Clinical Transplant Kidney Function Loss Due to Small Intestinal Bacterial Overgrowth.

Small intestinal bacterial overgrowth (SIBO) is a clinical syndrome involving gastrointestinal symptoms caused by the presence of excessive bacteria in the small intestine. SIBO often leads to diarrhea and poses diagnostic and treatment challenges. Here, we report about a renal transplant recipient who experienced diarrhea-induced hypovolemic shock due to SIBO, necessitating the reintroduction of dialysis, and aim to provide insights to aid health-care providers in diagnosing and managing severe diarrhea in this specific patient group. A 14-year-old boy, who had undergone renal transplantation at the age of 2 years, experienced severe, recurring diarrhea leading to hypovolemic shock. The patient underwent volume loading and continuous hemodiafiltration. Upper gastrointestinal endoscopy findings suggested Whipple's disease. Antibiotics were initiated; however, the diarrhea did not improve. Examinations for infectious enteritis and food allergies yielded negative results. The diarrhea improved with rifaximin (RFX), but recurred repeatedly after its discontinuation. Antibiotic rotation, wherein RFX, amoxicillin hydrate and potassium clavulanate, ciprofloxacin, and RFX were administered in this order for 4 weeks each, improved the diarrhea. A lactulose breath test performed immediately before the second RFX course yielded negative results. The patient's condition was diagnosed as SIBO based on the clinical course, although the diagnostic criteria were not met. SIBO should be considered in cases of gastrointestinal symptoms in patients with transplanted kidneys. Antibiotic rotation should be considered for SIBO treatment in immunosuppressed patients.