Liver, biliary tract and pancreas

Published on 01/04/2015 by admin

Filed under Radiology

Last modified 22/04/2025

Print this page

This article have been viewed 1478 times

Chapter 4 Liver, biliary tract and pancreas

Methods of imaging the hepatobiliary system

2. Ultrasound (US):

a Transcutaneous

b Intraoperative

3. CT including:

a Routine ‘staging’ (portal venous phase) CT

b Triple phase ‘characterization’ CT

c CT cholangiography.

5. Endoscopic retrograde cholangiopancreatography (ERCP)

6. Percutaneous transhepatic cholangiography (PTC)

7. Operative cholangiography

8. Post-Operative (t-tube) Cholangiography

9. Angiography – diagnostic and interventional

10. Radionuclide imaging:

a Static, with colloid

b Dynamic, with iminodiacetic acid derivatives.

PLAIN FILMS

May be useful to demonstrate air within the biliary tree or portal venous system, opaque calculi or pancreatic calcification.

ULTRASOUND OF THE LIVER

Contraindications

Patient preparation

Not imperative, but fasting or restriction to clear fluids only required if the gallbladder is also to be studied.

Equipment

3–5-MHz transducer and contact gel. Selection of the appropriate pre-set protocol and positioning of focal zone will depend upon the type of machine, manufacturer and patient habitus.

Technique

1. Patient supine

2. Time-gain compensation set to give uniform reflectivity throughout the right lobe of the liver

3. Suspended inspiration

4. Longitudinal scans from epigastrium or left subcostal region across to right subcostal region. The transducer should be angled up to include the whole of the left and right lobes

5. Transverse scans, subcostally, to visualize the whole liver

6. If visualization is incomplete, due to a small or high liver, then right intercostal, longitudinal, transverse and oblique scans may be useful. Suspended respiration without deep inspiration may suffice for intercostal scanning. In patients who are unable to hold their breath, real-time scanning during quiet respiration is often adequate. Upright or left lateral decubitus positions are alternatives if visualization is still incomplete

7. Doppler studies:

a Pulsed Doppler

b Colour Doppler

c Power Doppler

d Doppler with US contrast media or ‘US echo-enhancing agents’

e Second harmonic Doppler with contrast

f Pulse inversion Doppler with contrast.

Additional views

Hepatic veins

These are best seen using a transverse intercostal or epigastric approach. During inspiration, in real time, these can be seen traversing the liver to enter the inferior vena cava (IVC). Hepatic vein walls do not have increased reflectivity in comparison to normal liver parenchyma. The normal hepatic vein waveform on Doppler is tri-phasic reflecting right atrial pressures. Power Doppler may be useful to examine flow within the hepatic segment of the IVC since it is angle-independent.

Portal vein

The longitudinal view of the portal vein is shown by an oblique subcostal or intercostal approach. Portal vein walls are of increased reflectivity in comparison to parenchyma. The normal portal vein blood flow is towards the liver. There is usually continuous flow but the velocity may vary with respiration.

Hepatic artery

This may be traced from the coeliac axis, which is recognized by the ‘seagull’ appearance of the origins of the common hepatic artery and splenic artery. There is normally forward flow throughout systole and diastole with a sharp systolic peak.

Common bile duct

See below in ‘Ultrasound of the gallbladder and biliary system’

Spleen

The spleen size should be measured in all cases of suspected liver disease or portal hypertension. 95% of normal adult spleens measure 12 cm or less in length, and less than 7×5 cm in thickness. The spleen size is commonly assessed by ‘eyeballing’ and measurement of the longest diameter.¹ In children, splenomegaly should be suspected if the spleen is more than 1.25 times the length of the adjacent kidney,¹ normal ranges have also been tabulated according to age and sex.²

1 Loftus W.K., Metreweli C. Ultrasound assessment of mild splenomegaly: spleen/kidney ratio. Pediatr. Radiol.. 1998;28(2):98-100.

2 Megremis S.D., Vlachonikolis I.G., Tsilimigaki A.M. Spleen length in childhood with US: normal values based on age, sex, and somatometric parameters. Radiology. 2004;231(1):129-134.

Further reading

Albrecht T., Hohmann J., Oldenburg A., et al. Detection and characterisation of liver metastases. Eur. Radiol.. 2004;8(14 Suppl):25-33.

Kim T.K., Jang H.J., Burns P.N., et al. Focal nodular hyperplasia and hepatic adenoma: differentiation with low-mechanical-index contrast-enhanced sonography. Am. J. Roentgenol.. 2008;190(1):58-66.

Kono Y., Mattrey R.F. Ultrasound of the liver. Radiol. Clin. North Am.. 2005;43(5):815-826.

Shapiro R.S., Wagreich J., Parsons R.B., et al. Tissue harmonic imaging sonography: evaluation of image quality compared with conventional sonography. Am. J. Roentgenol.. 1998;171:1203-1206.

Wilson S.R., Burns P.N. An algorithm for the diagnosis of focal liver masses using microbubble contrast-enhanced pulse-inversion sonography. Am. J. Roentgenol. 2006;186(5):1401-1412.

Ultrasound of the Gallbladder and Biliary System

Indications

1. Suspected gallstones

2. Right upper quadrant pain

4. Fever of unknown origin

5. Acute pancreatitis

6. To assess gallbladder function

7. Guided percutaneous procedures.

Contraindications

Patient preparation

Fasting for at least 6 h, preferably overnight. Water may be permitted.

Equipment

3–5-MHz transducer and contact gel. Selection of the appropriate pre-set protocol and positioning of focal zone will depend upon the type of machine, manufacturer and patient habitus. A stand-off may be used for a very anterior gallbladder.

Technique

1. The patient is supine.

2. The gallbladder can be located by following the reflective main lobar fissure from the right portal vein to the gallbladder fossa

3. Developmental anomalies are rare but the gallbladder may be intrahepatic or on a long mesentery

4. The gallbladder is scanned slowly along its long axis and transversely from the fundus to the neck leading to the cystic duct.

5. It must be re-scanned in the left lateral decubitus or erect positions because stones may be missed if only supine scans are used.

