Predicting renal calculus occurrence in spinal cord injury patients

This case-control study develops a model to predict the occurrence of renal calculi in patients with spinal cord injury (SCI). Risk factors were assessed at the time of diagnosis in 25 patients who developed calculi, and at a comparable postinjury time period in 100 patients with SCI who remained calculus-free several years after injury. Logistic regression analysis was used to develop a predictive model; accuracy was assessed by using the model to classify all 125 patients studied. Renal calculi occurred more frequently on the right side and 72% of the affected patients developed a second calculus within two years. Patients who developed renal calculi were more likely to be older, have neurologically complete quadriplegia, have Klebsiella or Serratia infections, a history of bladder calculi, and high serum calcium values. The predictive model was 84% sensitive and 81% specific. While other determinants of renal calculi undoubtedly exist, these findings demonstrate that high risk patients may be identified with a comparatively small set of predictor variables. Although these findings are encouraging, use of any predictive model is meant only to supplement and not replace clinical judgement.