High urine amylase level and the risk of enteric conversion in solitary pancreas transplant recipients

Compared with enteric drainage, bladder-drained solitary pancreas transplants can be monitored for rejection by measuring urine amylase levels. However, bladder drainage is associated with a higher risk of infection and metabolic complications, necessitating enteric conversion in about one third of patients. We hypothesized that hypersecreting pancreata with high urine amylase levels have a higher propensity for enteric conversion from an antecedent elevated enzymatic effect on the urinary tract and increased fluid losses. Patients and Methods. We analyzed the risk for enteric conversion in 312 bladder-drained solitary pancreas transplant recipients. Urine amylase levels at 30 days were used to identify those at risk for enteric conversion. Time-to-event analysis was used to evaluate the risk of enteric conversion at 10 years, adjusting for urine amylase level and other confounding factors. Confounding risk factors statistically related to enteric conversion were incorporated into the multivariable analysis by using Cox proportional hazards regression at 3 years' posttransplant. Results. During the median follow-up of 184.6 months, 31% of recipients underwent duct conversion. A majority of recipients (84.5%) who required duct conversion were primary transplants. The 30-day median urine amylase level was 1749 IU/h (quartile 1, <777 IU/h; quartile 3, ≥3272 IU/h). Using receiver operating characteristic analysis, it was determined that urine amylase levels >3272 IU/h had the greatest specificity for predicting risk of enteric conversion. In the multivariate analysis, high urine amylase levels increased the risk of enteric conversion only in repeated pancreas transplants. Conclusions. Primary transplants are more likely to undergo enteric conversion than retransplants. High urine amylase levels increase the risk of enteric conversion in retransplants only, and therefore this enzyme alone cannot serve as the sole predictor for conversion in primary transplants. Other factors, such as fluid and bicarbonate losses, increased bladder pressure, and a pre-existing lower urinary tract pathologic condition may be also responsible for the development of complications; these factors warrant additional study.