6. Visualization of the neck and cystic ducts may be improved by head down tilt.

The normal gallbladder wall is never more than 3-mm thick.

Additional views

Assessment of gallbladder function

1. Fasting gallbladder volume may be assessed by measuring longitudinal, transverse and antero-posterior (AP) diameters.

2. Normal gallbladder contraction reduces the volume by more than 25%, 30 min after a standard fatty meal. Somatostatin, calcitonin, indometacin and nifedipine antagonize this contraction.

Intrahepatic bile ducts

1. Left lobe: transverse epigastric scan

2. Right lobe: subcostal or intercostal longitudinal oblique.

Normal intrahepatic ducts are visualized with modern scanners. Intrahepatic ducts are dilated if their diameter is more than 40% of the accompanying portal vein branch. There is normally acoustic enhancement posterior to dilated ducts but not portal veins. Dilated ducts have a beaded branching appearance.

Extrahepatic bile ducts

1. The patient is supine or in the right anterior oblique position.

2. The upper common duct is demonstrated on a longitudinal oblique, subcostal or intercostal scan running anterior to the portal vein. The right hepatic artery is often seen crossing transversely between the two.

3. The common duct may be followed downwards along its length through the head of the pancreas to the ampulla and, when visualized, transverse scans should also be performed to improve detection of intraduct stones.

The segment of bile duct proximal to the junction with the cystic duct (the common hepatic duct) is 4 mm or less in a normal adult; 5 mm is borderline and 6 mm is considered dilated. The lower bile duct (common bile duct) is normally 6 mm or less. Distinction of the common hepatic duct from the common bile duct depends on identification of the junction with the cystic duct. This is usually not possible with US. Colour-flow Doppler enables quick distinction of bile duct from ectatic hepatic artery. In less than one-fifth of patients the artery lies anterior to the bile duct.

Post-cholecystectomy

There is disagreement as to whether the normal common duct dilates after cholecystectomy. Symptomatic patients and those with abnormal liver function tests should have further investigations if the common duct measures more than 6 mm.

Further reading

Foley W.D., Quiroz F.A. The role of sonography in imaging of the biliary tract. Ultrasound Q.. 2007;23(2):123-135.

Ultrasound of the Pancreas

Indications

1. Suspected pancreatic tumour

2. Pancreatitis or its complications

3. Epigastric mass

4. Epigastric pain

6. To facilitate guided biopsy and/or drainage.

Contraindications

Patient preparation

Nil by mouth, preferably overnight.

Equipment

3–5-MHz transducer and contact gel. Selection of the appropriate pre-set protocol and positioning of focal zone will depend upon the type of machine, manufacturer and patient habitus. A stand-off may be required in thin patients.

Technique

1. The patient is supine.

2. The body of the pancreas is located anterior to the splenic vein in a transverse epigastric scan.

3. The transducer is angled transversely and obliquely to visualize the head and tail.

4. The tail may be demonstrated from a left intercostal view using the spleen as an acoustic window.

5. Longitudinal epigastric scans may be useful.

6. The pancreatic parenchyma increases in reflectivity with age, being equal to liver reflectivity in young adults.

7. Gastric or colonic gas may prevent complete visualization. This may be overcome by left and right oblique decubitus scans or by scanning with the patient erect. Water may be drunk to improve the window through the stomach and the scans repeated in all positions. One cup is usually sufficient. Degassed water is preferable.

The pancreatic duct should not measure more than 3 mm in the head or 2 mm in the body.

Endoscopic US (see p. 81) and intra-operative US are useful adjuncts to transabdominal US. EUS may be used to further characterize and biopsy pancreatic mass lesions. Intra-operative US is used to localize small lesions (e.g. islet cell tumours prior to resection).

Further reading

Eloubeidi M.A., Jhala D., Chhieng D.C., et al. Yield of endoscopic ultrasound-guided fine-needle aspiration biopsy in patients with suspected pancreatic carcinoma. Cancer. 2003;99(5):285-292.

Rizk M.K., Gerke H. Utility of endoscopic ultrasound in pancreatitis: a review. World J. Gastroenterol.. 2007;13(47):6321-6326.

Computed Tomography of the Liver and Biliary Tree

Contraindications

Contraindication to iodinated intravenous (i.v.) contrast medium (contrast-enhanced computed tomography (CECT)) – see Chapter 2.

Technique

Single-phase (portal phase) contrast-enhanced CT

This is the technique for the majority of routine liver CT imaging. The liver is imaged during the peak of parenchymal enhancement, i.e. when contrast-medium-laden portal venous blood is perfusing the liver. This begins about 60–70 s after the start of a bolus injection. Oral contrast may be given but is not necessary if only the liver is being investigated. Slice thickness will depend upon the CT scanner specification but should be 5 mm or less.

Multi-phasic contrast-enhanced CT

The fast imaging times of helical/multi-slice CT enable the liver to be scanned multiple times after a single bolus injection of contrast medium. Most liver tumours receive their blood supply from the hepatic artery, unlike the hepatic parenchyma, which receives 80% of its blood supply from the portal vein. Thus liver tumours (particularly hypervascular tumours) will be strongly enhanced during the arterial phase (beginning 20–25 s after the start of a bolus injection) but of similar density to enhanced normal parenchyma during the portal venous phase. Some tumours are most conspicuous during early-phase arterial scanning (25 s after the start of a bolus injection), others later, during the late arterial phase 35 s after the start of a bolus injection. Thus a patient who is likely to have hypervascular primary or secondary liver tumours should have an arterial phase scan as well as a portal venous phase CT scan (see above). Early and late arterial phase with portal venous phase is appropriate for patients with suspected hepatocellular cancer (triple phase). In general, late arterial and portal venous scans are appropriate to investigate suspected hypervascular metastases, although an alternative strategy would be to perform an unenhanced scan followed by a portal venous phase scan.

Haemangiomas often show a characteristic peripheral nodular enhancement and progressive centripetal ‘fill-in’. After the initial dual- or triple-phase protocol, delayed images at 5 and 10 min are obtained through the lesion.

