The authors retrospectively evaluated radiologic, clinical, and pathologic findings in 23 cases of mature teratoma arising within peri- or pararenal spaces. Radiologic studies--including abdominal radiographs (21 cases), excretory urograms (12 cases), sonograms (17 cases), and computed tomographic (CT) scans (18 cases)--were evaluated for tumor location, mass effect, calcification, fat, tumor invasion, echo pattern, and tissue characteristics. Most patients were female (3.4:1), younger than 6 months (50%), and asymptomatic. Abdominal radiography demonstrated a mass in 95%, calcium in 92%, and fat in 60% of cases in which CT revealed these components. Similarly, sonography showed uncomplicated fluid in 76% and calcium in 50% of cases. Fat was not reliably distinguished from other soft-tissue components on sonograms. The most characteristic radiologic findings of mature teratoma of the retroperitoneum are a complex mass containing a well-circumscribed fluid component of variable volume, adipose tissue and/or sebum in the form of a fat-fluid level, and calcification in either a congealed or linear strand pattern. These findings are better demonstrated by CT than by sonography.

The imaging studies done on 62 patients hospitalized for acute renal infections were retrospectively reviewed. Thirty-six (58%) had one or more abscesses, 17 (27%) had focal or diffuse acute bacterial nephritis, five (8%) had pyonephrosis, and four (6%) had pyelonephritis. All had prolonged fever (greater than or equal to 72 hours) and leukocytosis. Among 25 patients examined with both ultrasound (US) and computed tomography (CT), US failed to depict three of five (60%) cases of acute bacterial nephritis and seven of 15 (47%) intrarenal and extrarenal abscesses. One renal abscess was misdiagnosed as a tumor at CT. US is not an adequate screening test for detecting lesions that may require invasive therapy. CT is more sensitive for the detection of acute renal inflammatory disease and for defining the extent of disease for planning of radiologic or surgical intervention.

Tumors metastasized to liver (n = 9), lung (n = 5), and lymph nodes (n = 5).

Clinical radiographic, and pathologic findings of multilocular cystic nephroma (MLCN) in 58 patients are presented. The lesion that affects predominantly boys in childhood and women in adulthood is usually solitary but rarely can be multiple, and it commonly occurs as an asymptomatic mass, occasionally with hematuria. Tumors may grow slowly over years or rapidly within months. A mass that is usually identified on plain radiographs occasionally has curvilinear calcification. Excretory urography and retrograde pyelography are helpful when pelvic herniation of the tumor is recognized, or when septae are noted with total body opacification. Angiography showed an avascular mass (six lesions), a hypovascular mass (14 lesions), or a hypervascular mass three lesions). Ultrasonography is helpful when multiple circumscribed sonolucent areas are identified. Similarly, a multilocular mass with septae is usually identified by computed tomography (six of seven cases). Our findings and a review of the literature indicate that this lesion is a neoplasm that can be strongly suspected preoperatively if pelvic herniation or a multilocular pattern is noted on imaging studies.

There is no general agreement on which terms to use to report abnormalities on imaging studies in patients with kidney infection. The Society of Uroradiology recommends a simplified nomenclature that is based on the traditional and widely understood term acute pyelonephritis. To provide a framework for the simplified terminology, the authors review the relevant pathophysiology with its imaging correlates and offer a historic perspective on the terminology issues.