Mistakes in ... Booklet 2020 - 25

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Mistakes in... 2020

a

b

Figure 3 | IgG4 cholangiopathy. a | Hilar biliary stricture Bismuth type II (arrow) with upstream dilatation on MR
cholangiogram. b | No visible mass on contrast enhanced CT (arrow). Cytology brushings were negative but
surgical histology revealed IgG4 cholangiopathy.

The specificity of MRCP for differentiating
between benign and malignant biliary strictures
varies widely, from 30% to 98%.3 In general, benign
strictures tend to have smooth borders with
tapered margins, whereas malignant strictures
are suggested by the presence of an irregular,
asymmetric, longer (>12mm) stenosis with
shouldered margins, increased enhancement and
an indistinct outer margin.8 Furthermore, a
diffuse or multifocal character mostly relates
to autoimmune or inflammatory causes.3
Cross-sectional T1-weighted and T2-weighted MRI
sequences add specificity, and the presence
of an associated mass lesion is suggestive of a
malignant cause.3 Conversely, mass-forming
IgG4-related sclerosing cholangitis resembling
hilar cholangiocarcinoma has been described,
thus potentially leading to unnecessary
surgery owing to suspected malignancy
(figure 3).9

Mistake 4 Considering all biliary strictures
without a mass and negative brushings as
benign

Figure 4 | Cholangiocarcinoma. Long common bile duct stricture (arrow) without mass on
MRI T2 W coronal sequence (a) and MR cholangiogram (b). Cytology brushings were negative but surgical
resection revealed stage T2 cholangiocarcinoma.

other modalities such as CT can help narrow the
diagnosis (figure 2a-c).
Similarly, images depicting ductal strictures
may be false and these findings can be attributable
to patient-related factors, secondary to the MR
imaging technique used or due to post-processingrelated factors.6 Frequent causes suggestive of a
false image of a biliary stricture include the
'blooming artifact' (a susceptibility artifact due to
cholecystectomy metal clips) and the 'pulsation
artifact' of the hepatic artery.6 The pulsation artifact
can also give the impression that there is a stricture
of the pancreatic duct, related to the splenic
artery (figure 2d-f). When assessing a possible
stricture, careful review of axial and coronal
images obtained during MRI help to avoid
misinterpretation.

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b

Mistake 3 Assuming all biliary strictures
are malignant
Despite the fact that the majority of biliary
strictures are malignant (only 5-25% have a
benign cause), the potential morbidity and even
mortality related to unnecessary surgical resection
should be taken into consideration.7 Causes of
benign biliary strictures include iatrogenic
biliary injury following hepatobiliary surgery,
primary sclerosing cholangitis, IgG4-related
cholangiopathy, ischaemic cholangitis, recurrent
pyogenic cholangitis, AIDS-related cholangitis,
and eosinophilic cholangitis.8,9 The clinical context
(pain, weight loss, previous medical and surgical
history, laboratory tests and associated diseases)
is crucial to improve the diagnostic yield.8

c

As already stated, the presence of a mass adjacent
to a biliary stricture is suggestive of malignancy.
Nevertheless, the absence of a mass does not
always mean the cause is benign. Indeed,
cholangiocarcinoma can be categorized into
different growth types on the basis of morphologic
features and growth patterns-mass-forming,
periductal infiltrating and intraductal.6 On MR
imaging, the periductal infiltrating and intraductal
growth types appear as single or multifocal
biliary strictures, with focal or diffuse ductal
thickening with or without contrast enhancement,
and intraductal polypoid growth.6 These findings
are nonspecific and may mimic a wide spectrum of
inflammatory conditions involving the bile ducts
(figure 4).
ERCP has an important role in the diagnosis of
cholangiocarcinoma as intraductal brush cytology
and forceps biopsies may establish the diagnosis.
Nevertheless, the sensitivity of the techniques
described, even combined, does not exceed 60%,
leaving the possibility of false-negative results.10
Therefore, an intraductal brushing or forceps
biopsy revealing no malignant cells should be
repeated or complemented with additional

d

Figure 5 | Autoimmune pancreatitis. a | T2-weighted image shows focal pancreatic gland enlargement (arrow) with mild peripancreatic infiltration. b | Irregular
hypersignal in DWI (arrow). c | MRCP shows multifocal duct narrowing (arrows) and diffuse irregularity suggesting autoimmune pancreatitis. d | Complete resolution of
abnormalities of the duct after steroid treatment.

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