Kenneth K. Lau

Attenuation of aortic calcification with lanthanum carbonate versus calcium-based phosphate binders in haemodialysis: A pilot randomized controlled trial

Background:  Vascular calcification (VC) contributes to cardiovascular disease in haemodialysis (HD) patients. Few controlled studies have addressed interventions to reduce VC but non‐calcium‐based phosphate binders may be beneficial. No published randomized study to date has assessed the effect of lanthanum carbonate (LC) on VC progression.

Abnormal vocal cord function in difficult-to-treat asthma.

RATIONALE Upper airway dysfunction may complicate asthma but has been largely ignored as an etiological factor. Diagnosis using endoscopic evaluation of vocal cord function is difficult to quantify, with limited clinical application. OBJECTIVES A novel imaging technique, dynamic 320-slice computerized tomography (CT), was used to examine laryngeal behavior in healthy individuals and individuals with asthma. METHODS Vocal cord movement was imaged using 320-slice CT larynx. Healthy volunteers were studied to develop and validate an analysis algorithm for quantification of normal vocal cord function. Further studies were then conducted in 46 patients with difficult-to-treat asthma. MEASUREMENTS AND MAIN RESULTS Vocal cord movement was quantified over the breathing cycle by CT using the ratio of vocal cord diameter to tracheal diameter. Normal limits were calculated, validated, and applied to evaluate difficult-to-treat asthma. Vocal cord movement was abnormal with excessive narrowing in 23 of 46 (50%) patients with asthma and severe in 9 (19%) patients (abnormal > 50% of inspiration or expiration time). Imaging also revealed that laryngeal dysfunction characterized the movement abnormality rather than isolated vocal cord dysfunction. CONCLUSIONS Noninvasive quantification of laryngeal movement was achieved using CT larynx. Significant numbers of patients with difficult-to-treat asthma had excessive narrowing of the vocal cords. This new approach has identified frequent upper airway dysfunction in asthma with potential implications for disease control and treatment.

Effect of Alendronate on Vascular Calcification in CKD Stages 3 and 4: A Pilot Randomized Controlled Trial

BACKGROUND Vascular calcification contributes to cardiovascular disease in patients with chronic kidney disease (CKD). Few studies have addressed interventions to decrease vascular calcification; however, experimental studies report benefits of bisphosphonates. Recent studies of hemodialysis patients also suggest benefits of bisphosphonates on vascular calcification; however, no study exists in nondialysis patients with CKD. STUDY DESIGN We conducted a randomized controlled trial to determine the effect of bisphosphonates on vascular calcification in patients with CKD. SETTING & PARTICIPANTS 51 patients with CKD stages 3-4 were recruited from a hospital outpatient setting; 50 were treated with study medication. INTERVENTIONS Patients were randomly assigned to either alendronate, 70 mg (n = 25), or matching placebo (n = 25), administered weekly. OUTCOMES The primary outcome was change in aortic vascular calcification after 18 months. Secondary outcomes included superficial femoral artery vascular calcification, arterial compliance, bone mineral density (BMD), renal function, and serum markers of mineral metabolism. MEASUREMENTS At baseline and 12 and 18 months, computed tomography, pulse wave velocity using SphygmoCor (AtCor Medical, PWV Inc, www.atcormedical.com), and dual-energy x-ray absorptiometry were performed to measure vascular calcification, arterial compliance, and BMD, respectively. Analysis was by intention to treat, with a random-effect linear regression model to assess differences. RESULTS 46 patients completed the study (24 alendronate, 22 placebo); baseline mean age was 63.1 +/- 1.8 years, estimated glomerular filtration rate was 34.5 +/- 1.4 mL/min/1.73 m(2), 59% had diabetes, and 65% were men. 91% had aortic vascular calcification at the start and 78% showed progression. At 18 months, there was no difference in vascular calcification progression with alendronate compared with placebo (adjusted difference, -24.2 Hounsfield units [95% CI, -77.0 to 28.6]; P = 0.4). There was an increase in lumbar spine BMD (T score difference, +0.3 [95% CI, 0.03-0.6]; P = 0.04) and a trend toward better pulse wave velocity (-1 m/s [95% CI, -2.1 to 0.1]; P = 0.07) with alendronate. Femoral BMD was similar between groups. There was a nonsignificant decrease in kidney function in patients on alendronate therapy compared with placebo (-1.2 mL/min/1.73 m(2) [95% CI, -4.0 to 1.7]). LIMITATIONS Small sample size and baseline differences, especially with aortic vascular calcification, may have diminished any potential difference between groups. CONCLUSIONS Unlike previous studies of hemodialysis patients, alendronate did not decrease the progression of vascular calcification compared with placebo in patients with CKD during 18 months.

