PICTORIAL ESSAY Mert Koroglu Æ John D. Wendel Æ Randy D. Ernst Aytekin Oto Alternative diagnoses to stone disease on unenhanced CT to investigate acute flank pain Received: 16 January 2004 / Accepted: 30 January 2004 / Published online: 11 May 2004 Ó ASER 2004 Abstract Acute flank pain is a common problem in emergency medicine. The most frequent cause is uro- lithiasis, but many other entities can cause the same clinical presentation. In many institutions unenhanced computed tomography (CT) of the abdomen is used in this setting. One of the major advantages of unenhanced CT is its ability to detect other pathologies causing flank pain. In this pictorial review, we present the CT findings of pathologies other than stone disease in patients with acute flank pain. Keywords Computerized tomography (CT) Æ Emergency Æ Acute flank pain Introduction Although urolithiasis is the most common cause of acute flank pain, a variety of other urinary and extraurinary abnormalities may also present with flank pain [1]. Unenhanced helical computed tomography (CT) is now recognized as the imaging technique of choice for acute flank pain in most centers. CT identifies the exact size and location of urinary tract calculi and can also be used to establish or suggest significant alternative or addi- tional diagnoses [2, 3, 4, 5, 6, 7, 8, 9]. Nearly one-half of patients with acute flank pain have no evidence of stone disease on CT examination [3, 10]. Among those who do not have urolithiasis, an alterna- tive cause of the flank pain is found in up to one-third of cases [3]. It is therefore important for radiologists to be familiar with other pathologies which can cause acute flank pain. Some of the most commonly encountered alternative or additional diagnoses are: appendicitis, diverticulitis, mesenteric lymphadenitis, cholelithiasis, choledocholithiasis, cholecystitis, pancreatitis, colitis, aortic aneurysm and dissection, abdominal wall hernia, pyelonephritis, complicated renal cyst, renal cell carci- noma, polycystic kidney disease, pelvic mass, uterine fibroids, and ovarian cyst [11, 12]. Some of those alter- native or additional diagnoses are obvious, others much less so. Extreme attention must be paid to all aspects of unenhanced CT examinations to prevent misdiagnosis [13]. All slices must also be reviewed in both bone and lung windows to detect bone lesions and intraabdominal free air. We reviewed the CT reports of 714 consecutive patients (376 men, 338 women; age range 5–103 years; mean age 41.1 years) who presented to the emergency department with acute flank pain and underwent renal stone protocol CT examination between October 2001 and October 2003. All abdominal CT scans were obtained without oral or intravenous contrast, from the upper border of the T12 vertebral body to the lower border of the symphysis pubis, using 5 mm collimation and 2.5 mm reconstruction. Four hundred and fifty-five patients had urolithiasis, 259 patients were found to be without urinary stone. Alternative or additional diagnoses for flank pain Significant alternate diagnoses explaining the flank pain were found in 196 patients (27.4%) (Table 1). Hepatic pathologies Both benign and malignant hepatic lesions can present with right-sided acute abdominal pain radiating to the flank. In the case of a hepatic abscess, fever, increased white cell count, malaise, and anemia usually M. Koroglu (&) Æ J. D. Wendel Æ R. D. Ernst Æ A. Oto Department of Radiology, University of Texas Medical Branch at Galveston, Galveston, Texas, USA E-mail: mertkoroglu@hotmail.com Tel.: +90-246227-9469 M. Koroglu, Hizirbey M. 1544 S. No 72/3, 32040 Isparta, Turkey Emergency Radiology (2004) 10: 327–333 DOI 10.1007/s10140-004-0336-5