Total Colonic Aganglionosis: Reappraisal of Contrast Enema Study

Total colonic aganglionosis (TCA) is a rare form of Hirschsprung disease (HD). It is difficult to be diagnosed on contrast enema because the radiographic findings are variable. The study aims to re-evaluate the contrast enema findings of TCA. From 2001 to 2009, 14 patients (11 males, 3 females; ages from 1 day to 6 months) with pathologically proven TCA were reviewed for demographic features, clinical presentations, pathology reports, radiographic and contrast enema findings. In addition, the radiographic and contrast enema findings of 53 patients with non-TCA HD were reviewed and compared with those of TCA. Among the imaging findings, a short and rigid colon, small bowel dilatation, microcolon, and radiographic transition zone proximal to the cecum were statistically more significant in patients with TCA than in patients with non-TCA HD (P < 0.001). In conclusion, TCA is a colon disease presenting as small bowel obstruction clinically and radiographically. Although the radiographic findings of TCA are variable, TCA could be suspected when the initial radiograph shows small bowel dilatation and contrast enema shows a short and rigid colon, radiographic transition zone proximal to the cecum, poor rectal distensibility, colonic wall irregularity and delayed contrast emptying. In addition, biopsy should be performed to make a definite diagnosis. According to the caliber of the colon on contrast enema, a subgrouping approach may be useful in the differential diagnosis and be helpful in early diagnosis and exclusion of TCA. Correspondence Author to: Chao-Jan Wang Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan No. 5, Fu-Xing Street, Gui-Shan, Taoyuan 333, Taiwan J Radiol Sci 2012; 37: 11-19 Imaging of total colonic aganglionosis 12 J Radiol Sci March 2012 Vol.37 No.1 preoperative evaluation, the sensitivity and specificity of contrast enema are less favorable than other diagnostic tools such as anorectal manometry and rectal suction biopsy [9]. However, contrast enema plays an important role in the diagnosis of HD. First, comprehensive assessment of the clinical presentations and the radiographic findings on contrast enema may help in appropriate selection of patients who need to receive rectal biopsy [10]. Second, besides TCA, contrast enema may not only identify some diseases which also cause distal bowel obstruction, but may potentially treat them (e.g., meconium plug syndrome, meconium ileus) [1]. Third, contrast enema may help the preoperative evaluation of the level of transition zone. The anticipated level of transition zone can greatly influence the surgical approach to HD [11-13]. The preoperative knowledge of the extent of aganglionic bowel might potentially reduce the operative time and prevent an incorrect determination of transition zone in the operation [14]. Previous studies have shown that contrast enema easily misleads surgeons in evaluating the level of transition zone in patients with TCA [12, 13]. There is a wide spectrum of radiographic features of TCA on contrast enema, which can mimic other causes of distal bowel obstruction in the neonate and young infants. The diagnosis of TCA is difficult to be established by contrast enema studies [14-18]. Radiographic diagnostic rate was suspected in only 20% to 30% of patients with TCA [19]. In this article, we reviewed the cases of TCA in our institute and addressed our experiences with contrast enema in establishing the diagnosis of TCA. MATERIALS AND METHODS Research design This study was approved by our institutional review board. We retrospectively searched the medical record database for patients who were diagnosed with HD by surgical pathology at our institution from 2001 to 2009. Eighty patients with HD were identified (63 males, 17 females; age from 1 day to 10 years). Among these patients, 15 had TCA. One patient with TCA was excluded because contrast enema was not performed. The medical records of the 14 patients (11 males, 3 females; age from 1 day to 6 months) with TCA were reviewed for demographic features, clinical presentations, pathology reports, radiographic and contrast enema findings. In addition, among the 65 patients with non-TCA HD, 53 had available contrast enema images. The radiographic and contrast enema findings of the 53 patients with non-TCA HD were reviewed and compared with those of TCA. In our institution, we performed contrast enema with water-soluble contrast medium in neonates and patients with enterocolitis. Compared with barium enema, water-soluble contrast enema is a potential treatment and examination modality of mecoium plug syndrome and meconium ileus. In addition, it will result in fewer complications if there is a bowel perforation. Assessment of imaging findings The initial abdominal plain radiographs and contrast enema images of the 14 patients with TCA and the 53 patients with non-TCA HD were reviewed in consensus by two pediatric radiologists: one with 15 years of experience (C.-J. W.) and one with 10 years of experience (W.-C. L.). Seven imaging findings were assessed: small bowel dilatation, microcolon, a short and rigid colon, poor rectal distensibility, colonic wall irregularity, radiographic transition zone, and delayed contrast emptying. There were some terms to be defined in the following. First, the caliber of the colon was further classified into microcolon (Fig. 1a) and non-microcolon (Fig. 1b). Microcolon was defined as a colon caliber which was generally less than the interpedicular space of the L1 vertebra. The normal caliber colon or dilated colon was classified into the subgroup of non-microcolon. Second, a short and rigid colon was defined as the loss of redundancy of the sigmoid colon with rounding of the splenic and hepatic flexures. Sometimes, it could appear as a question mark-shaped colon (Fig. 1c). Third, poor rectal distensibility was defined as a persistent poor distention of the rectum (Fig. 1d). Fourth, colonic wall irregularity was defined as a serrated contour of the colon (Fig. 1e). Fifth, the radiographic transition zone was the location of obvious caliber change in the bowel (Fig. 1f). Sixth, delayed contrast emptying was defined as retained contrast medium proximal to the sigmoid colon on a radiograph which was obtained from 24 to 48 hours after the contrast enema. Statistical analysis The Fisher’s exact test was used to compare the imaging findings of the two patient groups, those with TCA and those with non-TCA HD. A P value of less than 0.05 was considered to indicate a statistically significant difference.