High resolution MRI for preoperative work-up of neonates with an anorectal malformation: a direct comparison with distal pressure colostography/fistulography

Abstract

Objective: To compare MRI and colostography/fistulography in neonates with anorectal malformations (ARM), using surgery as reference standard.

Methods: Thirty-three neonates (22 boys) with ARM were included. All patients underwent both preoperative high-resolution MRI (without sedation or contrast instillation) and colostography/fistulography. The Krickenbeck classification was used to classify anorectal malformations, and the level of the rectal ending in relation to the levator muscle was evaluated.

Results: Subjects included nine patients with a bulbar recto-urethral fistula, six with a prostatic recto-urethral fistula, five with a vestibular fistula, five with a cloacal malformation, four without fistula, one with a H-type fistula, one with anal stenosis, one with a rectoperineal fistula and one with a bladderneck fistula. MRI and colostography/fistulography predicted anatomy in 88 % (29/33) and 61 % (20/33) of cases, respectively (p = 0.012). The distal end of the rectal pouch was correctly predicted in 88 % (29/33) and 67 % (22/33) of cases, respectively (p = 0.065). The length of the common channel in cloacal malformation was predicted with MRI in all (100 %, 5/5) and in 80 % of cases (4/5) with colostography/fistulography. Two bowel perforations occurred during colostography/fistulography.

Conclusions: MRI provides the most accurate evaluation of ARM and should be considered a serious alternative to colostography/fistulography during preoperative work-up.

Key points: • High-resolution MRI is feasible without the use of sedation or anaesthesia. • MRI is more accurate than colostography/fistulography in visualising the type of ARM. • MRI is as reliable as colostography/fistulography in predicting the level of the rectal pouch. • Colostography/fistulography can be complicated by bowel perforation.

Keywords: Anorectal malformation; Colostography; Fistulography; MRI; Neonates.

Fig. 1

a–h A 2-month-old boy with proven recto-bladder neck fistula. a represents a midsagittal view through the pelvis (T2-weighted fast spin echo sequence; slice thickness 1.5 mm) with s-form of the distal rectal segment which enters the prostate from posterior. The axial MRI slices (b–g) (T2-weigthed fat-suppressed fast spin echo sequence; slice thickness 1.5 mm) are shown from higher to lower levels in the pelvis. The rectum turns in a fistula (pink) with a short transprostatic course. This fistula ends in the bladder neck (yellow), which turns in the urethra (black). Although on first sight of a complex case, all elements could easily be discerned by both readers based on a combination of axial and sagittal views. On the other hand, correct analysis of colostography (h) images was found to be impossible, mainly due to overlapping contrast opacities in all directions

Fig. 2

One-month-old female neonate with a vestibular fistula (a–d). MRI and correlated drawing shows axial slices (a, b) of the distal orifice with typical layered aspect of the intrasphincteric region (like a starfish), which was therefore interpreted as a normal colon (b). This starfish sign (*) refers to the layered aspect of the bowel on perpendicular view. c shows the anterior position of the rectal orifice on fistulography, with a normal composition of the intrasphincteric part, as in normal colon