Recently, in South Korea, an increase in the numbers of patients with gastroesophageal reflux (GER), gastroesophageal reflux disease (GERD), or functional gastrointestinal disorders such as chronic epigastric pain, functional nausea, and functional vomiting is being observed due to changes in diet and lifestyle [1,2]. The prevalence of gastrointestinal disorders in children and adolescents is increasing due to obesity, changes in dietary habits, and psychological factors. Additionally, the use of proton pump inhibitors (PPIs) is also increasing [3-5]. Gastric acid suppressive therapy with PPI is also used in the management of gastric or duodenal ulcers and Helicobacter pylori disease, as well as GER. PPIs are more potent than histamine receptor antagonists with generally good treatment outcomes. At the same time, the possibility of side effects in the gastrointestinal tract, is high [6-9].

Gastric acid is an important factor in suppressing bacterial overgrowth in the small intestine [10]. It is known that gastric acid suppression therapies, such as use of PPI, can induce bacterial overgrowth in the gastrointestinal tract [6-9]. Various studies have reported on gastric acid suppression and bacterial overgrowth; with most being limited to the diagnosis of bacterial overgrowth itself through a hydrogen breath test (HBT) or duodenal aspiration, or by the identification of certain strains such as Clostridium difficile and H. pylori [6,9,11]. However, even if there is bacterial overgrowth, it is not always clinical significance such as intestinal inflammation. Nevertheless, few studies have investigated the intestinal inflammation. Although studies to confirm the clinical symptoms associated with bacterial overgrowth have been conducted, there persists a shortage of research involving pediatric patients. Furthermore, previous studies have compared subjective symptoms; however, there has been no objective analysis of intestinal inflammation [12].

Analysis of fecal calprotectin (FC) is a noninvasive method of diagnosing the activity of inflammatory bowel diseases (IBDs) such as Crohn disease and ulcerative colitis [13,14]. In addition, it is a useful method for the detection of inflammatory conditions in various intestinal diseases such as polyps, necrotizing enterocolitis, and bacterial colitis [14-16].

In the present study, we investigated the effects of PPI therapy on intestinal inflammation, in children and adolescents as confirmed by clinical manifestations and objectively assessed by measurement of FC levels.

We conducted a prospective study on consecutive children (age, 3–18 years) at the Chung-Ang University Hospital between October 2015 and February 2018. The study protocol was approved by the Institutional Review Board (IRB) of the Chung-Ang University Hospital (IRB No. C2015157), and written informed consent was provided. Patients who presented with GER symptoms (such as chronic epigastric pain, nausea, and vomiting) and were treated with or without PPI for at least 1 month, were enrolled. The treatment duration was not randomized, and patients were treated for 4 or 8 weeks based on the clinical symptoms. The subjects who agreed to participate in the study collected stool samples for evaluation of FC (GEMINI, Stratec Biomedical AG, Birkenfeld, Germany) concentration at baseline and after 4 or 8 weeks of treatment with PPI and FC results were measured up to 2,000 mg/kg. Exclusion criteria were as follows: use of PPI in the previous 3 months, use of other drug such as nonsteroidal anti-inflammatory drug, IBD, gastrointestinal involvement of Henoch-Schönlein purpura, and presence of significant intestinal disease that could be associated with inflammatory changes such as bacterial colitis.

Enrolled patients were divided into 2 groups, PPI group treated with PPI for at least 1 month and non-PPI group treated without the drug. Prokinetic agents, such as domperidone, were used to relieve symptoms in both groups. All subjects were instructed to continue dietary and lifestyle modifications. The subjects in the PPI group were treated with lansoprazole 15 mg (body weight ≤30 kg), or 30 mg (body weight >30 kg or age ≥12 years), or esomeprazole 20 mg for 4 weeks or 8 weeks. Therefore, the PPI group was further subdivided according to the treatment duration (4 weeks vs. 8 weeks) and type of PPI used (lansoprazole vs. esomeprazole).

We collected the following clinical data from the medical records of the patients: patient age, sex, clinical symptoms (epigastric pain, nocturnal abdominal pain, abdominal distension, nausea, vomiting, loose stool, nocturnal defecation, bloody stool, and abdominal tenderness), and laboratory findings (C-reactive protein [CRP] level, white blood cell [WBC] count, and absolute neutrophil count [ANC] from blood) before and after PPI treatment. Clinical data and FC level were analyzed after 4 or 8 weeks depending on the duration of PPI treatment in the PPI group, while the parameters were only analyzed after 8 weeks in the non-PPI group.

