The utility of transperineal ultrasound in anorectal malformation: a cross-sectional analytical study at the Kenyatta National and Referral Hospital.

Abstract

INTRODUCTION: Imaging in anorectal malformations (ARM) has evolved over the years to include ultrasound and magnetic resonance imaging. However the pressure colostogram has remained as the widely accepted ‗gold standard‘ imaging tool for delineating fistulae and to assess the pouch to perineum (P-P) distance. Studies have shown that the transperineal ultrasound can be as effective as the pressure colostogram in the preoperative surgical management planning of ARM and yet it is not regularly utilized locally. This study assessed the effectiveness of the transperineal ultrasound in comparison to the distal colostogram in the radiological management of ARMs. OBJECTIVE: To evaluate the utility of the transperineal ultrasound (TPUS) and its effectiveness when compared to pressure colostogram in the classification of ARM, at the Kenyatta National and Referral Hospital (KNH). METHODOLOGY: Transperineal ultrasound was performed using a linear transducer (7-12 MHz) with the patient supine and the pelvis elevated using pillows. The probe was placed in the mid-sagittal plane over the anal dimple in the perineum without compression. No patient preparation was required. The findings were compared to distal pressure colostogram findings and correlated to surgical findings where applicable. FINDINGS: A total of 20 patients were included in the study during a five month period (September 2015 to January 2016). Transperineal ultrasound was performed in all the 20 patients and showed the mean Pouch to perineum distance of 1.95 ± 0.97 (SD) cm compared to a mean P-P distance of 2.1 ± 1.19cm on the distal colostogram. There was no significant statistical difference between pressure colostography and TPUS findings in the 8 children who had both imaging performed; p value of 0.001. A strong positive Spearman‘s correlation 0.98; p value 0.0001 was established. However, only seven patients underwent surgery. Intra-operative findings showed positive correlation with TPUS in 6 out of the 7 cases. There was one case of an anocutaneous fistula that was missed on both TPUS and distal colostogram. Findings showed that the TPUS has a sensitivity of 80% and 100% specificity. xi CONCLUSION: This study shows that the TPUS can be an effective tool with comparable accuracy to pressure colostogram in the clinical work up of the pediatric patient with ARM. One limitation of the study was that comparative colostogram and surgical data was available in only a minority of patients (35%). Follow-up studies are required to correlate TPUS and surgical findings to further underline the effectiveness of TPUS.