COMPUTED TOMOGRAPHIC CHOLANGIOGRAPHY

Magnetic resonance (MR) cholangiography is non-invasive but sometimes fails to display the normal intra-hepatic ducts. Multidetector CT cholangiography can be useful in this instance. With this technique the biliary tree is opacified using an i.v. cholangiographic agent. Isotropic data from 0.625 mm section thickness can be reconstructed to provide high-resolution three-dimensional images.

Contraindications

Allergy to iodinated contrast agents.

Indications

1. Screening for cholelithiasis

2. Pre-operative screening of anatomy

3. Supected traumatic bile-duct injury

4. Other biliary abnormalities, e.g. cholesterol polyps, adenomyomatosis and congenital abnormalities.

Technique

1. Patient fasted for at least 6 h

2. 100 ml i.v. cholangiographic agent, e.g. meglumine iotroxate, infused for 50 min as a biliary contrast ¹ or iodipamide meglumine 52%- 20 ml diluted with 80 ml of normal saline infused over 30 min.²

3. CT scans should be obtained at least 35 min after infusion of contrast agent.²

1 Hashimoto M., Itoh K., Takeda K., et al. Evaluation of biliary abnormalities with 64-channel multidetector CT. Radiographics. 2008;28(1):119-134.

2 Schindera S.T., Nelson R.C., Paulson E.K., et al. Assessment of the optimal temporal window for intravenous CT cholangiography. Eur. Radiol.. 2007;17(10):2531-2537.

Further reading

Francis I.R., Cohan R.H., McNulty N.J., et al. Multidetector CT of the liver and hepatic neoplasms: effect of multiphasic imaging on tumor conspicuity and vascular enhancement. Am. J. Roentgenol.. 2003;180(5):1217-1224.

Erratum in. Am. J. Roentgenol.. 2003;181(1):283.

Oto A., Tamm E.P., Szklaruk J. Multidetector row CT of the liver. Radiol. Clin. North Am.. 2005;43(5):827-848.

Computed Tomography of the Pancreas

Indications

1. Epigastric pain

2. Obstructive jaundice

3. Suspected pancreatic malignancy

4. Acute pancreatitis and its complications

5. Chronic pancreatitis and its complications.

Contraindications

2. Contraindication to iodinated intravenous contrast medium – see Chapter 2.

Technique

1. Negative (e.g. water) or positive (e.g. iodinated) oral contrast may be given. A positive oral contrast agent is contraindicated if CT angiography is to be performed. Volume and timing of oral contrast agent will depend upon whether it is necessary to opacify distal bowel loops.

2. Venous access is obtained.

3. The patient is supine on the CT scanner.

4. A scout view is obtained.

5. A non-contrast enhanced examination can be performed initially if detection of subtle calcification is required.

6. The volume of i.v. contrast used will depend upon the type of scanner. Faster acquisition will necessitate a smaller volume of contrast, generally 100 ml or less. The timing of the scan in relation to i.v. contrast will depend upon the clinical question. Pancreatic phase enhancement (40 s after commencement of bolus injection) is necessary for optimum contrast differences between pancreatic adenocarcinoma and normal pancreatic tissue, with portal venous phase scans included in the protocol to investigate hepatic metastatic disease. Islet cell tumours and their metastases may show avid enhancement on arterial phase scans and become isodense with normal pancreatic tissue on portal phase scans. A portal phase scan is generally necessary to investigate flow and the relationship of the tumour to the portal vein.

7. The volume and strength of the i.v. contrast will depend upon the speed of the scanner.

8. Slice thickness should be 3 mm or less.

Further reading

Fletcher J.G., Wiersema M.J., Farrell M.A., et al. Pancreatic malignancy: value of arterial, pancreatic, and hepatic phase imaging with multi-detector row CT. Radiology. 2003;229(1):81-90.

Goshima S., Kanematsu M., Kondo H., et al. Pancreas: optimal scan delay for contrast-enhanced multi-detector row CT. Radiology. 2006;241(1):167-174.

Magnetic Resonance Imaging of the Liver

Indications

1. Lesion detection particularly prior to hepatic resection for hepatic metastatic disease.

2. Lesion characterization following detection by CT or US.

Magnetic resonance (MRI) is rapidly emerging as the imaging modality of choice for detection and characterization of liver lesions. There is high specificity with optimal lesion-to-liver contrast and characteristic appearances on differing sequences and after contrast agents. Focal lesionsmay be identified onmost pulse sequences. Most metastases are hypo- to isointense on T1 and iso- to hyperintense on T2-weighted images. However, multiple sequences are usually necessary for confident tissue characterization. The timing, degree and nature of tumour vascularity form the basis for liver lesion characterization based on enhancement properties. Liver metastases may be hypo or hyper-vascular.

Magnetic resonance imaging pulse sequences

Common pulse sequences are:

1. T1-weighted spoiled gradient echo (GRE)

This has replaced the conventional spin-echo sequence. In and out of phase scans are used to investigate patients with suspected fatty liver.

2. Magnetization-prepared T1-weighted GRE

A further breath-hold technique with very short sequential image acquisition.

3. T1-W GRE fat suppressed volume acquisition

This sequence can be obtained rapidly following i.v. gadolinium.

4. T2-weighted spin echo (SE)

T2-weighted fast spin-echo (FSE; General Electric) or turbo spin-echo (TSE; Siemens)

Compared with conventional T2-weighted SE images, FSE/TSE images show:

1. fat with higher signal intensity

2. reduced magnetic susceptibility effects which are of advantage in patients with embolization coils, IVC filters, etc., but disadvantageous after injection of superparamagnetic oxide contrast agent

3. increased magnetization transfer which may lower signal intensity for solid liver tumours. These sequences may be obtained with fat suppression.

Fat suppression:

1. decreases the motion artifact from subcutaneous and intra-abdominal fat

2. increases the dynamic range of the image

3. improves signal-to-noise and contrast-to-noise ratios of focal liver lesions.

Very heavily T2-weighted sequences can be used to show water content in bile ducts, cysts and some focal lesions. These may be obtained as:

1. gradient echo breath-hold sequences (e.g. fast imaging with steady state prescession (FISP), fast imaging employing steady state acquisition (FIESTA))

2. as breath-hold very fast spin echo, e.g. half fourier acquisition single shot turbo spin echo (HASTE)

3. as non-breath-hold respiratory gated sequences used for magnetic resonance cholangiopancreatographic (MRCP).

