Diagnostic value of the microcolon by ultrasonography in small bowel atresia

doi:10.21203/rs.3.rs-1518571/v1

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Diagnostic value of the microcolon by ultrasonography in small bowel atresia

https://doi.org/10.21203/rs.3.rs-1518571/v1

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Purpose: To find the Ultrasonography (US) criteria of microcolon and analyze its value in diagnosis of SBA.

Methods: US was performed in 46 neonates within 7 days old. As a study group (n = 15), neonates of SBA was confirmed with followed surgery. As a study group without SBA (n = 15), neonates with other gastrointestinal problems different that SBA were confirmed by surgical or clinical follow up. Sixteen neonates without gastrointestinal problems was classified as control group. Diameter of the colon was measured. Colonic gas were sought and observed. Statistical analysis was performed to compare US parameters between study group with other groups. Optimal cut off value of the colonic diameter for SBA diagnosis were obtained with receiver operating characteristic analysis.

Results: Colonic diameters in study group 0.5cm (interquartile ranges (IQR), 0.5-0.6 cm) was significantly smaller than that in study group without SBA 0.9cm (IQR, 0.8-1.2cm) (P < 0 .001) and in control group 1.2cm (IQR, 0.8-1.35cm) (P < 0 .001). Optimum cut off value for diagnosis of SBA was 6.5 mm (sensitivity, 90.3%; specificity, 86.7%; accuracy, 89.1%) for colonic diameter. A combination of microcolon and gas negative in it showed the best performance in US diagnosis of SBA, with the highest accuracy (91.3%).

Conclusion: A colon less than 6.5mm in diameter should be called microcolon by US, combined with gas negative can be highly suggestive of SBA.

neonate

intestinal atresia

intestinal obstruction

ultrasonography

small bowel atresia

Congenital small bowel atresia (SBA), including duodenum atresia, jejunum atresia, and ileum atresia, is a common causes of neonatal intestinal obstruction with an incidence ranging from 1.3 to 2.8 out of 10000 live births [1]. Prenatal ultrasound can diagnose intestinal obstruction [2]. But it can only play a role of preliminary screening for SBA, as both dilated loops of bowel and polyhydramnios provided a low overall detection rate [3]. Neonates with SBA need further examination for diagnosing after birth. The diagnosis of neonatal SBA mainly depends on clinical manifestations and imageological examination. Plain abdominal radiographs can conclude intestinal obstruction. Upper gastrointestinal contrast study can identify the obstruction level and rule out diseases of volvulus and malrotation [4]. Contrast enema is useful in the investigation of suspected Hirschsprung disease [5]. Although barium enemas can detect microcolon and facilitate the diagnosis of SBA, the radiation and the risk of intestinal perforation caused by barium enemas has led many scholars to recommend minimizing the use of barium enemas [6–8]. Being a safe, convenient and inexpensive imaging method, US is suitable for neonates because of their thin abdominal wall. The microcolon without gas, smaller than a normal colon significantly, can be used for diagnosis of SBA by US [9]. But there is no standard colonic measurement available for newborns, given the lack of consistency in the US scan. Besides, there is no standard diameter value for diagnosis SBA, which limits the diagnostic ability of sonographers in their clinical work. A better US method for differentiating patients with SBA from those without SBA could reduce the need for barium enema and upper gastrointestinal contrast. Thus, the purpose of our study was to prospectively evaluate the accuracy of colon and some other characteristics for the diagnosis of SBA by US, with surgical or clinical information used as the reference standard.

Patients

Institutional review board approval was obtained for this study. The need for informed consent was waived because our examination was performed as a routine abdominal US. From July 2019 to October 2021, 71 consecutive neonates within 7 days underwent US in ultrasound department of our hospital (Fig. 1). Of these, 19 neonates were excluded because they underwent upper gastrointestinal or barium enema contrast before US. We also excluded 5 neonates whose colon can not be notified clearly by ultrasound and 1 neonate who were lost to follow-up. As a result, 46 neonates were included in our study ( male-to-female ratio, 25:21; preterm-to-term ratio, 20:26 ). Thirty vomiting neonates underwent upper gastrointestinal contrast or barium enema after ultrasound examination. As a study group, SBA was confirmed with surgical in 15 vomiting cases (male-to-female ratio, 7:8; preterm-to-term ratio, 5:10), including duodenal atresia (n = 2), jejunal atresia (n = 7) and ileal atresia (n = 6). As a study group without SBA, 15 vomiting cases with other gastrointestinal problems different that SBA was confirmed with surgical or clinical follow up (male-to-female ratio, 9:6; preterm-to-term ratio, 5:10), including annular pancreas (n = 5), intestinal stenosis (n = 3), anal atresia (n = 1), congenital megacolon (n = 2), gastroesophageal reflux (n = 1) and neonatal vomiting (n = 3) according to surgery or upper gastrointestinal contrast. The remaining 16 cases without gastrointestinal problem were classified as control group (male-to-female ratio, 9:7; preterm-to-term ratio, 10:6). Clinical follow up was carried up until they were 1 month old (Table 1).

