POCUS for Nephrologists: Basic Principles and a General Approach

Abstract

Point-of-care ultrasonography (POCUS) has evolved as a valuable adjunct to physical examination in the recent past and various medical specialties have embraced it. However, POCUS training and scope of practice remain relatively undefined in nephrology. The utility of diagnostic POCUS beyond kidney and vascular access is under-recognized. Assessment of fluid status is a frequent dilemma faced by nephrologists in day-to-day practice where multiorgan POCUS can enhance the sensitivity of conventional physical examination. POCUS also reduces fragmentation of care, facilitates timely diagnosis, and expedites management. Although the need for further imaging studies is obviated in selected patients, POCUS is not meant to serve as an alternative to consultative imaging. In addition, the utility of POCUS depends on the skills and experience of the operator, which in turn depend on the quality of training. In this review, we discuss the rationale behind nephrologists performing POCUS, discuss patient examples to illustrate the basic principles of focused ultrasonography, and share our experience-based opinion about developing a POCUS training program at the institutional level.

Keywords: POCUS; clinical nephrology; educational personnel; nephrologists; nephrology; physical examination; point of care ultrasound; sonography; training.

Figure 1.

Expedited patient care with point-of-care ultrasonography (POCUS). This infographic illustrates how POCUS can provide answers to focused clinical questions (pericardial effusion in this case) within minutes as opposed to consultative imaging.

Figure 2.

Scope of nephrology-related POCUS: Organ-specific focused questions that can be answered by bedside ultrasonography. Those marked with asterisk (*) indicate advanced sonographic applications requiring a higher operator skill level/additional training. Human body illustration licensed from Shutterstock. COVID-19, coronavirus disease 2019.

Figure 3.

Sonographic images from patients one and two. (A) Transverse and (B) longitudinal images of the suprapubic area demonstrating pelvic ascites. Note the irregular border with anechoic free fluid interdigitating among loops of bowel, better seen in long axis. (C) Subxiphoid four-chamber view of the heart showing an echogenic structure indicated by arrow in the right ventricle, suggestive of a thrombus. (D) Follow-up scan demonstrating resolution of the thrombus after anticoagulation therapy.

Figure 4.

Sonographic images from patients three, four and five. (A) Subxiphoid four-chamber view of the heart demonstrating pericardial effusion (arrowheads). (B) Mitral inflow Doppler in the apical four-chamber view demonstrating minimal variation in the flow velocity with respiration. Inspiratory reduction of peak velocity by approximately 25% is suggestive of tamponade physiology. (C) Lung ultrasound demonstrating vertical hyperechoic artifacts, that is B lines indicated by asterisks. (D) Right pleural effusion: anechoic area indicated by asterisk.

Figure 5.

Comparison of sonographic images from a cart-based machine and handheld devices. (A) Right kidney image obtained using a cart-based portable ultrasound system, GE logiq P9. The same kidney imaged using a (B) high-resolution (relatively expensive) handheld ultrasound device, Kosmos, and (C) low-resolution (less expensive) handheld ultrasound device, GE Vscan. (D) Parasternal long-axis view of the heart obtained using GE logiq P9, (E) Kosmos, and (F) GE Vscan systems. Note how the image quality changes from well defined to grainy when using a low-resolution system. As mentioned in the article text, adequacy of image quality essentially depends on the focused questions being asked.

Figure 6.

Flow chart demonstrating the key elements of setting up a POCUS program.