film anymore. With a likelihood ratio of 2, the air-fluid
level on an upright film will no longer
significantly increase the high post-test probability after a recumbent film is
done.
Suppose the recumbent plain abdomen does not reveal
generalized bowel distention, should an upright film be requested? The answer is still no since chances of
seeing an air-fluid level in an upright film in nondistended bowels are
small. Furthermore, the likelihood
ratio of 2 of air-fluid level, if present, will not significantly affect the
pre-test probability.
In
the survey of radiologists, the tendency to look for an air-fluid level in an
upright film, despite the belief that the degree of distention of the bowel and
presence or absence of gas in the rectosigmoid is the most reliable cue to
differentiate between mechanical and non-mechanical obstruction, is more of a
habit.
With all the limitations of gathering data (with questions of validity
and reliability, especially of secondary data) on the sensitivity and
specificity of the radiologic signs of obstruction both on recumbent and
upright films of the abdomen and the differing opinions of the radiologists,
the consensus of the MCCCARS members is that the strongest evidence that will
be needed to really say that a supine film is sufficient is the validation
study from various centers that will omit the use of the upright films in the
evaluation of patients with possible acute intestinal obstruction. The validation data showed an overall
94% accuracy rate with one center
having an accuracy rate of 87% and another center, 100%. The center with an accuracy rate of 100%
actually has not been using upright films since 1993. This center does not
claim 100% accuracy rate all the time.
It claims it has a butting average of 95% accuracy without the use an
Plain Abdomen in
Intestinal Obstruction 11
upright film, just relying on history,
physical examination, recumbent x-ray of the abdomen, and monitoring.
With the validation
data in place, the last step in this action research is institutionalization of
the recommendation. In Hospital A and
Hospital C, the recommendation is part of the clinical practice guidelines
already. In Hospital A, a memo of
understanding between the Department of Surgery and Department of Radiology has
been forged that stipulated the following: 1) there is no need to request for
an upright film of the abdomen in patients with possible acute intestinal
obstruction and 2) if a paraclinical diagnostic procedure in the form of x-ray
of the abdomen is needed, a supine film is sufficient. Hopefully, in the near future, other centers
will follow suit, not only because of the evidences presented by this action
research but also because of the benefits of cost-reduction in omitting an
unnecessary upright film. The
cost-reduction benefit will not only be
on the part of the government hospitals that have meager resources but also on
the part of the paying patients and health care insurers.
Notes on action reseaarch:
The action research methodology used in this
project followed the concept as defined by Cohen and Manion6 that
is, "small scale intervention in
the functioning of
the real world and a close examination of the effects
of such intervention." It is
situational in that it is concerned with diagnosing a problem in a specific
context and attempting to solve it in that context. Usually collaborative teams of researchers and practitioners work
together on a project. It is participatory in the sense that the team members
themselves take part directly or indirectly by implementing the research. Lastly, it is self-evaluative in that
modifications are continually Plain Abdomen in Intestinal Obstruction 12
Plain Abdomen in Intestinal Obstruction 12
evaluated within the ongoing situation, the
ultimate objective being to improve practice in some way or another.
While
experimental research is concerned mainly with establishing relationships and
testing theories, action research has, as a focus, a specific problem in a
specific setting. It makes no attempt to identify one particular factor and
study it in isolation divorced from the context giving it meaning.
As
Margules7 points out, "in combining action processes (planning,
implementation, and evaluation) with research processes (problem
identification, hypothesis formation, and testing), the result is a sequence of
steps and activities that identify the relevant events that must happen in the
initiation and implementation of change."
The
essential steps in action research are the following: analysis of the problems,
research designs on how to solve the problems, implementation of an action plan
and evaluation of results of implementation.
In
the Philippines, most of the medical researches done are not of the action
research type. Thus, their utility just
end in being published in journals.
They are not being used by the people in the institution of origin of the
research papers. More so, they are not
being used by people outside the institution of origin.
The
other problems in conducting research projects in the country are the number of
clinical subjects and lack of resources.