Fat suppression is also used to allow better delineation of fluid-containing structures.

Short tau inversion recovery (STIR) also suppresses fat, which has a short T1 relaxation time. Other tissues with short T1 relaxation (haemorrhage, metastases and melanoma) are also suppressed.

Contrast-enhanced magnetic resonance liver imaging

Gadolinium-enhanced T1-weighted MRI

These probably do not increase sensitivity for focal abnormalities but may help in tissue characterization. When used in conjunction with spoiled GRE sequences it is possible to obtain images during the arterial phase (ideal for metastatic disease and hepatocellular carcinoma), portal phase (hypovascular malignancies) and equilibrium phase (cholangiocarcinoma, slow-flow haemangiomas and fibrosis). Hepatic arterial phase and fast spin-echo T2-weighed sequences are the most sensitive sequences for the detection of hepatic metastases of neuroendocrine tumours.

Liver-specific contrast agents

Standard gadolinium extracellular agents are commonly used for liver MRI as described above, but other contrast agents have been developed to enhance the distinction between normal liver and lesions, especially malignant lesions. These are mostly used in patients who are potentially suitable for major liver surgery, e.g. resection or transplantation:

1. Reticuloendothelial (RE) cell agents, e.g. super paramagnetic iron oxides (SPIO), are taken up by the RE or Kuppfer cells in normal liver giving a decrease in signal on T2- and especially T2*-weighted sequences. They can also be used with T1-weighted sequences for characterization. On T2*-weighted images, malignant lesions without RE cells show as higher signal than the background normal liver.

Examination with a SPIO agent may be combined with dynamic gadolinium enhancement in order to maximize the detection and characterization of metastases (and benign lesions) in a patient being considered for surgical resection of metastases. The same combination can be used in a patient with cirrhosis to maximize diagnosis and characterization of HCC v dysplastic or regenerative nodules.

2. Hepato-biliary agents are taken up by normal hepatocytes and excreted by normal liver into the bile. The normal liver shows increased signal on T1-weighted sequences for a prolonged period which varies according to the particular agent. Metastases, and other lesions not containing normal functioning hepatocytes, show as a lower signal than the background liver. Lesions containing hepatocytes will enhance to varying extents.

High signal contrast can be seen in the bile ducts. These agents are also excreted by the kidneys. Further details may be found in Chapter 2.

Magnetic resonance angiography

Contrast-enhanced spoiled GRE images may be obtained to give information with respect to the hepatic artery, portal vein and hepatic venous system.

Further reading

Catalano O.A., Sahani D.V., Kalva S.P., et al. MR imaging of the gallbladder: a pictorial essay. Radiographics. 2008;28(1):135-155.

Dromain C., de Baere T., Baudin E., et al. MR imaging of hepatic metastases caused by neuroendocrine tumors: comparing four techniques. Am. J. Roentgenol.. 2003;180(1):121-128.

Lutz A.M., Willmann J.K., Goepfert K., et al. Hepatocellular carcinoma in cirrhosis: enhancement patterns at dynamic gadolinium – and superparamagnetic iron oxide-enhanced T1-weighted MR imaging. Radiology. 2005;237(2):520-528. Epub 2005 Sep 28

Onishi H., Murakami T., Kim T., et al. Hepatic metastases: detection with multi-detector row CT, SPIO-enhanced MR imaging, and both techniques combined. Radiology. 2006;239(1):131-138. Epub 2006 Feb 16

Rappeport E.D., Loft A., Berthelsen A.K., et al. Contrast-enhanced FDG-PET/CT vs. SPIO-enhanced MRI vs. FDG-PET vs. CT in patients with liver metastases from colorectal cancer: a prospective study with intraoperative confirmation. Acta Radiol.. 2007;48(4):369-378.

Ward J., Robinson P.J., Guthrie J.A., et al. Liver metastases in candidates for hepatic resection: comparison of helical CT and gadolinium – and SPIO-enhanced MR imaging. Radiology. 2005;237(1):170-180. Epub 2005 Aug 26

Magnetic Resonance Cholangiopancreatography (MRCP)

MAGNETIC RESONANCE IMAGING OF THE PANCREAS

ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY

Diagnostic endoscopic retrograde cholangiopancreatography (ERCP) has almost been replaced by non-invasive investigations, e.g. CT and MRI. With the advances in non-invasive imaging of the biliary tree and pancreas, over 90% of ERCP procedures are performed with therapeutic (interventional) intent. ERCP is performed by physicians most commonly, but surgeons and radiologists do perform this technique.

Contraindications

1. Oesophageal obstruction; pyloric stenosis/gastric or duodenal obstruction

2. Previous gastric surgery that prevents access to the duodenum

3. Severe cardiac/respiratory disease.

Contrast medium

Pancreas

Bile ducts

LOCM 150; dilute contrast medium ensures that calculi will not be obscured.

Equipment

1. Side-viewing endoscope

2. Polythene catheters

3. Fluoroscopic unit with spot film facilities.

Patient preparation

1. Nil orally for 4–6 h prior to procedure

2. Premedication (see Chapter 18)

3. Antibiotic cover for patients with biliary obstruction, pseudocyst or high risk of endocarditis.

Preliminary film

Prone AP and left anterior oblique (LAO) of the upper abdomen, to check for opaque gallstones and pancreatic calcification/calculi.

Technique

The pharynx is anaesthetized with 50–100mg Xylocaine spray and the patient is sedated until conscious sedation is achieved. The patient then lies on the left side and the endoscope is introduced. The ampulla of Vater is located and the patient is turned prone. A polythene catheter prefilled with contrast medium is inserted into the ampulla, having ensured that all air bubbles are excluded. A small test injection of contrast under fluoroscopic control is made to determine the position of the cannula. It is important to avoid over-filling of the pancreas. If it is desirable both to opacify the biliary tree and the pancreatic duct, the latter should be cannulated first. A sample of bile should be sent for culture and sensitivity if there is evidence of biliary obstruction.

