Omental infarction as a delayed complication of abdominal surgery.

Omental infarction, an uncommon cause of acute abdominal pain, is the result of compromised perfusion to the greater omentum. Although its etiology remains uncertain, predisposing factors include obesity [Surg. Today 30 (2000) 451], strenuous activity [N. Z. Med. J. 111 (1998) 211], trauma, and idiopathic omental torsion. Often confused with acute appendicitis or cholecystitis on clinical grounds [Surg. Today 30 (2000) 451], its diagnosis has traditionally been one of exclusion, based on intraoperative and pathologic findings. This diagnosis can be made radiologically based on the characteristic findings of an inflammatory mass containing fat and fluid. We describe a case of right lower quadrant omental infarction temporally related to bowel surgery.

Acute appendicitis: comparison of helical CT diagnosis focused technique with oral contrast material versus nonfocused technique with oral and intravenous contrast material.

PURPOSE: To compare the diagnostic accuracy of focused helical computed tomography (CT) with orally administered contrast material with that of nonfocused helical CT with orally and intravenously administered contrast material. MATERIALS AND METHODS: After receiving oral contrast material, 228 patients with clinically suspected appendicitis underwent focused appendiceal CT (5-mm section thickness, 15-cm coverage in the right lower quadrant). Immediately thereafter, helical CT of the entire abdomen and pelvis was performed following intravenous administration of contrast material (abdomen, 7-mm section thickness; pelvis, 5-mm section thickness). Studies were separated and independently interpreted by three observers who were blinded to patient names. Diagnoses were established by means of surgical and/or clinical follow-up findings. RESULTS: Fifty-one (22.4%) of 228 patients had acute appendicitis. Readers diagnosed appendicitis with 83.3%, 73.8%, and 71.4% sensitivity and 93.0%, 92.3%, and 97.9% specificity with focused nonenhanced appendiceal CT. Readers diagnosed appendicitis with 92.9%, 92.9%, and 88.1% sensitivity and 93.7%, 95.1%, and 96.5% specificity with nonfocused enhanced CT. Summary areas under the receiver operating characteristic curve estimates for focused nonenhanced and nonfocused enhanced CT were 0.916 and 0.964, respectively; the differences were statistically significant (P <.05) for two of three readers. All readers demonstrated higher sensitivities for detecting the inflamed appendix with nonfocused enhanced CT. Appendicitis was missed with focused CT in two patients whose inflamed appendix was not included in the imaging of the right lower quadrant. All readers were significantly more confident in diagnosing alternative conditions with nonfocused enhanced CT. CONCLUSION: Diagnostic accuracy of helical CT for acute appendicitis improved significantly with use of intravenous contrast material.

Quantitative and qualitative evaluation of volume of low osmolality contrast medium needed for routine helical abdominal CT.

OBJECTIVE: The purpose of our study was to determine the minimum optimal dose of IV contrast medium for helical CT that can preserve image quality while reducing cost. SUBJECTS AND METHODS: Four hundred sixty-three patients from six centers were enrolled in a prospective trial in which patients were randomized into one of four weight-based dose categories of iopromide, 300 mg I/mL: 1.25, 1.50, 1.75, and 2.0 mL/kg. Six of 463 patients were excluded from analysis. A radiologist at each center who was unaware of the volume of contrast medium administered determined whether the scans were acceptable. The responses were analyzed by dose, in aggregate, and by weight. Enhancement values (in Hounsfield units) in regions of interest in the liver, pancreas, aorta, and kidneys were obtained at a single time during the scan. The participating radiologist was unaware of these values. Finally, three additional nonparticipating site observers assessed the images for acceptability, diagnostic quality, and overall level of confidence. A cost model comparing incurred charges in using 150 or 100 mL, or 1.5 mL/kg, of low osmolality contrast medium was developed from experience in an additional 303 patients. RESULTS: We found no clinically significant difference in acceptability of scans at doses greater than 1.5 mL/kg. However, significant variability occurred among the centers. The use of 1.5 mL/kg led to a savings of $9927.16 for 303 patients when compared with the use of 150 mL at list price. The cost is the same for 1.5 mL/kg or use of 100 mL of contrast medium. CONCLUSION: A weight-based dose at 1.5 mL/kg of low osmolality contrast medium can provide acceptable scans in most patients, with a significant cost savings.