This
action research has shown how a real world problem was being solved
systematically, cooperatively, and collaboratively. The multicenter cooperative and collaborative effort has
illustrated the advantages of sharing of resources. The ultimate impact of
Plain Abdominal X-ray in Intestinal
Obstruction 13
this action research consists of solutions
of problems and implementation of improvement measures in patient care being
simultaneously undertaken in several centers in the country.
Plain Abdominal
X-ray in Intestinal Obstruction 14
References:
1.
de Lacey GJ, Wignall BK, Bradbrooke S, Reidy J, Hussain S, Cramer B.
Rationalising
abdominal radiography in the accident and
emergency department. Clin Radiol 1980
Jul;31(4):453-5.
2.
Harlow CL, Stears RL, Zeligman BE, Archer PG. Diagnosis of bowel obstruction on
plain
abdominal radiographs: significance of
air-fluid levels at different heights in the same loop of
bowel. Am J Roentgenol 1994
Jul;163(1):223-4.
3.
Mirvis SE, Young JW, Keramati B, McCrea ES, Tarr R. Plain film evaluation of
patients with
abdominal pain: are three radiographs
necessary? Am J Roentgenol 1986 Sep;147(3):501-3.
4.
Simpson A, Sandeman D, Nixon SJ, Goulbourne IA, Grieve DC, Macintyre IM. The
value of
an erect abdominal radiograph in the
diagnosis of intestinal obstruction. Clin Radiol 1985
Jan;36(1):41-2.
5.
Cohen L, Manion L. Research Methods in Education. London, Croom Helm, 1980.
6.
Marguiles N. Managing change in health care organization. Medical Care
1977;15:693-704.
7.
Bohner H, Yang Q, Franke C, Verreet PR, Ohmann C. Simple data from history and
physical
examination help to exclude bowel
obstruction and to avoid radiographic studies in patients
with acute abdominal pain. Eur J Surg 1998 Oct;164(10):777-84.
Plain Abdominal
X-ray in Intestinal Obstruction 15
Table 1:
Sensitivity, specificity, and likelihood ratios of radiologic air-fluid level.
|
|
Sensitivity |
Specificity |
Likelihood
(+) Ratio |
Likelihood
(-) Ratio |
|
Harlows2 |
52% |
71% |
1.79 |
0.67 |
|
MCCCARS
(hospital
A) |
73% |
40% |
1.21 |
0.67 |
|
MCCCARS
(hospital
B) |
63% |
70% |
2.1 |
0.52 |
Table
2A: Sensitivity, specificity and likelihood ratios of diffuse bowel distention
with no gas in the rectosigmoid area in patients with acute intestinal
obstruction (hospital B data).
|
|
Mechanical
Obstruction |
Non-Mechanical
Obstruction |
|
|
Diffuse
distention with NO gas |
7 |
0 |
7 |
|
Diffuse
distention with gas |
3 |
1 |
4 |
|
|
10 |
1 |
11 |
Sensitivity
= 70%
Specificity
= 100%
Positive
predictive value = 100%
Negative
predictive value = 25%
Likelihood
ratio = ~70
Plain Abdomen in Intestinal
Obstruction 16
Table
2B: Sensitivity, specificity, and likelihood ratios of segmental distention
with no gas in the rectosigmoid area in patients with acute intestinal
obstruction (hospital B data)..
|
|
Mechanical
Obstruction |
Non-Mechanical
Obstruction |
|
|
Segmental
distention with NO gas |
3
|
3
|
6 |
|
Segmental
distention with gas |
6
|
5
|
11 |
|
|
9 |
8 |
17 |
Sensitivity
= 33%
Specificity
= 62%
Positive
predictive value = 50%
Negative
predictive value = 45%
Likelihood
ratio = 0.49
Plain Abdominal X-ray in Intestinal Obstruction 17
Table
3. Results of survey of radiologists on use and interpretation of upright and
recumbent films of abdomen in patients with possible acute intestinal
obstruction.
