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Biomedical subjects

K E Applegate

Publications and source records attributed to K E Applegate.

At least 19 recordsLinked to original sources
PubMed2001

Assessing physicians' accuracy in diagnosing paediatric patients with acute abdominal pain: measuring accuracy for multiple diseases.

In evaluating the accuracy of diagnostic tests there are many situations where the true disease status can be one of multiple disorders. For example, when paediatric patients suffer acute abdominal pain, the underlying diagnosis could be appendicitis, intestinal obstruction, gastroenteritis, urinary tract infection, etc. In this paper we describe a format for collecting data for the case of multiple truth states. This new format allows one to make pairwise comparisons of the diagnostic accuracy between all of the different truth states. We propose a summary measure of accuracy which is a weighted average of the pairwise estimates of accuracy. Estimators are derived for the variance and covariance of the estimated summary accuracy. The small sample properties of the estimators are evaluated in a Monte Carlo simulation study. The new data collection format and summary measure were used in a paediatric acute abdominal pain study; data from this study are used to illustrate the methods.

Abdomen, Acute↗
PubMed2001

Unenhanced helical CT in the evaluation of the urinary tract in children and young adults following urinary tract reconstruction: comparison with sonography.

PURPOSE: To compare the accuracy of unenhanced, helical CT with sonography for the detection of complications of urinary tract reconstruction. MATERIALS AND METHODS: Forty-six kidneys in 24 patients were examined with CT and sonography. All scans were assessed for ease of renal visualization, presence of renal, ureteral, and bladder calculi, renal scars, hydronephrosis, and abdominal wall hernia. The results of both imaging modalities were independently reported. RESULTS: CT provided excellent visualization of all 46 kidneys, while sonography provided poor visualization of 8 kidneys (17%) (P < 0.001). CT detected calculi in 10 kidneys, 1 ureter, and 7 bladders. Sonography detected calculi in only 2 kidneys, and 2 bladders. Overall, CT detected significantly more calculi than US (18 vs 4, P = 0.01). CT detected scarring in 15 kidneys, while sonography detected scarring in 10. Hydronephrosis was detected in 6 kidneys by CT and in 8 kidneys by sonography. Three abdominal wall hernias were seen at CT that were not seen at sonography. CONCLUSION: CT is superior to sonography for the detection of urinary tract calculi and renal scarring. CT will demonstrate abdominal wall hernias that are unsuspected.

Adolescent↗
PubMed2001

Spiral CT scanning technique in the detection of aspiration of LEGO foreign bodies.

BACKGROUND: Radiolucent foreign bodies (FBs) such as plastic objects and toys remain difficult to identify on conventional radiographs of the neck and chest. Children may present with a variety of respiratory complaints, which may or may not be due to a FB. OBJECTIVE: To determine whether radiolucent FBs such as plastic LEGOs and peanuts can be seen in the tracheobronchial tree or esophagus using low-dose spiral CT, and, if visible, to determine the optimal CT imaging technique. MATERIALS AND METHODS: Multiple spiral sequences were performed while varying the CT parameters and the presence and location of FBs in either the trachea or the esophagus first on a neck phantom and then a cadaver. Sequences were rated by three radiologists blinded to the presence of a FB using a single scoring system. RESULTS: The LEGO was well visualized in the trachea by all three readers (both lung and soft-tissue windowing: combined sensitivity 89 %, combined specificity 89 %) and to a lesser extent in the esophagus (combined sensitivity 31 %, combined specificity 100 %). The peanut was not well visualized (combined sensitivity < 35 %). The optimal technique for visualizing the LEGO was 120 kV, 90 mA, 3-mm collimation, 0.75 s/revolution, and 2.0 pitch. This allowed for coverage of the cadaver tracheobronchial tree (approximately 11 cm) in about 18 s. Although statistical power was low for detecting significant differences, all three readers noted higher average confidence ratings with lung windowing among 18 LEGO-in-trachea scans. CONCLUSION: Rapid, low-dose spiral CT may be used to visualize LEGO FBs in the airway or esophagus. Peanuts were not well visualized.

Arachis↗
PubMed2001

The "differential diagnosis" for multiple diseases: comparison with the binary-truth state experiment in two empirical studies.