Extra-medullary haematopoiesis: A pictorial review of its typical and atypical locations

Extra‐medullary haematopoiesis (EMH) occurs in many haematological disorders and is secondary to insufficient bone marrow function or ineffective erythropoiesis. It usually presents as haematopoietic masses in several typical and atypical body locations. This pictorial review briefly discusses the common EMH locations encountered in clinical practice, including the liver, spleen, lymph nodes and paravertebral regions. Unusual presentation as focal hepatic and splenic masses is also discussed. Some atypical EMH locations are then presented together with their pathophysiology and relevant illustrations. These include EMH in the intra‐spinal canal, pre‐sacral region, nasopharynx and paranasal sinuses. Intra‐spinal EMH can cause cord compression and present with neurological symptoms. In these cases, urgent treatment may be required. Haematopoietic masses in the other atypical locations can present with obstructive symptoms or may be diagnosed incidentally on imaging. EMH in unusual locations need to be monitored with follow‐up imaging to ensure their stability. In some circumstances, tissue biopsy is appropriate to confirm the diagnosis and exclude other sinister pathology (e.g. malignancy). Treatment is only required where symptoms are present. Management options include blood transfusion, radiotherapy, hydroxyurea or surgical resection in selected cases.

Relationship between vascular calcification, arterial stiffness and bone mineral density in a cross-sectional study of prevalent Australian haemodialysis patients.

Background:  Cardiovascular disease in dialysis patients is associated with increased vascular calcification (VC) and arterial stiffness, both inversely correlated with bone mineral density (BMD). Few studies have correlated VC in the dialysis population with measurements of BMD and arterial compliance.

Diagnosis of vocal cord dysfunction in asthma with high resolution dynamic volume computerized tomography of the larynx

Background and objective:  Vocal cord dysfunction (VCD) often masquerades as asthma and reports have suggested that up to 30% of patients with asthma may have coexistent VCD. Diagnosis of VCD is difficult, in part because it involves laryngoscopy which has practical constraints, and there is need for rapid non‐invasive diagnosis. High speed 320‐slice volume CT demonstrates laryngeal function during inspiration and expiration and may be useful in suspected VCD.

Ins and outs of inferior vena cava filters in patients with venous thromboembolism: the experience at Monash Medical Centre and review of the published reports

Background:  Inferior vena cava (IVC) filters are an alternative management strategy to anticoagulation in patients with venous thromboembolism (VTE). However, an IVC filter has its own inherent risks and complications and may not be the best management strategy. The aims of this study were to evaluate our institution’s practice of permanent Vena Tech (B. Braun Medical S.A., Boulogne, France) and retrievable Gunther Tulip (William Cook Europe, Bjaeverskov) IVC filters and to review the available published reports.

Determination and Validation of Aortic Calcification Measurement from Lateral Bone Densitometry in Dialysis Patients

BACKGROUND AND OBJECTIVES Vascular calcification (VC) contributes to increased cardiovascular (CV) disease in dialysis patients and is inversely correlated with bone mineral density (BMD). Screening for VC may determine patients at greater CV risk and bone densitometry may have dual role in assessing VC as well as BMD. The aim of this study was to determine measurement of VC using dual-energy x-ray absorptiometry (DXA) with correlation to gold standard computed tomography (CT). DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Forty hemodialysis patients had abdominal aortic CT and lateral DXA of lumbar spine to determine aortic VC and BMD. Semiquantitative measurement of aortic VC from lateral DXA was determined using previously validated 24- and 8-point scales and correlated with aortic VC with CT. Anteroposterior (AP) and lateral DXA-reported BMD was compared with BMD from L2 through L4 with CT. RESULTS Patients, 70% men, 38% diabetic, had median age 58.5 yr. Aortic VC was present in 94% with CT and 68% on lateral DXA. For 24- and 8-point scores, intraclass correlation coefficients for intrarater agreement were 0.93 and 0.88, respectively. DXA-measured VC correlated with CT. Sensitivity and specificity for CT aortic VC > or = 500 HU was 50 and 86%, respectively, for DXA VC > or = 6 on a 24-point scale. Lateral DXA-reported BMD significantly correlated with BMD from CT, but AP DXA did not. CONCLUSIONS Lateral DXA may be useful because images may provide concurrent assessment of aortic calcification as well as more accurate lumbar spine BMD, avoiding some of the limitations of AP DXA.

Excessive dynamic airway collapse co-morbid with COPD diagnosed using 320-slice dynamic CT scanning technology

Tracheomalacia is a term used to describe weakness of the trachea. Strictly speaking, tracheomalacia means weakness of cartilaginous structures of the trachea, while excessive dynamic airway collapse (EDAC) describes invagination of the posterior membrane of the trachea leading to a ≥50% reduction in airway lumen.1 Tracheomalacia and EDAC are thought to exist in a significant portion of patients suffering from chronic obstructive pulmonary disease (COPD).2 An 88-year-old man presented with a 2 day history of episodic dyspnoea, wheeze and non-productive cough, on a background of COPD. Despite treatment …

Lateral lumbar X-ray assessment of abdominal aortic calcification in Australian haemodialysis patients

Aim:  Vascular calcification is prevalent in patients with chronic kidney disease. Abdominal aortic calcification (AAC) can be detected by X‐ray, although AAC is less well documented in anatomical distribution and severity compared with coronary calcification. Using simple radiological imaging we aimed to assess AAC and determine associations in prevalent Australian haemodialysis (HD) patients.