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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_770_Библиотеки_им_академика_М_И_Перельмана
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12 CTC Traps andArtefacts
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c(ii) d(i)
d(ii) e
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Fig. 12.12
arrows). (d) (i) Streaks due to beam hardening artefact
from surgical clips (arrows). (ii) 2D coronal view shows
(ii) 2D view streaks from surgical clip (white
surgical clip (red arrow) in appendiceal region. (e) 2D
axial view showing streak artefact (open white arrows)
from an intrauterine device (green arrow)
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J. H. Bortz
a
b(i)
b(ii) b(iii)
Fig. 12.13 (a) 2D sagittal view shows multivitamin capsule (arrow). (b) (i) 3D view shows density due to sh oil
capsule (arrows). (ii) 2D axial view shows oil capsule (arrow). (iii) 2D sagittal view shows oil ‘fat’ centrally (arrow)
12.2.11 Mucus Strand
A mucus strand may sometimes be confused with
a pedunculated polyp. It has a thin linear strand
which extends across normal haustral folds as
shown in Fig.12.14 (i) and (ii). Occasionally, the
tagging agent (barium) may be incorporated into
the strand and will show as a high density of TD.
12.2.12 Tampon andVaginal Pessary
Figure 12.15a (i) and (ii) is an example of a tampon visualised on 2D. Figure 12.15b shows a
vaginal pessary. A vaginal pessary is a removable device that is used to support pelvic organ
prolapse, such as the bladder, uterus, and/or
rectum.
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167
(i) (ii)
Fig. 12.14 (i) Arrow points to mucus strand between two haustral folds. (ii) 2D axial view shows mucus strand
between folds (green arrow)
a(i)
a(ii)
b
Fig. 12.15 (a) (i) Axial 2D showing vaginal tampon (white arrow). (ii) Sagittal 2D showing vaginal tampon (white
arrow). (b) Axial 2D showing curvilinear density (arrow) in keeping with vaginal pessary supporting uterus
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J. H. Bortz
Key Messages
• Poor bowel preparation could be a potential
pitfall as adherent stool may obscure polyps.
• Poor bowel distension could result in non-
visualisation of lesions.
• Extrinsic impressions on the colon lumen
could result in misdiagnosis.
• Lack of knowledge of colon anatomy, and
normal variants, could be a potential pitfall in
terms of anatomical location of structures.
• Incorrect positioning of the rectal catheter
could be a potential pitfall.
• Movement and breathing artefacts could pres-
ent confusing images.
• The ‘dense waterfall’ sign is a luminal
artefact.
• Ingested artefacts could be misinterpreted as
polyps.
• Beam hardening artefacts could obscure
lesions.
• Electronic cleansing could introduce
artefacts.
• 2D and 3D views are complementary for
interpreting CTC images.
12.3 Summary
There are many potential traps that may cause an
unwary person performing and reading CTC
studies to ‘trip up’. An adequately cleansed bowel
and good distension of the colon with CO2 minimises most potential pitfalls. For example, a
well-prepared colon minimises the potential pitfall of the presence of stool in the colon; good
bowel distension using a CO2 insufator enables
good visualisation of all segments of the colon.
Beam hardening artefacts, caused by metal hip
prosthesis, for example, may be present on both
2D and 3D images. Movement and breathing
artefacts should not be evident if there is good
patient co-operation. By using combined 2D-3D
interpretation methods, a vast majority of these
potential pitfalls should be recognised and handled in the appropriate manner. Electronic cleansing of the colon is not recommended at this stage
as it produces artefacts.
Acknowledgements Viatronix Stony Brook, NewYork
is thanked for providing the electronic cleansing images
of the colon.
References
1. Pickhardt PJ, Kim DH.CT colonography: principles
and practice of virtual colonoscopy. Philadelphia:
Saunders; 2009. p.239–313.
2. Yee J.Virtual colonoscopy. Philadelphia: Lippincott,
Williams & Wilkins; 2008. p.94–154.
3. Boas FE, Fleischmann D. CT artefacts: causes
and reduction techniques. Imaging Med.
2012;4(2):229–40.
4. Bortz JH. CT colonography: an approach
for a successful examination. S Afr J Rad.
2014;18(1):607, 11 pages. https://doi.
org/10.4102/sajr.v18i1.607.
5. Pickhardt PJ.Screening CT colonography: how I do
it. AJR. 2007;189(2):290–8. https://doi.org/10.2214/
ajr.07.2136.
6. Kim DH, Hinshaw L, Lubner MG, etal. Contrast coating for the surface of at polyps at CT colonography:
a marker for detection. Eur Radiol. 2014;24(4):940–6.
https://doi.org/10.1007/s00330- 014- 3095- z.