Radiologic and endoscopic diagnosis of Crohn's disease.

This article reviews the radiologic and endoscopic diagnosis of Crohn's disease. Radiographic and endoscopic findings of Crohn's disease are discussed; a practical approach to the selection of radiologic modalities is presented; and the role of endoscopy in diagnosis and treatment is explained.

Disseminated aspergillosis inciting intestinal ischaemia and obstruction.

Invasive aspergillosis is an opportunistic infection that characteristically affects the immunocompromised host, resulting in a high degree of morbidity and mortality. Although the portal of entry is usually pulmonary, there are rare reports of invasive aspergillosis localized to the gastrointestinal tract. In addition, haematological spread may develop, with life threatening disseminated infection involving the vital organs and the gastrointestinal tract. Although disseminated infection is well recognized, the CT findings of gastrointestinal disease have not been reported to our knowledge. We describe the CT findings in a patient with invasive aspergillosis involving the gastrointestinal tract, which resulted in intestinal ischaemia complicated by small bowel obstruction.

The costs of CT procedures in an academic radiology department determined by an activity-based costing (ABC) method.

PURPOSE: The purpose of this work was to determine the costs of computed tomography (CT) procedures in a large academic radiology department, including both professional (PC) and technical (TC) components, by analyzing actual resource consumption using an activity-based costing (ABC) method and comparing them with Medicare payments. METHOD: Over a 12 month period from July 1, 1996, to June 30, 1997, 1,011 CT procedures, representing 16 Physicians' Current Procedural Terminology (CPT) codes and 98.3% of CT studies performed, were carefully observed by a research assistant trained in ABC methodology. Information collected during these time and motion studies included personnel/machine time and direct materials used. Actual resource units used during the different activities in each CT procedure were valued using appropriate cost drivers. Unit values for both direct and overhead costs were calculated: the cost of an individual procedure equaled the sum of component costs. Costs were compared with PC and TC payments according to the 1997 Medicare Fee Schedule. RESULTS: Total costs of CPT codes 70450 (CT Head unenhanced), 71260 (CT Chest enhanced), and 74160 (CT Abdomen enhanced), which represented 71.2% of CT studies performed, were $189.19, $273.53, and $343.20, respectively. For all 16 nonmodified CPT codes analyzed, Medicare's professional reimbursement was less than the professional cost, whereas its technical reimbursement exceeded respective cost in 14 of the 16 codes. CONCLUSION: In the setting and time period studied, Medicare underreimbursed professional costs while overreimbursing technical costs.

Appendicitis at the millennium.

Acute appendicitis is a common clinical problem. Accurate and prompt diagnosis is essential to minimize morbidity. While the clinical diagnosis may be straightforward in patients who present with classic signs and symptoms, atypical presentations may result in diagnostic confusion and delay in treatment. Helical computed tomography (CT) and graded compression color Doppler ultrasonography (US) are highly accurate means of establishing the diagnosis. These imaging modalities have now assumed critical roles in the treatment of patients suspected to have appendicitis. The purpose of this article is threefold: to provide an update on new information regarding the pathophysiology, clinical diagnosis, and laparoscopic treatment of acute appendicitis; to describe the state-of-the art use of CT and US in diagnosing this disease entity; and to address the role of medical imaging in this patient population.

Isolated infarction of the cecum: CT findings in two patients.

Colonic ischemia isolated to the cecum is a rare entity. The authors evaluated two patients who underwent computed tomography (CT) because appendicitis was suspected at clinical examination. CT findings were suggestive of isolated cecal ischemia or infarction. Surgical-histopathologic findings helped confirm the presumptive CT diagnoses. Isolated cecal infarction should be included in the differential diagnosis of acute right lower quadrant pain.

Renal cyst pseudoenhancement: beam-hardening effects on CT numbers.

