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【medical-news】超声在腹部钝伤的应用价值（胃肠
A 3.5-MHz sector or curvilinear ultrasound transducer is most commonly used. Sector probes may be better suited to scanning in the intercostal spaces and are slightly more useful if multiple superficial wounds or surgical emphysema limits the available acoustic windows. Use of either 2.5- or 5-MHz probes is not crucial, but if available, these probes will improve image quality. Transducer selection depends on the patient’s size and body habitus. Lower frequency transducers penetrate better in large and obese patients, and those of higher frequencies are generally reserved for smaller and pediatric patients.
Spectral or color Doppler modes are not necessary in basic applications but are a bonus if the integrity of major vascular pedicles needs to be assessed.
A hard-copy camera is considered mandatory for both medicolegal and record-keeping purposes and for comparison if subsequent follow-up examinations are performed. Thermoprints are the cheapest and quickest form of hard-copy images, although image quality is inferior to conventional or laser films. If the patient is examined in a bed that can be tilted head-down, the sensitivity of fluid detection may be increased, but this may not be practical in emergency situations.1
The sonographic appearance of free-flowing uncoagulated intraperitoneal blood is typically anechoic or contains multiple low-level echogenicities (Figure 1). Small amounts of fluid collect initially at the most dependent areas, usually the hepatorenal fossae, especially on the right side (Morrison’s pouch) (Figure 2), and the paravesical spaces and cul-de-sac. It also collects as a thin film on the surface of solid organs, probably as a result of capillary action. Moderate to large amounts of blood will spread to the paracolonic gutters and the subphrenic and perihepatic areas, sharply outlining the solid organs and bowel loops. Several routine sites are generally viewed to ensure a systematic and complete examination of the peritoneal spaces.2,7
Our usual practice is to begin the examination at the mid-coronal plane on the right side to detect fluid at Morrison’s pouch and the perinephric space. The right posterior costophrenic angle and diaphragm are also viewed to look for pleural fluid (Figure 3) or a subphrenic collection. This is followed by a transverse view with slight cranial tilting at the subxiphoid region to ensure that no pericardial free fluid is missed (Figure 4). The left side of the abdomen is screened in the mid-coronal plane for perisplenic and perinephric collections, as well as for left-sided free pleural fluid. The examination is concluded with a midline suprapubic view to assess the paravesical spaces and cul-de-sac. The entire examination can be completed in less than five minutes. In several studies, the sensitivity of fluid detection has been found to be over 90%.8-11
Blood that has coagulated may become isoechoic in relation to solid organ parenchyma, making its detection more difficult. Minor lacerations of solid organs or intraparenchymal hematoma may appear only as a subtle inhomogeneity of parenchymal echotexture and can easily be missed by the untrained eye.12 Figure 5 shows the ultrasound examination of a back-seat passenger who suffered upper abdominal trauma in a road traffic accident (RTA). The only ultrasound finding is a subtle change of parenchymal echogenicity indicative of minor liver laceration. There is no free peritoneal fluid or subcapsular hematoma to indicate its presence.
Figure 6 shows a young RTA victim who presented with delayed colic-type abdominal pain after minor abdominal trauma. Ultrasound showed an echogenic focus within the gallbladder. Without a history of, or predisposing factors for, gallstones, the appearance was suggestive of a blood clot within the gallbladder. The diagnosis was confirmed when ultrasound showed the lesion to be completely resolved several weeks later.
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作者:admin@医学,生命科学 2010-10-01 17:11
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