Strangulating Obstruction of the Bowel: A Reevaluation of Radiographic Criteria

Transcription

1 Strangulating Obstruction of the Bowel: A Reevaluation of Radiographic Criteria DAVID BRYK1 Fifty consecutive cases of strangulating obstruction were compared with 100 consecutive cases of surgically proven simple obstruction due to adhesions or hernia. All cases were studied by the usual supine and either erect or decubitus abdominal films, and by two successive supine films made at 5 mm intervals. Radiographic criteria previously described as signs of possible strangulation were evaluated in the two series. Reduced activity of the small bowel loops on the successive supine films was the only frequent sign (58% of the cases with strangulating obstruction) which showed a statistically significant difference in Incidence between the two groups. Other signs seen with some frequency (22%-28% of the group with strangulation) were long air-fluid levels, loss of valvulae conniventes, retention of bubbly fecal matter in the right colon, and predominance of fluid-filled loops; however, they occurred with the same frequency in simple obstruction. The more specific signs of bowel congestion and necrosis (I.e., a narrow rigid loop or intramural gas) were seen in 10% and 2% of the cases, respectively. Only the incidence of a narrow rigid loop in strangulation reached statistical significance. This study confirms the difficulty of diagnosing strangulating obstruction using plain films of the abdomen. Successive abdominal films were shown to be valuable in providing Information about small bowel activity, which can help in the differential diagnosis. Strangulating obstruction is defined as small bowel obstruction with evidence of compromised blood supply, varying from slight compression of the mesenteric veins with bluish discoloration of the segment to frank hemorrhagic infarction and gangrene [1]. Strangulation may result from volvulus, incarcerated hernia, passage of the small bowel through an abnormal opening in the mesentery such as produced by certain surgical procedures, or by twisting of the intestine about a band [1]. A classic study of the radiographic signs of strangulating obstruction on plain abdominal films was published in 1954 by Mellins and Rigler [1]. They studied 26 cases and analyzed 10 radiographic signs. Subsequent studies described additional signs [2-8]. Despite the numerous signs described, other publications [9-13] stress the difficulty in making the diagnosis, even in conjunction with clinical and laboratory findings such as localized tenderness, leukocytosis, fever, tachycardia, or an abdominal mass. This study attempts to determine the incidence and statistical reliability of the various radiographic signs described. Materials and Methods A series of 50 consecutive cases of surgically proven strangulating obstruction studied radiographically at the Jewish Hospital and Medical Center of Brooklyn was compared with 100 consecutive cases of simple small bowel obstruction due to adhesions or hernia. All cases had supine and either erect or left lateral decubitus films. In addition, all cases had two successive supine abdominal films exposed at 5 mm intervals which were evaluated using the criteria of small bowel activity previously described [8]. All but one of the 11 basic signs of strangulating obstruction described in the literature were evaluated. The exception was, absence of decompression of a localized loop following suction siphonage [1], because long tube small intestinal decompression was rarely used at this hospital. The statistical significance of the results was evaluated by x analysis. The following signs were evaluated. 1. Reduced small bowel activity on successive 5 mm abdominal films. The dilated small bowel loops show no significant change, except for minimal fluid gas shifts within the loops or at their periphery [1] (fig. 1). 2. Long air-fluid levels. Each loop is flattened in the erect film and does not show a hoop shape [14]. The maximum length of the levels is at least 2 cm longer than the maximum diameter of the loops in the recumbent film [8] (fig. 2). 3. Loss of valvulae conniventes. The valvulae conniventes usually seen in the dilated loops of jejunum are absent, leaving a smooth or formless lumen [1] (fig. 3). 4. Retention of bubbly fecal matter in the right colon. Bubbly appearing fecal matter is noted in the right colon associated with gas-distended loops of small bowel [7] (fig. 4). 5. Predominance of fluid-filled loops. The small bowel is dilated but the loops are filled with fluid with only minimal gas [3] (fig. 5). 6. Fixation of loops. There is lack of alteration in the position of the loops on films made in the supine and erect positions, or on follow-up films [1, 14] (fig. 6). 7. Predominant gaseous distention of one segment. One segment is distended far out of proportion to the remaining loops. Occasionally, this results in a coffee bean configuration on the recumbent film. Gas is seen in the two distended limbs of the incarcerated loop, with a thicker shadow between them produced by the apposed edematous intestinal walls [1] (fig. 7). 8. Pseudotumor. The fluid-filled incarcerated loops appear as a tumorlike density with a polycyclic outline. The pseudotumor is outlined by adjacent indented gas-containing loops, while fluid levels are seen in the mass in the upright or lateral decubitus positions [1, 6, 14] (fig. 8). 9. Rigid narrow loop. The strangulated loop shows a narrow gas-containing lumen with an irregular serrated contour due to thickening and edema of the bowel wall. The configuration of the narrow gas collection does not change in distribution on films in various positions [2, 14] (fig. 9). 10. Intramural gas. Crescentic, linear, ringlike, or bubbly gas collections are noted outside the lumen of the bowel. A stripe of increased density between the abnormal gas collections and Received October 12, 1977; accepted January 6, 1978 Department of Radiology, State University of New York Downstate Medical Center and Jewish Hospital and Medical Center of Brooklyn, 555 Prospect Place, Brooklyn, New York Am J Rontg.nol 130: , May American Roentgen Ray Society X/78/ $02.00

