HEPATOBILIARY ULTRASOUND REFERRAL PATTERNS

REFERRAL PATTERNS FOR HEPATOBILIARY ULTRASOUND
There is an almost infinite number of reasons for performing abdominal ultrasound. Some of the more common referrals are discussed below.

Jaundice
This symptom is a frequent cause of referral for abdominal ultrasound. It is therefore essential for the sonographer to have a basic understanding of the various mechanisms in order to maximize the diagnostic information from the ultrasound scan. Jaundice, or hyperbilirubinaemia, is an elevated level of bilirubin in the blood. It is recognized by a characteristic yellow coloration of the skin and sclera of the eye, often accompanied by itching if prolonged. Bilirubin is derived from the haem portion of haemoglobin. Red blood cells are broken down in the liver into haem and globin, releasing their bilirubin, which is non-soluble. This is termed unconjugated bilirubin. This is then taken up by the liver cells and converted to a water-soluble form, conjugated bilirubin, which is excreted via the biliary ducts into the duodenum to aid fat digestion. By knowing which of these two types of bilirubin is present in the jaundiced patient, the clinician can narrow down the diagnostic possibilities. Ultrasound then further refines the diagnosis.

Jaundice can fall into one of two categories:
● obstructive (sometimes called posthepatic) in which the bile is prevented from draining out of the liver because of obstruction to the biliary duct(s)
● non-obstructive (prehepatic or hepatic) in which the elevated bilirubin level is due to haemolysis (the breakdown of the red blood cells) or a disturbance in the mechanism of the liver for uptake and storage of bilirubin, such as in inflammatory or metabolic liver diseases. Naturally, the treatment of jaundice depends on its cause. Ultrasound readily distinguishes obstructive jaundice, which demonstrates some degree of biliary duct dilatation, from nonobstructive, which does not.

Abnormal liver function tests
Altered or deranged liver function tests (LFTs) are another frequent cause of referral for abdominal ultrasound. Biochemistry from a simple blood test is often a primary pointer to pathology and is invariably one of the first tests performed as it is quick and easily accessible. Most of these markers are highly unspecific, being associated with many types of diffuse and focal liver pathology.

Other common reasons for referral
In some cases, the presenting symptoms may be organ-specific or even pathognomonic, simplifying the task of ultrasound diagnosis. Often, however,the symptoms are vague and non-specific, requiring the sonographer to perform a comprehensive and knowledgeable search. The non-invasive nature of ultrasound makes it ideal for the first-line investigation.

Upper abdominal pain
● Upper abdominal pain, the origin of which could be linked to any of the organs, is one of the most frequent causes of referral. The sonographer can narrow the possibilities down by taking a careful history.
● Is the pain focal? This may direct the sonographer to the relevant organ, for example a thick-walled gallbladder full of stones may be tender on gentle transducer pressure, pointing to acute or chronic cholecystitis, depending on the severity of the pain.
● Bear in mind that gallstones are a common incidental finding which may be a red herring. Always consider multiple pathologies.
● Is the pain related to any event which may give a clue? Fat intolerance might suggest a biliary cause, pain on micturition a urinary tract cause, for example.
● Is it accompanied by other symptoms such as a high temperature? This may be associated with an infective process such as an abscess.
● Could it be bowel-related? Generalized abdominal pain could be due to inflammatory or obstructive bowel conditions and knowledge of the patient’s bowel habits is helpful.
● Has the patient had any previous surgery which could be significant?

Palpable right upper quadrant mass
A palpable right upper quadrant mass could be due to a renal, hepatobiliary, bowel-related or other cause. The sonographer should gently palpate to get an idea of the size and position of the mass and whether or not it is tender. Specifically targeting the relevant area may yield useful and unexpected results, for example a Reidel’s lobe, colonic carcinoma or impacted faeces, which will help to guide the nature of further investigations.