Gastrointestinal system symptoms and signs are frequently encountered in patients followed up with a diagnosis of CKD at all stages, from low clearance to those who underwent end-stage renal disease (ESRD) and RRT . Some previous studies have reported that gastrointestinal symptoms are seen at a frequency of 32–79% in patients undergoing dialysis [9, 10]. Our study showed that more than 90% of patients with CKD had GIS symptoms. In addition, patients in all groups had an average of four GIS symptoms. These findings indicate that the gastrointestinal system is frequently affected in CKD, regardless of the type of treatment modalities.
Gastrointestinal complaints are common in uremic patients. In the studies, it was determined that GIS symptoms resulting from impaired gastric myoelectric activity, gastric hypomotility and prolonged gastric emptying were found to be especially frequent in the predialysis period in end-stage renal disease patients. It has been reported that this situation is associated with uremia . However, the answer to the question of whether the impaired gastric motor function improves with dialysis treatment is not clear. Studies have evaluated whether the frequency of these complaints changes with the initiation of renal replacement therapy or changes according to the form of RRT. However, these studies give conflicting results. Schoonjans et al.  in their study in which they compared dyspeptic symptoms and gastric emptying times in patient groups receiving different renal replacement therapy; they found the prevalence of dysmotility-like dyspepsia to be the highest in peritoneal dialysis patients with 67.9%, then 53.6% in the predialysis group and 33.3% (p < 0.01) in the hemodialysis group (the difference was not statistically significant). Hiroshi et al.  reported that gastric motility improved and GIS symptoms decreased with HD treatment in their study in which they compared patients in the predialysis uremic period with those under hemodialysis treatment in terms of GIS symptoms and gastric motility. In a previous study done by Soffer et al.  comparing hemodialysis patients and normal subjects not on hemodialysis, no difference was found between hemodialysis patients and normal subjects in terms of gastric emptying time. In a later study by Van Vlem B et al., it was found that the gastric emptying time of patients with dyspeptic complaints in hemodialysis patients was significantly impaired compared to asymptomatic patients and normal individuals . Kosmadakis et al.  reported in their study that gastric emptying is impaired in PD patients, regardless of the composition of dialysate and even when tested with an empty peritoneal cavity. In our study, although dyspeptic signs were the highest in the PD group, no statistically significant difference was found compared to the HD and predialysis groups. Our results are similar to literature data.
In our study, uremic symptoms such as nausea, vomiting, anorexia, constipation, weight loss and dyspepsia were compared between the predialysis, HD and PD treatment groups, and no statistically significant difference was found between the three groups. Although these symptoms were associated with uremia and impaired gastric emptying time, they did not differ according to the treatment modality in our study. When we evaluated weight loss in particular, the prevalence was found to be statistically significantly higher in the predialysis group than in the PD group, but no significant difference was found between the predialysis and HD groups in our study. Weight loss is considered among the findings associated with uremia and is considered as one of the indicators of the need for renal replacement therapy. However, when evaluated together with other uremic symptoms and findings, no significant difference was found between predialysis, PD and HD groups in our study. In this case, the mentioned symptoms cannot be explained only by uremia; this suggests that it may be due to other factors that have not yet been identified beside the delay in gastric emptying time. These factors may be the underlying disease, drugs used, psychological status, hormonal status, nutritional status and nutritional parameters, impaired exocrine function of the pancreas and complications related to the treatment method [11, 15, 16]. These multifactorial variables may be the reasons why our study and previous studies gave conflicting and different results in terms of complaints and findings mentioned above.
Gastritis is a quite common finding in CKD. In the literature, there are limited studies on the evaluation and comparison of gastritis findings in patients with CKD according to the treatment method. Wee et al.  found the prevalence of endoscopic gastroduodenitis to be 49% in a series of 322 patients under HD and PD treatment, that they underwent endoscopy. In the same study, they detected gastritis histologically in 52% of the cases in 260 patients who underwent endoscopic biopsy. In the same study, more gastritis was observed in the PD group than in the HD group. Misra et al.  found that GIS abnormalities were more common in patients with CKD in a study that they evaluated the endoscopic findings in patients with CKD and compared them with normal individuals. In terms of gastritis prevalence, Usta et al.  determined the frequency of histological gastritis as 62.3% in dialysis patients, Fabian et al.  determined the frequency of histological gastritis was 71.5%, Al-Mueilo et al.  found the frequency of histological gastritis 51.9% in hemodialysis patients. In our study, the patients were evaluated symptomatically in terms of gastritis and compared according to the RRT modality. The results were evaluated as 70% in the PD group, 60% in the HD group and 55% in the predialysis group. The findings were in parallel with the findings of Wee et al.  and were statistically significantly higher in the PD group than in the HD and predialysis groups. Although our study was a symptomatic evaluation and was not supported endoscopically or histologically, the frequency of gastritis found in our study shows similar rates with other studies. This determined prevalence may also be useful in showing that the diagnosis of gastritis based on the complaints and histories of the patients is similar to the frequency of gastritis diagnosis made endoscopically and histologically. Our study shows a statistically significantly higher prevalence of gastritis in the PD group like the result of Wee et al. . Further studies are needed to clarify this result and its underlying causes.