RATIONALE AND OBJECTIVES: In practice readers must often choose between multiple diagnoses. For assessing reader accuracy in these settings. Obuchowski et al have proposed the "differential diagnosis" method, which derives all pairwise estimates of accuracy for the various diagnoses, along with summary measures of accuracy. The current study assessed the correspondence between the differential diagnosis method and conventional binary-truth state experiments. MATERIALS AND METHODS: Two empirical studies were conducted at two institutions with different readers and diagnostic tests. Readers used the differential diagnosis format to interpret a set of cases. In subsequent readings they interpreted the cases in binary-truth state experiments. Spearman rank correlation coefficients and the percentages of agreement in scores were computed, and the areas under the receiver operating characteristic curves were estimated and compared. RESULTS: The between-format Spearman rank correlation coefficients were 0.697-0.718 and 0.750-0.780 for the two studies; the between-reader correlations were 0.417 and 0.792, respectively. The percentages of agreement between formats for the two studies were 50.0%-51.7% and 72.9%-78.8%; the percentages of agreement between readers were 45.0% and 80%, respectively. In the first study there were several significant differences in the areas under receiver operating characteristic curves; in the second study these differences were small. CONCLUSION: The differences observed between the two formats can be attributed to within-reader variability and inherent differences in the questions posed to readers in the multiple-diagnoses versus binary-truth state reading sessions. The differential diagnosis format is useful for estimating accuracy when there are multiple possible diagnoses.

Confidence Intervals↗
PubMed2001

Cost-effectiveness analysis in radiology.

In the past 20 years, there has been increasing recognition of the need to consider cost in medical decision making. This period has seen an explosion in the number of economic evaluations appearing in the medical literature. Cost-effectiveness analysis is an objective systematic technique for comparing alternative health care strategies on both cost and effectiveness simultaneously. Cost-effectiveness analysis can be used to inform medical decision makers in the establishment of clinical practice guidelines and in the setting of health policy. Cost-effectiveness analysis is a state-of-the-art research tool with its own terminology and methods. It is critical that radiologists become familiar with the concepts and procedures of cost-effectiveness analysis so they can properly evaluate cost-effectiveness analysis studies and be more knowledgeable participants in the health care decision-making process. This article explains the rationale, terminology, and methods of cost-effectiveness analysis as applied to radiology.

Cost-Benefit Analysis↗
PubMed2001

Effect of cross-sectional imaging on negative appendectomy and perforation rates in children.

PURPOSE: To compare negative appendectomy and perforation rates in children who underwent ultrasonography (US), computed tomography (CT), or no imaging before urgent appendectomy. MATERIALS AND METHODS: All children who underwent urgent appendectomy during a 4(1/2)-year period were identified in a surgical billing database. Pathology reports were coded as negative or as showing acute inflammation or perforation. Imaging up to 14 days before appendectomy or abscess drainage was noted, and imaging-based diagnoses were compared with pathologic findings. Patient age and sex were recorded. RESULTS: Two hundred ninety-nine children, 176 (59%) male and 123 (41%) female (mean age, 10.4 years; age range, 1--21 years), underwent urgent appendectomy. One hundred twenty-six (42%) underwent no imaging, 121 (41%) underwent US with or without CT, and 52 (17%) underwent CT only; 44 (15%) underwent both US and CT. There were significantly higher rates of appendectomy with normal pathologic findings ("negative appendectomy") in patients who underwent no imaging (14% [18 of 126]) or US (17% [20 of 121]) versus the rates in those who underwent CT only (2% [one of 52]) (P =.02 and P =.007, respectively). The negative appendectomy rate was 7% in 96 patients who underwent CT with or without prior US. The perforation rates were not significantly different. CONCLUSION: As compared with children who underwent no preoperative imaging and those who underwent US, children who underwent CT had a significantly lower negative appendectomy rate, without a significantly higher perforation rate.

Acute Disease↗
PubMed2000

Evaluation of suspected appendicitis in children and young adults: helical CT.

