Myron A. Pozniak

Determination of stone composition by noncontrast spiral computed tomography in the clinical setting

OBJECTIVES Several investigators have evaluated noncontrast computed tomography (NCCT) in predicting stone composition in vitro. We assessed NCCT in predicting stone composition in patients presenting to our emergency room with flank pain and stone disease. METHODS One hundred twenty-nine patients presenting to our university hospital with flank pain underwent renal colic protocol NCCT scans at the request of the emergency room physicians. A General Electric, high-speed advantage CT scanner was used at 120 kV, 200 mA, and 1.4:1 pitch, with collimation varying between 3 and 5 mm. Ninety-nine patients with predominantly (greater than 50%) calcium oxalate or uric acid composition after either stone passage or stone removal were identified. Each scan was analyzed by one of two radiologists, who determined the predominant attenuation for each stone. Stones once passed or retrieved were analyzed by Urocor Laboratories. The attenuation and attenuation/size ratio (peak attenuation/size in millimeters) were compared with the results of the stone analysis. RESULTS Eighty-two calculi predominantly composed of calcium oxalate and 17 calculi predominantly composed of uric acid were identified in 99 patients. The calculi ranged in size from 1 to 28 mm. A significant difference (P = 0.017, unpaired t test) was found between the Hounsfield measurement of uric acid calculi (mean 344 +/- 152 HU) and the Hounsfield measurement of calcium oxalate calculi (mean 652 +/- 490 HU). If only the Hounsfield units from stones 4 mm or larger were compared, the data were even more compelling (P = 0.002). However, using an attenuation/size ratio cutoff of greater than 80, the negative predictive value was 99% that a stone would be predominantly calcium oxalate. CONCLUSIONS Using peak attenuation measurements and the attenuation/size ratio of urinary calculi from NCCT, we were able to differentiate between uric acid and calcium oxalate stones.

Neuromuscular adaptations to concurrent strength and endurance training

PURPOSE The purpose of this study was to examine muscle morphological and neural activation adaptations resulting from the interaction between concurrent strength and endurance training. METHODS Thirty sedentary healthy male subjects were randomly assigned to one of three training groups that performed 10 wk of 3-d x wk(-1) high-intensity strength training (S), cycle endurance training (E), or concurrent strength and endurance training (CC). Strength, quadriceps-muscle biopsies, computed tomography scans at mid-thigh, and surface electromyogram (EMG) assessments were made before and after training. RESULTS S and CC groups demonstrated similar increases (P < 0.0001) in both thigh extensor (12 and 14%) and flexor/adductor (7 and 6%) muscle areas. Type II myofiber areas similarly increased (P < 0.002) in both S (24%) and CC (28%) groups, whereas the increase (P < 0.004) in Type I area with S training (19%) was also similar to the nonsignificant (P = 0.041) increase with CC training (13%). Significant increases (P < 0.005) in maximal isometric knee-extension torque were accompanied by nonsignificant (P <or= 0.07) increases in root mean squared EMG amplitude of the quadriceps musculature for both S and C groups. No changes (P > 0.38) in the EMG/torque relation across 20 to 100% maximal voluntary contractions occurred in any group. A small 3% increase (P < 0.01) in thigh extensor area was the only change in any of the above variables with E training. CONCLUSIONS Findings indicate 3-d x wk(-1) concurrent performance of both strength and endurance training does not impair adaptations in strength, muscle hypertrophy, and neural activation induced by strength training alone. Results provide a physiological basis to support several performance studies that consistently indicate 3-d x wk(-1) concurrent training does not impair strength development over the short term.

Compatibility of adaptive responses with combining strength and endurance training

Impairment in strength development has been demonstrated with combined strength and endurance training as compared with strength training alone. The purpose of this study was to examine the effects of combining conventional 3 d.wk-1 strength and endurance training on the compatibility of improving both VO2peak and strength performance simultaneously. Sedentary adult males, randomly assigned to one of three groups (N = 10 each), completed 10 wk of training. A strength-only (S) group performed eight weight-training exercises (4 sets/exercise, 5-7 repetitions/set), an endurance-only (E) group performed continuous cycle exercise (50 min at 70% heart rate reserve), and a combined (C) group performed the same S and E exercise in a single session. S and C groups demonstrated similar increases (P < 0.0167) in 1RM squat (23% and 22%) and bench press (18% for both groups), in maximal isometric knee extension torque (12% and 7%), in maximal vertical jump (6% and 9%), and in fat-free mass (3% and 5%). E training did not induce changes in any of these variables. VO2peak (ml.kg-1.min-1) increased (P < 0.01) similarly in both E (18%) and C (16%) groups. Results indicate 3 d.wk-1 combined training can induce substantial concurrent and compatible increases in VO2peak and strength performance.