Aftercare

1. Nil orally until sensation has returned to the pharynx (0.5–3 h)

2. Pulse, temperature and blood pressure half-hourly for 6 h

3. Maintain antibiotics if there is biliary or pancreatic obstruction

4. Serum/urinary amylase if pancreatitis is suspected.

Further reading

Canlas K.R., Branch M.S. Role of endoscopic retrograde cholangiopancreatography in acute pancreatitis. World J. Gastroenterol.. 2007;13(47):6314-6320.

Intra-Operative Cholangiography

Indications

During cholecystectomy or bile duct surgery, to avoid surgical exploration of the common bile duct. This technique has been replaced in some centres by pre-operative MRCP.

Contraindications

Contrast medium

High osmolar contrast material (HOCM) or low osmolar contrast material (LOCM) 150, i.e. low iodine content so as not to obscure any calculi; 20 ml.

Equipment

1. Operating table with CR/DR available or a film cassette tunnel

2. Mobile X-ray machine.

Patient preparation

As for surgery.

Technique

The surgeon cannulates the cystic duct with a fine catheter. This is prefilled with contrast medium to exclude air bubbles which might simulate calculi.

1 Patey D.H., Le Quesne L.P., Whiteside C.G., et al. Discussion on cholangiography. Proc. R. Soc. Med.. 1960;53:851-860.

Post-Operative (T-Tube) Cholangiography

Indications

1. To exclude biliary tract calculi where (a) operative cholangiography was not performed, or (b) the results of operative cholangiography are not satisfactory or are suspect.

2. Assessment of biliary leaks following biliary surgery.

Contraindications

Contrast medium

HOCM or LOCM 150; 20–30 ml.

Equipment

Fluoroscopy unit with spot film device.

Patient preparation

Preliminary film

Coned supine PA of the right side of the abdomen.

Technique

1. The examination is performed on or about the 10th post-operative day, prior to removing the T-tube.

2. The patient lies supine on the X-ray table. The drainage tube is clamped off near to the patient and cleaned thoroughly with antiseptic.

3. A 23G needle, extension tubing and 20 ml syringe are assembled and filled with contrast medium. After all air bubbles have been expelled the needle is inserted into the tubing between the patient and the clamp. The injection is made under fluoroscopic control, the total volume depending on duct filling.

Films

PA and oblique views positioned under fluoroscopic control.

Aftercare

Complications

Due to the contrast medium

The biliary ducts do absorb contrast medium and cholangiovenous reflux can occur with high injection pressures. Adverse reactions are, therefore, possible, but the incidence is small.

Due to the technique

Injection of contrast medium under high pressure into an obstructed biliary tract can produce septicaemia.

PERCUTANEOUS TRANSHEPATIC CHOLANGIOGRAPHY

Indications

1. Prior to therapeutic intervention, e.g. biliary drainage procedure to relieve obstructive jaundice, or to drain infected bile

2. Place a precutaneous biliary stent

3. Dilate a post-operative stricture

4. Stone removal (see below)

5. To facilitate ERCP by rendez-vous technique

6. Rarely for diagnostic purposes only.

Contraindications

1. Bleeding tendency:

a Platelets less than 100 000

b Prothrombin time >2 s more than control.

If patient requires urgent procedure then platelet transfusion and FFP can be used to correct. Vitamin K will correct abnormal prothrombin time due to biliary obstruction.

2. Biliary tract sepsis except to control the infection by drainage.

Contrast medium

LOCM 150; 20–60 ml.

Equipment

1. Fluoroscopy unit with digital spot film device (tilting table optional)

2. Chiba needle (a fine, flexible 22G needle, 15–20-cm long)

3. Appropriate catheters and wire for drainage or interventional procedure planned.

Patient preparation

1. Haemoglobin, prothrombin time and platelets are checked, and corrected if necessary

2. Prophylactic antibiotics, e.g. ciprofloxacin 500–750 mg oral before and after procedure

3. Nil by mouth or clear fluids only for 4 h prior to the procedure

4. Ensure patient well hydrated, by i.v. fluids if necessary

5. Sedation (i.v.) and analgesia with oxygen and monitoring.

Preliminary imaging

US to confirm position of liver and dilated ducts.

Technique

1. The patient lies supine. Using US a spot is marked over the right or left lobe of the liver as appropriate. On the right side this is usually intercostal between mid and anterior axillary lines. For the left lobe this is usually subcostal to the left side of the xiphisternum in the epigastrium.

2. Using aseptic technique the skin, deeper tissues and liver capsule are anaesthetized at the site of the mark.

3. During suspended respiration the Chiba needle is inserted into the liver, but once it is within the liver parenchyma the patient is allowed shallow respirations. It is advanced into the liver with real-time US or fluoroscopy control.

4. The stilette is withdrawn and the needle connected to a syringe and extension tubing prefilled with contrast medium. Contrast medium is injected under fluoroscopic control while the needle is slowly withdrawn. If a duct is not entered at the first attempt, the needle tip is withdrawn to approximately 2–3 cm from the liver capsule and further passes are made, directing the needle tip more cranially, caudally, anteriorly or posteriorly until a duct is entered. The incidence of complications is not related to the number of passes within the liver itself and the likelihood of success is directly related to the degree of duct dilatation and the number of passes made.

5. Excessive parenchymal injection should be avoided and when it does occur it results in opacification of intrahepatic lymphatics. Injection of contrast medium into a vein or artery is followed by rapid dispersion.

6. If the intrahepatic ducts are seen to be dilated, bile should be aspirated and sent for microbiological examination. (The incidence of infected bile is high in such cases.)

7. Contrast medium is injected to outline the duct system and allow access for a guidewire or selection of an appropriate duct for drainage.

8. Care should be taken not to overfill an obstructed duct system because septic shock may be precipitated.

9. For diagnostic PTC only the needle is removed after suitable images have been recorded.

Films

Contrast medium is heavier than bile and the sequence of duct opacification is, therefore, gravity-dependent and determined by the site of injection and the position of the patient.

Using the undercouch tube with the patient horizontal:

4. If on a non-tilting table, rolling the patient onto the left side will fill the left ducts and common duct above an obstruction.

