Prevalence peritonitis
To determine PD-related peritonitis in the end-stage kidney disease patients undergoing CAPD, we excluded patients who had previous peritonitis, follow up for 3 years, the ratio of peritonitis in our study was 15.8% (Table 1). There were some reports about the prevalence of PD-related peritonitis. Ye H. et al [5] conducted a study with 1321 PD patients following-up 5 years, the ratio of peritonitis was 28.16% (372/1321 patients), in which in the first year of PD initiation, 169 (13%) patients had experienced episodes of peritonitis, and the proportion of patients with peritonitis fluctuated from 8% to 13% in the subsequent years. Gadola L. et al. [19] surveyed the rate of peritonitis in 222 PD patients following-up 6 years, the result showed 95 patients suffered 1 or more episodes of peritonitis (42.79%). In children, the ratio of peritonitis was 25.45% in Ponce’s study with 7 years follow-up (125 first episodes of peritonitis in 491 children PD patients) [21]. The ratio of peritonitis in our study was lower than others because our time of follow-up was shorter than other studies. There was 27.3% patient with positive bacteria culture in our study, that similar to other study results [5, 20].
In Viet Nam, peritoneal dialysis is concentrated only in 2 big cities, Ha Noi and Ho Chi Minh City. When recommending chronic kidney replacement therapy, most patients choose maintenance hemodialysis. Only about 20% of patients choose peritoneal dialysis because they do not have time to go to hemodialysis centers. When comparing groups of patients with peritonitis and non-peritonitis, we found some patient characteristics related to peritonitis. In peritonitis patients, the average age was older, the ratio of low education and DM were significantly higher than those of non-peritonitis group, p< 0.001 (Table 2). It remains controversial whether older PD patients have a substantially increased risk of peritonitis than their younger counterparts. More recently, retrospective studies found that older age (more than 65 years) was the only identified risk factor associated with peritonitis [21, 22]. It seems highly probable that touch contamination and bowel dysfunction are important underlying causes of peritonitis episodes in older PD patients [23]. Diabetic mellitus and low education were risk factors of PD-related peritonitis in previous studies [23-25]. As diabetes mellitus is regarded as a risk factor for infections in general, it seems to be reasonable to consider it also as a risk factor for peritonitis in PD patients [25]. In the study, we found the relationship between peritonitis and overhydration (Table 2,3). The result of our study was similar to others [13, 14]. The association between OH and peritonitis maybe by enteric germs [14]. This seems to be reasonable, by a trend toward an association between baseline levels of C-reactive protein and the PD-related peritonitis (Table 2,3).
The relationship between peritonitis and malnutrition was also expressed in our study (Table 2,3). The average level of serum albumin and prealbumin in peritonitis patients was lower significantly than the non-peritonitis group, p< 0,001. Peritoneal dialysis itself might lead to protein-energy wasting as continuous glucose absorption from peritoneal dialysis solutions, abdominal fullness induced by the dialysate. The result is a decrease in serum albumin and prealbumin concentration in patients with peritoneal dialysis [26]. Dong J et al. also confirmed that protein leakage predicts risk for peritonitis in patients on peritoneal dialysis, and this association remained even adjustment for systemic inflammation estimated by serum albumin, CRP, and IL-6 [27].
Factors predict peritonitis
In this study, we found that there are many independent factors related to peritonitis in CAPD patients, of which prealbumin and OH are closely related, p< 0.001 (Table 3). We also found that OH and serum prealbumin are the independent predictors of peritonitis compared to other factors such as hemoglobin, serum albumin, and CRP-hs (AUC of prealbumin was 0.838; of OH was 0.851, p< 0.001), (Figure 1). Predictive value for peritonitis of serum prealbumin, OH is also evident when we followed-up 3 years CAPD patients by Kaplan–Meier analysis (Figure 2,3). There are some previous reports about predictive factors of PD-related peritonitis in CAPD patients [19, 21, 22]. Gadola L. et al. [19] confirmed that multidisciplinary peritoneal educational program improved peritonitis rates, independently of other risk factors. Okayama M. et al found aging is an important risk factor for peritoneal dialysis-associated peritonitis [21]. In particular, Kerschbaum J et al. [25] reviewed 415 studies writing risk factors for peritonitis in PD patients. From those studies, the author found that the risk of peritonitis is divided into two groups: nonmodifiable and modifiable risk factors. Nonmodifiable risk factors consist of ethnicity, old age, female, cardiovascular comorbidities, DM, underlying renal disease as lupus, lose of residual renal function... Modifiable risk factors are malnutrition, overweight, smoking, comedication as immunosuppression, depression, low socioeconomic status… In summary, plenty of risk factors for PD-related peritonitis have been identified in studies of acceptable methodological quality. Overhydration is common among PD patients and related cardiovascular risk and death [28-30]. Prealbumin levels were an independent and sensitive predictor for mortality in incident PD patients, showing a good correlation with nutritional and inflammatory markers [16, 31]. Association between OH and the risk of peritoneal infection by enteric germs was reported in Carvalho Fiel D’s study [14]. It has been suggested that persistent oedema of the intestinal wall may favour microbial and bacterial endotoxin transmigration, in some cases leading to systemic infections including peritonitis [14]. Serum Albumin and prealbumin are the measures to evaluate the nutritional status of chronic patients in general, patients with peritoneal dialysis in particular. Decreased albumin and prealbumin concentrations associated with peritonitis in peritoneal dialysis patients have been mentioned by several authors [25-27]. It might be hypothesized that hypoalbuminemia, as a result of malnutrition, inflammatory response, or of uremia itself, may lead to a higher susceptibility to infection [25]. Thus, both OH and serum prealbumin are modifiable risk factors for PD-related peritonitis, which have predictive value for peritonitis in CAPD patients. This result once again confirms the role of OH and serum prealbumin in predicting outcomes of CAPD patients. From this result, good control of OH and serum prealbumin is needed to reduce the rate of peritonitis in CAPD patients.
Although our results showed that overhydration and low serum prealbumin level were the independent predictors of PD-related peritonitis in CAPD patients, this study still had some limitations. Firstly, various studies had shown that there were many factors associated to peritonitis in PD patients including both modifiable and non-modifiable factors. However, in this study, we still did not have the specific measures to eliminate the influence of these factors. Secondly, we were unable to obtain complete data from all patients during the 3-year follow-up. Therefore, in this study, we could only evaluate OH and prealbumin baseline values at the beginning of the study.