Abstract
Point-of-care ultrasound is an important imaging modality with a wide variety of uses. Its applications range from identification of life-threatening pathology to soft tissue foreign-body identification to procedural guidance. Because of its versatility, it is an ideal tool to be used in a setting where resources are limited and presentations vary widely such as urgent care.
Keywords
bedside ultrasound, point-of-care ultrasound
Introduction to Ultrasound
1
What is point-of-care (POC) ultrasound (US)?
US examinations performed at the bedside by practitioners, interpreted in real time, and used to answer specific clinical questions in order in improve or expedite patient care. Most US applications have a higher specificity than sensitivity, meaning that US is better as a “rule-in” tool for pathology.
2
What are the advantages of US in the urgent care setting?
When available to the trained provider, US is noninvasive, dynamic, and easy to repeat at the bedside. It has no radiation and does not require sedation. It has also been found to be cost-effective. It may be useful for augmenting the physical examination findings and for enhancing performance with procedures.
3
What common terminology is used to describe US images?
- •
Anechoic: complete absence of returning sound waves, appears black
- •
Isoechoic: structure has similar appearance to the surrounding tissue
- •
Hypoechoic: structure appears darker than the surrounding tissue
- •
Hyperechoic: structure appears brighter than the surrounding tissue
Fluids, including water and blood, are anechoic or hypoechoic (black or dark gray), and bone and air are hyperechoic (white) on US images. Soft tissue and muscle have echotextures with varying shades of gray.
4
What are the four main types of US probes and for what are they typically used?
- •
Phased Array: FAST, cardiac, abdominal imaging
- •
Linear: Thoracic, musculoskeletal, ocular, procedural guidance
- •
Curvilinear: Abdominal imaging, transabdominal obstetrical and gynecological imaging, cardiac
- •
Intracavitary probe: Transvaginal obstetrical and gynecological imaging, peritonsilar abscess evaluation
FAST
5
What is the purpose of the focused assessment with sonography for trauma (FAST) examination?
The FAST examination can provide quick and reliable information on potential bleeding into the peritoneal, pericardial, or pleural spaces and can identify clinically significant injury requiring operative intervention.
6
How do you perform the FAST examination?
There are four basic views:
- •
Right upper quadrant: Looking for fluid between the liver and kidney in Morison’s pouch. This is the most common site of fluid accumulation in adults. The probe is placed in the right mid-axillary line in the seventh to ninth intercostal spaces with the indicator toward the patient’s head.
- •
Left upper quadrant: Looking for fluid around the spleen and kidney. The probe is placed in the left posterior axillary line in the fifth to seventh intercostal spaces with the indicator toward the patient’s head.
- •
Suprapubic: To evaluate for fluid in the rectovesical pouch in male patients or pouch of Douglas in female patients. Two perpendicular views should be obtained, with the probe superior to the symphysis pubis and angled toward the patient’s feet, with the indicator oriented toward the patient’s head and to the patient’s right side.
- •
Subxiphoid: To evaluate for pericardial effusion and cardiac activity. The probe is placed almost flat on the patient’s abdomen just inferior to the xiphoid process, directed toward the patient’s left shoulder, with the indicator toward the patient’s right side.
7
What are the limitations of the FAST examination?
The FAST examination is not reliable for solid organ, retroperitoneal, or hollow viscous injuries.
8
What does blood look like on US?
Acute hemorrhage appears as an anechoic fluid collection, but as blood clots, may appear complex, hypoechoic, or even isoechoic to surrounding structures ( Fig. 54.1 ).
Soft Tissue/Musculoskeletal US
9
What utility does POC US have for soft tissue infections?
POC US improves the ability to detect the presence of drainable abscesses in the setting of soft tissue infections better than a physical examination. It also helps to identify important surrounding structures to aid in procedure planning and execution.
10
Describe how cellulitis and abscess appear on US
In cellulitis on US, there is fluid in the subcutaneous tissue, which appears as “cobblestoning” when hyperechoic fat lobules are separated by hypoechoic fluid ( Fig. 54.2 ). An abscess on US is a collection of hypoechoic fluid that has absence of internal vascular flow ( Fig. 54.3 ). The abscess size and depth can be measured, which can facilitate the drainage procedure.
