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116 P. Puca et al.
doctor-patient relationship. It has to be reminded that several patients postpone seeking
medical care when it comes to similar disturbances. It has been proven that a good
physician-patient relationship improves clinical diagnostic and therapeutic outcomes.
Together with the active lis tenings, an active interaction with the patient is also
recommended, with specific questions regarding anal discomfort that need to be
addressed.
The remainder of the physical examination is traditionally divided into: inspection, palpation, and instrumental examination.
1.2 Inspection
Good advice is to give a glimpse to the patient’s underwear, since incontinence is a
remarkable disturbance to be evaluated. Scars, skin abnormalities, stool, discharge of
blood or pus, anal tags, warts, hemorrhoids, and external openings have to be noted.
The anterior region and vaginal opening should be examined, as well as scrotum and
inguinal lymph nodes.
The patient is then asked to squeeze the anus, in order to evaluate the contraction
of anal sphincter and to assess the recruitment of gluteal muscles.
Next, the patient is asked to strain, in order to evaluate the perianal descent, that
should be <4 cm. In this phase, prolapse of vagina, rectum or hemorrhoid, should be
evaluated.
1.3 Palpation
A digital exploration is always suggested. If needed, it can be performed under local
anesthesia or sedation.
Asking the patient to squeeze the anus allows the examinator to evaluate the
strength of anal sphincter contraction.
Important findings to be noted and evaluated in patients with possible or proved
perianal Crohn’s disease are:
• Fistula tracts in the anal canal that feel like cords or linear induration
• Cancers, represented by masses or polyps
• Ulcers
1.4 Endoscopy
After concluding the physical examination, it is up to the physician to decide
whether to p roceed with an endoscopic evaluation or not. A wider discussi on of
8 Clinical Assessment of Crohn Perianal Abscesses and Fistulas 117
the role of endoscopy in perianal Crohn disease is given below. The endoscopy could
be complimentary to anoscopy as well as ultrasonography of the anal canal.
2 Clinical Presentation
Perianal findings may be divided into skin lesions, fistulas, and abscesses.
2.1 Skin Lesions
Skin lesions include maceration, superficial ulcers, abscesses, and skin tags.
Skin tags are generally of two types:
1. Type 1 (also called “elephant ears”) are characteristically soft, nontender, can be
quite large, and typically are not associated with underlying anal pathology.
2. Type 2, tipically associated with underlying anal pathology, that often rise from
healed fissures, ulcers, or hemorrhoids are typically edematous, hard, and tender.
2.2 Fistulas
An interesting study analyzed the characteristics of fistulizing Crohn’s disease in a
single center. One hundred thirty-nine patients with fistulizing CD were enrolled.
Fistulas can appear before (66 out of 139 cases, 47.5%), simultaneously (27 cases,
19.4%), or after (46 cases, 33.1%) the diagnosis of CD. Thirty-three cases (23.7%)
were complicated by concomitant abscess. In about 29% of cases, perianal symptoms were present alone. The most common concomitant symp toms were diarrhea
(64 patients, 46% of cases), followed by weight loss, abdominal pain, fever,
hematochezia, and anemia.
The main laboratory indexes were investigated as well. CRP and ESR presented
moderate or no elevation, and the majority of patients presented no cytopenia.
Albumin levels as well were predominantly normal. Laboratory parameters have
to be evaluated with caution when assessing perianal Crohn’s Disease, because their
alterations could be related to the activity of disease (Parks et al. 1976).
The intensity and acuity of symptoms’ presentation can suggest if the fistula is
complicated by an abscess. An acute presentation, together with fever and/or
purulent discharge from cutaneous openings could suggest the concomitant presence
of an abscess. On the contrary, patients with fistula without abscess often complain
chronic presentation of symptoms, and, if present, they show non-purulent discharge
from cutaneous openings.
However, it is far to be infrequent that patient could appear completely
asymptomatic.
118 P. Puca et al.
2.3 Abscesses
Superficial abscesses present acutely as tender, localized, erythematous swellings,
and some may present with discharge. Ischiorectal abscesses may take longer to
become visible externally. They may present with vague pelvic or perianal pain and
fever, and on examination the buttock may be red and indurated compared with the
unaffected side. Digital rectal examination can be painful.
Deep abscesses are often difficult to diagnose. Patients may present with sepsis,
even though there are no visible signs. Imaging may be required to confirm the
diagnosis in these cases. A combination of systemic sepsis and a clinical history of
recent pelvic infections, Crohn’s disease, or previous anorectal sepsis may point to
an underlying deep abscess (Sahnan et al. 2017).
2.4 Diagnostic Workup
2.4.1 General Principles
According to ECCO guidelines, since perianal manifestations such as abscesses and
fistulas could be the first presentation of Crohn disease, pati ents with perianal
unexplained abscesses or complex fistulae should be investigated for Crohn’s disease (evidence level 4). Such patients, in fact, should undergo ileocolonoscopy to
detect mucosal inflammation of ileum or colon that could address toward a diagnosis
of Crohn’s disease. If negative, video capsule endoscopy could provide useful
information about small intestine, suggesting a Crohn disease diagnosis. MRI is
the most accurate and precise imaging modality to detect and classify perianal CD
and is recommended as first choice exam (EL1). Transrectal ultrasonography
(TRUS) is a valid alternative to MRI, is superior to clinical examination, and can
be performed if MRI is not possible or available.
