Pyelonephritis may occur secondary to immunosuppression and frequent catheterization. Like acute rejection, it may present as fever and allograft pain. Urine dipstick and culture should be performed to assess for the presence of this complication.

Recurrence of a primary renal disease, such as focal segmental glomerulosclerosis, may also occur. Although glomerular disease may sometimes be distinguished from rejection based on the presence of heavy proteinuria or glomerular bleeding (i.e., red blood cell casts or dysmorphic red blood cells) on urine sediment, biopsy is often required to make the distinction.

Late Post-Transplant Period (After 6 Months). Many of the problems that can occur in the early post-transplant period may also occur in the late post-transplant period, including prerenal state, CNI nephrotoxicity, nephrotoxic ATN, pyelonephritis, recurrence of primary disease, and urinary tract obstruction. Late acute rejection may also occur in patients with inadequate immunosuppression or medication noncompliance. The other causes of late post-transplant graft dysfunction include chronic allograft nephropathy, BK virus infection, and renal artery stenosis.