Comparison of Diagnostic Accuracy for the Low-Type Imperforate Anus Between Prone Cross-Table Radiography and Sonography

Prediction of anorectal malformations with bladder-neck/urethral-prostatic fistula using classification and regression tree analysis

BACKGROUND

The anorectal malformations (ARMs) with bladder-neck/urethral-prostatic fistula in males are the most complex groups in ARMs. It is essential to diagnose them effectively before the primary operation for both surgical modalities and future functional prognosis can be quite different from other types. Our study aimed to develop a classification and regression tree (CART) model for the prediction of ARMs with bladder-neck/urethral-prostatic fistula.

METHODS

A total of 132 newborns with ARMs were included retrospectively and randomly assigned to the training sample and test sample in a 3:1 ratio. The pouch-perineum distance of ultrasound (PPDU), the pouch-perineum distance of invertogram (PPDI), and the rectum gas above the coccyx (RGAC) on the invertogram were hypothesized can serve as individual predictors. The CART analysis was used to determine the best combination of candidate predictors. The model's performance was assessed by the area under the receiver operating characteristic curve (AUC) and validated in the test sample.

RESULTS

All three individual predictors were included in the CART model to predict the ARMs with bladder-neck/urethral-prostatic fistula in the derivation cohort with the following test characteristics (95% CI): sensitivity 75.6% (60.1 to 86.6); specificity 88.9% (76.7 to 95.4); AUC 0.909 (0.854 to 0.965). The model's predicted accuracy was validated in the test cohort (AUC = 0.883). In all 132 subjects, the AUC of the tree model was significantly superior to that of the best individual index: PPDU (0.901 vs. 0.819; p = 0.005).

CONCLUSIONS

A predictive model that consists of PPDU, PPDI, and RGAC may be useful in predicting ARMs with bladder-neck/urethral-prostatic fistula.

Imaging of anorectal malformations: where are we now? Abdominal imaging task force of the European Society of Paediatric Radiology

Anorectal and cloacal malformations are a broad mix of congenital abnormalities related to the distal rectum and anus. Confusion exists between all the forms in this large and heterogeneous group. The spectrum includes everything from anal stenosis, ventral anus, anal atresia (with and without fistula) and the full spectrum of cloacal malformations. Imaging in these conditions is done through the whole armamentarium of radiologic modalities, with very different imaging strategies seen across the centres where these conditions are managed. In 2017, the European Society of Paediatric Radiology (ESPR) abdominal imaging task force issued recommendations on the imaging algorithm and standards for imaging anorectal malformations. This was followed by further letters and clarifications together with an active multispecialty session on the different imaging modalities for anorectal malformations at the 2018 ESPR meeting in Berlin. Through this paper, the abdominal task force updates its guidelines and recommended imaging algorithm for anorectal malformations.

Comparison of diagnostic accuracy for fistulae at ultrasound and voiding cystourethrogram in neonates with anorectal malformation

BACKGROUND

Recently, it has been reported that anorectal malformation with rectourethral fistula in male neonates can be managed by primary neonatal reconstruction without colostomy. To prevent urethral injury during anorectoplasty, the fistula's location is important. To date, the use of voiding cystourethrograms to determine the presence and location of fistulas in neonates with anorectal malformations has not been studied.

OBJECTIVE

To compare the accuracy of ultrasound (US) and voiding cystourethrogram for determining the presence and location of fistulas in neonates with anorectal malformation.

MATERIALS AND METHODS

We included 21 male neonates with anorectal malformation with rectourethral fistula (n=16), rectovesical fistula (n=1) or no fistula (n=4) who underwent US and voiding cystourethrogram preoperatively on the day of surgery. Fistula imaging was classified into three grades (0-2), and grades 1-2 were considered fistula positive. We compared the imaging-based location of the fistula with surgical findings.

RESULTS

US performed significantly better than voiding cystourethrogram for determining the presence of fistulas (area under the receiver operating characteristic curve, 0.90 vs. 0.71, respectively; P=0.044) (diagnostic accuracy 85.7%, 95% confidence interval [95% CI] 63.7-97.0% and 52.4%, 95% CI 29.8-74.3%, respectively). In cases with fistulas detected by either modality, the accuracy of locating the fistula by US was 50.0% (95% CI 24.7-75.3%) and by voiding cystourethrogram was 100% (95% CI: 59.0-100%).

CONCLUSION

US accurately detected, but did not accurately locate, fistulas in neonates with anorectal malformation. When planning primary neonatal reconstruction of anorectal malformation without colostomy, voiding cystourethrogram could provide additional information about fistula location.

Comparison Between the Pouch-Perineum Distance in Neonates With a Low-Type Anorectal Malformation With and Without an Opened Fistula: Pitfall of Measuring the Pouch-Perineum Distance on Sonography

OBJECTIVE

An anorectal malformation (ARM) in neonates requires urgent surgery, with the type of surgery being dependent on the type of malformation (low, intermediate, or high). Distal rectal pouch and perineum (pouch-perineum) distance is reported to be useful for differentiating the type of ARM; however, the impact of an opened fistula on pouch-perineum distance is not well known. The purpose of this study was to evaluate the difference in pouch-perineum distance between neonates with a low-type ARM with and without an opened fistula.

