TOPLINE:

Neutrophil tubulointerstitial infiltration (NTI) was identified in 10.2% of kidney transplant recipients and was associated with urinary tract infections (UTIs), female donor sex, delayed graft function, acute tubular injury, and rejection within the first transplant year. Long-term graft survival was poorer in patients with NTI, particularly in those with repeated or diffuse infiltration.

METHODOLOGY:

• Researchers conducted a study to determine the natural incidence of NTI in kidney grafts, identify associations with clinical or histologic factors, and assess its effect on long-term graft survival.
• They included 1753 kidney transplant recipients (median age, 50.9 years; 39% women) who underwent 6749 kidney graft biopsies (59.1% protocol biopsy and 40.9% indication biopsy) between 2000 and 2015.
• Protocol biopsies were performed up to 12 months post-transplantation, comprising 59.1% of all biopsies to determine the unbiased natural prevalence of NTI.
• Clinical, laboratory, and biopsy data were collected at transplantation and each biopsy and during annual follow-up.

TAKEAWAY:

• Overall, 178 patients (10.2%) had NTI, with 131 cases occurring within the first year after transplantation and 47 cases thereafter; NTI was identified in 2.3% of protocol biopsies, 4.1% of indication biopsies during the first year, and 4.7% of indication biopsies after the first year.
• During a long-term follow-up of 21 years, death-censored graft survival was poorer in patients with NTI, particularly in those with repeated or diffuse findings within the first transplant year.
• Within the first year, NTI was significantly associated with UTIs, female donor sex, delayed graft function, acute tubular injury, and antibody- or T cell-mediated rejection (P < .05 for all).
• After the first year, NTI was associated with female recipient sex, younger recipient age, and UTIs (P < .05 for all).

IN PRACTICE:

"The histomorphological diagnosis of NTI should prompt the search for UTI (even for rarer pathogens like mycobacteria, chlamydiae, ureaplasma) and rejection, and in cases with associated DGF [delayed graft function] or ATI [acute tubular injury] in the biopsy, investigation of the underlying causes," the authors wrote.

SOURCE:

This study was led by Julian Doricic, Hannover Medical School, Hannover, Germany. It was published online on October 23, 2025, in Nephrology Dialysis Transplantation.

LIMITATIONS:

The retrospective monocentric design limited causal inferences and generalisability of the findings to other settings. Protocol biopsies were performed in only the first transplant year, which limited long-term assessment. UTI-associated NTI cases may be underestimated due to biopsy avoidance in patients with overt UTI.

DISCLOSURES:

This study did not receive any specific funding. Some authors reported receiving travel support and accommodation, lecture fees, or honoraria from various pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.