Arcuate and interlobular phlebitis in renal allografts

Intimal arteritis in the renal allograft has a well-documented adverse effect on graft outcome. In contrast, venulitis is currently considered an innocuous finding, based largely on observations of thin-walled intermediary venules. Arcuate and interlobular veins have not been studied specifically. These veins have well-developed muscular walls, and inflammation at this level (phlebitis) could significantly alter renal hemodynamics. We studied the clinicopathologic correlates of arcuate and interlobular phlebitis in 31 renal allograft biopsy specimens. Phlebitis was seen in conjunction with borderline changes suggestive of acute cellular rejection (13 cases), or acute rejection Banff grade 1A (7 cases), Banff grade 1B (6 cases), Banff grade 2A (4 cases), and Banff grade 2B (1 case). Clinical follow-up (average 323 +/- 460 days) showed no adverse effects of phlebitis as judged by temporal changes in serum creatinine and the grade of chronic allograft nephropathy in follow-up biopsies. Thus it appears that arcuate and interlobular phlebitis in allograft biopsy specimens does not add prognostic information beyond that provided by conventional Banff criteria. However, this lesion frequently coexists with changes suggestive or diagnostic of acute cellular rejection, and intimal arteritis may be seen concurrently in up to 16% of cases.