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Re: Incidental findings on FAST scanning - a Welcome Bonus

Dear Editor

The use of Focused Assessment with Sonography for Trauma (FAST) is increasing widespread. The ability to perform a FAST scan is now a core skill required by the curriculum of UK Emergency Medicine Trainees. The use of FAST is, and only should be, used to answer binary “yes/no” questions. The limitations of the study should always be explained to the patient & documented in the notes. No Emergency Physician (EP) should consider themselves a radiologist.

I recently saw a patient with left sided abdominal pain & microscopic haematuria who presented late at night having sustained a blunt traumatic injury to the right side on his abdomen earlier that day. On examination, his abdomen was soft with mild left-sided tenderness that settled with paracetamol. The physiology, venous gas and blood tests were normal. Traditional teaching would suggest that minor renal trauma would require no further treatment or imaging and can be discharged. Motivated mainly be my desire to increase my numbers a FAST scan was performed. Whilst FAST negative his left kidney was clearly abnormal, it was swollen with dilated calyces. On this evidence he was admitted to our Clinical Decisions Unit overnight for formal Ultra Sound the next day. This confirmed the presence of obstructive hydronephrosis that required admission & further investigation by the Urologists.

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Re: Ultrasound training recommendations

Dear Editor,

I read with interest the recently published paper by J Brenchley et al concerning focussed assessment with sonography in trauma (FAST).[1] The authors stated that there is currently no agreed FAST training schedules. However, the Royal College of Radiologist has published ultrasound training recommendations for medical and surgical specialties which includes FAST scanning.[2] The working party included Mr PK Thompson (A&E Consultant, King’s College Hospital) as well as radiologists. The Faculty of Accident and Emergency Medicine have also approved these guidelines.

The training received by the emergency physicians in Brenchley’s study was less than that recommended by the royal college guidelines. This may have contributed to the slightly low sensitivity obtained. With more practical training, the accuracy could be further improved.

In addition, the study would show better correlation if it compares like with like. The FAST scans could be compared with an ultrasound scan performed by a consultant radiologist rather than with DPL, CT, laparotomy or post mortem. This may provide some suggestions for future research or audit.

References

1. Brenchley J, Walker A, Sloan JP, Hassan TB, Venables H. Evaluation of of focussed assessment with sonography in trauma (FAST) by UK emergency physicians. Emerge Med J. 2006;23:446-448.

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Re: Fast in children and other considerations

Dear Editor,

This study has proved the importance of focused assessment with sonography in trauma (1) (2) (3) in patients with blunt abdominal trauma. The same could have done for patients who are younger than 15 years and with a history of abdominal trauma and the results are shown to be the same (4).

The emergency physician sonographer's rate on the quality of the views as good, poor or inadequate for further further interpretation is arbitory and a more precise scoring system could have been implemented during the data collection. The ultrasound score can be defined as the depth of the deepest pocket of fluid collection measured in centimeters plus the number of additional spaces where fluid was seen (4).

The authors haven't thought of fluid in the pelvic cavity as a result pelvic pathology, more commonly due to a ruptured ectopic pregnancy. Unfortunately the authors haven't come across non of the patients who are suspected to have an ectopic pregnancy and the diagnosis of it by ultrasound scan is critical in the emergency department. The authors haven't mentioned about the sonographic appearance of small amount of intraperitoneal fluid over the uterine funds which is commonly known as the triangular cap (5). The over distended urinary bladder which mask small amount of intraperitoneal fluid has also to be considered and the authors haven't mentioned whether the bladder was empty or full during the sonographic assessment.

References

(1) Bode PJ et al. Abdominal ultrasound as a reliable indicator for coclusive laperotomy in blunt abdominal trauma. J Trauma 1993; 34(1):27-31.

(2) McKenney M. et al. Can ultrasound replace diagnostic peritoneal lavage in assessment off blunt abdominal trauma? J Trauma 1994; 37(3):439-41.

(3) Jehle D et al. Emmergency department ultrasound in the evaluation of blunt abdominal trauma. Am J Emerg Med 1993; 11(4):342-6.

(4) Ong AW.Predicting the need for laperotomy in pediatric trauma patients on the basis of the ultrasound score.J Trauma.2003 Mar; 54(3):503-8.

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Re: Sample size in sensitivity and specificity

Dear Editor,

First of all I would like to thank Dr. Brencley for his useful article about the usage of sonography in patients with abdominal trauma(1).

However there is an important limitation which was not pointed out in the discussion section. The sample size, 153 patients, was too little to predict the true sensitivity of foccused assesment with sonography in trauma (FAST). In this study there were 9 patients documented to have intraabdominal injury among 153 patients with abdominal trauma. This means the expected target disorder was %5.8. If we accept the expected sensitivity %95 with confidence interval of 95% and the rate of target disorder as above, the sample size will be 1258. If you you reduce the expected sensitivity, the needed sample size will also increase (2). Thus further studies with larger sample sizes are needed to determine the real sensitivity and specificity of FAST. Yours Sincerely.

References

1-Brenchley J, Walker A, Sloan JP, et al. Evaluation of of focussed assesment with sonography in trauma (FAST) by UK emergency physicians. Emerge Med J. 2006;23:446-448.