When the above films have shown an obstruction at the level of the porta hepatis, a further film after the patient has been tilted towards the erect position for 30 min may show the level of obstruction to be lower than originally thought.

Delayed films

Films taken after several hours, or the next day, may show contrast medium in the gallbladder if this was not achieved during the initial part of the investigation.

Aftercare

Bed rest, pulse and blood pressure half-hourly for 6 h.

Generalized

Bacteraemia, septicaemia and endotoxic shock. The likelihood of sepsis is greatest in the presence of choledocholithiasis because of the higher incidence of pre-existing infected bile.

BILIARY DRAINAGE

EXTERNAL DRAINAGE

This is achieved following transhepatic cannulation of the biliary tree as described above. The procedure may be performed to improve jaundice or sepsis prior to surgery or as a further percutaneous intervention.

INTERNAL DRAINAGE

This can be achieved following transhepatic (as above) or endoscopic cannulation of the biliary tree. A percutaneous drainage catheter may allow internal or external drainage with sideholes above and below the point of obstruction. At ERCP an endoprosthesis or stent is placed to drain bile from above a stricture or to prevent obstruction by a stone in the duct.

Indications

1. Malignant biliary stricture

2. Benign stricture following balloon dilatation.

Contraindications

As for percutaneous transhepatic cholangiography (PTC).

Contrast media

LOCM 200; 20–60 ml.

Equipment

1. Wide-channelled endoscope for introduction of endoprosthesis by ERCP

2. A biplane fluoroscope facility is useful but not essential for transhepatic puncture

3. Set including guidewires, dilators and endoprosthesis.

Patient preparation, see percutaneous transhepatic cholangiography above

Technique

Transhepatic

1. A percutaneous transhepatic cholangiogram is performed.

2. A duct in the right lobe of the liver is usually chosen that has a horizontal or caudal course to the porta hepatis. This duct is studied on US to judge its depth and then a 22G Chiba needle is inserted into the duct using US or fluoroscopic guidance. A coaxial introducer system is used over a 0.018 guidewire to allow 0.035 wire and catheter access into the bile ducts. If the duct is not successfully punctured, the Chiba needle is withdrawn but remains within the liver capsule allowing a further puncture attempt. Once a 0.035 wire is established in the bile duct a sheath can be inserted, e.g. 7-F. Bile can be drained through the side arm of the sheath while a catheter is manipulated over the wire. For internal drainage or stent insertion the wire and catheter must be passed through the stricture into the duodenum or post-operative jejunal loop. For external drainage, a suitable catheter can be inserted over the wire after the sheath is withdrawn. A variety of wires and catheters may be needed to cross difficult strictures. Failing this, external drainage is instituted and a further attempt is made to pass the stricture a few days later.

3. An internal/external catheter may be placed across the stricture and secured to the skin with sutures.

4. A metal biliary stent may be positioned and deployed across a malignant stricture to facilitate internal drainage of bile. Balloon dilatation may be required before or after stent deployment in some cases. A temporary external drainage tube may be left in place for 24–48 h.

Endoscopic

1. Cholangiography following cannulation of the biliary tree

2. Endoscopic sphincterotomy

3. A guidewire is placed via the channel of the endoscope through the sphincter and pushed past the stricture using fluoroscopy to monitor progress

4. Following dilatation of the stricture the endoprosthesis (plastic stent) is pushed over the guidewire and sited with its side-holes above and below the stricture. Metal biliary stents can also be placed at ERCP when appropriate.

Aftercare

1. As for percutaneous transhepatic cholangiography

2. Antibiotics for at least 3 days

3. An externally draining catheter should be regularly flushed through with normal saline and exchanged at 3-monthly intervals. (It is rare to leave a drain in situ for such a long period.)

Complications

1. As for PTC, ERCP and sphincterotomy

2. Sepsis – particularly common with long-term, externally draining catheters

3. Dislodgement of catheters, endoprostheses

4. Blockage of catheters/endoprostheses

5. Perforation of bile duct above the stricture on passage of guidewires.

Further reading

Burke D.R., Lewis C.A., Cardella J.F., et alSociety of Interventional Radiology Standards of Practice Committee. Quality improvement guidelines for percutaneous transhepatic cholangiography and biliary drainage. J. Vasc. Interv. Radiol.. 2003;14(9, part 2):S 234-S 236.

Republished from. J. Vasc. Interv. Radiol.. 1997;8:677-681.

Percutaneous Extraction of Retained Biliary Calculi (Burhenne Technique)

Indications

Retained biliary calculi seen on the T-tube cholangiogram (incidence 3%).

Contraindications

1. Small T-tube (<12-F)

2. Tortuous T-tube course in soft tissues

3. Acute pancreatitis

4. Drain in situ (cross connections exist between the drain tract and the T-tube tract).

Contrast medium

HOCM or LOCM 150. (Low-density contrast medium is used to avoid obscuring the calculus.)

Equipment

1. Fluoroscopy unit with spot film device

2. Steerable catheter system with wire baskets.

Patient preparation

1. Admission to hospital on the day prior to the procedure

2. Prophylactic antibiotics and pre-medication 1 h prior to the procedure

3. Analgesia during the procedure.

Technique

1. The patient lies supine on the X-ray table. A PTC is performed if a biliary drainage catheter is not already in situ.

2. The drainage catheter is removed over a guidewire and a sheath inserted in to the ducts (7 or 8-F).

3. Contrast is injected to identify stones and strictures.

4. If there is a stricture, advance a biliary manipulation catheter and guidewire (0.035) across it. Commence balloon dilatation over the guidewire (e.g. 8, 10 possibly 12 mm).