Regurgitation, heartburn, dyspeptic complaints, dry cough and burping are common symptoms of gastroesophageal reflux. It is stated that gastroesophageal reflux is more common in peritoneal dialysis patients than in the general population and hemodialysis patients. It is stated that the presence of excess dialysis fluid in the abdomen and high intraperitoneal pressure increase acid reflux from the stomach . Dejardin et al.  evaluated the relationship between intraperitoneal pressure, intraperitoneal volume and GER in a study and found that intraperitoneal pressure had no effect on reflux formation. Holscher et al.  reported that GER symptoms are seen around 30% in the normal population. In our study, the prevalence of GER was 38% in the predialysis patient group, 34% in the HD group and 45% in the PD group. Although these rates were higher than the general population, there was no statistically significant difference between the groups compared. Our study may give an idea that peritoneal dialysis treatment does not significantly increase the incidence of GER in patients with CKD; but the effect of peritoneal dialysis treatment on GER, the relationship of intraperitoneal pressure and intraperitoneal volume with GER is a less studied topic in the literature and deserves further studies.
A few other mechanical complications thought to be caused by intraperitoneal pressure (IPP) are constipation, hiatal hernia and hemorrhoids . It is stated that the prevalence of hemorrhoids is 4.4% in the normal population in the USA . In our patients, hemorrhoids were detected at a prevalence of 21% in the predialysis group, 12% in the HD group and 24% in the PD group. The prevalence of hemorrhoids was determined to be higher than the general population in all stages and treatment types of CKD. In addition, hemorrhoids were statistically significantly higher in the PD group than in the HD group; this supports the thesis that increased intraperitoneal pressure together with chronic constipation in peritoneal dialysis increases the risk of hemorrhoids, but it is not a sufficient result alone. Again, there was no statistically significant difference between the PD group and the predialysis group. In our clinic, an anti-constipation diet is recommended for patients under PD treatment and these patients are regularly treated with anti-constipation medications. In fact, it is seen in the study that there is no difference between PD and other groups in terms of constipation complaints. This may be due to the diet habits of the patients and the constipation-solving drugs they use. There is a close relationship between chronic constipation and hemorrhoids. There are many factors that can cause chronic constipation in chronic kidney disease and these factors have not been fully elucidated . Many factors such as electrolyte disturbances like hypercalcemia, hypokalemia, uremic neuropathy seen in patients on long-term dialysis, increased colonic transit time, gastric hypomotility, drugs used, dietary habits, increased intraperitoneal pressure in peritoneal dialysis, treatment-related lifestyle and limitation of movement may be the cause of chronic constipation [11, 16, 24, 26,27,28]. The prevalence of constipation is reported to be 2–27% in Western Societies . The results of our study show that the prevalence of constipation in CKD is higher than in the general population with a frequency of 32% in predialysis, 28% in HD and 35% in PD. There was no statistically significant difference between the groups. Although the prevalence of hemorrhoids was higher in the PD group, the lack of difference in the prevalence of constipation suggests that different factors such as IPP, which may be a factor in the formation of hemorrhoids in peritoneal dialysis, should be evaluated further.
The fact that the design of our study was in the form of a questionnaire and it included the subjective complaints of the patients may be misleading in determining the frequency. Although the results of some patients’ endoscopy, colonoscopy and abdominal imaging methods were included in the study, this does not cover the entire cohort. In terms of hiatal hernia, a statistically significant difference is observed in the HD group compared to the PD and predialysis groups. In terms of esophagitis, a statistically significantly higher frequency is seen in the HD group than in the predialysis group. However, in our study, the number of endoscopic cases was insufficient, and the distribution of endoscopy between groups was uneven. If the results of imaging examinations of all patients were included in the study, it would have been possible to reach a clearer judgment in these respects. However, evaluation and comparison of patients’ complaints with other findings in the study are important in terms of demonstrating gastrointestinal system involvement in CKD. Again, the results of our study should be supported by studies designed and evaluated with social averages and control groups without CKD.