2 836 BRYK Fig. 1.-Reduced bowel activity. 5upine successive 5 mm abdominal films showing no significant change in dilated small bowel except for minimal fluid-gas shifts. the normal intraluminal gas represents the bowel wall itself [4. 5] (fig. 10). 11. Relatively gasless abdomen. There is a relative absence of small intestinal gas in a case suspected clinically of small intestinal obstruction [1] (fig. 11). Results The incidence of the 1 1 signs in strangulating obstruction and simple small bowel obstruction is shown in table 1. The only frequent sign of strangulating obstruction was reduced activity of the small bowel loops seen on successive 5 mm films. In the group with strangulation, 58% showed reduced activity compared to 11% with simple obstruction (P <.001). Although long air-fluid levels, loss of valvulae conniventes, retention of bubbly fecal matter, and predominance of fluid-filled loops were seen in 22%-28% of the group with strangulation, they occurred with similar frequency in the group with simple obstruction. The only other statistically significant differential signs were predominant gaseous distention of one segment and a narrow rigid loop (P <.05 and P <.001, respectively). The three statistically significant signs were usually seen individually, unassociated with the other significant signs: 46% of the cases showed one sign, 16% showed two signs, while none demonstrated all three signs. Discussion The radiographic criteria described in strangulating obstruction are related to three physiologic anatomic findings: (1) a generalized inhibition of gastrointestinal activity that results when bowel is strangulated; (2) the incarcerated closed loop nature of the obstruction; and (3) pathologic changes in the strangulated loop. Generalized Inhibition of Gastrointestinal Activity Inhibition of bowel activity in strangulating obstruction has been well documented in various studies. In a canine experiment using intraluminal fluid-filled catheters, Dixon et al. [15] demonstrated virtually complete inhibition of jejunal activity after luminal occlusion and ligature of the vascular pedicle. They felt this was due to sympathoadrenal discharge resulting in activation of inhibitory alpha and beta adrenergic receptors of the intestine. This inhibition could be blocked experimentally by the administration of alpha and beta adrenergic blocking agents. In another experimental study, Dixon et al. [16] demonstrated marked prolongation of barium transport from the stomach in dogs after production of a strangulated closed loop. A similar finding was demonstrated in rabbits by Frimann-DahI [17]. In clinical strangulating obstruction, Vest [18] showed prolonged retention of oral water-soluble contrast material in the stomach. Nelson and Christoforidis [19] described a similar atonicity of the stomach using barium sulfate. This inhibition of bowel activity is the apparent basis of the following signs: reduced bowel activity on successive 5 mm films; long air-fluid levels; loss of valvulae conniventes; retention of bubbly fecal matter in the right side of the colon; predominance of fluid filled loops; and a relatively gasless abdomen. In a preliminary study which included several cases of strangulating obstruction [8], the usefulness of 5 mm

