Abdominal pain is a frequent complaint in the ED and often requires a great deal of physician time and hospital resources to ensure an appropriate diagnosis and safe disposition. Primary examinations involving the abdomen are the screening exam of the gallbladder, abdominal aorta, and kidney.

Cholelithiasis -- The classic clinical presentation of cholelithiasis is well described as post-prandial right upper quadrant pain combined with point tenderness in that area. Unfortunately this picture often seems confused in the ED due to atypical presentations and/or the presence of multiple medical problems including diabetes and peptic ulcer disease. The vast majority of gallbladder disease is secondary to stone formation. Gallstones are found in at least 20% of women and 8% of men over the age of 40. Unfortunately, due to the stones' composition, most commonly mixed, they are visible on only 15% of plain films Regardless of the calculi make-up they are normally very reflective to ultrasonic rays. Quite often the stones will create an acoustic shadowing affect distal to the stone itself . This finding is highly diagnostic for the presence of cholelithiasis. Other important ultrasonic findings of gallbladder disease include gallbladder thickening of greater than 3mm and a "Sonographic Murphy's sign". The Sonographic Murphy's sign is the elicitation of point tenderness beneath the probe upon pressure above the gallbladder. The sensitivity and specificity of this sign alone for the presence of cholecystitis has been quoted at 90%.²³ In a matter of minutes with a bedside exam the physician is able to confirm or rebuke his clinical suspicions. The examining physician can then narrow the focus of the work-up or discharge the patient home with a planned formal examination and primary care visit. It is important to note the purpose of this screening exam is only to detect stones, not to identify intrahepatic pathology, pancreatic pathology or evaluate the common bile duct. All these findings are beyond the scope of a screening ultrasound.

Abdominal Aortic Aneurysm -- Abdominal Aortic Aneurysm (AAA) is a condition which clearly meets all criteria for being considered as a primary ED ultrasound examination. Its rapid diagnosis is imperative for patient's survival. The patient who presents with abdominal pain radiating to the back, hypotensive with a pulsatile abdominal mass following a syncopal episode is not a diagnostic dilemma. However, as noted before, these classic presentations are few and far between. More often it is the elderly patient with vague abdominal complaints or the middle-aged patient with symptoms mimicking simple nephrolithiasis that are missed or have delayed diagnosis. Although angiography and contrasted CT are both more specific tests, ultrasound can provide a rapid and effective alternative. In cases where time and/or resources are limited as with an unstable patient or an already busy CT scanner, ultrasound is an ideal tool in the ED.   There is a significant decrease in time to diagnosis resulting in markedly improved outcomes in patients with ruptured AAA.
Again this is simply a screening exam. Its goal is to evaluate for the presence or absence of an AAA . Since the aorta is a retroperitoneal structure, US can only accurately evaluate for dilatation not rupture. Performance of the exam can be done at bedside in less than 5 minutes. Even in the busiest ED, this is time well spent from both a patient care aspect as well as a risk management issue. Obviously rapid evaluation and diagnosis can have a definite effect on patient outcome. This fact is even clearer when treatment of an aneurysm would require transportation to another facility. By providing an early diagnosis with a screening US, the patient avoids the 1-2 hour delay of obtaining a CT scan. There is no doubt that this skill is important to all emergency physicians but may be especially valuable to those practicing in rural communities.

Renal Colic -- The third indication for the primary sonographic examination of the abdomen is nephrolithiasis. Although renal calculi themselves are rarely seen on US, hydronephrosis is easily demonstrated. Currently there are multiple ways to evaluate for the presence of renal stones. These include IVP, ultrasound and limited non-contrasted helical CT studies. Each of these studies has its pros and cons. It should be noted that both IVP and helical CT are more sensitive and specific for the identification of stones. However, limited US can rapidly determine the presence or absence of obstructive uropathy by evaluating for hydronephrosis. Although it is possible to have renal stones without signs of obstruction, prolonged pain normally occurs with ureteral and renal pelvis dilatation. Therefore, patients with well-defined pain and without dehydration, should have some degree of sonographic findings. This study is particularly useful in patients with dye allergies, renal insufficiency, congestive heart failure, suspected pregnancy and where non-contrasted CT is not an option. Even in institutions where helical CT is available, it may not be financially feasible or time efficient to delay patients in the ED 30- 90 minutes when a 5 minute bedside test may be diagnostic. From a medical-legal standpoint, the ability to confirm this diagnosis in older patients where AAA or mesenteric ischemia are also in the differential is extremely important. Once this diagnosis is confirmed by US, the management can begin with appropriate disposition and arrangement of urology follow-up. The patient is then able to leave the ED with a firm understanding of their diagnosis. At the same time, the physician has the comfort of now discharging the patient in a timely manner and a definitive diagnosis. Follow-up confirmatory radiologic studies as an outpatient would be appropriate in the next 2-3 days.