AGE-RELATED CHARACTERISTICS OF COMBINED NEPHROLOGICAL AND GASTROENTEROLOGICAL DISEASES: A CROSS-SECTIONAL ANALYSIS ACROSS PEDIATRIC, ADULT, AND ELDERLY POPULATIONS

The increasing prevalence of comorbid kidney and gastrointestinal tract (GIT) disorders represents a growing challenge in contemporary medicine, with age serving as a critical determinant of clinical presentation, disease progression, and therapeutic outcomes. Nephrological and gastroenterological diseases are frequently interrelated through shared pathophysiological mechanisms involving metabolic disturbances, water-electrolyte imbalances, immune dysregulation, and bidirectional organ crosstalk. The gut-kidney axis has emerged as a key concept, wherein intestinal barrier dysfunction, dysbiosis, and inflammatory mediators can contribute to kidney injury, while chronic kidney disease (CKD) leads to accumulation of uremic toxins that impair gastrointestinal function and alter gut microbiota composition. Age profoundly influences disease patterns: pediatric patients predominantly present with congenital anomalies and functional disorders, working-age adults exhibit metabolic and inflammatory processes often related to lifestyle factors and cardiovascular comorbidities, while elderly patients demonstrate chronic degenerative changes and multi-organ failure with complex therapeutic challenges. Despite recognition of this age-dependent variation, comprehensive characterization of combined nephrological-gastroenterological pathology across the lifespan remains limited. This study aimed to investigate age-specific characteristics of combined renal and digestive system diseases by analyzing clinical patterns, comorbidity structures, and disease severity across pediatric, adult, and elderly populations to inform development of age-tailored diagnostic and therapeutic strategies.

This cross-sectional observational study enrolled 124 patients with documented combined nephrological and gastroenterological diseases monitored in the nephrology and gastroenterology departments of a clinical hospital in Tashkent, Uzbekistan, between 2019 and 2024. Patients were stratified into three age groups: 38 children and adolescents (mean age 10.2±3.4 years, range 2–17 years), 42 working-age adults (mean age 42.7±8.9 years, range 18–64 years), and 44 elderly patients (mean age 68.5±6.3 years, range ≥65 years). All participants underwent comprehensive evaluation including detailed medical history with particular attention to family history of renal or gastrointestinal disease, physical examination, and extensive laboratory assessment. Laboratory investigations included complete blood count, comprehensive metabolic panel with serum creatinine, urea, electrolytes, liver function tests (ALT, AST, alkaline phosphatase, bilirubin), complete urinalysis with microscopy, and calculation of estimated glomerular filtration rate (eGFR) using age-appropriate equations (Schwartz formula for children, CKD-EPI for adults). Instrumental examinations comprised renal and abdominal ultrasonography to assess organ morphology, identify structural abnormalities, and detect complications, as well as upper gastrointestinal endoscopy (esophagogastroduodenoscopy) when clinically indicated. CKD staging followed KDIGO guidelines. Gastrointestinal diagnoses were established based on Rome IV criteria for functional disorders and endoscopic/histological findings for organic pathology. Data collection included demographic characteristics, primary and associated diagnoses, disease duration, treatment regimens, and clinical outcomes. Statistical analysis was performed using SPSS version 22.0, employing descriptive statistics, chi-square tests for categorical variables, ANOVA or Kruskal-Wallis tests for continuous variables depending on distribution, and post-hoc comparisons where appropriate. Significance was set at p<0.05. The study protocol was approved by the institutional ethics committee, and informed consent was obtained from adult participants or parents/guardians of pediatric patients.

