Saudi Journal of Gastroenterology
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Year : 1996  |  Volume : 2  |  Issue : 2  |  Page : 74-79
Comparative study of plain abdominal films and small bowel enema in clinically unclear cases of small bowel obstruction


Department of Radiology, Drs. Dorothy Makanjuola and Saleh Al Damegh and Surgery, Dr Mohammed Koshim and Abdulkarim El Bakery, College of Medicine, King Khalid University Hospital, P.O. Box 7805, Riyadh 11472, Saudi Arabia

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   Abstract 

A study was undertaken to compare the usefulness of plain abdominal X-rays (PABR) and small bowel enema (SBE) in evaluating cases of clinically unclear small bowel obstruction.
The PABR of the patients taken just before the small bowel enema were compared to the films of the SBE.
Fifty-two out of 76 were eventually operated on. The results show the gross limitations of PABR in excluding the presence of small bowel obstruction. The sensitivity and negative predictive value of SBE in identifying or excluding obstruction were 100% each, while the corresponding values of PABR were 42 and 40%. However, the margin of specificity and positive predictive values were narrow; 94 and 97 percent in SBE and 86 and 88 in PABR. SBE was also superior in identifying the cause and location of obstruction.
In conclusion, due to the specificity of PABR it will remain the first line of investigations in suspected intestinal obstruction. However, its limitation in excluding the presence of obstruction cannot be overemphasized. The SBE confirms or excludes obstruction promptly and should be applied as the most accurate evaluation.

How to cite this article:
Makanjuola D, Khoshim M, El Bakery A, Al Damegh S. Comparative study of plain abdominal films and small bowel enema in clinically unclear cases of small bowel obstruction. Saudi J Gastroenterol 1996;2:74-9

How to cite this URL:
Makanjuola D, Khoshim M, El Bakery A, Al Damegh S. Comparative study of plain abdominal films and small bowel enema in clinically unclear cases of small bowel obstruction. Saudi J Gastroenterol [serial online] 1996 [cited 2019 Oct 15];2:74-9. Available from: http://www.saudijgastro.com/text.asp?1996/2/2/74/34030


When intestinal obstruction presents with a clear clinical symptomatology and unequivocal findings at plain abdominal radiography (PABR), surgery is usually performed without any delay. However, in clinically uncertain cases with equivocal plain abdominal X-ray, it is customary to request for follow-up plain abdominal X-ray views, or gastrografin or barium follow-through examination.

Reports have appeared in the literature expressing the limitation of the plain abdominal films in the evaluation of intestinal obstruction [1],[2],[3],[4] . There is also an increasing recognition of the superiority of the small bowel enema (SBE) or enteroclysis in the diagnosis of small bowel pathology including small bowel obstruction over PABR [5],[10] . However, SBE is still underutilized in several centers because its value is not fully known to all.

This communication reports our experience on a prospective comparative study of PABR and SBE in clinically suspected cases of small bowel obstruction (SBO), in order to assess the diagnostic value of both methods.


   Patients and Methods Top


Over a period of four years, 76 cases of suspected intestinal obstruction provided the material for the study. They were evaluated with plain abdominal X-ray and small bowel enema.

Standard plain abdominal views of the patients were obtained prior to the small bowel enema. These were used for the comparative study. The small bowel enema was performed in the conventional manner. Following a minimal lignocaine nasal spray, a nasoduodenal tube was inserted and advanced to a position at or just distal to the ligament of Treitz. A barium concentration of 20-30% weight per volume (W/V) was injected through the tube until the location of obstruction was reached in cases with complete obstruction. In cases with partial or non-obstructing lesion, injection of barium was continued until colonic filling was achieved. In high grade obstructions when the barium column failed to progress and the level of obstruction was not reached, the injection was discontinued and a delayed view obtained within 30 minutes. This often showed the exact level of obstruction even, if some uncontrollable vomiting occurred. Fulll views as well as spot views of the abnormal level or areas of localized tenderness were obtained.

The PABR patterns were categorized as normal, non-specific, bowel meteorism with no features to suggest partial or complete obstruction (SBO) as defined below:

Normal Three or less gas-filled small bowel loops with diameter less than 3 cm. Normal colonic gas fecal materials.

Non-obstructing Bowel Pattern Numerous proportionate gas and fluid, filled. Bowel Pattern small and large or bowel loops with or without fluid levels. No segmental distension of more than 3 cm.