Table 1

Clinical data findings of patients with study group and other groups.
Variable	Study group(n = 15)	Study group without SBA(n = 15)	Control group(n = 16)	P Value
Male-to-female ratio	7:8	9:6	9:7	0.715^†, 0.724^‡
Preterm-to-term ratio	5:10	5:10	10:6	1.000^†, 0.156^‡
Clinical feature	duodenal atresia (n = 2), jejunal atresia (n = 7), ileal atresia (n = 6)	annular pancreas (n = 5), intestinal stenosis (n = 3), anal atresia (n = 1), congenital megacolon (n = 2), gastroesophageal reflux (n = 1), neonatal vomiting (n = 3)	jaundice (n = 12) exomphalos (n = 4)
Study group, SBA neonates;
Study group without SBA, neonates with gastrointestinal problems different that SBA;
Control group, neonates without gastrointestinal disease.
† The P value concerns statistical comparison between study group and study group without SBA. The χ² test was used for statistical comparison.
‡ The P value concerns statistical comparison between study group and control groups. The χ² test was used for statistical comparison.

US Techniques

Neonates underwent US with the use of 3–9 MHz transducer (Philips iU22, Philips Healthcare, Bothell, WA, USA) and 5–12 MHz transducer (Philips EPIQ7C, Philips Healthcare, Bothell, WA, USA). The neonates were kept quiet by sucking the pacifier while the examine were taken. A transverse view of the kidney (usually left kidney) showing the short axis of the colon (Fig. 2). Then we measured the diameter of them. We evaluated the presence of micro small bowel and the presence of gas in colon and small bowel. The micro small bowel was defined as the diameter of small bowel less than 0.6 cm (Fig. 3). Gas negative in the colon was defined as no gas can be found in measured colon (Video 1). Gas negative in the small bowel was defined as no gas in the micro small bowel in one ultrasound image (Video 2). US was performed by one operator with more than 10 years of experience with pediatric US. All the measurements and evaluations were performed offline by other two pediatric radiologists who had more than 5 years of experience. They resolved their differences through discussion when necessary.

Statistical Analysis

Data are presented as medians and interquartile ranges (IQRs). The nonparametric wilcoxon test for paired data was used to test the difference between study group and the other groups. The chi-squared test and fisher exact test were used to assess categoric data (neonatal sex, preterm or term, presence of micro small bowel, gas in small bowel and colon or not). Receiver operating characteristic (ROC) curves were constructed to assess colon diameter yielded the most accurate SBA diagnosis. Fifteen neonates with SBA and 31 neonates without SBA were included in the ROC analysis. The optimal cut off points for the prediction of SBA were identified from the highest Youden index. Areas under the ROC curves with 95% confidence intervals were calculated for the colon diameter. The sensitivity and specificity of cut off value were calculated for the diameter of colon. We evaluated the sensitivities and specificities of other US findings of SBA in the abdomen (presence of micro small bowel, gas negative or not in small bowel and colon, respectively), as a combination with the preceding criteria for colon diameter, to assess the diagnostic accuracy added with measurement of the size of the colon. Statistical analysis was performed with software (IBM SPSS version 26.0 (IBM Corp. New York, USA)). A two tailed P value less than 0.05 was considered to indicate a statistically significant difference.

US Findings of abdomen

Clinical characteristics (including preterm or term, male or female) between the study group with any other group showed no significant difference (P > 0.05) (Table 1). The diameter of the colon in study group 0.5cm (IQR, 0.5–0.6 cm) was significantly smaller than that in Study group without SBA 0.9cm (IQR, 0.8–1.2 cm) (P < 0 .001) and in control group 1.2cm (IQR, 0.8–1.35 cm) (P < 0 .001) (Fig. 4). The micro small bowel can be found in all 15 neonates with SBA. For all of them, gas can not be seen both in micro small bowel and colon. Among neonates of Study group without SBA, the micro small bowel was visualized in 80.0% (12 of 15) cases, including annular pancreas (n = 5), intestinal stenosis (n = 3), congenital megacolon (n = 1), gastroesophageal reflux (n = 1), neonatal vomiting (n = 2). The proportion of gas negative in small bowel is about 40.0% (6 of 15), including annular pancreas (n = 2), intestinal stenosis (n = 2), congenital megacolon (n = 1), and neonatal vomiting (n = 1). The proportion of gas negative in colon is about 26.0% (4 of 15), including annular pancreas (n = 1), intestinal stenosis (n = 2), and anal atresia (n = 1). In control group, the micro small bowel was visualized in 68.8% (11 of 16). Gas negative in small bowel in 25.0% (4 of 16) cases. Only 1 neonate of 4 hours after birth was gas negative in colon. There was no significant difference about the presence of micro small bowel between study group and Study group without SBA (P = 0.224). Neonates of study group presence more micro small bowel than that in control group (P = 0 .043). There were significant differences about gas negative in colon and in small bowel between study group with any other group (P < 0 .001). Neonates in study group tend to contain less gas both in colon and distal small bowel (Table 2).

