Purpose: To evaluate the epidemiology and outcomes of renal transplant recipients diagnosed by renal biopsy with acute graft pyelonephritis (APGN).

Methods: We performed a retrospective review of all renal transplant recipients ≥18 years of age who received an allograft biopsy January 1, 2003-December 31, 2011. Subjects were included if the biopsy interpretation included any of the following terms: ‘neutrophilic tubulitis’, ‘neutrophil cast’, ‘pus cell cast’ or ‘pyelonephritis’. Demographic and clinical data included: sex, age, donor type, time from transplant to biopsy, indication for biopsy, creatinine at 90 days prior to biopsy, at time of biopsy and 90 days after biopsy, microbiologic data, antibiotic therapy, and graft and patient survival at 12 months after biopsy.

Results: 40/1798 (2.2%) patients had a biopsy with histopathologic findings suggestive of AGPN. Indications for biopsy were: rise in creatinine (72%), persistently elevated creatinine (15%), per protocol/post rejection treatment (10%), proteinuria (2.5%). 22/40 (55%) patients were male and the mean age was 46.7 years. 29/40 (72.5%) were deceased donor recipients. The mean time to diagnosis was 18.4 months (range 0.7-98.7) after transplant. 0/40 patients complained of symptoms of UTI or APGN prior to biopsy, although 17/42 (42.5%) had 1 or more UTIs in the 6 months preceding the biopsy. Urine studies (urinalysis, microscopy, culture) were performed within 14 days before to 7 days after biopsy in 35/40 (87.5%) of patients. 22/28 (78.6%) patients tested had a positive urine leukocyte esterase, 16/20 (80%) had >5 WBC/hpf, 4/20 (20%) had WBC casts, and 14/33 (42.4%) had positive urine culture. Biopsies showed concurrent acute or chronic rejection in 10/40 (25%) and 2/40 (5%) patients, respectively. 23/36 (57.5%) patients received antibiotic therapy (insufficient data for 4 patients). At 90 days after biopsy, those receiving antibiotics had an average 1.10 fold increase in creatinine compared to their baseline creatinine, versus a 1.32 fold increase in patients not treated with antibiotics. 12 month graft and patient survival were 75% and 90%, respectively.

Conclusions: Neutrophilic infiltrates are a common and unexpected finding in patients with post-transplant renal dysfunction. Improved renal outcome in patients treated with antibiotics suggests that this often represents an infectious etiology. Further studies will be needed to clarify the etiology, optimal treatment and outcomes associated with this finding.

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