PoCUS in nephrology: a new tool to improve our diagnostic skills

Abstract

Point-of-Care Ultrasonography (PoCUS) aims to include a fifth pillar (insonation) in the classical physical examination in order to obtain images to answer specific questions by the clinician at the patient's bedside, allowing rapid identification of structural or functional abnormalities, enabling more accurate volume assessment and supporting diagnosis, as well as guiding procedures. In recent years, PoCUS has started becoming a valuable tool in day-to-day clinical practice, adopted by healthcare professionals from various medical specialties, never replacing physical examination but improving patient and medical care and experience. Renal patients represent a wide range of diseases, which lends PoCUS a special role as a valuable tool in different scenarios, not only for volume-related information but also for the assessment of a wide range of acute and chronic conditions, enhancing the sensitivity of conventional physical examination in nephrology. PoCUS in the hands of a nephrologist is a precision medicine tool.

Keywords: PoCUS; focused cardiac ultrasound; lung ultrasound; nephrology; venous congestion assessment.

Figure 1:

Systemic consequences of congestion. Abbreviations: GFR: Glomerular filtration rate. Adapted from [6].

Figure 2:

PoCUS strategies to assess congestion: LUS (Lung Ultrasound), VExUS (venous excess ultrasound grading system) and FoCUS (Focused Cardiac Ultrasound).

Figure 3:

Compartmental phenotypes of congestion by PoCUS: (A) No congestion, (B) Predominant tissue congestion, (C) Predominant vascular congestion and (D) Tissue and vascular congestion. Adapted from [7]

Figure 4:

(A) 8-zone lung ultrasound probe positions. (B) A lines or normal lung. (C) B lines or comets tails. (D) Left pleural effusion.

Figure 5:

(A) Vascular congestion patterns: Normal pattern in US congestion assessment. IVC <2cm. HVs: normal S>D pattern. PV: Continuous flow or pulsatility <30% Mild-moderate congestion: IVC ≥2cm. HVs: S<D pattern. VP: Pulsatility 30–49%. Severe congestion: IVC: ≥2cm, VHs: Reverse S. PV: Pulsatility >50%. (B) Intrarenal Venous flow patterns in venous congestion: Pulsed Doppler normal and progressive congestion patterns visualised in the renal vein, in relation to the increase in RAP (with a reduced scale, 20–30 cm/sec).

Figure 6:

Focused Cardiac Ultrasound (FoCUS): Classical planes and targets to be visualized by FoCUS. Abbreviations: LV: left ventricle, RV: Right ventricle, LVOT: Left ventricular outflow tract, MV: Mitral valve, TV: Tricuspid valve, LA: Left atrium, RA: Right atrium, VTI: Velocity time integral.