PURPOSE: To determine if simple renal cysts may be accurately characterized with helical computed tomography (CT) during peak levels of renal enhancement. MATERIALS AND METHODS: Water-filled "cysts" were suspended in varying concentrations of iodine solution, meant to simulate varying levels of renal enhancement, within an abdominal phantom. Volume-averaging effects were minimized by scanning cylindric 5-30-mm cysts with a helical technique (collimation, 5 mm; pitch, 1:1). Axial and helical techniques were then compared, and volume-averaging effects were evaluated by scanning 10- and 20-mm round cysts with 3-, 5-, and 7-mm collimation at background attenuation levels of 100 and 200 HU. RESULTS: Cylindric cyst attenuation increased consistently with increasing background attenuation. As background attenuation increased by 90 HU, attenuation increased by 11-17 HU in small (5- or 10-mm) cysts, and by 7-9 HU in large (15-30-mm) cysts. As background attenuation increased by 180 HU, attenuation increased by 18-28 HU in small cysts and by 10-15 HU in large cysts. Spherical cyst attenuation differences were maximized when smaller cysts were imaged with larger collimation, which is when volume-averaging effects became apparent. Axial and helical CT numbers did not differ substantially. Computer simulation studies showed that the observed effect could not be explained by beam hardening alone. CONCLUSION: Pseudoenhancement of renal cysts may occur if helical CT is performed during peak renal enhancement. CT algorithm modification may be necessary to correct for this effect, which is likely related to an inadequate algorithmic correction for beam hardening.

The hypertrophied antral-pyloric fold: CT appearance.

We report a patient found to have a hypertrophied antral-pyloric fold on barium study, in whom CT demonstrated a smooth soft tissue mass on the anterior wall of the pre-pyloric antrum. When this finding is encountered on CT, a double-contrast upper GI study should be performed as the next diagnostic test. Endoscopy can probably be avoided if the barium study shows the typical findings of a hypertrophied antral-pyloric fold.

Extravasation detection accessory: clinical evaluation in 500 patients.

PURPOSE: To assess the ability of an extravasation detection accessory (EDA) to detect clinically important (> or = 10 mL) extravascular injection of iodinated contrast material delivered with an automated power injector. MATERIALS AND METHODS: Five hundred patients referred for contrast material-enhanced body computed tomography (CT) participated in a prospective, multi-institutional, observational study in which the EDA was used to identify and interrupt any injection associated with clinically important extravasation. The presence or absence of extravasation was definitively established with helical CT at the injection site (injection rate, from 1.0 to 5.0 mL/sec; mean, 2.9 mL/sec; median, 3.0 mL/sec). RESULTS: There were four true-positive (extravasation volumes, 13-18 mL), 484 true-negative, 12 false-positive, and no false-negative cases. The prevalence of overall and clinically important (> or = 10 mL) extravasation was 3.6% (18 of 500 cases) and 0.8% (four of 500 cases), respectively. The EDA had a sensitivity of 100% (four of four cases; 95% CI: 51%, 100%) and a specificity of 98% (484 of 496 cases; 95% CI: 96%, 99%) in the detection of clinically important extravasation. CONCLUSION: The EDA is easy to use, safe, and accurate in the monitoring of intravenous injections for extravasation, which could prove especially useful in high-flow-rate CT applications.

Assessment of a bolus-tracking technique in helical renal CT to optimize nephrographic phase imaging.

PURPOSE: To evaluate a bolus-tracking technique in helical computed tomography (CT) for identifying the onset of the nephrographic phase and to determine the effect of varying the volume and injection rate of contrast material on nephrographic phase onset. MATERIALS AND METHODS: Seventy-five patients underwent bolus tracking of contrast material followed by helical renal CT. In 50 patients, 150 mL of 60% iodinated contrast material (iohexol or iothalamate meglumine) was injected at either 2 mL/sec (25 patients [group 1]) or 3 mL/sec (25 patients [group 2]). In 25 patients who had previously undergone nephrectomy, 100 mL of 60% iodinated contrast material was injected at 3 mL/sec (group 3). Nephrographic phase onset was determined by visually assessing the transition to a homogeneous nephrogram during a monitoring scan series starting 40 seconds after injection. RESULTS: Nephrographic phase onset ranged from 60 to 136 seconds (mean, 89 seconds +/- 17 [+/- SD]). Statistically significant differences in mean onset times were observed among groups 1 (103 seconds +/- 12), 2 (91 seconds +/- 16), and 3 (75 seconds +/- 9) (P < .001). Multiple regression analysis showed patient age, contrast material volume, and injection rate to be independent predictors of nephrographic phase onset. Contrast material volume, patient age, and patient weight were independent predictors of the degree of renal enhancement. CONCLUSION: Nephrographic phase onset is highly dependent on methods of contrast material administration and patient characteristics.