Partial SBO Disproportionate distension of segmental or generalized small bowel loops more than 3 cm in diameter. Minimal colonic gas.

Complete SBO Disproportionate distension of small bowel loops over 4 cm. No gas in colon.

The findings of the SBE were categorized into normal, non-obstructing, partially obstructing and completely obstructing lesions. In non-obstructing lesions [Figure - 1] there were no changes in the luminal diameter before and after the lesions. Partially obstructing [Figure - 2]a & b lesions show some prestenotic dilatation. In total obstruction, there was complete obstruction to the flow of contrast at the time of infusion. The location and suspected causes of the lesions in PABR and SBE were compared with the final diagnosis.

The following criteria were used for surgery: Distinctly positive radiological findings plus unclear clinical features, negative radiological findings with strong clinical suspicion or positive radiological findings and clinical suspicion. The hospital charts were reviewed to determine the surgical and pathological findings as well as the follow-up conditions. The data was presented in 2 x 2 contingency tables and the sensitivity, specificity positive predictive values and negative predictive values were determined.


   Results Top


There were 41 males and 35 females with an age range of 13-68 and a median of 34 years. A total of 52 cases were operated on. This include six patients with negative SBE and PABR but strong clinical features all of whom had non-obstructive lesion at surgery.

[Table - 1] shows the comparative result in the determination of the presence or absence of obstruction. In comparison with the surgical findings SBE had a sensitivity and negative predictive value of 100% each while the corresponding values in PABR were 42 and 40 percent. The margin of performance in the specificity and positive predictive values were narrower; 94 and 97 percent in SBE and 86 and 88 in PABR. The only false positive cause of obstruction in SBE was a case of Ascaris ball (Ascaroma) [Figure - 3] which disimpacted by the time of surgery. PABR had 21 false negative diagnoses and two false positive diagnoses for the presence of obstruction.

[Table - 2] shows the final diagnosis as compared with those made by SBE and PABR. Out of the 76 patients, PABR correctly made the diagnosis in only 25 patients (33%) while SBE was correct in 68 cases (89%). In the 8 cases where SBE was incorrect, 6 were false negative cases due to non-obstructive lesions. These were four cases of non-obstructive adhesions, and one case each tuberculous mesenteric adenitis and non specific mesenteric adenitis. The rest of the two cases were wrongly diagnosed as bowel infarction instead of lymphoma and Crohn's disease. Twelve of these 28 cases had features of bowel obstruction and 16 had non-obstructive bowel pattern similar to bowel meteorism. The cause of the obstruction could not be determined in any of the 12 cases with obstruction.

About two-thirds of the lesions were in the ileum and SBE was superior identifying the location of the lesions as shown in [Table - 3]. A delay in transit of barium of up to 30 minutes occurred in only two cases with high grade obstruction.

In 24 cases, surgery was avoided and this included cases with normal SBE with unimpressive clinical features (22) and one case each of ascariasis and bezoar which were passed spontaneously. These patients were discharged free of clinical symptoms.


   Discussion Top


This study clearly demonstrates the superiority of SBE over PABR in predicting the presence or absence of intestinal obstruction, localizing the lesions accurately and identifying the cause in most cases. It also emphasizes the limitation of PABR in excluding the presence of obstruction and identifying the location. However, with a specificity of 86% and positive predictive value of 88% which are acceptable, PABR will remain the first line of evaluation for cases of suspected intestinal obstruction and may be used with caution for follow-up of such cases.

Oral barium or gastrografin follow- through is used by some departments. However, non­obstructing or minimally obstructing lesions can be missed by this examination particularly with gastrografin which has a greater fluidity and gets progressively diluted within the intestinal lumen. We have experience of such false negatives. Vomiting in these patients also creates problems due to the large quantity of contrast medium required for such investigations. The frequent delay in transit of the contrast medium lead to several radiological exposures and render the investigations tiring for both the patients and radiological staff. The prolonged transit time and vomiting also make frequent fluoroscopic visual data impracticable for a dedicated oral small bowel follow-through examination to be performed. Several physicians are probably unaware of the inherent limitations of oral small bowel follow-through and the unique value of SBE in providing a quick and conclusive result in the diagnosis of intestinal obstruction.