3 RADIOGRAPHY OF STRANGULATING OBSTRUCTION 837 Fig Long air-fluid levels. Erect film showing flat dilated loops with long air-fluid levels. successive abdominal films in differentiating simple and complicated obstruction was demonstrated. This was confirmed by the current comparative study which demonstrated reduced activity, based on the 5 mm successive films, in 58% of the cases of proven strangulating obstruction compared to 11% in simple obstruction. However, a significant percentage of cases of strangulation (42%) did not show reduced activity. These cases may have been studied radiographically before strangulation or its effects became apparent, or perhaps the mechanism which produces intestinal peristaltic inhibition did not operate or improved spontaneously due to lesser degrees of bowel compromise. Despite the large number of false negative cases, this was the only frequent and statistically significant differential sign. Frimann-DahI [14] popularized the concept that long fluid levels and straight flaccid loops are a manifestation of decreased bowel activity associated with strangulating obstruction, mesenteric vascular th rombosis, and pentonitis. The present study did not show this to be a useful Sign. Probably the length of the fluid levels in the dilated ioops is related to the amount of fluid in the lumen, rather than to the state of bowel activity. Loss of valvulae conniventes in jejunal loops in strangulation was thought to be due to stagnant anoxia with resultant loss of tone of the musculanis mucosae, leaving a smooth or formless lumen [1]. This was described both within the gas-filled incarcerated loops and within the intestine just above, providing there had been sufficient distention to compromise the intramural circulation. The I.- Fig. 3.-Loss of valvulae conniventes. Supine film showing that valvulae conniventes are mostly absent in dilated loops of jejunum in upper abdomen except for occasional edematous fold, leaving relatively smooth lumen. Fig. 4.-Retention of bubbly fecal matter in right colon. Supine film showing bubbly fecal matter in right colon (arrows) associated with dilated loops of small bowel. I

4 838 BRYK Fig. 5.- Predominance of fluid-filled loops. A, 5upine film showing small bowel loops filled with fluid making upper abdomen appear dense. B, Erect film showing fluid levels and gas bubbles in dilated fluid-filled loops. problem with this sign is that dilated ileum will not show valvulae, and it is difficult to differentiate it from jejunum if it is situated in the upper abdomen. Second, the dilatation of bowel in simple obstruction may conceivably produce the same effect on the valvulae as strangulation due to prolonged distention and resulting edema of the bowel wall [20]. The current study showed no differential value to this Sign, possibly related to these factors. Retention of bubbly fecal matter in the right colon was felt to be due to the failure of the colon to empty in strangulation, as compared to simple obstruction, because of penistaltic inhibition of the colon [7]. The current study showed this sign to be of no differential value. This may be explained by the fact that (1) the films may have been made before the colon emptied; and (2) the block is frequently incomplete, and as a result fecal matter forms in the colon distal to the obstruction from the food and intestinal secretions that bypass the obstruction. Predominance of fluid-filled loops in strangulating obstruction was felt to be due to partial paralysis of the intestine proximal to the occlusion, so that even if the patient swallowed some gas, it did not readily pass into the intestine, remained in the stomach, or was vomited [21]. In addition, if the strangulation involved a major portion of the small bowel, the strangulated loops were filled with fluid, since the closed loop obstruction prevented gas from entering the loops [6]. Because the latter type of strangulating obstruction is rare, predominant fluid-filled loops were not a significant differential sign in the current study. The degree of fluid in the loops may be related to other factors, such as the amount of gas the obstructed patient swallows and the ability of the obstructed intestine to absorb this gas. A relatively gasless abdomen in a patient suspected clinically of small intestinal obstruction may be due to lack of transport of swallowed air into the small bowel due to gastric penistaltic inhibition [1]. The swallowed gas is either vomited or removed by nasogastnic suction [20]. Because this sign was so rare (one case), it did not have enough diagnostic value. Incarcerated or Closed Loop Obstruction Strangulation is frequently due to twisting of a loop, so that the bowel lumen is narrowed or blocked at two points by a single constricting lesion. If the loop is only partially closed, it will admit gas. The loop will thus be dilated out of proportion to the remaining loops. The two limbs may be parallel in the recumbent radiograph, separated by the apposed intestinal walls, giving the coffee bean configuration [1]. This was a statistically significant sign of strangulation but was seen in only l2% of the cases. It was also occasionally seen in simple obstruction, since a closed loop does not necessarily strangulate and can even untwist spontaneously. It may also be simulated at times by overlapping loops of bowel in adjacent loops at different horizontal planes. The pseudotumor sign is presumably due to a greater degree of obstruction of the limbs of the closed loop, so that little gas is admitted, and the loop, for the most part, contains the bloody transudate resulting from strangulation. Films of the abdomen will show the fluid-filled closed loop as a tumonlike density with polycyclic con-