Exploration under anesthesia (EUA) with eventual drainage is recommended as
well if an abscess is suspected, especially if MRI is not available.
Though, the combination of two or more methods (MRI, TRUS, EUA) increases
sensitivity and specificity of the entire diagnostic workup.
Furthermore, endosco pic evaluation of the rectum (EL2) is essential to determine
the correct therapeutic follow-up, determining the level and extension of inflammation in the rectum (Maaser et al. 2019).
2.5 US
Ultrasonography is the best first-step imaging in evaluating perianal Crohn’sdisease
(abscesses and fistulas). Every patient in whom a perianal disease is suspected should
be firstly evaluated with US as a first approach. Ultrasonography, in fact, is a rapid,
cost-effective, and valuable imaging exam, especially if compared to MRI.
8 Clinical Assessment of Crohn Perianal Abscesses and Fistulas 119
Furthermore, US is widely available on the territory, thus giving the physician a
general overview about patients’ perianal Crohn’s disease before the execution of
an MRI.
Two ultrasonography modalities are available: endoanal US and transperineal
US. Endoanal US has generally been considered the best ultrasonography choice.
Though, transperineal US plays its role. What’s more, endoanal ultrasonography
requires specific expertise and training.
Transperineal US has been described in a couple of cohorts as a reliable imaging
methodic. The technic is simple, inexpensive, painless; it predicts with good accuracy the results of surgical exploration and performs well if compared to MRI and
endoanal US, which are considered “gold-standard” methods (Wright et al. 2015).
Transanal US: The EUS examination is easy to perform and well tolerated by
patients. No bowel preparation is needed. The preferred patient position for examination is prone, but other position s are sometimes used according to operator’s
experience or patient’s preference.
After reaching the ampulla, it is necessary to look for the recto-vaginal septum in
the female, or the prostate in the male as a point of reference. At the origin of the anal
canal the U-shaped sling of the puborectalis is the main point of reference. The
internal sphincter is visualized as a hypoechoic ring around the anal canal, whereas
the external sphincter is of mixed echogenicity. The intersphincteric space and
longitudinal muscle lie between these and are of mixed echogenicity.
Fistulous tracts may be visualized as small, hypoechoic, round to oval structures
that lie in an intersphincteric location when they are of cryptoglandular origin (Balcı
et al. 2019). Occasionally, they will be internally hyperechoic (incr eased or bright
echoes) instead of hypoechoic because of the presence of gas or air within an abscess
or a fistulous tract. The opening within the mucosa of the canal may present as a gap
or disruption of the integrity of the mucosa. These tracts may be difficult to define.
An abscess will be identified in different manners depending on features: if
manily fluid, abscesses are sonographically identified as an anechoic (without
internal echoes); if a solid component, such as cellular debris or necrosis, is present,
abscesses will appear hypoechoic (with internal echoes secondary to cellular debris).
The analysis of fistulas can be empowered by injecting contrast agents like
hydrogen peroxide inside the fistula by a small catheter (Ardizzone et al. 2007).
Transperineal ultrasonography is feasible and effective in pediatric setting as
well. Preliminary studies in pediatric populations have shown that transperineal
ultrasonography is able to detect active and silent fistulas and eventually associated
abscesses in under 18 populations.
Furthermore, TPUS was well tolerated, with the majority of young patients (up to
90%) not complaining any pain or complaining only mild pain during the examination.
The most interesting thing about this study is that the pain severity was moderately correlated with the fistula activity (correlation coefficient, 0.64; p < 0.01).
However, the degree of pain did not appear to be correlated with the presence of
either an abscess or anal-canal hyperemia (correlation coefficients, 0.38 and 0.36,
respectively; p < 0.05) (Hwang et al. 2014).
120 P. Puca et al.
2.6 Effectiveness and Sensitivity
In the field of US, endoanal US plays without doubt a central role. It requires targeted
training and specific expertise. In contrast, it gives quite satisfying results if compared to MRI and intraoperative exploration.
Endoanal US provides efficacy and sensitivity in detecting and classifying fistulas, as well in detection of abscesses and internal openings. In particular:
• Fistula detection: 88–100% sensitivity compared to gold standard (MRI,
intraoperative exploration)
• Fistula classification: 83– 100% sensitivity compared to gold standard
• Internal openings: 91% pooled sensitivity compared to gold standard
• Abscesses: 86% pooled sensitivity compared to gold standard (Maconi et al.
2017)
Endoanal ultrasonography can be performed both by three-dimensional scan and
bidimensional scan. The two methods are both effective. In general a good concordance between the two was found in detecting internal openings and primary tract.