7. Cai W, Zalis ME, Näppi J, Harris GJ, Yoshida
H.Structure-analysis method for electronic cleansing
in cathartic and noncathartic CT colonography. Med
Phys. 2008;35(7):3259–77.
8. Ahmed I, Asgeirsson K, Beckingham I, Lobo D.The
position of the vermiform appendix at laparoscopy. Surg Radiol Anat. 2007;29:165–8. https://doi.
org/10.1007/s00276- 007- 0182- 8.
9. Pickhardt PJ. Differential diagnosis of polypoidal
lesions seen at CT colonography (virtual colonoscopy). Radiographics. 2004;24(6):1535–56.
10. Boyce CJ, Vetter JR, Pickhardt PJ. MDCT artefact
related to the intra-scan gravitational ow of opacied
luminal uid (the “Dense Waterfall” sign). Abdom
Imaging. 2012;37(2):292–6.
11. Pickhardt PJ, Kim DH. CT colonography: pitfalls in interpretation. Radiol Clin North Am.
2013;51(1):69–88.
Internal Haemorrhoids, Anal
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Papilla, andOther Anorectal
Lesions
JoelH.Bortz
13
13.1 Introduction
During a CTC study, haemorrhoids are the most
frequently seen and diagnosed condition affecting the anorectal region [1]. Most anorectal conditions are benign; they may often be diagnosed
clinically by a rectal examination or anosocopy
without the need for a full endoscopic examination. During a CTC study, it is important to check
structures around the catheter. The structures
could be internal haemorrhoids, anal papillae,
polyps, or tumours.
As discussed in Chap. 10 when a patient is in
the prone position, the sterile disposable catheter’s balloon is deated in order to visualise internal haemorrhoids, if present [2]. The correct
placement of the catheter is important in
CTC. This chapter focuses on internal haemorrhoids. It is therefore important to describe their
causes and anatomical location [3]. In addition,
we need to consider anal papillae and tumours
[4].
The following abbreviations are used in this
chapter.
• 2D: two-dimensional
• 3D: three-dimensional
• CO2: carbon dioxide
J. H. Bortz (*)
LSG Imaging, Los Angeles, CA, USA
13.2 Rectal Tube Position
According to Pickhardt [4], we need to bear the
position of the rectal catheter in mind when evaluating the anorectal region. The catheter tip may
cause extrinsic impression of an adjacent rectal
fold, for example, or the tip itself may appear polypoidal at three-dimensional (3D) images. When
the author examines this region, his standard technique is to y 360° around the catheter to check
that there are no polyps being obscured by the balloon. This technique is also described in Chap. 14.
There are several catheters available. For
example, the Vimap catheter, which is available
in Europe can withstand 100 cc air ination. A
3-way connection has a separate drainage connection for any residual uid in the rectum. By
having this drainage connection there is no contamination of incoming CO2 because the latter
has its own connection. The 3-way connection
catheter is no longer available in the United
States. The author now uses a 2-way connection
(see Fig. 10.2c in Chap. 10); maximum air ination is 50cc.
Distension of the balloon catheter may produce a ‘pseudolesion’ or ‘lling defect’ on the
3D study. Figure13.1a (i, ii) depicts a meniscal
defect, which is visualised on the supine studies,
and presents as a pseudolesion caused by the
inated balloon abutting on the rectal mucosa.
Occasionally, a meniscal defect will be to the side
of the catheter. Deating the balloon when the
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2023
J. H. Bortz et al. (eds.), CT Colonography for Radiographers,
https://doi.org/10.1007/978-3-031-30866-6_13
169
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J. H. Bortz
patient is in the prone position usually eliminates
such interpretation problems. Figure 13.1a (iii)
shows a 3-way connection catheter and inated
balloon. Figure13.1a (iv) shows an inated balloon defect and residual rectal stained uid. To
minimise visualisation of the latter, the patient
should be sent to the restroom/lavatory as the rectum must be emptied of any residual uid before
commencing the CTC study (see Chap. 10).
a(i) a(ii)
Occasionally, the catheter may be inserted too
far into the rectum as shown in Fig. 13.1b (i).
This may then cause the tip of catheter to protrude beyond the valve of Houston; this may simulate a polyp in appearance. It may also push
against the valve of Houston causing an extrinsic
impression as shown in Fig.13.1b (ii). Correct
placement of the catheter is essential to avoid
interpretation problems.
Fig. 13.1 (a) (i) 3D supine view shows meniscal defect (open black arrows) due to inated balloon. (ii) 3D supine
image shows inated balloon to the side of the catheter causing a meniscal defect (open black arrows).
