Kidney Pathology Findings in Pediatric Patients with Kidney Injury and Inflammatory Bowel Disease: A Case Series

Background: Patients with inflammatory bowel disease (IBD) are at increased risk of renal pathologies such as IgA Nephropathy (IgAN) and tubulointerstitial nephritis (TIN). Data describing the spectrum of renal pathology abnormalities and treatment approaches in pediatric IBD patients who develop kidney disease are limited. We aim to describe the spectrum of kidney pathology, treatments, and outcomes in pediatric IBD patients who underwent kidney biopsy at our centre. Methods: This is a single-centre retrospective case series conducted at a quaternary pediatric center in Toronto, Canada. We included pediatric patients diagnosed with IBD who underwent kidney biopsy between June 2018 and February 2024. Clinical data were obtained from chart review, and all biopsies were retrospectively reviewed by a renal pathologist. Results: 12 patients were included. 11 of 12 patients had Crohn’s disease, and 4 patients were female. Renal pathology diagnoses included TIN (33%) in four patients, focal segmental glomerulosclerosis (FSGS) in one, IgA nephropathy in one, and acute tubular necrosis in one. Five patients (42%) had normal or non-specific findings on biopsy. Indications for kidney biopsy included abnormal serum creatinine (n=10), nephrotic range proteinuria (n=1), and steroid-resistant nephrotic syndrome/SRNS(n=1). Kidney abnormalities were detected before IBD diagnosis in 2 patients, within one year of diagnosis in four, and 2-11 years post-diagnosis in six. TIN treatments included prednisone, cessation of suspected triggers such as ustekinumab and vedolizumab, and/or IBD therapy escalation. All patients with TIN did not have significant improvement in kidney function after treatment. The patient with IgA nephropathy had complete recovery of kidney function after steroid treatment. The patient with FSGS presented with SRNS and responded to Rituximab, while his IBD was independently treated successfully with infliximab. Conclusion: TIN was the most common renal pathology this pediatric patients with IBD cohort, but was associated with poor renal recovery despite steroids and cessation of potential triggers. A large proportion of biopsies showed no diagnostic abnormalities. Improved kidney function surveillance in pediatric IBD patients could be beneficial for earlier detection and management of diseases such as TIN.