Modern approach of diagnosis and management of acute flank pain: review of all imaging modalities.

Acute flank pain is a common and complex clinical problem which might be caused by a variety of urinary and extraurinary abnormalities among which ureterolithiasis being the most frequent cause. Plain abdominal radiographs combined with intravenous urography (IVU) have been the standard imaging procedures of choice for the evaluation of acute flank pain over the last decades. Direct detection of even small ureteral calculi is achieved in 40-60%, whereas using indirect signs such as ureteral and renal pelvic dilatation stone detection is possible in up to 80-90% of all cases. However, IVU might be hampered by poor quality due to lack of bowel preparation, by nephrotoxicity of contrast agents, by serious allergic and anaphylactic reactions in 10% and 1% of the patients, respectively, and by significant radiation exposure. The use of ultrasonography (US) in the management of acute flank pain has been growing and when combining the findings of pyeloureteral dilatation, direct visualization of stones, and the absence of ureteral ejaculation, the sensitivity to detect ureteral dilatation can be as high as 96%. Recently, unenhanced helical CT (UHCT) has been introduced as imaging modality with a high sensitivity and specificity for the evaluation of acute flank pain. UHCT has been demonstrated to be superior since (1) it detects ureteral stones with a sensitivity and specificity from 98% to 100% regardless of size, location and chemical composition, (2) it identifies extraurinary causes of flank pain in about one third of all patients presenting with acute flank pain, (3) it does not need contrast agent, and (4) it is a time saving imaging technique being performed within 5min. Based on the data published, one can predict that UHCT will become the imaging procedure of choice for evaluation of acute flank pain within the next years. The purpose of this review is to critically evaluate the role all imaging modalities available for a modern approach of diagnosis and management of acute flank pain with regard to their sensitivity, specificity, positive and negative predictive values and their complications, toxicicty and morbidity.