Statistical analyses were performed using SPSS ver. 18.0 (SPSS Inc., Chicago, IL, USA). Fisher exact test and Mann-Whitney test were used to analyze differences between groups. Data are presented as median (range) or numbers and the level of statistical significance was set at P<0.05.

In the present study, the clinical symptoms, laboratory findings, and FC levels of patients who underwent treatment with PPI were not statistically different from those who did not receive PPI. There were no significant differences in FC levels before and after therapy based on the duration and type of PPI used. These results suggest that clinical intestinal inflammation does not occur in patients because of PPI treatment.

Calprotectin is a 36.5-kDa calcium-binding heterodimer consisting of S100A8 (MRP-8) and S100A9 (MRP-14) subunit proteins [15-17]. It is mainly derived from neutrophilic granulocytes in the bowel mucosa, and the accumulation of neutrophils results in release of calprotectin in the stool. Calprotectin remains stable in stools for 3–7 days, and since the levels have been shown to correlate with inflammatory activity, analysis of FC has been proposed as a useful marker of bowel inflammation. Several studies have demonstrated the role of FC in the diagnosis and monitoring of the disease activity of IBD. FC has also been suggested as a reliable tool to screen patients with gut inflammation such as infectious colitis or necrotizing enterocolitis [13-15,17,18]. Some publications have shown use for FC in identifying the presence of small bowel inflammation in patients with intestinal inflammation [19-21].

Previous studies have suggested that PPI therapy is a risk factor for the development of intestinal problems including bacterial overgrowth [6-9]. However, bacterial overgrowth does not cause intestinal inflammation, and the overgrowth alone would not be a significant factor, unless clinically relevant. Therefore, in the present study, we investigated whether PPI therapy caused significant inflammation in the intestine. The results demonstrated that although there were patients who had worsened clinical symptoms, such as abdominal pain, tenderness, and nocturnal defecation after PPI therapy, there were no significant differences between the PPI and non-PPI groups. In addition, there was no significant difference in terms of the evidence of inflammation as assessed by FC levels. From these results, we considered it unlikely that the use of PPI further exacerbated the inflammatory response in the intestines. Additionally, other hematologic tests to assess inflammatory responses such as CRP level, WBC count, and ANC showed no significant differences between the 2 groups.

In addition to intestinal inflammation, there are other side effects of PPI; indeed, there are reports that respiratory infections or otitis media may be increased [6,22,23]. There is also an increased risk of polyps or hyperplasia in the stomach following PPI therapy [23]. However, the GERD guidelines published by the North American Society for Pediatric Gastroenterology, Hepatology, and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition suggest that the reported side effects of PPI use, such as upper and lower respiratory infections, constipation, and eczema, are not more common than placebo groups [22]. Our results also support the above-mentioned observations. In the GERD guidelines, PPI treatment is usually recommended to last 4 to 8 weeks. In the present study, there was no difference in FC levels based on the duration of treatment.

There are several limitations in our study. First is the lack of randomization to treatment; however, this would not alter the results as the demographic characteristics and baseline laboratory findings, including FC levels, were not different between the PPI and non-PPI groups. Given that there was no significant difference between the 2 groups before and after treatment, this is evidence that there was no difference in the actual levels of FC due to gastric acid suppression treatment. This could be attributed to the fact that PPI treatment was initiated due to more severe symptoms in patients in the PPI group. Therefore, the impact of such a limitation would be minimal. Second, the number of patients included was small and it would have been better if the results of FC were compared with those of previous studies, such as HBT or gastrointestinal inflammatory marker. However, due to the nature of the study conducted in children, it was difficult to involve a greater number of patients and the compliance was inevitably low. Invasive tests were also difficult to perform and could not be compared with well-known tests such as HBT or duodenal aspiration. It would be interesting to conduct further studies comparing the HBT with more participants.

Despite these limitations, in the present study, we attempted to confirm the influence of PPI on intestinal inflammation in pediatric patients as confirmed by clinical manifestations and objectively assessed by measurement of FC levels; however, no significant changes were observed. In the future, further studies will be needed with larger sample sizes and other markers of intestinal inflammation as well as analysis of FC.