Infiltrative Nephropathy in Chronic Lymphocytic Leukaemia/Small Lymphocytic Lymphoma: A Systematic Review and Attribution Analysis.

BACKGROUND: Renal infiltration by chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL) is frequently identified histologically but is an uncommonly recognised cause of clinically significant kidney injury. As CLL/SLL cells may be incidental or coexist with other renal pathology, biopsy alone does not establish causality. METHODS: We performed a PROSPERO-registered systematic review of MEDLINE and Embase (January 1990 to March 2026). Adults with native-kidney biopsy-confirmed CLL/SLL infiltration and extractable clinical or outcome data were included. Data were synthesised descriptively, and an exploratory clinicopathological attribution analysis evaluated infiltration burden and pattern alongside competing renal lesions. RESULTS: Thirty studies comprising 54 extracted data rows were included. Acute kidney injury occurred in 40/49 (81.6%), and dialysis was required at presentation in 17/47 (36.2%). Concurrent glomerular pathology was present in 19/54 (35.2%). Stronger attribution features were identified in 19/54 cases (35.2%), whereas alternative dominant renal lesions were present in 18/54 (33.3%). End-stage kidney disease (ESKD) was more frequent in the stronger-attribution group (7/18, 38.9%) than with an alternative dominant lesion (1/12, 8.3%). Renal recovery followed CLL/SLL-directed therapy in 34/47 (72.3%). CONCLUSIONS: Attribution of kidney dysfunction to CLL/SLL infiltration requires integrated clinicopathological assessment. Diffuse or extensive infiltration without competing renal pathology provides the strongest evidence for causality and carries a higher risk of ESKD, while renal recovery after CLL/SLL-directed therapy suggests AKI may be reversible in selected patients. Dialysis dependence at presentation was the clearest predictor of ESKD. All findings derive from case reports and small series and are of very low certainty (GRADE).