PURPOSE: To evaluate the accuracy of helical computed tomography (CT) for the diagnosis of appendicitis in children and to assess the utility of CT in establishing alternative diagnoses. MATERIALS AND METHODS: The medical records of 154 children (median age, 12 years; age range, 1-20 years) who were suspected to have appendicitis and who underwent CT were reviewed. The gastrointestinal tract was opacified in 151 of 154 patients: Only orally administered contrast material was used in 126 patients; only rectally administered contrast material, in 21 patients; and both oral and rectal contrast material, in four patients. CT findings were correlated with surgical and histopathologic findings or with clinical follow-up findings. RESULTS: Sixty-four CT scans were interpreted as positive for appendicitis and included 58 true-positive and six false-positive scans. Ninety scans were interpreted as negative and included 87 true-negative and three false-negative scans. CT had a sensitivity of 95% and a specificity of 94% for the diagnosis of appendicitis. In addition, in 32 (34%) of 93 patients without appendicitis, an alternative diagnosis was established on the basis of CT findings. CONCLUSION: Helical CT is useful in a pediatric population to diagnose or exclude appendicitis and to establish an alternative diagnosis.

Administration, Oral↗
PubMed2000

Imaging evaluation of suspected appendicitis in a pediatric population: effectiveness of sonography versus CT.

OBJECTIVE: The purpose of this study was to compare the diagnostic accuracy of graded compression sonography with that of helical CT for the diagnosis of appendicitis in a pediatric and young adult population. SUBJECTS AND METHODS: Between June 1996 and April 1999, 386 pediatric and young adult patients with suspected appendicitis were examined using sonography, CT, or both: 233 underwent sonography only, 71 underwent CT only, and 82 underwent sonography and CT. All sonograms and CT scans were prospectively interpreted as showing positive or negative findings for appendicitis by one of six pediatric radiologists. CT and sonographic findings were correlated with surgical and histopathologic findings or findings at clinical follow-up. RESULTS: Helical CT had a significantly higher sensitivity (95% versus 78%, p = 0.009) and accuracy (94% versus 89%, p = 0.05) than graded compression sonography for the diagnosis of appendicitis in children, adolescents, and young adults. The specificity of both techniques was 93%. Twenty of 82 patients who underwent both sonography and CT had discordance between the findings of the two examinations. The CT results were correct in a significantly greater number of patients with discordant examinations (17/20 patients [85%]). CONCLUSION: Helical CT has a significantly higher sensitivity and accuracy than graded compression sonography for the diagnosis of appendicitis in a pediatric and young adult population, particularly in children more than 10 years old.

Adolescent↗
PubMed2000

Impact in the emergency department of unenhanced CT on diagnostic confidence and therapeutic efficacy in patients with suspected renal colic: a prospective survey. 2000 ARRS President's Award. American Roentgen Ray Society.

OBJECTIVE: Our objective was to evaluate the impact of unenhanced CT on clinician diagnostic confidence and therapeutic efficacy in emergency department patients with clinically suspected renal colic. SUBJECTS AND METHODS: Questionnaires were completed on 93 patients who were referred to the radiology department with clinically suspected renal colic. We prospectively surveyed the clinician's diagnostic confidence and treatment plan before and after unenhanced abdominal and pelvic CT. RESULTS: Fifty-six patients (60%) had positive findings for calculi, 20 patients (22%) had normal findings, and alternative diagnoses were found in 17 patients (18%). The clinician's diagnostic certainty of stones before CT was variable with the largest frequencies at 41-60% (n = 30) and 71-90% (n = 35). The diagnostic certainty of stones after CT showed movement toward either less than or equal to 10% (n = 25) or greater than or equal to 91% (n = 51). The mean change in diagnostic confidence was 34%. Fifty-seven patients (61%) had a change in treatment plan. Specifically, the need for urology consultation as the initial treatment plan was reduced from 24 patients to one patient. Plans for admissions suggested before CT (n = 11) were nearly cut in half (n = 6) after imaging. Lastly, seven patients who would have initially been discharged were admitted to the hospital after imaging. CONCLUSION: CT significantly increased emergency department clinician diagnostic confidence and altered initial treatment decisions in patients with suspected renal colic. Most often, CT confirmed a ureteral stone and allowed appropriate discharge or urologic intervention. In a smaller subset of patients, CT established a significant alternative diagnosis that allowed the prompt initiation of appropriate treatment.

