Certain abdominopelvic vascular structures may be compressed by adjacent anatomic structures or may cause compression of adjacent hollow viscera. Such compressions may be asymptomatic; when symptomatic, however, they can lead to a variety of uncommon syndromes in the abdomen and pelvis, including median arcuate ligament syndrome, May-Thurner syndrome, nutcracker syndrome, superior mesenteric artery syndrome, ureteropelvic junction obstruction, ovarian vein syndrome, and other forms of ureteral compression. These syndromes, the pathogenesis of some of which remains controversial, can result in nonspecific symptoms of epigastric or flank pain, weight loss, nausea and vomiting, hematuria, or urinary tract infection. Direct venography or duplex ultrasonography can provide hemodynamic information in cases of vascular compression. However, multidetector computed tomography is particularly useful in that it allows a comprehensive single-study evaluation of the anatomy and resultant morphologic changes. Anatomic findings that can predispose to these syndromes may be encountered in patients who are undergoing imaging for unrelated reasons. However, the diagnosis of these syndromes should not be made on the basis of imaging findings alone. Severely symptomatic patients require treatment, which is generally surgical, although endovascular techniques are increasingly being used to treat venous compressions.

Page 105, paragraph 2, lines 2-10: The sentences should read as follows: "A significantly higher ratio of peak velocity [not peak systolic velocity] at the point of renal vein compression to peak velocity [not peak systolic velocity] in the hilar renal vein has been reported in patients with nutcracker syndrome compared with asymptomatic control subjects (56,57). A peak velocity [not peak systolic velocity] ratio of over 4.7 has been reported to have a sensitivity of 100% and a specificity of 90% for the diagnosis (58)."Page 109, Figure 18 legend, lines 4-5: The sentence should read as follows: "Duplex US showed a marked increase in peak velocity [not peak systolic velocity] distal to the narrowing."