5. Attempt to dislodge stones with balloons into the Roux loop.

6. If this is unsuccessful pass Dormier basket through sheath and attempt to catch the stone in the basket.

7. Advance the basket into the Roux loop and release the stone into the loop.

8. Remove the basket.

9. Pass the guidewire, remove the sheath and place the biliary drainage catheter.

10. Intermittently inject the contrast media to clarify the position of the stones.

Aftercare

1. Pulse and blood pressure half-hourly for 6 h

2. Bed rest for 4–6 h.

Complications

Due to the contrast medium

1. Allergic reactions – rare

2. Pancreatitis.

Due to the technique

2. Perforation of the T-tube tract.

RADIONUCLIDE IMAGING OF LIVER AND SPLEEN

Indications

1. To assess liver for space-occupying lesions – essentially no longer performed because of greater utility of CT, MR and US

2. To characterize a focal liver lesion as possible focal nodular hyperplasia (these lesions contain Kupffer cells and hence take up colloid; other liver masses will be manifest as photopenic lesions)

3. To detect splenunculi (ectopic splenic tissue)

4. Assessment of liver function (displacement of activity of spleen and bone marrow).

Contraindications

Radiopharmaceuticals

^99mTc tin or sulphur colloid 80 MBq (ED 1 mSv), for SPECT 200 MBq (ED 2 mSv). Cleared by phagocytosis into the reticuloendothelial cells, where it is retained. Spleen is demonstrated as well as liver.

Equipment

1. Gamma-camera

2. Low-energy general purpose collimator.

Patient preparation

Technique

1. Patient lies supine

2. Image at 20 min post injection

3. Films: anterior with costal margin markers, posterior, left and right laterals.

500 kilocounts are used for each view. SPECT can be used when necessary.

An additional technique is first-pass dynamic flow study, which may occasionally be performed to improve differential diagnosis of liver masses.

Aftercare

Complications

Alternative investigative imaging modalities

1. Multidetector CT

2. MRI with reticuloendothelial contrast agent

3. ¹⁸FDG-PET for investigation of primary or secondary malignancy (see Chapter 11)

4. Platelet or denatured red-cell scan for splenunculi.

Further reading

Harding L.K., Notghi A. Gastrointestinal tract and liver. In: Sharp P.F., Gemmell H.G., Murray A.D., editors. Practical Nuclear Medicine. 3rd edn. London: Springer-Verlag; 2005:273-304.

Radionuclide Hepatobiliary and Gallbladder Radionuclide Imaging

Indications

1. Suspected acute cholecystitis

2. Assessment of gallbladder, common bile duct and sphincter of Oddi function ^1,²

3. Assessment of neonatal jaundice where biliary atresia is considered

4. Suspected bile leaks after trauma or surgery ³

5. Investigation of biliary drainage.

Contraindications

Radiopharmaceuticals

^99mTc-trimethylbromo-iminodiacetic acid (TBIDA) or other iminodiacetic acid (IDA) derivative; 80 MBq typical (1 mSv ED), 150 MBq max (2 mSv ED). ^99mTc-pertechnetate 10 MBq (0.13 mSv ED) to demonstrate stomach outline.

These ^99mTc-labelled IDA derivatives are rapidly cleared from the circulation by hepatocytes and secreted into bile in a similar way to bilirubin;⁴ this allows the assessment of biliary drainage and gallbladder function. A number have been developed with similar kinetics, but the later ones, such as TBIDA, have high hepatic uptake and low urinary excretion, giving better visualization of the biliary tract at high bilirubin levels than the early agents.

Equipment

1. Gamma-camera

2. Low-energy general purpose collimator.

Patient preparation

1. Nil by mouth for 4–6 h

2. For the investigation of biliary atresia, infants are given Phenobarbital orally 5 mg kg⁻¹ day⁻¹ in two divided doses for 3–5 days prior to the study to enhance hepatic excretion of radiopharmaceutical.

Technique

The imaging protocol depends upon the clinical question being asked. A dynamic study should be performed where it is important to visualize the progress of the bile in detail, e.g. post-surgery:

1. The patient lies supine with the camera anterior and liver at the top of the field of view

2. The radiopharmaceutical is injected i.v.

Films

1. 1-min 128×128 dynamic images are acquired for 45 min after injection.

2. 30–45 min post-injection when the gallbladder is well visualized, a liquid fatty meal (e.g. 300 ml full cream milk) is given through a straw to stimulate gallbladder contraction and imaging continued for a further 45 min. A gallbladder ejection fraction can be calculated.

3. If the gallbladder and duodenum are not seen, static images are obtained at intervals up to 4–6 h.

4. If images are suggestive of reflux, 100–200 ml of water is given through a straw to diffuse any activity in the stomach and thereby differentiate it from nearby bowel activity. 4 min before the end of imaging, 100 ml of water containing 10 MBq ^99mTc-pertechnetate may be given to delineate the stomach.

5. If no bowel activity is seen by 4–6 h and it is important to detect any flow of bile at all, e.g. in suspected biliary atresia, a 24-h image should be taken.

Additional techniques

Cholecystokinin (CCK) and morphine provocation ¹

Pharmacological intervention can be used in combination with TBIDA scanning to improve diagnosis of diseases affecting the gallbladder, common bile duct or sphincter of Oddi. CCK causes gallbladder contraction and sphincter of Oddi relaxation. An i.v. infusion of CCK is given over 2–3 min when the gallbladder is visualized 30–45 min after TBIDA administration. Dynamic imaging is continued for a further 30–40 min.

Quantitative measures of gallbladder ejection fraction and emptying rate can be calculated. It has been suggested that a slow CCK infusion over 30–60 min may improve specificity.⁵

Morphine causes sphincter of Oddi contraction. In a clinical setting of suspected acute cholecystitis, if the gallbladder is not observed by 60 min, an infusion of 0.04 mg kg⁻¹ over 1 min can be given and imaging continued for a further 30 min. Continued non-visualization of the gallbladder up to 90 min is considered to confirm the diagnosis. Morphine provocation has also found success in diagnosis of elevated sphincter of Oddi basal pressure.²

Quantitative analysis

Some investigators have calculated liver function parameters from dynamic studies, e.g. in order to attempt to differentiate between transplant rejection and hepatocyte dysfunction.

Aftercare

Complications

Monitor for adverse reactions to CCK and morphine.

1 Krishnamurthy S., Krishnamurthy G.T. Cholecystokinin and morphine pharmacological intervention during ^99mTc-HIDA cholescintigraphy: a rational approach. Semin. Nucl. Med.. 1996;26:16-24.

2 Thomas P.D., Turner J.G., Dobbs B.R., et al. Use of ^99mTc-DISIDA biliary scanning with morphine provocation for the detection of elevated sphincter of Oddi basal pressure. Gut. 2000;46(6):838-841.

