Hounsfield unit density in the determination of urinary stone composition.

OBJECTIVES: Noncontrast computed tomography (NCCT) has emerged as the diagnostic study of choice in the evaluation of acute flank pain. Recent in vitro studies have suggested that NCCT can be used to predict the composition of urinary stones on the basis of differences in radiodensity (measured in Hounsfield units, HUs). We sought to determine whether the analysis of in vivo urinary stones seen on NCCT could predict their composition. METHODS: Between March 1997 and August 1999, 100 pure stones from patients seen at the Wilford Hall Medical Center in San Antonio, Texas were submitted for analysis. All had been visualized by NCCT before stone passage or retrieval. A General Electric High-Speed Advantage CT scanner evaluated most of these patients by a "flank pain protocol" (ie, helical technique with breath-holding at 120 kV, 200 mA with 5 mm collimation). Each scan was interpreted by one of two staff radiologists who measured the HUs for each stone. A statistical comparison was made between the stone composition and radiodensity. To allow for subsequently observed increases in radiodensity with increasing stone size regardless of composition, the HU value was divided by each stone's largest transverse diameter in millimeters to give the HU density. A statistical comparison was then made between stone composition and HU density. RESULTS: No significant difference was noted between the HU values of calcium oxalate and calcium phosphate stones, and thus they were analyzed collectively as "calcium stones." When the HU values of calcium (n = 87), uric acid (n = 7), struvite (n = 4), and cystine (n = 2) stones were compared, the overlap of ranges precluded accurate identification, and the mean HU values were not significantly different from one another. There was less overlap noted when comparing the HU densities of the stones studied, and no noncalcium stone had an HU density greater than 76 HU/mm. Using one-way analysis of variance, significant differences were noted between the mean HU density of calcium (105 +/- 43) and uric acid (50 +/- 24) stones (P = 0.006). A trend toward significance was found between the mean HU density of the calcium and struvite stones (53 +/- 28, P = 0.073). No significant differences were found among the other stones. CONCLUSIONS: HU density compared with the HU value alone better characterized differences in radiodensities among urinary stones; calcium stones can be distinguished from uric acid stones on the basis of this value. However, neither the HU density nor the mean HU value was able to identify urinary stones in vivo.

Appendiceal CT in pediatric patients: relationship of visualization to amount of peritoneal fat.

OBJECTIVE: This study was performed to determine the rate of visualization of the normal pediatric appendix on CT and to evaluate the relationship of the appendix to parameters such as amount of intraperitoneal fat, use of contrast material, patient age, and slice thickness. MATERIALS AND METHODS: Three board-certified radiologists retrospectively reviewed 248 successive pediatric abdominal and pelvic CT examinations performed from 1995 to 1999. Each radiologist independently assessed the degree of intraperitoneal fat (minimal, moderate, or marked compared with a standard slice), appendiceal visualization (definite, unsure, not seen), cecal and terminal ileal opacification, and the outer diameter of visualized appendixes. The age and sex of the patient, collimation thickness (3-10 mm), and use of enteric or IV contrast material was also recorded. RESULTS: A normal appendix was identified in 120 (48.4%) of 248 examinations. The only individual variable with statistically significant correlation was the degree of intraperitoneal fat. This was determined using the Pearson chi-square test, the likelihood ratio, and logistic regression. The appendix was seen in 68.8% (n = 93) of patients with moderate or marked intraperitoneal fat versus 36.1% (n = 155) with minimal fat (p<0.001). A trend toward decreased visualization in children younger than 10 years old with minimal peritoneal fat was identified and confirmed with a 95% confidence limit. The outer diameter of the visualized appendix varied from 3 to 10 mm, with a mean value of 6 mm. CONCLUSION: Increased peritoneal fat significantly increases the rate of identification of the normal appendix in pediatric patients. Although less fat is generally seen in younger patients, there is significant overlap of appendix visualization among age groups.

The utility of screening chest radiographs for flight physicals.

Previous studies have shown low efficacy of screening chest radiographs in various populations. Findings of approximately 3,500 screening chest radiographs performed for flight duty were reviewed to determine the rate of detection of significant abnormalities. There were abnormal findings in 107 chest radiographs (3%). Fifty-five of these (1.6% of total), after additional evaluation, were found to be false positive. Only two medically significant conditions were found in the screening population. Based on our data, routine screening of flight duty applicants does not appear to be justified.

