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COMMENTARY Table of Contents   
Year : 2007  |  Volume : 17  |  Issue : 2  |  Page : 78-80
Hepatobiliary ascariasis


Dept. of Surgical Gastroenterology, SKIMS, Srinagar, Kashmir, India

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How to cite this article:
Shah O. Hepatobiliary ascariasis. Indian J Radiol Imaging 2007;17:78-80

How to cite this URL:
Shah O. Hepatobiliary ascariasis. Indian J Radiol Imaging [serial online] 2007 [cited 2020 Aug 15];17:78-80. Available from: http://www.ijri.org/text.asp?2007/17/2/78/33615
The authors [1],[2] of the two articles in this issue have demonstrated nicely that, using ultrasonography (USG), radiologists can make a diagnosis of hepato-biliary ascariasis.

Ascaroids have a tendency to explore small openings and once they are in the duodenum, enter the ampullary orifice, leading to biliary ascariasis. The worms may find their way into the ramifications of the intrahepatic ducts, especially those of the left lobe of liver. The liberated ova either dead or live, as well as the disintegrated worms provoke a non-specific foreign body reaction leading to formation of chronic granulomatous lesions in the liver parenchyma. Secondary infection of these lesions leads to the development of hepatic abscesses. In a study conducted by our group over a period of 10 years on 510 patients, 75 (14.5%) patients presented with liver abscess that was causally related to ascariasis. [3]

The "inner tube" or the "double tube" sign is due to the visualization of the hypoechoic alimentary canal of the parasite containing fluid and possibly due to the adjacent extra-intestinal fat. In case the digestive tract is collapsed or contains air, it appears as a hyperechogenic line [Figure - 1]. Sometimes due to incomplete distension, the central lumen may not appear as an uninterrupted line. Rarely four echogenic lines may be visible, the inner two representing the walls of the distended intestinal tract [Figure - 2].

Thus, the USG appearance of the parasite is fairly typical and an experienced sonologist especially in an endemic area can make a confident diagnosis. USG is the imaging modality of choice, as it is inexpensive, accurate, safe and non-invasive. Besides being quick it has can be used along the bedside of an acutely ill patient, to monitor the progress of medical treatment and during pregnancy. [4] The authors [1] have clearly demonstrated the echogenic non-shadowing tubular structure with a relatively hypoechoic center and echogenic walls. Besides various signs already well-described by the authors, worms may look like hyperechoic pseudotumors, if densely packed within the duct. The coexisting USG features may include dilatation of the bile ducts, distention of the gall-bladder with edematous walls, biliary calculi, swollen pancreas and liver abscess.

False positive diagnoses may arise rarely when vague echoes are observed in the bile duct due to blooming of its wall or due to reverberations from more anterior tissue interfaces. A curvilinear, angulated main duct along with the proper hepatic artery and adjacent tissue interfaces may mimic a "strip" or "spaghetti sign". For a "strip" sign to be positive, an unequivocal length of the main bile duct lumen needs to be seen. Further, the "spaghetti" sign also needs to be in a clear-cut intra-luminal situation within the main bile duct.

False negative results may occur if the "strip" sign is not recognized in an undilated main bile duct or if the duct lumen is concealed due to its replacement by the "spaghetti" appearance. Use of dynamic and static scanning with higher resolution may minimize this. CT scan has a limited role in biliary ascariasis, though it is of immense value in patients having liver and pancreatic involvement. MRCP though an excellent modality, is not cost-effective in developing countries where the prevalence of ascariasis is quite high.

We recommend USG as the ideal imaging tool for the diagnosis of biliary ascariasis. ERCP should be reserved for suspected cases of biliary ascariasis in whom USG is technically inadequate, is non-diagnostic or an endoscopic therapeutic biliary procedure is planned [Figure - 3],[Figure - 4].

Ascariasis related acute pancreatitis is rarely seen and thus adequate description of this clinical entity is lacking. This is probably due to the narrowness of the pancreatic duct, which hinders worm migration. We believe that in cases of anomalous insertion of the pancreatic duct, such a separate insertion may allow equal opportunity to the worm to enter either the common bile duct or the pancreatic duct. However, worm-induced pancreatitis may also occur due to other mechanisms, such as a worm blocking the pancreatic duct in biliary ascariasis or worm invasion of the pancreatic duct as well as the bile duct.

Mild pancreatitis is observed in patients with isolated pancreatic ascariasis. This is possibly due to incomplete blockage of the duct of Wirsung and a patent Santorini's duct. The combined biliary and pancreatic ascariasis burden is usually severe in such situations and may be associated with a high mortality. USG has a restricted role in diagnosing pancreatic ascariasis due to its high false negative rate. In our experience, delineation of the worm in the pancreatic duct may be missed unless there is a high index of suspicious and careful transverse scans of pancreas are made. ERCP is not only an excellent modality for diagnosis but also has a major therapeutic role. Upon endoscopic removal of the worms from the pancreatic duct, rapid relief of symptoms is usually noted.

 
   References Top

1.Oswal K, Agarwal A. Images: Hepato-biliary ascariasis. Indian J Radiol Imaging 2007;17:(in current issue).   Back to cited text no. 1    
2.Rajagopal KV, Vijayalakshmi Devi B. Quiz: Pancreatic ascariasis. Indian J Radiol Imaging 2007;17:(in current issue).   Back to cited text no. 2    
3.Javid G, Wani NA, Gulzar GM, Khan BA, Shah AH, Shah OJ, et al . Ascaris induced liver abscess. World J Surg 1999;23:1191-4.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Shah OJ, Robanni I, Khan F, Zargar SA, Javid G. Management of biliary ascariasis in pregnancy. World J Surg 2005;29:1294-8.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]

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Correspondence Address:
Omar Shah
Dept. of Surgical Gastroenterology, SKIMS, Srinagar, Kashmir
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.33615

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  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]



 

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