The Common Vein Copyright 2008
Author: Charles Allison, MB ChB
Editor: Ashley Davidoff MD.
BACKGROUND:
The differential of right upper quadrant pain is wide. Visceral pain from the foregut (including liver and pancreas) typically presents in the epigastric region but may localize to the RUQ if there is sufficient parietal inflammation. Some possible etiologies of RUQ include:
Biliary colic, acute cholecystitis, cholangitis
Hepatitis, hepatic abscess, hepatoma
Renal colic, pyelonephritis, renal infarction
Retrocecal appendicitis
Right lower lobe pneumonia
Herpes zoster
Choice of imaging clearly hinges on the suspected diagnosis.
WHAT STUDY?
Ultrasound, CT and MR are the modalities most likely to be required.
Ultrasound is the investigation of choice in this patient with suspected biliary colic or cholecystitis and can also provide information on liver, pancreatic and renal lesions. It is relatively inexpensive and non-invasive but may be somewhat operator dependent.
CT is perhaps the investigation of choice when the differential cannot be narrowed. It is preferred over ultrasound for renal colic or pyelonephritis as it has a higher sensitivity and specificity (>90%) for detecting stones. It will also pick up appendiceal inflammation that ultrasound would clearly not image. It is fast and provides information on the full spectrum of liver, pancreatic and bowel pathologies as well as catching the bases of the lungs and hence possible pneumonias as the cause of the pain. It does however involve a relatively large dose of radiation.
MRI provides excellent cross sectional imaging, providing superior images of the soft tissues and organs. It is non invasive but expensive and may be more geographically limited than CT. It also takes much more scanning time in somewhat claustrophobic conditions hence some patients are not able to tolerate the procedure.
Some diagnoses are not aided by imaging, such as herpes zoster.
WHY?
Ultrasound is relatively inexpensive and non-invasive but may be somewhat operator dependent. It may be limited by some patient factors such as excessive size or presence of bowel gas obscuring the image.
CT scanning is very fast and provides information on the full spectrum of liver, pancreatic and bowel pathologies as well as catching the bases of the lungs and hence possible pneumonias as the cause of the pain. It does however involve a relatively large dose of radiation. The administration of iv contrast may enhance some pathologies such as the outer ring of abscesses or the rich vascular supply of tumors. Gas within low attenuation liver lesions is pathognomonic of abscess.
MRI provides equivalent diagnostic accuracy to CT in most pathologies. Though it does not carry the radiation burden of CT, it is more expensive, time consuming and may be more geographically limited and less acceptable to the patient. These factors make it less used than CT as a diagnostic modality in RUQ.
Plain abdominal radiographs are rarely helpful in the setting of RUQ pain. It may be possible to see renal stones (90% radioopaque), most commonly at the pelvocalcyceal junction, as the ureter crosses the pevic brim or at the trigone as the ureter enters the bladder. However, not all radio-opaque stones are visible on KUB. Intravenous urography (IVU) was previously performed, looking for delayed excretion of hydroureter, but the procedure may take a number of hours, and has now been supplanted by CT (without intravenous contrast) when renal stones are suspected.
WHEN?
Imaging should be performed at time of presentation if the patient is in acute pain to expedite diagnosis / management.
HOW TO ORDER?
It is important to reference the symptom or the sign as the clinical indication and not the diagnosis.
ie Patient with “RUQ pain” is acceptable, whereas R/O liver abscess is not acceptable.
Optimal ordering would list symptoms/signs as well as the putative diagnosis being investigated: ?RUQ pain, fever r/o liver abscess?. This allows the radiologist to suggest alternative imaging strategies if a suboptimal approach has been ordered.
PATIENT PREPARATION
The patient should be fasting for 4 hours before an ultrasound examination; the procedure takes about 30 minutes.
CT preparation depends on the use of contrast. For renal stones no contrast in required and the patient may be scanned immediately. Administration of oral contrast required drinking or NG administration of 30cc gastrograffin diluted in 900cc water to ensure it adequately coats the length of the bowel. Intravenous contrast in given in the scanner and may be timed to highlight the arterial or venous supply to a specific organ. The patient?s allergies, medications and renal function need to be identified before hand as the contrast is iodine based and carried risk of precipitating renal failure in at risk patients (diabetic, on metformin etc). The study itself takes about 1 minute once the patient is on the table
Patients undergoing MRI should be warned that they will be required to lie still in a confined tunnel-like space for up to 30 minutes. The machine is very noisy and ear protection will be provided. They will have a call button to abort the procedure if problem arises.
CLINICAL RED FLAGS:
RUQ pain in the setting of fever and jaundice (Charcot’s triad) suggests cholangitis, requiring prompt treatment with antibiotics and surgical referral for biliary drainage.
REFERENCES
Family Practice Notebook
http://www.fpnotebook.com/about.htm
Lecture Notes on General Surgery ? Ellis H, Calne R, Watson C; Blackwell Science 2001
Leçons sur les maladies du foie, des voies biliaires et des reins faites à la Faculté de Médecine de Paris.
– J. M. Charcot
Recueillies et publliées par Bourneville et Sevestre.
Paris: Bureaux du Progrés Médical & Adrien Delahaye, 1877. 480 pages.
English translation, New York, 1878.