Sonographic appearance of the bladder after endoscopic incision of ureteroceles.

OBJECTIVE: Our intent was to describe the range of postoperative sonographic appearances of the bladder after endoscopic incision of ureteroceles. CONCLUSION: Preoperative and postoperative sonographic examinations of the bladder were reviewed in 14 patients (15 ureteroceles) who underwent endoscopic ureterocele incision. Five different appearances of the ureterovesical junction after endoscopic incision were found: a pseudomass (5/15), focal mucosal thickening (3/15), residual ureterocele with decrease in size (3/15), persistent unchanged ureterocele (1/15), and no residual abnormality (3/15). The most common postoperative sonographic appearance associated with development of vesicoureteral reflux was a mucosal pseudomass (4/6). The other bladder sonographic appearances had no correlation with development of reflux, degree of hydronephrosis, or success of the surgery.

A simulation of hand impairments: effects on upper extremity function and implications toward medical impairment rating and disability determination.

OBJECTIVES: To determine whether simulation of significant impairment of the hand will have a predictable impact on degree of functional loss at the wrist and hand. DESIGN: Single subject repeat measures using before-after trial comparisons and healthy volunteer subjects. SETTING: Occupational therapy section of a large academic medical center. OTHER PARTICIPANTS: Twenty adult volunteer student subjects from an occupational therapy education (OTE) department were included. All were between ages 18 and 43 years, right hand dominant, and in excellent general health. There were 19 women and 1 man, reflecting gender distribution of the OTE student body. INTERVENTION: A simulated fusion of the carpometacarpal (CMC) joint of the thumb was achieved by immobilization in an individually fabricated splint designed to maximally restrict motion at the first CMC joint. Impairment ratings (baseline vs splinted) according to the AMA Guides were obtained by Greenleaf testing, and upper extremity function was quantitatively assessed before and after splinting. MAIN OUTCOME MEASURES: Measures of upper extremity function included grip and pinch strength, wrist torque, and speed of performance on the Valpar Small Tools test, Jebsen Hand Function test, and an exploratory measure, the Functional Life Activity Test (FLAT). RESULTS: Significant impairments were achieved for all subjects after splinting and according to Greenleaf testing. Splinting resulted in significant reductions in grip and pinch strength, wrist torque, and significant slowing of performance on the Valpar, Jebsen, and FLAT tests. Regressions of degree of impairment on degree of functional loss after splinting, and according to each of the above measures, were not significant. CONCLUSIONS: Impairment of the hand was simulated to a mild-to-moderate degree as measured according to the AMA Guides. This imposed significant reductions in motion at key joints of the wrist and hand as well as significant reductions in grip and pinch strength and wrist torque. A corresponding and significant slowing of performance on a variety of measures of upper extremity function of an industrial and nonindustrial nature was also seen. However, and for the first time, correlation and regression reveals that it is not possible to predict degree of functional loss attributable to degree of impairment for the hand. It thus appears that, for mild-to-moderate clinical impairments, the associated impairment rating is a poor estimator of functional loss at the hand and should be used cautiously, if at all, as a criterion for disability determination.

Abdominal wall hernias: review of herniography and correlation with cross-sectional imaging.

Herniography is an accurate means of identifying groin hernias when the clinical diagnosis is uncertain. Its role in evaluation of other types of ventral hernias is less clear; however, with minor modifications in technique, herniography is also useful in these cases. This article reviews the technique of herniography, normal variations in anatomy, and interpretation of herniograms of the groin and anterior abdominal wall on the basis of 72 patients studied over 3 1/2 years. Herniography is also compared with cross-sectional imaging techniques. Inguinal and femoral hernias are best shown and classified with herniography. Ventral hernias are well demonstrated by both herniography and cross-sectional imaging; however, herniation of only fat and supine imaging may lead to misdiagnosis with computed tomography or ultrasound. Spigelian hernias are probably best depicted with cross-sectional imaging. Diagnostic pitfalls of herniography are reviewed, including the need for obtaining postexercise radiographs, oblique radiographs, and tangential radiographs.