METHODS

We included 24 neonates with low-type ARM who underwent sonography before surgery. Eight neonates already had an opened fistula before sonography, and 16 did not. The pouch-perineum distance was measured using the perineal approach. Mann-Whitney U and Spearman's correlation coefficient tests were used for statistical analysis.

RESULTS

The mean pouch-perineum distance in all neonates with a low-type ARM was 8.3 ± 2.9 mm. The pouch-perineum distance was substantially longer for an ARM with than without an opened fistula (10.6 ± 3.4 mm vs. 7.1 ± 1.7 mm; P = .02). No appreciable correlation was identified between the pouch-perineum distance and the postnatal day of examination (ρ = -.23, P = .26) or birth weight (ρ = .15, P = .47).

CONCLUSION

The pouch-perineum distance is substantially longer in neonates with an ARM with an opened fistula than in those without an opened fistula. Caution should be exercised by the sonographic examiner in evaluating pouch-perineum distance in neonates with an opened fistula to prevent an incorrect surgical procedure based on misdiagnosis of the type of ARM.

Ultrasound imaging of the anorectal malformation during the neonatal period: a comprehensive review

Anorectal malformation (ARM) is classified as low, intermediate, or high; accurate diagnosis of the type during the early neonatal period is important to determine the appropriate initial surgical approach. This review assesses the role of ultrasound examination in the classification of ARM during the neonatal period, with a focus on landmarks on the sonogram, the approach used for sonography, and the optimal examination timing. The following three factors on the sonogram are used for the classification: location of the fistula, the distance between the distal rectal pouch and the anal dimple (perineum) (P-P distance), and the relationship between the puborectalis muscle and the distal rectal pouch. Three approaches can be used to evaluate ARM by ultrasonography, namely, suprapubic, perineal, and infracoccygeal approaches. Each approach has its own advantages and disadvantages. Optimal timing of the ultrasound examination is also important with respect to each factor to classify ARM. We have described the pitfalls of ultrasound in diagnosis of cases, namely ARM with Down syndrome (which tends to be without fistula), ARM with low birth weight, ARM with unusual location of fistula, ARM with opened fistula (where the P-P distance is unreliable), and cloacal malformation (variation of the high-type ARM).

Distance Between the Distal Rectal Pouch and Perineum in Neonates of Low-Birth Weight With Imperforate Anus

This study was to evaluate the correlation between birth weight and the distance between distal rectal pouch and perineum (P-P distance) and to determine a cutoff value for P-P distance to diagnose low-type imperforate anus in neonates with low-birth weight (LBW).We included 15 neonates with LBW (mean weight, 2012 ± 470 g; range, 906-2452 g) and imperforate anus (surgically confirmed: 11 low type and 3/1 intermediate/high type), who underwent ultrasonography on the day after birth. Type of imperforate anus was defined based on the International Classification of Anorectal Anomalies. The P-P distances on ultrasonograms were measured. Pearson correlation coefficient test and receiver operating characteristic curve were used for statistical analyses.Among all 15 neonates, nonsignificant correlation was observed between the birth weight and P-P distance (r = 0.36; P = 0.18). Mean P-P distance was 9.0 ± 6.6 mm (range, 1.0-24.0 mm) in all neonates, 5.7 ± 2.8 mm (range, 1.0-11.0 mm) in the 11 neonates with low-type imperforate anus, and 18.3 ± 9.1 mm (range, 14.0-24.0 mm) in the 4 neonates with intermediate-/high-type imperforate anus. Using cutoff P-P distance of 12.5 mm, sensitivity and specificity for diagnosis of low-type imperforate anus were 100% (11/11) and 100% (4/4), respectively.In conclusion, nonsignificant correlation was observed between P-P distance and birth weight, and cutoff P-P distance to diagnose low-type imperforate anus was 12.5 mm. Despite the very small sample size in our study, and only 4 neonates with intermediate-/high-type imperforate anus, these findings are important because surgical management whether transperineal anoplasty or diverting colostomy is decided based on the type of imperforate anus, and P-P distance to diagnose the type of imperforate anus was feasible even in neonates with LBW.

Sonography for an Imperforate Anus: Approach, Timing of the Examination, and Evaluation of the Type of Imperforate Anus and Associated Anomalies

This systematic review outlines the role of sonography in an imperforate anus. The diagnostic performance for type of imperforate anus is superior on the day after birth than that on the day of birth by using the pouch-perineum distance. Three approaches can be used (suprapubic, infracoccygeal, and perineal). The pouch-perineum distance, fistula location, and relationship between the puborectalis muscle and distal rectal pouch are useful for classifying the type of imperforate anus. However, the pouch-perineum distance measured has an overlap between the low and high/intermediate types of imperforate anus. Sonography can be useful for some of the associated anomalies and helpful for surgeons in some cases.