3 Rayter Z., Tonge C., Bennett C., et al. Ultrasound and HIDA: scanning in evaluating bile leaks after cholecystectomy. Nucl. Med. Commun.. 1991;12:197-202.

4 Krishnamurthy G.T., Turner F.E. Pharmacokinetics and clinical application of technetium 99m-labeled hepatobiliary agents. Semin. Nucl. Med.. 1990;20:130-149.

5 Ziessman H.A. Cholecystokinin cholescintigraphy: victim of its own success? J. Nucl. Med.. 1999;40:2038-2042.

Further reading

Harding L.K., Notghi A. Gastrointestinal tract and liver. In: Sharp P.F., Gemmell H.G., Murray A.D., editors. Practical Nuclear Medicine. 3rd edn. London: Springer-Verlag; 2005:273-304.

Investigation of Specific Clinical Problems

THE INVESTIGATION OF LIVER TUMOURS

Investigation

This falls into three stages:

2. Characterization of the tumour

3. Assessment for surgical resection or staging for chemotherapy.

The clinical context and proposed management course usually determine the extent of investigation. Liver metastases are much commoner than primary liver cancers. Benign haemangiomas are also common, being present in 5–10% of the population. Other benign liver lesions, except cysts, are less common.

The clinical data correlated with the radiological investigations usually enable the character of a liver tumour to be determined with a high degree of probability. This can be confirmed with image-guided or surgical biopsy when appropriate. Many surgeons are averse to pre-operative biopsy in a patient with a potentially resectable/cureable lesion because of the small risk of disseminating malignant cells and the possibility of misleading sampling error. If biopsy is performed, it is sometimes important to sample the ‘normal’ liver as well as the lesion. The presence of cirrhosis may have a major impact on management. Hepatic resection is an established procedure for the management of selected hepatic metastases and primary liver tumours. Imaging is used to assess the number and location of tumours.

Ultrasound

Often the first modality to detect an unsuspected focal liver lesion or lesions, but no longer appropriate for screening all patients for liver metastases.

Computed tomography

Widely used for general screening and staging. The remainder of the abdomen and chest may also be imaged for full staging.

Magnetic resonance imaging

Very useful for determining the nature of an unknown liver lesion and for characterizing and staging patients who are considered to be suitable for surgical resection based on CT findings.

THE INVESTIGATION OF JAUNDICE

The aim is to separate haemolytic causes of jaundice from obstructive jaundice or hepatocellular jaundice. Clinical history and examination are followed by biochemical tests of blood and urine, and haematological tests.

Investigations

Obstructive jaundice

US is the primary imaging investigation. The presence of dilated ducts suggests obstructive jaundice. The bile ducts, gallbladder and pancreas should be examined to determine the level and cause of obstruction. MRCP or CT is often required to confirm the cause of the obstruction. If the suspected cause is tumour, a CT or MRI scan is performed to stage the tumour. MRCP is a non-invasive method of imaging the ducts to demonstrate the presence of stones and the level and cause of obstruction, especially combined with cross-sectional MRI in cases of tumour or suspected tumour. Endoscopic ultrasound also can be very helpful in cases where the diagnosis is in doubt after cross-sectional imaging and to confirm or exclude small tumours or very small stones.

ERCP and/or PTC for higher level obstruction should be reserved for those cases where a non-operative management strategy has been determined or in cases with severe jaundice requiring drainage before definitive treatment.

Non-obstructive jaundice

When US shows no dilated ducts and hepatocellular jaundice is suspected, liver biopsy is considered. There may be other US evidence of parenchymal liver disease or signs of portal hypertension.

If obstructive jaundice is still suspected despite the US result, then MRCP is required. Extrahepatic obstruction may be present in the absence of duct dilatation, and patients with primary sclerosing cholangitis or widespread intrahepatic metastases may have obstruction without duct dilatation.

THE INVESTIGATION OF PANCREATITIS

US can be the first investigation, but in acute pancreatitis the presence of a sentinel loop of bowel will often obscure the pancreas and prevent good visualization. Even if the pancreas is seen, it can appear normal in acute pancreatitis. The gallbladder and biliary tree should always be examined in the fasted patient to exclude the presence of gallstones which may be causing the pancreatitis.

CT is the next investigation. It should be performed initially without oral or i.v. contrast enhancement to look for the presence of calcification within the pancreas itself and to look for small gallstones, which can be obscured by the presence of oral contrast medium. Scans of the pancreas should then be obtained during portal venous phase enhancement. This will enable identification of non-perfused areas of pancreas, and the presence of pseudocysts, abscesses and phlegmons should be sought.

PANCREATIC PSEUDOCYSTS

Initial investigation can be with US. It should be remembered that pseudocysts can occur anywhere in the abdomen or pelvis and can even be found in the thorax. The spleen and left kidney provide acoustic windows to visualize the region of the tail of the pancreas.

CT scanning may also be performed if bowel loops prevent adequate visualization and should always be performed prior to radiologically guided intervention to prevent drainage of a pseudoaneurysm. (During ultrasonography supposed fluid collections can be interrogated with colour or duplex Doppler.)

Further reading

Burns P.N., Wilson S.R. Focal liver masses: enhancement patterns on contrast-enhanced images – concordance of US scans with CT scans and MR images. Radiology. 2007;242(1):162-174. Epub 2006 Nov 7

Hussain S.M., Semelka R.C. Hepatic imaging: comparison of modalities. Radiol. Clin. North Am.. 2005;43(5):929-947.

Rubens D.J. Hepatobiliary imaging and its pitfalls. Radiol. Clin. North. Am.. 2004;42(2):257-278.

Siddiqi A.J., Miller F. Chronic pancreatitis: ultrasound, computed tomography, and magnetic resonance imaging features. Semin. Ultrasound CT MR. 2007;28(5):384-394. Review

Wilson S.R., Kim T.K., Jang H.J., et al. Enhancement patterns of focal liver masses: discordance between contrast-enhanced sonography and contrast-enhanced CT and MRI. Am. J. Roentgenol.. 2007;189(1):W7-W12.

Related

A Guide to Radiological Procedures