ROLE OF THE RESISTIVE INDEX IN THE EVALUATION OF ACUTE RENAL OBSTRUCTION

Sonography is well established as a screening tool to evaluate the kid ney for the presence of renal obstruction [1]. The role of sonography in the evaluation of acute obstruction is less clear, however. Despite recent reports emphasizing the ability of gray-scale sonography and k idney/urinary/bladder films to screen for acute colic [2], experience indicates that the sonographic diagnosis of acute renal stone disease may be unreliable. Multiple studies have demonstrated the many potenti al pitfalls of the sonographic examination for acute obstruction [3-5] . False-negative studies may result if the kidney is evaluated before hydronephrosis occurs. Conversely, nonobstructive pyelocaliectasis and parapelvic cysts may result in false-positive studies. Because of the se sonographic limitations, many imaging practices exclusively have ut ilized excretory urography for the evaluation of patients with symptom s of renal colic.