# Retrospective case-control study of the impact of dialysis on bowel preparation scores

## TL;DR

This study found that dialysis patients can achieve adequate bowel preparation for colonoscopies, with preparation regimen being more important than dialysis status.

## Contribution

The study is novel in showing that dialysis does not impair bowel preparation quality and that split-dose regimens are effective in this population.

## Key findings

- Dialysis patients had similar bowel preparation scores and adenoma detection rates as controls.
- Split-dose regimen was the strongest predictor of adequate bowel preparation.
- Age, BMI, and preparation type significantly influenced bowel preparation quality.

## Abstract

Inadequate bowel preparation (BP) negatively affects diagnostic performance of colonoscopy. Most trials assessing adequacy of bowel preparation regimens have excluded patients affected by chronic kidney disease (CKD), especially patients on dialysis. This study aimed to assess the impact of dialysis on BP quality and adenoma detection rate (ADR) and identify factors related to quality of BP.

We retrospectively compared patient-specific, preparation-specific (preparation solution, preparation regimen (split-dose vs. 1-day preparation, outpatient preparation), and colonoscopy-specific data (indication, Boston Bowel Preparation Score [BBPS], sedation type, presence of adenoma or cancer) between 79 patients on dialysis and 158 matched controls. Adequate BP was defined as a BBPS score ≧2 in every colonic segment. Significant contributors to BP were assessed by logistic regression.

Despite matching, dialysis patients were significantly older (69.0 ± 11.9 vs 64.2 ± 14.6,
P
= 0.008) and less frequently women (30% vs 52%,
P
= 0.002). There was no significant difference in BP or ADR between patients on dialysis and controls (85% vs 89%,
P
= 0.39 and 35% vs 35%,
P
= 1.00, respectively). Older age (
P
= 0.03), lower body mass index (
P
= 0.03), type of BP regimen (
P
<0.001), outpatient preparation (
P
= 0.03), and residency in residential care (
P
= 0.05) were significantly associated with BP adequacy. According to the logistic regression model, split-dose regimen was the main predictor of adequate BP (
P
<0.001, odds ratio 3.1 [1.65–5.81]).

Safe and adequate BP is achievable in dialysis patients. Bowel preparation regimen rather than treatment with dialysis influences BP quality. Split-dose preparation remains the most important determinant of adequate BP for colonoscopy, irrespective of regimen.