The reasons for the indecisive nature of PABR include vomiting and nasogastric suction which decompresses the abdomen and gives a false improvement. It also modifies intestinal gas-fluid pattern required for accurate evaluation of the PABR. Vomiting and nasogastric suction could also cause a gasless abdomen which falsely implies high intestinal obstruction, or severe small bowel obstruction with fluid-filled bowel loops or total colitis.

Although SBE can decisively confirm or exclude the presence of intestinal obstruction, non­obstructive lesions can be difficult to recognize. Hence during the early stage of the study, such lesions were the cause of false negative study. Also, high grade obstruction often posed some difficulty by causing delay in getting to the level of obstruction. Recent studies [11] have shown the value of computed tomography (CT) in the evaluation of such patients and is commendable. In the absence of suspicion of large bowel obstruction, there is no contraindication to SBE provided the patient is able to tolerate the examination. Water soluble contrast medium is advised, if bowel perforation is suspected and in postoperative cases with questionable intestinal obstruction.

Although duodenal intubation and higher radiation dose may be considered disadvantageous, the decisive and prompt results of SBE outweigh any of these disadvantages. The importance of discovering lesions missed [Figure - 4] elsewhere or totally unexpected conditions such as complete bowel obstruction due to mesenteric infarction [Figure - 5] requiring immediate surgery and bezoar and ascaroma which passed spontaneously after the study, thus obviating surgery cannot be overemphasized.

About two-thirds of the lesions were found in the ileum. This is presumably because the caliber is less than that of the jejunum and transit through the small bowel is often slower.

The commonest cause of intestinal obstruction was adhesions constituting 46 percent of the abnormal findings. This was followed by inflammatory conditions like tuberculosis and Crohn's disease. Food bezoar are likely to be one of the factors causing recurrent obstruction in patients with adhesions. We were able to show the location of adhesion in a follow-up SBE after an initial SBE had shown an obstructing bezoar which was spontaneously passed.

In conclusion, in clinically suspected cases of intestinal obstruction, PABRs are often unhelpful and can be misleading. The small bowel enema could therefore be considered as the gold standard in the evaluation of such cases and should be applied for prompt and conclusive diagnosis.

 
   References Top

1.Tibbin S. Diagnosis of intestinal obstructions with special regard to plain roentgen examination of the abdomen. Acta Chir Scand 1969;135;249-52.  Back to cited text no. 1    
2.Gough IR. Strangulating adhesive small bowel obstruction with normal radiographs. Bri J Surg 1978;65:431-4.  Back to cited text no. 2    
3.Kingsnorth AN. Fluid-filled intestinal obstruction. Br J Surg 1976;63:289-91.  Back to cited text no. 3  [PUBMED]  
4.Harlow CL, Sters RLG, Zeligman BE et al. Diagnosis of bowel obstruction on plain abdominal radiographs. The significance of air-fluid levels at different heights in the same loop of bowel. AJR 1993;161;291-5.  Back to cited text no. 4    
5.Nolan DJ, Marks CG. The barium infusion in small intestinal obstruction. Clin Radiol 1981;32:651-5.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Maglinte DT, Miller RE. lntubation infusion method. Reliability in diagnosis of mechanical partial small bowel obstruction. Mt. Sinai J Med 1984;51:362-77.  Back to cited text no. 6    
7.Shrake PD, Douglas MD, Rex K et al. Radiographic evaluation of suspected small bowel obstruction. Am J Gastroenterol 1991;86:175-8.  Back to cited text no. 7    
8.Dehn TCB, Nolan DJ. Enteroclysis in the diagnosis of intestinal obstruction in the early postoperative period. Gastrointes Radiol 1989;14:14-21.  Back to cited text no. 8    
9.Dixon PM, Roulston ME, Nolan DJ. The small bowel enema: A ten- year review 1993;47:46-8.  Back to cited text no. 9    
10.Thoenin RE. Radiography of the small bowel and enterolysis: a perspective. Invest Radiol 1987;22:930-6.  Back to cited text no. 10    
11.Taownel P, Baron MP, Pradel J, et al. Acute abdomen of unknown origin: impact of CT on diagnosis and management. Gastrointestinal Radiol 1992;17:287-91.  Back to cited text no. 11    

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Correspondence Address:
D Makanjuola
Department of Radiology, College of Medicine, King Khalid University Hospital, P.O. Box 7805, Riyadh 11472
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


PMID: 19864831

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    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]
 
 
    Tables

  [Table - 1], [Table - 2], [Table - 3]



 

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