Right flank pain: a case report of an interesting sonographic finding.

Background: Focused bedside ultrasound is a screening tool frequently used by emergency physicians to evaluate hepatobiliary and renal pathology in patients presenting with abdominal complaints in the emergency department (ED).
Objective: This case report describes a sonographic finding that was interpreted as free fluid in the right upper quadrant. Computed tomography (CT) was used to confirm the diagnosis.
Case Report: A 44-year-old man presented to the ED with the sudden onset of right-sided abdominal pain and exhibited right costovertebral angle tenderness on physical examination. Focused bedside ultrasound of the right upper quadrant revealed severe hydronephrosis of the right kidney and free fluid of either subcapsular, perinephric, or peritoneal location represented by an anechoic stripe in Morison's pouch. On CT evaluation, this patient was found to have perinephric fluid accumulation from a presumed ruptured renal calyx in the setting of chronic ureteropelvic junction obstruction with severe hydronephrosis.
Conclusion: The exact location of anechoic fluid in the abdomen is not always apparent on bedside ultrasound. To minimize misinterpreting focused bedside ultrasound examination findings, we recommend a number of sonographic techniques to identify possible mimics of free fluid. Suspected free fluid findings on bedside ultrasound should always be evaluated within the clinical context of the patient's presentation.
(Copyright © 2012 Elsevier Inc. All rights reserved.)