Table 2

Comparison of US findings of small bowel and colon in the three groups.
US Finding	Study group ( n = 15 )	Study group without SBA ( n = 15 )	Control group ( n = 16 )	P value
Colon diameter (IQR)	0.5cm (0.5–0.6 cm)	0.9cm (0.8-1.2cm)	1.2cm (0.8-1.35cm)	< 0.001^†; 0.001^‡
Micro small bowel (༜0.6 cm)	15 (100%)	12 (80%)	11 (68.8%)	0.224^†; 0.043^‡
Gas negative in small bowel	15 (100%)	6 (40%)	4 (25%)	< 0.001^†; 0.001^‡
Gas negative in colon	15 (100%)	4 (26.0%)	1 (6.3%)	< 0.001^†; 0.001^‡
IQR, interquartile ranges.
† The P value concerns statistical comparison between study group and study group without SBA. The χ² test was used for statistical comparison.
‡ The P value concerns statistical comparison between study group and control group. The χ² test was used for statistical comparison.

Cut off Value and Accuracy

According to ROC analysis, the optimal cut off value of the colon was defined as 6.5 mm (area under the ROC curve, 0.924). This criterion showed 90.3% (28 of 31) sensitivity, 86.7% (13 of 15) specificity, and 89.1% (41 of 46) accuracy. When the colonic diameter was 8.5 mm, the criterion showed 71.0% (22 of 31) sensitivity, 100% (15 of 15) specificity. A combination of the colonic diameter and micro small bowel provided sensitivity of 93.5% (29 of 31), specificity of 86.7% (13 of 15), and accuracy of 91.3 (42 of 46)%. A combination of the colon diameter and gas negative in small bowel showed sensitivity of 87.1% (27 of 31), specificity of 100% (15 of 15), and accuracy of 91.3% (42 of 46) (Table 3). A combination of the colonic diameter and gas negative in colon provided sensitivity of 93.5% (27 of 31), specificity of 100% (15 of 15), and accuracy of 91.3 (42 of 46)%. A combination of the colon diameter and colonic gas negative showed the best performance in US diagnosis of SBA, with the highest area under the curve (AUC) (Fig. 5).

Table 3

Diagnostic performance of the combination of each US findings for SBA.
US Finding of abdomen	True-Positive Findings in Patients with SBA (n = 15)	True-Negative Findings in Neonate Without SBA (n = 31)	Sensitivity (%)	Specificity (%)	Accuracy (%)	95% CI	AUC
Colon diameter	13	28	0.903	0.867	0.8913	0.8466-1	0.9237
Colon diameter and micro small bowel	13	29	0.935	0.867	0.9130	0.8648-1	0.9366
Colon diameter and gas negative in small bowel	15	27	0.871	1.0	0.91304	0.9268-1	0.9699
Colon diameter and gas negative in colon	15	27	0.871	1.0	0.91304	0.9305-1	0.9720
CI, confidence interval; AUC, area under the curve.

Few ultrasound studies focused on neonatal intestine, possibly because it can be interference by intestinal gas and stool mass. In fact, many intestinal diseases can be diagnosed by US even with interference [10–13]. US has become an important diagnostic method in many children’s diseases, such as intussusception [14], malrotation of intestine [15, 16] and intestinal polyp [17]. For neonates, US has proven to be of great value in necrotizing enterocolitis [18]. For neonates with SBA, the proximal intestine is often dilated filling with amniotic fluid or milk. Whereas, in order to avoid aspiration and relieve pain, clinicians usually carry out gastrointestinal decompression for neonates when intestinal obstruction was suspected, which not only makes more intestinal gas, but also makes the dilation state relieved and disturbing doctors to find the dilated bowel. The distal intestine of SBA was not affected by swallowing and gastrointestinal decompression. As no amniotic fluid and milk passed, the distal intestine (including the colon and a part of small bowel), remained in a state of diminution for a long time. It only has a little meconium contents and without any gas. These characteristics are easily detected on ultrasound and can be used to distinguish with other types of intestinal obstruction. In brief, the present study examined the distal small bowel and colon characteristics to determine the accuracy of the diagnosis of SBA.

