Elective adhesiolysis for chronic abdominal pain reduces long-term risk of adhesive small bowel obstruction

Study design and patients

This study is a longitudinal follow-up study expanding on a previous prospective cohort (registered at clinicaltrials.gov under NCT01236625) of patients with chronic adhesion-related abdominal pain [5]. All patients referred to the outpatient clinic of the Radboud University Medical Center in Nijmegen, the Netherlands, from January 2012 to December 2019 for evaluation of adhesion-related pain were eligible. Patients were primarily referred for chronic abdominal pain, some also presented with recurrent episodes of small bowel obstruction or a combination of both. Patients were included if the diagnosis of adhesions was confirmed on CineMRI.

All included patients had a minimum of 2 years of follow-up. Exclusion criteria were age below 18 years, mental incompetence, and absence of adhesions on CineMRI. All patients gave written informed consent for participation in the study. A waiver was obtained from the medical ethical committee of the Radboud University Medical center (registration number: 2021/7398) for this study, according to Dutch law. The study was conducted in accordance with the principles of the revised version of the Declaration of Helsinki (2013, Fortaleza). Data were analyzed anonymously.

For this study, we grouped patients according to their initial treatment. The first group consisted of patients who had undergone elective adhesiolysis with the use of an adhesion barrier (operative group). Patients in the second group were non-operatively treated receiving only conservative symptomatic treatments. The decision on whether or not to perform adhesiolysis was made through shared-decision making, incorporating the results of CineMRI (localization and extent of adhesions), individualized operative risks and benefits (comorbidities, number of previous laparotomies), and patient preferences [5]. Adhesiolysis was either performed by laparoscopy or open approach, depending on safe abdominal entry considerations and the patient’s (and surgeon’s) preference.

In laparoscopic completed adhesiolysis, the liquid icodextrin 4% (Adept®) anti-adhesion barrier was applied. A 1500 ml infusion bag of icodextrin 4% was applied using the laparoscopic irrigator. The first 500 to 800 ml were used for rinsing and to remove remaining blood cloths, leaving between 700 to 1,000 milliliters of barrier fluid to be installed at closure of the abdomen. During converted or open adhesiolysis, in addition to icodextrin 4%, sheets of hyaluronate carboxymethylcellulose (Seprafilm®) were applied on large regular shaped surfaces, such as between bowel and omentum, or bowel and ventral, lateral of posterior abdominal wall. Typically, between three to six hyaluronate carboxymethylcellulose sheets measuring 7.5 by 13 cm were used.

All included patients were contacted to answer a questionnaire regarding current abdominal symptoms focusing on adhesive small bowel obstruction, analgesic medication, and healthcare utilization. Further, they were asked for permission to send queries to obtain medical data from their general practitioners and local hospitals. This was deemed necessary because the Radboud University Medical Center is a tertiary referral center and new cases of ASBO might have been treated in a local hospital.

Data collection

To identify potential readmissions for ASBO, we reviewed the results from the patient questionnaires and general practitioners. In the Netherlands, all patients are assigned to a general practitioner who keeps a full medical record and receives hospital correspondence from any admission by any hospital [18, 19]. Therefore, the general practitioner record is a reliable source to identify readmissions. When a potential readmission for ASBO in a different hospital was identified, additional data was requested from that hospital to confirm the diagnosis and gather data on treatment and outcomes.

Data collected from medical records included age and sex, number of previous abdominal surgeries, abdominal or pelvic radiotherapy in history, number of ASBO episodes in history, previous adhesiolysis for ASBO, and the extent of adhesions described on CineMRI for both groups. The extent of adhesions on CineMRI and the extent of adhesions assessed during adhesiolysis was graded on a 5-point scale (0 = no adhesions, 1 = single strand, 2 = adhesions in one quadrant, 3 = adhesions in two quadrants and 4 = adhesions in three or four quadrants). In the group undergoing elective adhesiolysis, we assessed surgical approach (open or laparoscopic), conversion, inadvertent bowel injury, length of hospital stay, complications graded according to the Clavien–Dindo classification, and admission to the ICU [20].

Questionnaire

The project steering group conceived the first set of multiple-choice survey questions. These questions were edited by two independent researchers, with experience in surveys and questionnaire research. The questionnaire was subsequently tested for clarity and ease of use by a group of laymen. After processing the feedback on our questionnaire, the final version was conceived.

The questionnaire consisted of eight required multiple-choice questions and 19 dependent questions. Further, a free text field for clarifications and personal comments was included. The questionnaire collected data regarding readmission for small bowel obstruction, and gastrointestinal symptoms pointing at motility disturbances such as nausea, vomiting, and difficulties with stools. Further, we screened for pain disability and medical consumption. An English translation of the questionnaire can be found in Online Additional file 1.

The questionnaire data were managed using Castor software (Ciwit, Amsterdam, The Netherlands) which has been optimized for data capture in medical research according to good clinical practice standards. The questionnaires were directly collected using a secured link sent with Castor or in a paper version, depending on the patient’s preference and digital literacy. The questionnaire was open for three months. Reminders were sent out after one month and two months. Participants were also contacted by phone in conjunction with a second reminder.

Data analysis

The primary outcome of this study was the incidence of a new episode of ASBO compared between the operative and non-operative groups. Subgroup analysis was performed for patients with and without a previous episode of ASBO. Multivariable analysis was performed to correct for baseline differences and to identify independent risk factors for developing ASBO.

Main secondary outcome was the incidence of reoperation for ASBO. Additional outcomes were results of ASBO treatment, daily gastrointestinal symptoms related to obstruction such as nausea, vomiting, daily pain, use of medication, and visits to medical specialists or other healthcare providers. Secondary outcomes were descriptively analyzed.

The incidence of ASBO was analyzed using 1-survival Kaplan–Meier methods. Comparison between groups was made using Cox regression analysis, and a p-value < 0.05 was considered significant.

Categorical data were analyzed using a Chi-square or Fisher’s exact test, as appropriate. Continuous data were analyzed using an independent t test or Mann–Whitney U test if not normally distributed. Continuous variables are presented as means with standard deviation, or medians and range in case of non-normal distribution. Dichotomous or categorical variables are presented as absolute numbers and percentages. All analyses are performed using SPSS version 28°0 (Armonk, NY: IBM Corp). Univariable and multivariable Cox regression analyses were performed to identify factors that independently affect the incidence of readmission for ASBO. Predictive factors with p ≤ 0.20 in univariable were selected as candidate risk factors for multivariable analysis. In multivariable analysis, a stepwise backward selection procedure was used with a P-entry ≤ 0.20 and P-stay ≤ 0.10. Potential predictors for readmissions for ASBO we used in univariable analysis were sex, the number of abdominal surgeries, ASBO in history, number of ASBO in history, the extension of adhesion on CineMRI, treatment of adhesions (operative vs. non-operative), and type of surgery during elective adhesiolysis (laparoscopy, converted, open).

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