5 RADIOGRAPHY OF STRANGULATING OBSTRUCTION 839 tours [1, 6, 14]. The sign had no significant differential diagnostic value in this series. Presumably fluid-filled loops of bowel in simple obstruction, especially if they are fixed by adhesions, can give a similar pseudotumor sign [13]. Fixation of bowel loops is the other sign previously considered suggestive of a closed loop obstruction [1, 14]. Although it occurred more frequently in strangulating obstruction, the difference was not statistically sig- -I.. Intramural intestinal gas is another useful sign of intestinal necrosis [4, 5]. It is more commonly seen in mesentenic infarction and only rarely in strangulation [5] (2% in this series), and thus is of relatively little diagnostic value. Conclusions Reduced activity of the small bowel loops on 5 mm successive supine radiographs was the only frequent sign (58% of the cases of strangulation) which showed a statistically significant difference in incidence between

6 840 BRYK Fig. 7.-Two cases with predominant gaseous distention of one segment. A, Supine film showing coffee bean configuration of dilated loop (arrows). B, Supine film showing predominant distention of one segment without coffee bean configuration (arrows). Fig. 8.- Pseudotumor. A, Supine film showing fluid-filled loops as tumorlike density in midabdomen with polycyclic outline indenting adjacent gascontaining loops (arrows). B, Erect film showing fluid levels in pseudotumor (arrows).

7 RADIOGRAPHY OF STRANGULATING OBSTRUCTION 841 Fig. 9.-Rigid narrowed loop, barium small bowel study. Supine (A) and left posterior oblique (B) films showing relatively narrow loop of gas-filled bowel in lower abdomen with irregular nodular contour which maintains same configuration in both films (arrows). Fig. 10.-Intramural gas. Supine (A) and erect (B) films showing linear and bubbly gas collections within walls of bowel loops in left side of abdomen (arrows). the two groups. However, since simple obstruction is about six to 10 times as frequent as strangulating obstruction [1], less than one-half of the cases with reduced activity will eventually be proven to have strangulated bowel. Since clinical and laboratory criteria are also nonspecific in the diagnosis of strangulation [9], early surgical intervention is frequently necessary for proper patient management. ACKNOWLEDGMENTS I thank Eli Bryk for assistance with the statistical material and Marvin Ehlin for the illustrative material.