The microcolon has been recognized and proposed by surgeons for nearly 100 years [19]. It has now become an important basis for barium enema in the diagnosis of SBA, but it was barely mentioned on the ultrasound. Although Hao [9] reviewed the ultrasonographic findings of 19 neonates with SBA and confirmed that US can detect microcolon without gas, the study did not provide the criteria of microcolon, the data on false negative and false positive rates. In order to ensure the consistency, we selected a transverse view of the kidney (usually left kidney) showing the short axis of the colon for measurement. This area was chosen because the anatomic locations of the ascending colon and descending colon are more constant and hardly disturbed by intestinal gas at the specified section. Finding colon requires some experience and patience. Gently pressure if necessary to avoid crying influence. Avoid treating dilated small bowel as colon. In this study, there were 5 neonates with unclear or unexplored colon. In addition to high display rate (93.1%, 67/72), the colonic diameter of the study group was significantly smaller than that of the other two groups, indicating that the colonic diameter has a more intuitive value in the diagnosis of SBA. Combined with the cut-off value of ROC curve, we believe that the ultrasonic colon with diameter less than 6.5mm has the maximum predictive value for SBA, which can be called ultrasonic microcolon. SBA can be ruled out when the colon diameter is greater than 8.5mm on ultrasound.

We assumed that distal micro small bowel might be a secondary change of the SBA due to prolonged complete obstruction. But it is difficult to assess and repeatable measurement, as they perform small, peristalsis slower, no fixed location and often obscured by dilated intestines. For atresia of the ileocecal junction or near the ileocecal junction, the micro small bowel will also be absent or difficult to search [7]. We made a periumbilical scan to find the section with the most small intestine and the least intestinal gas for analysis. The diameter less than 6 mm and without wriggle defined as the micro small bowel. Ideally, all neonates with SBA not only had micro small bowel, but also were gas negative. However, micro small bowel was also present in study group without SBA and control group. It possibly because the neonates has not accumulated food in the intestinal tract soon after birth. Especially some neonates with heavy intestinal stenosis in the study group without SBA, who have a high proportion of micro small bowel.

Gas negative in distal intestine is an important diagnostic basis for SBA. Except for very few individuals has a biliary fistula [20]. In the study group without SBA, neonates without colonic gas were mostly patients with severe intestinal obstruction. In the control group, there was only 1 case of 1-day-old newborn with colon of gas negative. Possibly because the neonate did not eat much after birth, and the gas in the intestinal lumen had not moved to the colon. Since the amount of gas can be changed over time, to find a micro small bowel without gas need more experience which can not be an independent diagnosis for SBA.

Of course, the current findings do not justify the use of colon ultrasound as a substitute for barium enema in the diagnosis of SBA. But our study could provide clinicians and neonates with more options. For neonates with suspected SBA, US can be done firstly, and if SBA can be diagnosed, maybe barium enema should be canceled. The difference in diagnostic accuracy between US with barium enema is what we will study next.

Our study had several limitations. First, although our study spanned two years, we did not have enough cases, including the control group of normal newborns, because they rarely received routine abdominal ultrasound. More clinical data need to be accumulated for comparison in the differentiation of colonic diameter between SBA and other diseases. Second, the amount of micro small bowel is difficult to accurately determine, and the amount of gas in it can be changed over time. The results may vary depending on the doctor's experience. Third, Given the benefits of timely gastrointestinal decompression, we could not require eliminate gastrointestinal decompression in suspicious SBA neonates before US. Therefore, the dilation of proximal bowel was not analyzed in this study. However, barium enema or upper gastrointestinal contrast cannot be performed before ultrasound examination is still required.

A colon less than 6.5mm in diameter should be called microcolon by ultrasonography, combined with gas negative can be highly suggestive of SBA.

FUNDING

This study was supported by grants from the Guide Project for Key Research and Development Foundation of Liaoning Province (No. 2019JH8/10300008), 345 Talent Project and Liaoning BaiQianWan Talents Program.

CONFLICT OF INTEREST

The authors declare no conflict of interest, financial or otherwise.

CONSENT FOR PUBLICATION

Not applicable.

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No competing interests reported.

Video1.avi.avi
Video_1 Microcolon without gas, surrounding by some dilating small bowel.
Video2.avi.avi
Video_2 Micro small bowel without gas, surrounding by some dilating small bowel.

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Diagnostic value of the microcolon by ultrasonography in small bowel atresia

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Abstract

Figures

Introduction

Materials And Methods

Patients

US Techniques

Statistical Analysis

Results

US Findings of abdomen

Cut off Value and Accuracy

Discussion

Conclusion

Declarations

References

Additional Declarations

Supplementary Files

Archived Versions:

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