ULTRASOUND EXAMINATION IN POLYTRAUMA: PROBLEMS, POSSIBLE MISTAKES
Federal Scientific Clinical Center of Miners’ Health Protection,
Leninsk-Kuznetsky, Russia
The ultrasound examination in polytrauma is aimed for rapid acquisition of significant diagnostic information which characterized with high sensitivity and high negative predictive value that favor the right management of patient and good outcomes [1].
The ultrasound technique in examination of patients with injuries is used in Europe since 1970s. During this time it showed its consistency. Ultrasound is informative, as well as safe, available and cost effective technique [1, 2, 3, 4]. In comparison to computer tomography the technique has a number of advantages in view of mobility, ability of simultaneous realization with resuscitation procedures and the possibility of frequent repetitive examinations. The advantages determined the function of ultrasound in polytrauma from one side, and the number of the serious limitations from the other side.
The objective of this analysis was the characterization of the possibilities and the disadvantages, as well as object-conditioned limitations of ultrasound in polytrauma.
METHODS
Focused Assessment with Sonography in Trauma (FAST) takes place in severity of state and clinical instability. The presupposition of FAST is associated with the fact that traumatic injuries are accompanied by bleeding and appearance of free liquid in the certain regions. FAST is the screening aimed examination which is performed at patient’s bed and is aimed to help clinicians to identify presence of free liquid in abdominal, pleural and pericardial cavities [1, 5, 10]. In many clinics FAST is performed by doctors specialized in ultrasound diagnostics and by surgeons. FAST is not aimed to uniform identification of all possible pathologies, because patients’ state severity requires decrease in the time of examination. The duration has not to exceed 5 minutes. That’s why FAST is performed only as the primary investigation with the aim of rapid triage [1].
The main moments of the rapid and qualitative examination are presence of high quality equipment, adequate selection of transducers, clear adherence to methodology and experience of a doctor.
The carrying out of FAST must have the maximal closeness to patient (in operating room, in reception ward etc.). That’s why the portable scanners are used mostly. For exclusion of possible errors associated with bad quality of image it is desirable to use high quality scanners with the mode of color duplex scanning and possibility of digital recording. At the last time, with market appearance of lots of models of the digital portable scanners this objective became completely decidable.
The convex transducer with frequency of 2.5-5 MHz is most often used for examination. It is possible to use both the transducer with wide surface and the microconvex one, which is more comfortable for heart scanning.
In ultrasound examination the adherence to the guidelines is obligatory. A specialist has to look thorough all regions of possible fluid accumulation. In FAST for fluid identification in abdominal cavity the technique of fast scanning in four quadrants is recommended [1, 9-12]. It includes the estimation of the perihepatic space in section through the hepatorenal recess (Morison space), the estimation of the perisplenic space through the splenorenal section (Fig. 1, 2).
Fig. 1
Hepatorenal section
Fig. 2
Splenorenal sectionDuring examination of perihepatic and perisplenic spaces one ought to
simultaneously investigate the nearest regions of the left and the right pleural spaces (Fig. 3).
Fig. 3
Fluid in the pleural cavity. Hemothorax
In the pelvic section the presence of the liquid is estimated in the rectovesical space in men and in the deepening between the rectum and the poster
The fourth section is pericardial one (subcostal) which allows to visualize the fluid in the pericardium (Fig. 5)
Fig. 5
Pericardial section. No fluid in the pericardium
.ior wall of the uterus (Douglas pouch) in women (Fig. 4).
Fig. 4
Pelvic section
At all other conditions being equal the key factors of qualitative examination of patient are promptness and experience of doctor who performs an examination.
If a patient’s state is stable and time limit is more than 5 minutes, the profound scanning of the abdominal organs and the retroperitoneal space is performed for identification of signs of injuries to organs, vessels and for identification of hematoma.
RESULTS AND DISCUSSION
The full description of the possible changes in trauma identified with ultrasound technique is given in the monography “Polytrauma” [13].
