Biliary Obstruction: Double Barrel sign, Monkey Puzzle sign

Images and text Genevieve Carbonatto

A 73 year old man presents to your department jaundiced. He says he has not been feeling unwell but that over  the past 4 days  the white of his eyes have turned yellow as well as the skin of his face. His urine turned very yellow 4 days ago  and has progressively become dark. He has no pain anywhere. His GP has sent him in for investigation. He admits to being a heavy drinker. He has a past history of hypertension.  On examination he is jaundiced, has palmar erythema, a soft non tender abdomen and mild hepatomegaly. He is not distressed in any way.

You decide to do a point of care abdominal ultrasound focussing on the liver and the biliary system. The first thing you notice is the number of what appear to be vessels in the liver especially around the porta hepatis.

This apparent proliferation of vessels are actually a mixture of very dilated bile ducts and portal veins. The bile ducts are not usually seen if they are not dilated.

This conglomeration of  dilated bile ducts  has been referred to as the “monkey puzzle sign”.

With colour Doppler  the bile ducts can be distinguished from the vessels

With colour Doppler                                                              CBD 1.18 cm

Another feature of this liver exam is what has been referred to as the “double barrel sign” which essentially describes 2 tubes running side by side, which in this case is due to dilated bile ducts travelling along with the portal veins through the liver. Usually these bile ducts are not visible.

Left lobe of liver                                                                            Right lobe of liver

The patient also has large gallstones and gallbladder wall thickening with some pericolic fluid if you look very carefully at the scan through the GB in the transverse plane.

Gall bladder demonstrating large round stones and thickened gallbladder wall.

Pancreas, CBD not dilated at the level of the pancreas, pancreatic duct was also not dilated

These are his blood tests: Total bilirubin 410 micromol/l, albumin 35 g/l, GGT 510U/l, ALP 510 U/l,GGT 340 U/l,ALT 155 U/l, AST120U/l, WCC 5.5 , Hb 134 g/l platelets 280


How do we define point of care ultrasound? Where do we stop? What our our limits? Point of care ultrasound is an ultrasound performed by a medical practitioner  in a non radiology setting which tries to answer a very specific question. In this case – Is there biliary obstruction. It has severe limitations as it is operator dependent both in terms of skill and knowledge. It should direct our ongoing definitive investigations but not  necessarily replace these investigations.  The ultrasound in this case demonstrates biliary obstruction and a gallbladder full of stones with a thickened GB wall. The pancreas is bulky but the CBD is not dilated at that point nor is the pancreatic duct dilated. There is good information here which doesn’t replace a formal ultrasound (you have not followed the CBD to the pancreas or looked at  the liver  carefully for tumours or metastases ). A cause for this patient’s jaundice has been found – biliary obstruction. The surgical team can be  called to see the patient.  Further investigations and management include a CT scan, a formal abdominal ultrasound followed by an ERCP and  stent placement  and further blood tests to look for tumour markers.

Ultimately this man had a cholangiocarcinoma and on CT and formal US numerous liver lesions.

What are the causes of painless biliary obstruction?

Unfortunately the most likely cause for  painless jaundice is cancer, however inflammatory and post inflammatory causes are also a possibility.


  • cholangiocarcinoma
  • gallbladder adenocarcinoma
  • pancreatic adenocarcinoma
  • metastasis

Post inflammatory

  • pancreatitis
  • post radiation chemotherapy


  • AIDS cholangiopathy
  • Biliary parasites
  • Primary scerosing cholangitis

Teaching point: Understand your limitations when performing any point of care ultrasound. If you are insonating the liver  and you are surprised by the number of “vessels”, think about biliary obstruction and go back to basics – check the size of the CBD, look at the gallbladder, use colour to differentiate bile ducts from vessels.







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