Background Fluctuation of Kidney Function Versus Contrast-Induced Nephrotoxicity

OBJECTIVE The reported incidence of contrast-induced acute kidney injury varies widely. Almost no studies have been conducted to quantify the background fluctuation of kidney function of patients receiving iodinated contrast medium. The purpose of this study was a retrospective comparison of the incidence of acute kidney injury among patients undergoing CT with low-osmolar (iohexol) or isoosmolar (iodixanol) contrast medium with the incidence among patients undergoing CT without contrast administration. MATERIALS AND METHODS Creatinine concentration and estimated glomerular filtration rate were evaluated for 11,588 patients. Rates of acute kidney injury (defined as a 0.5 mg/dL increase in serum creatinine concentration or a 25% or greater decrease in estimated glomerular filtration rate within 3 days after CT) were compared among groups and stratified according to creatinine concentration and estimated glomerular filtration rate before the imaging examination. RESULTS In all groups, the incidence of acute kidney injury increased with increasing baseline creatinine concentration. No significant difference in incidence of presumed contrast-induced kidney injury was identified between the isoosmolar contrast medium and the control groups. The incidence of acute kidney injury in the low-osmolar contrast medium cohort paralleled that of the control cohort up to a creatinine level of 1.8 mg/dL, but increases above this level were associated with a higher incidence of acute kidney injury. CONCLUSION We identified a high incidence of acute kidney injury among control subjects undergoing unenhanced CT. The incidence of creatinine elevation in this group was statistically similar to that in the isoosmolar contrast medium group for all baseline creatinine values and all stages of chronic kidney disease. These findings suggest that the additional risk of acute kidney injury accompanying administration of contrast medium (contrast-induced nephrotoxicity) may be overstated and that much of the creatinine elevation in these patients is attributable to background fluctuation, underlying disease, or treatment.

Extraneous factors affecting resistive index.

Recently, numerous studies have referred to the resistive index as an accurate indicator of acute renal transplant rejection. We encountered several factors other than rejection that resulted in an elevation of the resistive index in both clinical and experimental situations. Any compressive effect on the kidney will elevate the resistive index. This compression may arise from an adjacent mass such as a fluid collection, most commonly hematoma, or even from excessive pressure transmitted via the transducer by a heavy-handed technician. Resistive index elevation also has been demonstrated in experimentally induced hypotension. Technically inaccurate scanning can yield a falsely low resistive index, but these previously mentioned entities can falsely elevate it, leading to an incorrect diagnosis of acute rejection.

Popliteal entrapment as a result of neurovascular compression by the soleus and plantaris muscles

Intermittent claudication may occur in well-conditioned athletes because of an unusual form of popliteal artery entrapment that results from overtraining. These patients complain of calf muscle cramping, rapid limb fatigue, and occasional paresthesias on the plantar surface of the foot when running on inclines or when repetitive jumping is performed. Results of plethysmographic screening tests for popliteal entrapment are positive in these patients. Magnetic resonance angiography and intravenous digital subtraction angiography studies, however, do not demonstrate findings typical of anatomic popliteal entrapment. No evidence exists of aberrant positioning of the popliteal artery in foot neutral positioning, but with forced plantar flexion, the neurovascular bundle is deviated and compressed laterally. Surgical exploration of the popliteal fossa demonstrates no obvious musculotendinous abnormality. Symptoms of claudication and arterial compression are relieved by surgical release of the soleus muscle from its tibial attachments, resection of its fascial band, and resection of the plantaris muscle.

Endovascular Abdominal Aortic Aneurysm Repair: Nonenhanced Volumetric CT for Follow-up

PURPOSE To evaluate the clinical usefulness of volumetric analysis at nonenhanced computed tomography (CT) as the sole method with which to follow up endovascular abdominal aortic aneurysm repair (EVAR) and to identify endoleaks causing more than 2% volumetric increase from the previous volume determination. MATERIALS AND METHODS The study had institutional review board approval. Images were reviewed retrospectively in a HIPAA-compliant manner for 230 CT studies in 70 patients (11 women, 59 men; mean age, 74 years) who underwent EVAR. The scannning protocol consisted of three steps: (a) contrast material-enhanced CT angiography before endovascular stent placement, (b) contrast-enhanced CT angiography 0-3 months after repair to depict immediate complications, and (c) nonenhanced CT at 3, 6, and 12 months after repair. At each follow-up visit, immediate aortic volume analysis was performed. If the interval volumetric change was 2% or less, no further imaging was performed. If the volume increased by more than 2% on the nonenhanced CT image, contrast-enhanced CT angiography was performed immediately to identify the suspected endoleak. Confidence intervals (CIs) were obtained by using bootstrapping to account for repeated measurements in the same patients. RESULTS Mean volume decrease was -3.2% (95% CI: -4.7%, -1.9%) in intervals without occurrence of a clinically relevant endoleak (n = 183). Types I and III high-pressure endoleaks (n = 10) showed a 10.0% (95% CI: 5.0%, 18.2%) interval volumetric increase. Type II low-pressure endoleaks (n = 37) showed a 5.4% (95% CI: 4.6%, 6.2%) interval volumetric increase. Endoleaks associated with minimal aortic volume increase of less than 2% did not require any intervention. This protocol reduced radiation exposure by approximately 57%-82% in an average-sized patient. CONCLUSION Serial volumetric analysis of aortic aneurysm with nonenhanced CT serves as an adequate screening test for endoleak, causing volumetric increase of more than 2% from the volume seen at the previous examination.

