Analgesia for the Renal Colic Patient

SCOPE OF THE PROBLEM Kidney stones occur in an estimated 5% of the population at any given time. The estimated lifetime risk for the passage of a renal stone is approximately 10%. After having one episode of renal colic, an estimated 50% of individuals will suffer a recurrence. It is not surprising, therefore, that there are more than 1 million visits to U.S. emergency departments (EDs) each year because of renal colic. CLINICAL ASSESSMENT Several studies have assessed the accuracy of the diagnosis of renal colic based on clinical presentation. Although the constellation of flank pain, nausea and vomiting, and hematuria has appeared to be reasonably specific in the classical approach to these patients, more recent investigations have suggested that when computed tomography (CT) scanning of the abdomen and pelvis is performed in the acute setting, important alternate diagnoses are identified relatively frequently. In one study of subjects who were thought by the treating physician to have a 90–100% likelihood of suffering a first episode of renal colic, 17% were found to have alternate significant pathology. It, therefore, seems prudent to consider imaging in the majority of patients with a suspected initial episode of renal colic (Figure 19-1). PAIN CONSIDERATIONS It is believed that the pain of renal colic is largely mediated by the synthesis of prostaglandin E2 in the renal medulla, leading to increased flow through the afferent arterioles and increased renal pelvis pressure. Ureteral smooth muscle spasm may also be a factor.