Dr. Matthew Kaptein (MK), from the University of Southern California in Los Angeles, California, discusses his abstract for the National Kidney Foundation’s 2016 Spring Clinical Meetings (SCM16), Real-Time Ultrasonography Enhances the Renal Consult: A Typical Case, with Dr. Kenar Jhaveri, AJKD Blog Editor.
AJKDblog: Why don’t you tell us a little about your research and abstract being presented at the NKF 2016 Spring Meetings?
MK: Physical examination is an integral part of patient assessment, and like any aspect of medicine, it can be improved. Real-time ultrasonography is an extension of the physical exam using more sophisticated tools. We use ultrasound to visualize internal structures non-invasively to assess their physiologic function in real time.
We started four years ago by focusing primarily on the inferior vena cava (IVC), which we thought was highest yield, and with time added to our assessment by including the heart, bladder, and eventually kidneys.
Nephrologists have the opportunity to be masters of volume management. We can give it intravenously, remove it with diuretics or ultrafiltration, or when it is near optimal, maintain it. Given such power, we should not proceed blindly. This is crucial in hospitalized patients, who are not in steady state and frequently have mismatch between blood pressure and intravascular volume, or between intravascular and extravascular volume, which may not otherwise be evident on physical exam.
Using ultrasound, we can see how the heart squeezes to qualitatively estimate cardiac contractility and get an idea of the cardiac output. We frequently see pericardial effusions that are not detected by auscultation or physical exam.
We use ultrasound of the IVC to estimate intravascular volume status, and guide volume management. The Starling curve demonstrates that for any given patient, there is a venous filling pressure which maximizes cardiac output. IVC ultrasound is most reliable when the IVC is overtly “flat” (small maximum diameter or large collapsibility, ascending limb of Starling curve, consistent with intravascular hypovolemia) or “FAT” (large diameter and small collapsibility, descending limb of Starling curve, consistent with intravascular hypervolemia).
As patients are frequently found to have IVCs that are overtly flat or FAT, we propose to optimize intravascular volume by giving volume to those with flat IVCs and removing volume from those with FAT IVCs, monitoring with frequent reassessment in the absence of overriding contraindication.
On the post-renal side, obstruction is a serious reversible and frequently asymptomatic comorbidity, commonly found incidentally in patients with AKI, CKD, or ESKD when we screen with bladder ultrasound. By performing the sonogram of the kidneys, we can qualitatively check for moderate to large hydronephrosis, multiple cysts, and—with practice—reliably estimate kidney size.
By the time we complete our physical exam, which includes ultrasonography, we have learned new information about our patient, which may alter our assessment and management plans.
AJKDblog: What do you think is the most common limiting factor in obtaining real-time ultrasounds to expedite care in the emergency room by the renal consultant?
MK: We use real-time ultrasound in the ICU, ward, emergency department, and clinic. A fairly serious limiting factor can be not having an available machine, as in our dialysis unit. Once you have the machine, you need to pick it up and use it daily for physical assessment of patients. This takes practice for proficiency. At least one person in each group has to get good enough to mentor the others.
The alternative is relying on formal ultrasonography, which creates a disconnect between those who order, perform, and interpret studies, creates delays between when clinical questions are asked and answered, and increases expense. These prohibit frequent or real-time use.
AJKDblog: Where do you and your group go from here?
MK: We have formalized what we believe is the focused ultrasound exam highest yield to nephrologists at the time of evaluation.
Ultrasound machines today are smaller and cheaper than ever. Focused real-time ultrasound is part of my physical exam of the present, and for the past two years I have most frequently used a model that fits in my coat pocket. We believe it has enhanced our ability to care for patients, and we aim to promote this as widely as possible.
We are teaching as many people as we can to become proficient during daily real-time patient assessment, starting with our fellows, residents, students, and nurse practitioner, so they can go out and teach others.
In our emergency department there is an ultrasound machine available at every bedside, and the RUSH and FAST exams are standard of care. We don’t see any reason why nephrologists should not also be using modern technology to improve patient care.
All Spring Clinical Meeting abstracts are available in the May issue of AJKD.