Contrast media extravasation during dynamic CT: detection with an extravasation detection accessory.

To detect extravasation of contrast media during mechanical power injection at dynamic computed tomography, a 5 x 8-cm pliable adhesive patch was applied to the skin over the intravenous cannula and connected to the power injector with a cable to monitor electrical skin impedance. If the rate of change or the slope of impedance over time indicated an extravasation event, the power injector was set into a pause mode. In animal and human studies, monitoring with the device was successful. Extravasation of ionic contrast agents decreased impedance and that of nonionic agents increased impedance.

Contrast media reactions and extravasation: relationship to intravenous injection rates.

PURPOSE: To evaluate the belief that the frequencies of contrast material extravasation and minor, nonidiosyncratic contrast material reactions correlate with intravenous injection rates. MATERIALS AND METHODS: Complications of 6,660 consecutive injections of contrast material for computed tomography were prospectively recorded. Ionic (n = 4,851) or nonionic (n = 1,809) contrast material was injected at 0.5-4.0 mL/sec. The injection rate was 1.9 mL/sec or less in group 1 (n = 2,899), 2.0-2.9 mL/sec in group 2 (n = 2,475), and 3.0-4.0 mL/sec in group 3 (n = 1,286). RESULTS: The extravasation rate (0.6%) did not differ significantly between the groups. The reaction rate (8.4%) also did not differ significantly between the groups. The rate of minor reactions (8.0%) was higher with ionic (9.9%) than nonionic (2.9%) contrast material (relative risk = 3.4). The rate of major reactions (0.4%) did not vary significantly with type of contrast material. The rate of nausea or vomiting (3.8%) did not differ significantly between the groups but was higher with ionic (4.9%) than nonionic (1.1%) contrast material (relative risk = 4.5). The rate of severe warmth (2.1%) was significantly higher in group 3 (2.8%) than group 1 (2.0%) or 2 (1.8%). CONCLUSION: No correlations exist between injection rate and extravasation rate or overall reaction rate.

Diagnostic criteria for fatty infiltration of the liver on contrast-enhanced helical CT.

OBJECTIVE: The purpose of the study was to develop quantitative and qualitative criteria for diagnosing fatty liver on contrast-enhanced helical CT. SUBJECTS AND METHODS: Differential liver-spleen attenuation was evaluated between 80 and 120 sec after injection in 76 patients who underwent contrast-enhanced helical CT. Unenhanced CT images had earlier established fatty liver when the liver minus spleen attenuation difference was less than or equal to -10 H (n = 18). Four observers who had not seen the unenhanced images used contrast-enhanced CT images to assess the presence of fatty liver on a five-point Likert scale, the presence of geographic areas spared from fatty infiltration, and the relative liver-spleen attenuation. The diagnostic accuracies of various imaging criteria were compared using McNemar's chi-square test (for sensitivity and specificity) and analysis of receiver operating characteristic curves. RESULTS: Sensitivity, specificity, and receiver operating characteristic curve areas for observers' qualitative judgments were 54%, 95%, and .91, respectively; for quantitative differential liver-spleen attenuation (80-100 sec; -20.5 H discriminatory value), the values were 86%, 87%, and .94, respectively; and for quantitative differential liver-spleen attenuation (101-120 sec; -18.5 H discriminatory value), the values were 93%, 93%, and .98, respectively. Differential liver-spleen attenuation was time-dependent; overlap was noted between healthy subjects and patients with fatty liver. Qualitatively, geographic sparing was highly specific (94%) for fatty liver, whereas liver attenuation greater than or equal to spleen attenuation excluded fatty liver in all but one case. CONCLUSION: Although quantitative and qualitative criteria for diagnosing fatty liver on helical CT can be determined, they are protocol-specific. Limited unenhanced hepatic CT remains the optimal technique for detection of fatty infiltration of the liver.