The identification of fluid in abdominal cavity in patients with unstable hemodynamics after abdominal injury is an indication for emergent laparotomy. In patients with stable hemodynamics the presence of liquid in abdomen is an indication for computer tomography of abdomen and pelvis for estimation of localization and incidence of injuries to internal organs [1]. A possibility of false positive result of FAST is not high. The intestinal walls and the duodenum walls near the liver as anechoic strip (also inferior vena cava, gall-bladder) can be improperly considered as free fluid. For prevention of errors it is necessary to use the different transversely-spaced scans allowing to identify these structures and to use the mode of color mapping.
According to the study performed by S.M. Faisal Mosharraf, Vaqar Bari (The Aga Khan University Hospital, Karachi, Pakistan, 2011) the sensitivity of the ultrasound technique in identification of hemoperitoneum in abdominal trauma achieved 93.75 %, specificity – 99.24 %, accuracy – 98.64 %, the positive prognostic value – 93.75 % and the negative prognostic value – 99.29 %. The other authors indicate the lower sensitivity of the technique. Generally, the sensitivity of FAST in identification of free fluid in abdominal cavity is 63-100 % [5, 6, 7, 8]. The sensitivity of the ultrasound depends on the volume of identified fluid. In the figures 6 and 7 the cases of identification of free fluid in the abdominal cavity are indicated.
The figure 6 shows the case of severe trauma with severe bleeding. The large volume of blood in the abdomen was easy found during scanning in hepatorenal and pelvic sections. For the patient the laparotomy was performed urgently. The liver injury was found as the bleeding source, though the ultrasound did not show any precise signs. Nevertheless, the main objective of the ultrasound was achieved in this case: the patient was operated timely. In the figure 7 the other case of polytrauma is shown. The ultrasound physician found the signs of spleen injury and the presence of liquid in the abdomen. However, the blood volume was not enough and was identified with difficulties during the ultrasound examination. It is reasonable to assume that in the case of insufficient experience of the physician-researcher little amount of the liquid could be missed.
Also the ultrasonography has high sensitivity in identification of fluid in pleural spaces, pericardial cavity and in identification of pneumothorax.
At the same time, the multiple studies proved that the ultrasound had the low sensitivity (41 %) in identification of injuries to parenchymal organs in abdominal trauma as a source of hemoperitoneum. The above mentioned liver injury presents the example (Fig. 6).
Fig. 6
Hemoperitoneum in the patient with polytrauma and injury to the liver. Large volume of fluid identified during scanning in the pelvic section
Fig. 7
Small volume of fluid between intestinal loops in the patient with spleen injury
The very low sensitivity of the ultrasound was noted in identification of injuries to pancreas, diaphragm, bowel, in identification of hematoma in region of mesentery and in injuries to retroperitoneal structures. The disruptions of the hollow organs are practically impossible to identify with the ultrasound technique.
Despite of actuality of collection of the diagnostic findings during the ultrasound examination for patients with polytrauma, many reasons exist which do not allow to achieve the qualitative image. The reasons include mainly patient obesity, air and food mass in stomach and bowel, the adhesive process in the bowel after previous surgical interventions, the impossibility of breath holding and motor anxiety. Sometimes trauma is accompanied by subcutaneous emphysema. At that, the air can shield the image entirely (Fig. 8). In presence of the above mentioned scanning difficulties small amount of fluid or organ injury could be unidentified (Fig. 8).
Fig. 8
Full shielding of the pancreas and the part of the liver appeared as result of gas accumulation in the bowel and in the stomach
One or several hematomas can develop in injury to the tissues of the liver or the spleen without injury to the capsule. In case of small size of hematoma and in the lineal structure of the subcapsular formations it is difficult or impossible to identify them in the first hours after trauma. As hematomas present the organized clots with high content of aggregated erythrocytes and other blood components, they are similar to the organ according to the echogenicity. Even in serious injuries the parenchymal organs may have the normal appearance during the ultrasound examination. Sometimes in the first hours the site of the liver contusion appears as the region of higher echogenicity. The formation of hematoma happens in the following several days. In this regard it is very important to perform the dynamic ultrasound examination of patient.