Demographic analysis revealed balanced sex distribution across groups with slight male predominance (56% overall). Significant age-related differences emerged in the structure and severity of combined pathology (p<0.001). In the pediatric group (n=38), congenital anomalies of the kidney and urinary tract (CAKUT) predominated, including megaureter (n=12, 31.6%), hydronephrosis (n=10, 26.3%), vesicoureteral reflux (n=8, 21.1%), and renal hypoplasia/dysplasia (n=5, 13.2%). These structural abnormalities were frequently accompanied by functional gastrointestinal disorders: functional dyspepsia (n=18, 47.4%), chronic gastritis (n=14, 36.8%), and irritable bowel syndrome (n=9, 23.7%). Among adolescent subgroup, pyelonephritis associated with irritable bowel syndrome was notably common (n=11, 28.9%). Mean eGFR in pediatric patients was 78.5±22.3 mL/min/1.73m², with most children having CKD stages I–II. In the adult working-age group (n=42), the disease spectrum shifted markedly toward acquired chronic conditions. CKD stages I–III predominated (n=35, 83.3%), with mean eGFR 52.4±18.7 mL/min/1.73m². Common etiologies included hypertensive nephrosclerosis (n=16, 38.1%), diabetic nephropathy (n=12, 28.6%), and chronic glomerulonephritis (n=9, 21.4%). Concomitant gastroenterological pathology included chronic gastroduodenitis (n=24, 57.1%), peptic ulcer disease predominantly duodenal (n=15, 35.7%), chronic pancreatitis (n=8, 19.0%), and gastroesophageal reflux disease (n=7, 16.7%). Metabolic syndrome components were present in 26 patients (61.9%), highlighting the role of lifestyle factors. Laboratory findings showed elevated inflammatory markers with mean CRP 8.7±4.2 mg/L. In the elderly group (n=44), advanced multi-organ pathology was characteristic. CKD stages III–V predominated (n=38, 86.4%), with mean eGFR 28.6±15.2 mL/min/1.73m². Fifteen patients (34.1%) were on renal replacement therapy or approaching dialysis initiation. Gastrointestinal comorbidities were severe, including cirrhotic liver changes (n=12, 27.3%), chronic atrophic gastritis (n=22, 50.0%), colonic diverticulosis (n=9, 20.5%), and significant digestive dysfunction manifesting as malnutrition (n=18, 40.9%) and anemia (n=28, 63.6%). The clinical picture was dominated by multi-organ failure, cachexia, and markedly reduced quality of life. Polypharmacy averaged 8.2±2.5 medications per patient. Statistical comparison confirmed highly significant differences in CKD stage distribution (p<0.001), gastrointestinal pathology patterns (p<0.001), and complication rates (p<0.01) across age groups.

This study demonstrates that combined nephrological and gastroenterological diseases occur across all age groups but exhibit profoundly different clinical patterns, severity, and management challenges depending on patient age. In pediatric populations, congenital structural anomalies of the urinary tract coexist with functional gastrointestinal disorders, necessitating early surgical correction when indicated and family-centered multidisciplinary care emphasizing growth and development. Working-age adults present predominantly with acquired chronic kidney disease driven by metabolic and cardiovascular risk factors, combined with inflammatory and ulcerative gastrointestinal pathology, requiring aggressive modification of lifestyle factors, optimization of blood pressure and glycemic control, and gastroprotective strategies. Elderly patients suffer from advanced multi-organ degenerative disease with severe CKD often requiring renal replacement therapy, complicated by hepatic dysfunction and nutritional compromise, demanding complex medication management, attention to polypharmacy risks, and palliative care considerations. These age-specific patterns underscore the critical importance of individualized diagnostic and therapeutic approaches tailored to particular life stages. Key management principles should include dietary modifications appropriate for both renal and gastrointestinal disease, minimizing toxic burden on liver and kidneys through judicious medication selection and dosing adjustments, early detection and treatment of comorbid conditions, and coordinated multidisciplinary care involving nephrologists, gastroenterologists, nutritionists, and primary care providers. Development and implementation of age-stratified clinical protocols for managing combined nephrological-gastroenterological pathology represents a promising direction for improving outcomes. Future research should focus on longitudinal studies examining disease progression patterns, intervention trials testing age-specific management strategies, and health economic analyses to optimize resource allocation across age groups.