Sonography of Testicular Tumors and Tumor-Like Conditions: A Radiologic-Pathologic Correlation

Malignant testicular tumors are an important clinical problem, and ultrasound is the most frequently ordered imaging modality once a palpable scrotal mass is discovered. Numerous articles discussing the role of ultrasound in the evaluation of testicular pathology have confirmed the value of preoperative imaging. This article presents a review of imaging literature regarding testicular neoplasms, with an emphasis on correlation of gross and microscopic tumor pathology and imaging findings. Also included are sections on anatomy, epidemiology, histogenesis, and tumor markers.

Automated renal stone volume measurement by noncontrast computerized tomography is more reproducible than manual linear size measurement.

PURPOSE We compared the reproducibility of automated volume and manual linear measurements using same study supine and prone, low dose, noncontrast computerized tomography series. MATERIALS AND METHODS The patient cohort comprised 50 consecutive adults with a mean age of 56.4 years in whom renal calculi were identified during computerized tomography colonography screening. The largest stone per patient was assessed with the supine and prone computerized tomography series serving as mutual controls. Automated stone volume was derived using a commercially available coronary artery calcium scoring tool. Supine-prone reproducibility for automated volume was compared with intra-observer supine-prone manual linear measurement. Interobserver variability was also assessed for manual linear measurements of the same supine or prone series. RESULTS Mean ± SD linear size and volume of the 50 index calculi was 4.5 ± 2.7 mm (range 1.8 to 16) and 141.7 ± 456.1 mm(3), respectively. The mean supine-prone error for automated stone volume was 16.3% compared with an average 11.7% 1-dimensional intra-observer error for manual axial measurement. Only 2 of 15 cases with a volume error of greater than 20% were 5 mm or greater in linear size. The average interobserver linear error for the same computerized tomography series was 26.3% but automated volume measurement of the same series did not vary. CONCLUSIONS Automated noncontrast computerized tomography renal stone volume is more reproducible than manual linear size measurement and it avoids the often large interobserver variability seen with manual assessment. Since small linear differences correspond to much larger volume changes, greater absolute volume errors are acceptable. Automated volume measurement may be an improved clinical parameter to use for following the renal stone burden.

Phlegmasia cerulea dolens with compartment syndrome: a complication of femoral vein catheterization.

Objective: Central venous catheterization is commonly performed in the critically ill. The femoral vein is widely accepted as an insertion site with complications thought to be comparable to other central access sites. We used serial ultrasound examinations with Doppler to examine the evolution of a heretofore undescribed complication of femoral vein catheterization, phlegmasia cerulea dolens with compartment syndrome. Design: Serial ultrasounds were performed in patients before the insertion of femoral venous catheters and sequentially every 48 hrs while the catheters were in place. The noncatheterized leg served as a control. Setting: A trauma and life support center of a tertiary multidisciplinary critical care unit. Patient: A 32‐yr‐old man with respiratory failure as a consequence of a severe community‐acquired pneumonia that required central venous access for antibiotics because no peripheral sites could be obtained. Interventions: None. Measurements and Main Results: The initial ultrasound examination of both legs before femoral catheter insertion revealed no sign of venous thrombosis. Ultrasound of the catheterized leg at 48 hrs revealed a small nonocclusive thrombosis, whereas the opposite leg remained normal. At 72 hrs, the catheterized leg had clinical and ultrasonographic evidence of a massive thrombosis. A compartment syndrome defined by pressure measurements soon ensued and required emergent surgical release. Conclusions: This case report and a review of the available literature suggest that thrombosis associated with femoral vein catheterization should be considered when clinicians decide where to obtain central venous access when multiple sites are available. This report also suggests the utility of serial ultrasound examinations to define clinically nonapparent thrombosis as an early indicator of a potentially catastrophic complication.