“Nonspecific abdominal gas pattern”: An interpretation whose time is gone

Abstract

S everal 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 (PAP,) 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 this to be "normal or probably normal," 22% interpreted this as "cannot tell if normal or abnormal," and 13% defined this term as "abnormal but cannot tell if it is mechanical obstruction or adynamic ileus." O f the referring physicians in the same survey who received the report, 44% defined it as "normal," 51% defined it as "normal or abnormal," and 5% defined it as "abnormal, representing either mechanical obstruction or adynamic ileus." Some did not know what the term meant. It is obvious that the term has a wide range of meaning for both 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" and "definite small bowel obstruction" gas patterns. This is likely why there is difficulty in "ignoring" or abandoning this interpretation in the absence of an applicable alternative recommendation. How does one report this intestinal gas pattern, and what are its clinical implications? A recent report of a blinded analysis of plain radiographic 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 SBO were, in fact, not obstructed. O f "normal" plain radiographic interpretations, 21% had low-grade SBO. O f the so-called "abnormal but nonspecific" plain radiographic interpretations, 13% had lowgrade and 9% had high-grade SBO. The investigators defined the latter pattern as borderline or slightly dilated (2.5-3 cm) small bowel with more than two air fluid levels. O f the "probable" SBO plain radiographic interpretations, 37% had low-grade SBO and 16% had high-grade SBO. O f the "definite" SBO interpretations, 26% had lowgrade 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 (10) recognized this pattern to mean ileus (i.e., the small bowel is unable to push fluid along). 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. Plain radiographic examination has remained a mainstay in the evaluation of patients with suspected intestinal obstruction because of its ready availability, its relative cheapness, and its acceptable clinical record. It is the usual starting point in the radiologist's involvement in the workup of this group of patients. The interpretation "nonspecific abdominal gas pattern" should be avoided. I propose the term "mild small bowel stasis." If the term "nonspecific abdominal gas pattern" is used, it should be qualified as abnormal and should be followed by a specific recommendat ion for