8 842 BRYK Fig. 11.-Relatively gasless abdomen. A, Supine plain film showing relative absence of small intestinal gas. B, Barium study showing markedly dilated partially closed loop in lower abdomen (arrows) with irregular contours and distorted folds, which on surgical exploration was strangulated. TABLE 1 Incidence of Radiographic Signs Strangulating Simple Obstruction Obstruction Radiographic Sign (N = 50) (N = 100) No. *1* No. *1* Reduced activity on successive 5 minabdominalfilms...,, 29* (58) 11* (11) Long air-fluid levels 14 (28) 30 (30) Loss of valvulae conniventes..,. 14 (28) 21 (21) Retention of bubbly fecal matter in right colon 13 (26) 30 (30) Predominance of fluid-filled loops 1 1 (22) 23 (23) Fixationofloops 7 (14) 8 ( 8) Predominant gaseous distention of one segment 6t (12) 4t ( 4) Pseudotumor 5 (10) 7 ( 7) Rigid narrow loop 5* (10) 1* (1) Intramural gas 1 ( 2) 0 Relatively gasless abdomen 1 ( 2) 0 Difference significant at.001 level. t Difference significant at.05 level. REFERENCES 1. Mellins HZ, Rigler LG: The roentgen findings in strangulating obstructions of the small intestine. Am J Roentgenol 71 : , Nelson SW, Eggleston W: Findings on plain roentgenograms of the abdomen associated with mesenteric vascular occlusions with possible new signs of mesentenic venous thrombosis. Am J Roentgenol 83 : , Williams J: Fluid filled loops in intestinal obstruction. Am J Roentgenol 88 : , Schorr 5: Small intestinal intramural air. Radiology 81 : , , Rigler LG, Pogue WL: Roentgen signs of intestinal necrosis. Am J Roentgenol 94 : , Shauffer IA, Ferris EJ: The mass sign in primary volvulus of the small intestine in adults. Am J Roentgenol 94: , Schmidt AG: A roentgen sign in strangulating obstructions of the small intestine. Radiology 85 : , Bryk D: Functional evaluation of small bowel obstruction by successive abdominal roentgenograms. Am J Roentgenol 116: , Becker WF: Acute adhesive ileus-a study of 412 cases with particular reference to the abuse of tube decompression in treatment. Surg Gynecol Obstet 95 : , Miller EM, Winfield JM: Acute intestinal obstruction secondary to postoperative adhesions. Arch Surg 78: , Lasser EC: Dynamic Factors in Roentgen Diagnosis. Baltimore, Williams & Wilkins, JuIerGL, Stemmer EA, ConnollyJE: Preoperative diagnosis of small bowel volvulus in adults. Am J Gastroeriterol 56: , Aakhus T: Angiography in acute mechanical obstruction of the small intestine. Acta Radiol [Suppl] (Stockh) 306:1-202, Frimann-Dahl J: Roentgen examinations in acute abdominal diseases, 3d ed. Springfield, Ill., Thomas, Dixon JA, Harman CG, Nichols RL, Englert E: Intestinal motility following luminal and vascular occlusion of the

9 RADIOGRAPHY OF STRANGULATING OBSTRUCTION 843 small intestine. Gastroenterology 58: , Dixon JA, Nichols RL, Hunter DC Jr: Strangulation obstruction of the intestine-early detection. Arch Surg 88: , Fnimann-Dahl J: Experimental ileus in rabbits. Acta Radiol (Stockh) 35: , Vest B: Roentgenographic diagnosis of strangulating closed-loop obstruction of the small intestine. Surg GynecolObstet 115: , Nelson SW, Christoforidis AJ; The use of barium sulfate suspensions in the diagnosis of acute diseases of the small intestine. Am J Roentgenol 104: , Levin B: Mechanical small bowel obstruction. Semin Roentgenol 8: , Williams JL: Obstruction of the small intestine. Radiol Clin NorthAm 2:21-31, 1964

10 This article has been cited by: 1. A. Pea Aldea, C. Amors Garca, A. Escudero Garca, A. Benages Martnez Patolog?a obstructiva del intestino delgado. Medicine - Programa de Formaci?n M?dica Continuada Acreditado 9:4, [CrossRef] 2. Tim B. Hunter, Laurie L. Fajardo, J. Luther Jarvis, Hugo V. Villar Altered gastric and duodenal motility in intestinal obstruction. Gastrointestinal Radiology 15:1, [CrossRef]