According to a new study, a simple ultrasound approach might allow kidney dialysis patients to routinely check themselves for dialysis graft failure -- a condition that can result in morbidity or hospitalization.
Two studies that appear in the March 2000 issue of the American Journal of Kidney Diseases relied on sonography to survey patients while they underwent dialysis. Researchers from the department of surgery at the University of Washington School of Medicine in Seattle tested continuous-wave Doppler ultrasound to measure the flow rate of dialysis access.
While duplex ultrasonography and radiograph angiography has been used in the past to monitor graft access, "these methods require special training and/or laboratory tests. The purpose of this study is to test a simple CW Doppler method...that would take one minute, require less than one hour of training, and could be performed with a low-cost instrument," the authors wrote (AJKD, March 2000, Vol.35:3, pp.477-481).
Ideally, the authors suggest, "at some point in the future, the home dialysis patient may even be able to perform this examination without a trained professional."
A total of 20 patients at the Scribner Kidney Center in Seattle were part of this study. Fifteen of the volunteers had polytetrafluoroethylene (PTFE) grafts; the remainder had arteriovenous (AV) fistulae dialysis access grafts. Using a directional CW Doppler with a 4-MHz transducer, 253 examinations were performed over eight months.
Doppler spectral waveforms were obtained with a pump on, pump off, pump on sequence. In three cases, it was determined that the access grafts required revision.
"In a normally functioning hemodialysis access, there are higher Doppler frequencies in the dialysis access when the pump is off compared to when the pump is on ... in all three cases, studied before graft revision, the diastolic and systolic Doppler frequencies with the pump on were higher than with the pump off," the paper stated.
In addition to improving the efficiency of evaluating dialysis in patients who are at risk for graft failure, only the Doppler method is able to separate diastolic recirculation from systolic recirculation, where the presence of the former is a sign of access dysfunction, the authors concluded.
In a second case report in AJKD, clinicians from the division of nephrology at the University of Michigan in Ann Arbor used ultrasound for the first time to detect microembolic signals (MES) in hemodialysis accesses (AJKD, March 2000, Vol.35:3, pp.526-528).
In the first case, a 65-year-old woman with end-stage renal disease from type 2 diabetes mellitus was receiving chronic hemodialysis through a left forearm synthetic PTFE dialysis access graft. Because of severely compromised blood flow, the patient had a high rate of access recirculation. A 6 MHz ATL CL10-5 linear array transducer was used to measure the volume flow through her graft and examine the retrograde blood flow. MES was seen in the bloodstream within the graft, the authors noted.
In the second case, a 79-year-old patient with end-stage renal disease from thrombotic microangiopathy was receiving dialysis through a left arm AV fistula. Ultrasound detected MES downstream from the venous needle returning to the central circulation.
The authors could not pinpoint why MES occurred but offered several possible reasons, including air cavitation bubbles developing from turbulent blood flow around the needles or air introduced into the circulation from the dialysis circuit.
Finally, Japanese researchers used computed axial tomography to create an alternate muscle mass index for nutritional assessment of hemodialysis patients. Their findings are reported in the February 2000 issue of the American Journal of Clinical Nutrition.
By quantifying muscle mass, which represents the largest protein pool in the body, doctors can assess nutritional intake, a task that is difficult to achieve with conventional methods in hemodialysis patients because of an inability to clear creatinine, wrote the authors from the University of Shizuoka and Miyaji Hospital in Shimizu (Am J Clin Nutr, February 2000, Vol. 71:2, pp.485-490).
The group measured the cross-sectional area of the thigh with CT and compared the results with other muscle mass indicators. A high correlation was found between thigh muscle area (TMA) and creatinine production, indicating that TMA reflects total-body muscle mass, the study said.
Imaging also played a major role in the following studies:
- Dual-energy X-ray absorptiometry was used to assess skeletal muscle weakness in Dutch patients with chronic obstructive pulmonary disease. By imaging the whole-body and subregional fat-free mass, the clinicians from the University Hospital Maastricht in Horn found that both were significantly lower in patients with emphysema and chronic bronchitis (Am J Clin Nutr, March 2000, Vol. 71:3, pp.733-738).
- MRI was used to evaluate the development of cerebral lacunes in children who undergo therapy for brain tumors. The team from St. Jude Children's Research Hospital in Memphis retrospectively studied MR scans of 525 children with brain tumors over a decade. They determined that lacunar development was most likely for children under the age of 5 who underwent radiotherapy (Journal of Clinical Oncology, Feb. 2000, Vol. 18:4, pp.824).
- Children with obsessive-compulsive disorder or tics associated with streptococcal infection were imaged with MR. Researchers at National Institute of Mental Health in Bethesda, MD found that the average size of the caudate, putamen, and globus pallidus were greater in the 34 children with streptococcus-associated OCD and/or tics (American Journal of Psychiatry, Vol.157:2, pp.281-283).
- The severe complications that can be happen after pediatric mycoplasma pneumonia were imaged with high-resolution CT by clinicians from several Korean institutions including the Inje University Sanggye Paik Hospital in Seoul. Abnormalities, such as mosaic perfusion and bronchial wall thickening, were discovered with HRCT in 37% of the patients with pneumonia (Pediatrics, Feb.2000, Vol. 105:2, pp.372-378).
By Shalmali Pal
AuntMinnie.com staff writer
March 27, 2000
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