Study design
We retrospectively reviewed patients with a history of undergoing surgery for Hirschsprung disease, who visited our outpatient clinic between December 2018 and December 2019, and underwent 3D-EAUS. Patients who underwent surgery in other hospitals and those younger than 3 years old at the time of evaluation (owing to difficulty assessing anorectal function) were excluded from the study.
The study protocol complied with the Helsinki Declaration and was approved by the Research Ethics Committee of Saitama Children’s Medical Center. The requirement for written informed consent was waived, and opt-out on the web was obtained instead because of the retrospective nature of the study.
Surgical procedures
We performed a laparoscopic-assisted pull-through surgery for Hirschsprung disease, and a transanal procedure was performed per the Soave–Denda procedure [10]. All operations were performed with at least one attending pediatric surgeon.
The patient was placed in the lithotomy position. We inserted the first trocar (5 mm) through the umbilicus using the open method. We subsequently added two additional trocars (5 mm) in the left and right abdomen to obtain a co-axial position. If necessary, we added one additional trocar (4 mm) in the suprapubic area.
During the laparoscopic procedure, we estimated the caliber change or transitional zone, followed by taking a full-thickness biopsy. We then dissected the colorectum sufficiently for the pull-through. When we reached the peritoneal reflection, we began the transanal procedure. A Lone Star Retractor System (CooperSurgical, Inc., Trumbull, CT) was used to expose the anal canal, and was hooked to the dentate line. We usually began the initial incision approximately 5–10 mm above the dentate line or around the anorectal line depending on the surgical team. We then started the mucosectomy until the peritoneal cavity. We added a myectomy of the posterior wall of muscular cuff to avoid anastomotic stricture according to Lynn’s technique [11]. Afterwards, we confirmed the normal ganglionic colon by biopsy, and anastomosed the colon with the distal anus.
Bowel management
During the preoperative period, we used a glycerin enema to control constipation. In patients with relatively long aganglionic colons in whom constipation could not be controlled with only a glycerin enema, we inserted a long transanal drainage tube to irrigate the bowel instead of creating a stoma.
Postoperatively, we prescribed laxatives to manage constipation, and we prescribed loperamide to manage fecal incontinence. In the infant or toddler patients, we often prescribed a glycerin enema to control either constipation or fecal incontinence.
Data collection
We collected data on clinical characteristics including age, sex, birth weight, gestational age, comorbidities, operative management, and postoperative complications. We used the Krickenbeck classification to evaluate postoperative anorectal function [12]. We did not perform a manometry during the postoperative follow-up. We used 3D-EAUS (type 8838, BK Medical, Herlev, Denmark) to measure the DBAI (Fig. 1). The patient was placed in the supine position, then leg up or legs flexed position (similar to a lithotomy position), and the probe was introduced into the anal canal. The endoprobe was covered by a hard cone (outer diameter, 16.4 mm) with a built-in linear array that rotated 360° inside the transducer at a frequency range of 6–12 MHz, allowing a computer-controlled, automatic acquisition of the images in approximately 30 s without any external movement of the probe. The series of closely spaced two-dimensional images were combined to create a 3D volume shown as a cube. Because the IAS was shown as hypoechoic and the EAS as hyperechoic through the 3D-EAUS [9], we can find the intersphincteric groove clearly. Therefore, we could measure the DBAI (Fig. 1). The examination was performed without sedation (except in instances where the patient was undergoing other examinations requiring sedation, such as magnetic resonance imaging or computed tomography). The acquired images were read by a pediatric surgeon (KH) and confirmed by a proctologist (TT).
Statistical methods
The primary endpoint was the relationship between the DBAI and anal function according to Krickenbeck classification, regarding constipation and fecal incontinence (soiling).
Categorical variables were presented as percentages (%) and continuous variables presented as medians (range). Univariate analyses were performed using a non-parametric analysis (Mann-Whitney U test) for continuous variables and Fisher’s exact test for categorical variables. Statistical analyses were performed using EZR software (Saitama Medical Center, Jichi Medical University, Saitama, Japan), which is a graphical user interface for R version 3.3.1 (The R Foundation for Statistical Computing, Vienna, Austria) [13].