Adult↗
PubMed1999

Prenatal detection of a Wilms' tumor.

Kidney tumors occur very rarely in utero but when present, they are most often congenital mesoblastic nephroma. A newborn boy was transferred to our hospital with a history of fetal renal mass which proved to be a Wilms' tumor. The clinical history, imaging results, and differential diagnosis are presented with a discussion of neonatal Wilms' tumor. While imaging may not specify the exact diagnosis, it provides staging and anatomic information for the surgeon and the oncologist.

Diagnosis, Differential↗
PubMed1999

Prenatal detection of a solitary liver adenoma.

Solitary liver adenomas are rare in children, especially in neonates, and can be difficult to distinguish from other more common liver tumors of newborns and infants. An otherwise healthy male neonate with a prenatal diagnosis of a liver mass underwent ultrasound and MRI followed by resection of the mass. The final histopathological diagnosis was hepatic adenoma. A discussion of the imaging evaluation, differential diagnosis, and literature review is presented.

Adenoma↗
PubMed1999

The "circle sign": a new sonographic sign of pneumatosis intestinalis - clinical, pathologic and experimental findings.

BACKGROUND: Pneumatosis intestinalis (PI) represents gas in the bowel wall. The appearance of PI using high-resolution ultrasound (HRUS) has not been well described. OBJECTIVE: The purpose of this report is to describe a new ultrasound sign of pneumatosis seen in three patients. This sign, called the "circle sign", is indicative of bubbles of gas within the circumference of the bowel, producing an appearance of a continuous echogenic ring on ultrasound. Further studies of the sonographic characteristics of pneumatosis were performed with an in vitro model. MATERIALS AND METHODS: HRUS was performed prospectively in three patients demonstrating extensive PI radiographically. The appearance of the gas was characterized and the behavior of the intramural bubbles was studied when the bowel was compressed with the ultrasound transducer. Either CT scan or pathologic correlation was obtained in all patients. Experimental models of PI using air injected into the wall of sausage casing were developed. RESULTS: The presence of echogenic gas bubbles within the circumference of the wall of the bowel seen with HRUS was shown to represent pneumatosis intestinalis at histologic examination or by CT scanning in the three study patients. In vitro studies confirmed the clinical impression that the use of compression is helpful in distinguishing intramural from intraluminal air. CONCLUSION: The presence of echogenic gas bubbles in the wall of the bowel, often seen as a circle within the circumference of the bowel, may be helpful in diagnosing PI on ultrasound using HRUS.

Adolescent↗
PubMed1998

Atypical manifestations of two cases of trisomy 9 syndrome: rethinking development delay.

Trisomy 9 syndrome is characterized by "bulbous" nose, microphthalmia, dislocated limbs, and other anomalies of skeletal, cardiac, genitourinary, and central nervous systems. With the exception of one reported case study, all surviving infants have had severe mental impairment. The prospect of severe mental retardation often overwhelms parents who are faced with prenatal diagnosis of trisomy 9. We report on two new cases of mosaic trisomy 9, both of whom are only mildly developmentally delayed. One patient presented with the distinctive facial appearance, large fontanels, and joint abnormalities. The other had none of the typical congenital abnormalities. However, the patient was found to have a congenital heart defect and hypoplastic left heart syndrome, which to our knowledge has not been reported previously in the trisomy 9 syndrome. When these two patients are added to the published patients with this syndrome, there appears to be a range of manifestations, especially with respect to mental status, which has not fully been recognized.

Abnormalities, Multiple↗
PubMed1997

Stricture of the duodenum and jejunum in an abused child.

We report a case of abdominal injury secondary to child abuse in which the child had both a duodenal hematoma and contained perforations of the duodenum and proximal jejunum. These injuries were evaluated by both CT scan and upper gastrointestinal (GI) series. The child's nausea and vomiting persisted despite conservative treatment; after 3 weeks a repeat upper GI series demonstrated high-grade duodenal obstruction. An exploratory laparotomy was performed and a calcified, fibrotic mesentery and strictures in the distal duodenum and proximal jejunum were found. To our knowledge, this unusual complication of blunt abdominal trauma has not been described in association with child abuse.

Abdominal Injuries↗