Impact of Norovirus/Sapovirus-Related Diarrhea in Renal Transplant Recipients Hospitalized for Diarrhea

BACKGROUND: Diarrhea of unspecified cause frequently occurs after renal transplantation and is usually ascribed to mycophenolic acid toxicity. Norovirus (NoV) and sapovirus (SaV) have been sporadically reported to cause chronic diarrhea in immunocompromised patients. METHODS: We undertook a retrospective study (2008-2009) to examine the clinical and epidemiologic significance of NoV and SaV infections in adult renal transplant recipients hospitalized for acute or chronic diarrhea. RESULTS: Ninety-six renal transplant recipients were hospitalized for diarrhea at our institution during a 16-month period, 87 of whom were included in the study, including 46 patients with chronic diarrhea. Among 41 patients with unexplained diarrhea, 20 patients were screened for NoV/SaV, 16 of whom were positive. Fifteen of them (94%) had chronic diarrhea. When compared with bacterial and parasitic infections, NoV/SaV infections were associated with a greater weight loss at the time of admission, a 8.7-fold longer duration of symptoms and a more frequent need for mycophenolic acid dosage reduction. Eighty-one percent of patients hospitalized for NoV/SaV-associated diarrhea experienced acute renal failure. Five and one patients subsequently had biopsy-diagnosed active graft rejection and oxalate nephropathy, respectively. Ten of the 14 patients who underwent a longitudinal study of NoV/SaV stool's clearance exhibited a prolonged viral shedding period with a median time of 289 days (107-581 days). CONCLUSIONS: Our study indicates that NoV/SaV infection causes posttransplant chronic diarrhea potentially complicated by severe kidney graft impairment.