The figure 9 shows the liver sonogram of the adolescent at the age of 15. During the primary examination in the first hours after trauma the presence of fluid in the abdomen and the signs of organ injuries were not found. The dynamic ultrasound was indicated. At the third day the repetitive examination in the 7th liver segment showed the formation of the small hematoma. The round hypoechogenic formation was found which had clear contours, non-uniform structure, with single anechoic regions. This means that in the first 24 hours the region of the liver contusion did not differ from the surrounding regions, and in the case of absence of control ultrasound examination the liver injury could be missed.
Fig. 9
The hematoma in the liver segment VII
The localization of hematomas in the liver segment VII is the most frequent, because this is the region of countercoup against the spine. Also the lateral segments VI and VII are often affected. Sometimes it is useful to use the color mapping mode. The identification of the region with poor vascular pattern can present the sign of the liver contusion.
The figure 10 shows another case of late diagnosis of the liver hematoma.
Fig. 10
Liver sonogram. Delayed hematoma
The patient at the age of 35 was admitted to the clinic from other city after eight days after the trauma. The patient had the severe skeletal trauma and traumatic brain injury. The ultrasound examination of the abdomen was performed during the primary admission at the day of the injury. It did not show any changes in parenchymal organs and signs of free fluid in the abdomen. The injury to the abdominal organs was excluded. The repetitive ultrasound examination was not performed. During the ultrasound examination in our clinic the liver hematoma was identified. Most likely, during the primary ultrasound examination the significant organ changes were absent, but the error was the absence of the control investigation for exclusion of delayed bleeding. After eight days the developed hematoma was easy found with the ultrasound examination.
Usually the injuries to extraperitoneal organs are not accompanied by intraabdominal bleeding. This category includes the renal injuries, injuries to pancreas and the duodenum (in injuries associated with seatbelt or in pelvic fractures). In renal injuries the ultrasound technique has lesser sensitivity than in liver and splenic injury. There is no possibility to study the kidneys with different approaches in the supine position. In the ultrasound examination it is impossible to distinguish the pararenal hematoma from pararenal urinoma. Therefore, the absence of fluid in the abdominal cavity after the ultrasound examination does not exclude possibility of severe injury in central abdominal compression trauma or hematuria. For patients with hematuria and pelvic and lumbar spine fractures the computer tomography should be performed for exclusion of significant organ injuries even in negative results of the ultrasound examination. The injuries to the mesentery and the bowel are even more complicated for the ultrasound diagnostics. A hematoma can be limited or adjoined to the bowel wall, without penetration into the low-lying lateral or low regions of the abdomen. Therefore, during the scanning in fourth sections the fluid will not be found. Air and masses in intestinal loops most commonly do not allow to locate such formations, especially in patients with supernutrition.
The figure 11 shows the sonogram of the patient with abdominal trauma. The hypoechogenic rim around the spleen pole was initially considered as the subcapsular hematoma of the spleen. During the operation the bleeding from the place of disruption of the mesentery and blood in the abdomen were found. There was no spleen injury.
Fig. 11
Free fluid in the splenorenal space
CONCLUSION
Surgeons must know about the high sensitivity of the technique in identification of free liquid in the abdominal cavity and about the low sensitivity in identification of bleeding source. Attending physician must understand clearly the possibilities and the limitations of the ultrasound technique. That’s why, in any discrepancy between clinical manifestations and results of the ultrasound diagnostics it is necessary to spread the diagnostic search (computer tomography, laparoscopy). The overreliance in ultrasound results can result in a number of errors. A negative result of FAST examination cannot exclude the presence of bleeding completely.
It is very important that bleeding can be continuous or delayed. Therefore, patients must receive dynamic examination in their stable state, but with such states as fractures of pelvis, spine, in hematuria etc.