|
|
YES |
NO |
|
The usual x-rays
being requested by clinicians for patients with possible acute intestinal
obstruction are recumbent and upright (or lateral decubitus) plain x-ray of
the abdomen. |
17 |
2 |
|
If there are
already air-fluid levels on upright or lateral decubitus film, there are
usually distended small bowels on the recumbent film. |
14 |
5 |
|
If there are
distended small bowels on the recumbent film, there may or may not be
air-fluid levels on the upright or lateral decubitus film. |
17 |
2 |
|
Is the presence
of a differential air-fluid level on upright or lateral decubitus film by
itself pathognomonic or has a 100% specificity for mechanical intestinal
obstruction? |
2 |
17 |
|
From your point
of view as a radiologist, do you think that a recumbent plain abdomen
correlated with clinical signs and symptoms is sufficient (without an upright
film) for the clinician to make a diagnosis of acute intestinal obstruction
with an accuracy of more than 95%? |
8 |
11 |
Plain Abdominal X-ray in Intestinal Obstruction 18
|
|
< 25% |
>25<50% |
>50<90% |
>90% |
|
In your experience, how often do you see differential
air-fluids in the radiology of patients with possible acute intestinal
obstruction? |
1 |
3 |
13 |
2 |
|
In your experience, how often do you see
distended bowels in the radiology of
patients with possible acute intestinal obstruction? |
0 |
0 |
7 |
12 |
Plain Abdominal X-ray in Intestinal Obstruction 19
|
Most
reliable sign for |
Mechanical
Obstruction |
Non-Mechanical
Obstruction |
|
diffuse distention of small
bowels with gas in the rectosigmoid or presacral area |
1 |
14 |
|
diffuse distention of small
bowels with no gas in the rectosigmoid or presacral area |
10 |
0 |
|
segmental distention of
small bowels with gas in the rectosigmoid or presacral area |
0 |
5 |
|
segmental distention of small
bowels with no gas in the rectosigmoid or presacral area |
2 |
0 |
|
differential air-fluid level |
6 |
0 |
|
|
|
Primary Radiologic Diagnosis |
||
|
Case |
Radiologic findings on Plain Abdomen,
recumbent and upright |
Mechanical Obstruction |
Adynamic Ileus |
No Obstruction |
|
1 |
(-) distended small bowels (+) gas in rectosigmoid or presacral area (-) air-fluid level |
0 |
1 |
18 |
|
2* |
(-) distended small bowels (+) gas in rectosigmoid or presacral area (+) air-fluid level |
0 |
5 |
10 (*4– not possible) |
|
3 |
(+) distended small bowels (+) gas in rectosigmoid or presacral area (-) air-fluid level |
0 |
19 |
0 |
|
4 |
(+) distended small bowels (+) gas in rectosigmoid or presacral area (+) air-fluid level,
nondifferential |
0 |
18 |
1 |
|
5 |
(+) distended small bowels (+) gas in rectosigmoid or presacral area (+) air-fluid level,
differential |
8 |
11 |
0 |
|
6 |
(+) distended small bowels (-) gas in rectosigmoid or presacral area (-) air-fluid level |
9 |
9 |
1 |
Plain Abdominal X-ray in
Intestinal Obstruction 20
|
7 |
(+) distended small bowels (-) gas in rectosigmoid or
presacral area (+) air-fluid level, nondifferential |
9 |
9 |
1 |
|
8 |
(+) distended small bowels (-) gas in rectosigmoid or
presacral area (+) air-fluid level, differential |
18 |
1 |
0 |
Table
4: Validation of algorithm without use of upright film.
|
|
N |
Error in diagnosis |
Accuracy rate (%) |
|
Center 1 |
23 |
3 |
87 |
|
Center 2 |
26 |
0 |
100 |
|
Centers 1 and 2 |
49 |
3 |
94 |
Plain Abdominal X-ray in Intestinal Obstruction 21
Fig 1.
Conceptual Framework
(serve as bases
for)
Plain Abdomen in Intestinal
Obstruction 22
