Several reports have addressed the need for radiologists to be clear and pertinent in their interpretation or reporting of radiologic procedures.1-5 Imprecise or poorly understood reports can adversely affect the workup and management of patients.

Plain abdominal radiography (PAR) is one of the more frequently requested examinations in emergency medicine. In our experience, emergency physicians frequently utilize the term "nonspecific abdominal gas pattern" in their preliminary interpretations when, in fact, they mean that the bowel gas pattern is normal.6 A recent survey of community-based teaching hospital radiologists showed that 70% of the radiologists used this term;7 65% of these radiologists considered the phrase to mean "normal or probably normal," 22% interpreted this as "cannot tell if normal or abnormal," and 13% use this term to mean that findings are abnormal but it cannot be determined if it is due to mechanical obstruction or adynamic ileus." Of the rererring physicians in the same survey who received the report, 44% defined it as "normal"; 51% delined it as "normal or abnormal"; and 5% defined it as abnormal, representing either mechanical obstruction or adynamic ileus. It is obvious that the term has a wide range of meaning, both for radiologists and referring clinicians. At one extreme, it appears to signify a normal condition; whereas at the other extreme it is perceived as a pathologic state, such as obstruction. Few other radiologic interpretations have more consistent disagreement about their meaning, both among radiologists and between radiologists and referring clinicians.

Prior communications have called for the abandonment of the term "nonspecific abdominal gas pattern,7,8 and yet the term continues to be used. It is pertinent to consider why this is so. Is it because radiologists and emergency physicians do not read the literature, or is it because a "nonspecific" intestinal gas pattern really exists? My experience suggests that there is a group of patients whose abdominal radiographs do not fit the definition of "normal", "probable small bowel obstruction", or "definite small bowel obstruction" gas patterns. As there is no applicable alternative recommendation, there is likely to be difficulty in "ignoring" or abandoning this interpretation. How does one report this intestinal gas pattern and what are its clinical implications?

A recent report of a blinded analysis of plain film abdominal examinations in the diagnosis of small bowel obstruction (SBO) by experienced gastrointestinal radiologists showed a sensitivity of 66%.9 This report differed from other studies in that the PAR patterns were defined and a follow-up for every defined interpretive category was given. In this report, 62% of the patients clinically suspected of SB0 were in fact not obstructed. Of "normal'' plain film interpretations, 21% had low grade SBO. Of the so-called "abnormal but nonspecific'' plain film interpretations, 13% had low grade and 9% had high grade SBO. The investigators defined the latter pattern as a borderline or slightly dilated (2.5 cm to 3 cm) small bowel with more than two air-fluid levels. Of the "probable" SBO plain film interpretations, 37% had low grade SBO and 16% had high grade SBO. Of the "definite" SBO interpretations, 26% had low grade SBO and 23% had high grade SBO; 13% had complete SBO. This report clearly showed that there is a pattern which is neither normal nor fits the categories of probably or definitely obstructed. Gammill and Nice recognized this pattern to mean ileus (i.e., the small bowel is unable to push fluid along).10 Indeed, the word "ileus" means stasis and does not differentiate between mechanical and nonmechanical causes. Our acceptance of the term "ileus" to mean an adynamic etiology when in fact it simply means stasis that can result from any cause may be part of the problem.

The interpretation "nonspecific abdominal gas pattern" should be avoided. I propose the term "mild small bowel stasis." However, if the term nonspecific abdominal gas pattern is used, it should be qualified as abnormal and should be followed by a specific recommendation for further workup. This interpretation satisfies a group of plain film findings that does not fit the normal and definitely abnormal categories, but may still have clinical implications.9 Based on the current literature, the various intestinal gas patterns are defined as follows:

1. A "normal" intestinal gas pattern is defined as either an absence of small intestinal gas (without abnormal increase in abdominal density or loss of soft tissue planes) or the presence of gas within a few (3 to 4) variably shaped small intestinal loops measuring less than 2.5 cm in diameter. In addition, there is a normal gas and/or fecal distribution in a nondistended colon.

2. "Mild small bowel stasis" (abnormal but nonspecific pattern) is defined as those cases demonstrating single or multiple loops of borderline or slightly dilated small intestine (2.5 cm to 3 cm) with 3 or more air-fluid levels on upright or decubitus films. There is no disproportionate distention of the small intestine relative to the colon. Gas and/or feces are present in a nondistended colon. The term is used to indicate an abnormal gas distribution, but does not allow distinction between mild reflex or adynamic ileus and mechanical obstruction. Some of the patients in this category have low grade obstruction and are difficult to diagnose clinically, and others may have reflex or reactive ileus secondary to a variety of processes, e.g. trauma, critical illness, or urinary tract calculus. Some may be related to medication-induced hypoperistalsis and air swallowing.10

3. A "probable" SBO pattern is defined as unequivocally dilated multiple gaseous and/or fluid-filled loops of small intestine with a moderate amount of colonic gas, but the degree of distention of small intestine relative to the colon is insufficient to make a definite diagnosis. Air-fluid levels are generally present, but there is an element of uncertainty in diagnosing SBO.

4. A "definite" SBO pattern is defined as abnormal and clearly disproportionate gaseous and/or fluid distention of small bowel relative to the colon (or other segments of small intestine). Air-fluid levels are evident, and the diagnosis of SBO is considered unequivocal.

The use of a precise definition of plain film intestinal patterns will enable radiologists to prevent misunderstandings with referring clinicians, and allow us to make more cost effective recommendations for further work-up in suspected SBO.11 The radiologic report should include a recommendation for further imaging if this is needed, so that erroneous application of radiologic resources, which can increase the cost of work-up and management, is avoided. An algorithm is proposed for additional imaging in the work-up of patients with suspected intestinal obstruction (figure 1). This is based on the acknowledged limitations of PAR,9 the value of CT in the emergent situation,12,13 and the problem-solving ability of enteroclysis in the subacute or chronic setting.11,14 The recommendations given are based not on firm scientific evidence, but on continuing clinical radiologic observations over the last decade.9,11-17 As the value of other imaging modalities are established, their use can be added to the recommendations. The role of radiology has undergone significant changes in the last decade with the use of CT, enteroclysis, and the rebirth of the long decompression table.18

Radiologists must understand each other if we expect other physicians to understand us. The lack of a definition of the meaning of the various terms used in plain film interpretation has resulted in confusion and has prevented meaningful comparison of different reports. A careful analysis and clear reporting of the plain film is crucial to prevent erroneous application of imaging resources and clinical mismanagement. The "misleading" patterns in intestinal obstruction appear to be largely plain film misinterpreations, miscommunication, and the use of undefined terms. Our reports should be concise and as precise as possible.

"Nonspecific abdominal gas pattern" is an interpretation whose time should have been long gone. lt serves no useful purpose and deserves permanent burial.

Acknowledgement:

The author would like to thank Frederick M. Kelvin, MD, for his advice and Fran Shaul for secretarial assistance.

This editorial is reprinted with permission from Maglinte DDT: Nonspecific abdominal gas pattern: An interpretation whose time is gone (editorial). Emerg Radiol 3:93-95, 1996.

References

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