13 Internal Haemorrhoids, Anal Papilla, andOther Anorectal Lesions
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a(iii)
a(iv)
b(i)
b(ii)
Fig. 13.1
Connection to inate balloon with 35 cc air (red open
arrow). Insufator connection (closed black arrow).
Connection for drainage bag (closed red arrow/orange
ring on tube). Inated balloon=open black arrows. (iv)
2D axial image shows inated balloon (open black arrow)
(iii) Vimap 3-way connection catheter.
and residual rectal stained uid (open white arrow). (b) (i)
3D image shows the catheter incorrectly placed. Its tip
(open white arrow) extends beyond the valve of Houston.
(ii) 3D image shows tip of catheter projecting beyond the
valve of Houston simulating a polyp (open white arrows)
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J. H. Bortz
13.3 Denition andCauses
ofHaemorrhoids
Haemorrhoids are vascular structures in the anal
canal. They are the result of varicose dilatations
of the rectal veins [4]. They are very common in
both males and females, and most patients are
asymptomatic. Haemorrhoid frequency increases
with age. Causes of haemorrhoids include vigorous straining, chronic constipation, and pregnancy. They are often complicated by
inammation, thrombosis, and bleeding. There
are four types of haemorrhoids: internal, external
[5], prolapsed, and thrombosed.
a(i)
13.4 Anatomical Location
ofInternal andExternal
Haemorrhoids
There are two types of haemorrhoids based on their
location: internal and external haemorrhoids [5]. An
external haemorrhoid is one that is in a vein of the
inferior haemorrhoidal plexus. It is below the dentate line which divides the squamous epithelium of
the anus from the columnar epithelium of the rectum
[1, 3]. An internal haemorrhoid is above this line.
Figure13.2 (i, ii) demonstrates the anatomy of rectum as well as location of internal and external
haemorrhoids. Haemorrhoids are vascular structures
a(ii)
Fig. 13.2 (i) Anatomy of rectum. Middle rectal fold of
valve of Houston (MRV). Internal rectal fold of valve of
Houston (IRV). 1=submucosal space and internal hemorrhoidal plexus. 2=external hemorrhoidal plexus in peri-
anal spaceϕ. (ϕ Adapted from [5]). (ii) Internal haemorrhoid
above the dentate line (top). External haemorrhoids
(bottom)ϕ. (ϕ Adapted from [5])
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in the anal canal. They may become pathological
when swollen and/or inamed, and in such a situation there may be bleeding associated with pain.
Internal haemorrhoids may grow in size and become
large. This may occasionally result in large haemorrhoids prolapsing externally; most times they retract
spontaneously. However, some may not retract;
when this happens they are referred to as ‘prolapsed
piles’. Care has to be taken when inserting the rectal
catheter in a patient with ‘prolapsed piles’.
dentate line [3]. They have a smooth contour
and are located in a concentric manner around
the rectal tube. An inated balloon can obscure
the presence of internal haemorrhoids; the
prone position with the balloon deated shows
the internal haemorrhoid as evident in
Fig. 13.3a (i, ii). Both two-dimensional (2D)
and 3D views may visualise internal haemorrhoids: on 2D they present as small protrusions, whereas on 3D they may be raised linear
defects or polypoidal in shape. Figure 13.3b
(i)–f (ii) illustrates 2D and 3D views of internal
13.4.1 2D and3D Architecture
haemorrhoids.
ofInternal Haemorrhoids
On CTC scans, internal haemorrhoids appear
as small protrusions in the rectal vault at the
a(i) a(ii)
Fig. 13.3 (a) (i) 3D view of inated balloon. Internal haemorrhoid (open white arrow). (ii) 3D prone view with deated
balloon shows internal haemorrhoids more prominently (open black arrows).
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b(i) b(ii)
c(i) c(ii)
J. H. Bortz
d(i) d(ii)
Fig. 13.3
haemorrhoid (open black arrows). (ii) 2D axial view
shows internal haemorrhoid (h). C=rectal catheter (open
white arrow). (c) (i) 3D image of four internal haemorrhoids. Closed black arrow = polypoidal form defect.
Open white arrows=linear internal haemorrhoids. (ii) 2D
(b) (i) 3D image shows polypoidal internal
axial of polypoidal internal haemorrhoids (h). C= rectal
catheter (open white arrow). (d) (i) 3D supine image of
large polypoidal internal haemorrhoids (open white
arrows). (ii) 2D axial image showing internal haemorrhoids (h). C=rectal catheter (open white arrow).
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