Though, if both ultrasound techniques are adequate for the diagnosis of low transphincteric fistulas, 3D-EAUS is superior for the diagnosis of high transphincteric
fistulas (Garcés-Albir et al. 2016).
2.6.1 Endoscopy
Though not being able to provide complete information about perianal disease,
endoscopy still plays a central role. In fact, since in a large proportion of patients
with Crohn disease presents perianal disea se at disease onset, it is fundamental in
establishing the diagnosis and assessing the level of rectal inflammation in this
specific subset of patients.
Lower endoscopy helps recognizing Crohn’s Disease by identifying key characteristics such as apthous ulcers, cobblestoning, and discontinuous or “skip” lesions.
Furthermore, even a limited lower endoscopy can visualize internal opening of
fistulas inside de anal canal, rectum, or sigma.
Upper endoscopy, on the other side, is not considered mandatory in the diagnosis
of Crohn’s disease (Spiceland and Lodhia 2018).
Endoscopic evaluation can be performed in four different modes, with different
levels of invasiveness and accuracy:
• Anoscopy: it is the simplest and least-invasive exam. It allows the visualization of
the anal canal and of the distal rectum; in contrast, it does not allow to perform
biopsies; a variant of anoscopy, called high-resolution anoscopy, is used to detect
zones of suspect intraepithelial neoplasia in patients at risk.
• Rigid proctoscopy: very accurate exam to determine the distance of rectal lesions
from the anal verge and their position. Furthe rmore, the rigid proctoscope is
quicker and easier to use than the flexible sigmoidoscope. It allows to perform
biopsies. In particular, in the setting of patients with established Crohn disease
8 Clinical Assessment of Crohn Perianal Abscesses and Fistulas 121
and perianal disease (fistula), rectoscopy plays a pivotal role in the diagnostic
path. In fact, the presence of proctitis at rectoscopy can influence the therapeutic
follow-up. According to many authors, the presence of proctitis addresses the
surgeon toward positioning a seton; vice versa, the absence of proctitis at
endoscopy compels to a more invasive surgical management (fistulectomy or
other local surgical treatment plus medical management). (Mendoza, 2005).
• Flexible sigmoidoscopy: lesions can be biopsied and the colon can be explored
up to the left colon (the instrument is about 60 cm long). Of course, it represents a
more invasive and bothersome procedure than proctoscopy.
• Pancolonoscopy and ileoscopy: it is the most complex and invasive exam,
requiring fasting and proper preparation. It allows to visualize the entire colon
with biopsies. It is usually not strictly necessary when examining perianal disease.
Though, it can provide excellent accuracy when staging Crohn disease of the
colon.
An interesting and frequent situation in which a physician could find himself in is
the presence of perianal disease with negative worku p for Crohn’s disease. In fact, it
is notable to remind that in up to 30% of patients, perianal disease precedes the
insurgence and diagnosis of Crohn disease.
In these cases, capsule endoscopy, when feasible, reveals endoscopic features of
small bowel Crohn disease in about 24% of patients, thus anticipating diagnosis and
improving prognosis (Adler et al. 2012).
2.7 MRI
MR imaging is widely considered, together with intraoperative under anesthesia
exploration, among the gold standards in the diagnosis and evaluation of perianal
Crohn disease.
MRI are usually performed with body-phase array coils. They are well tolerated,
do not require special patient’s preparation, and, last but not least, they give a large
field of view, thus avoiding an overestimation of the fistula extension. Another
fundamental advantage of MRI is the possibility of extending the image to the
elevators, to the perineum, and to the presacral space, which are common sites for
extension of fistula.
T2-weighted sequences (with or without fat suppression) are the mainstay in a
pelvis MRI exam, because they provide excellent soft-tissue contrast, thus allowing
to identify pathological processes like fistulas, seconda ry fistulous tracks, and fluid
collections. They appear as areas of iperintensity compared to the sphincters,
muscles, and fat. Identifying fistulous tracts within an acute abscess may be difficult
due to high signal intensity on T2-weighted images of pus and edema, which can
be confounding factors by obscuring the underlying fistula tracks. Unenhanced
T1-weighted images provide an excellent anatomic view of the sphincter complex
and the ischiorectal fossae. Fistulous tracks, inflammation, and abscesses appear as
areas of relative hypointensity and have to be distinguished from normal structures.
122 P. Puca et al.
T1-weighted contrast-enhanced fat-suppressed MR sequences distinguish inflamed
tissues from normal tissues, and help to differentiate fluid and scarring/granulation
tissue, that are central features of abscesses.
Furthermore, because inflammatory tissues usually appear as hyperintense at
DWI (diffusion-weighted imaging), this technique is used in addition to
T2-weighted imaging for diagnosing anal fistulas (Baskan et al. 2014).
It has to be reminded that the anatomical classification of fistulas made by Parks
in 1972 (for more, patients with Crohn disease were originally excluded by this
classification) differs from radiological classifications. Many radiological classifications have been proposed throughout years.
The radiological equivalent of the Parks classification system is known as
St James’ University Hospital (SJUH) grading scheme. This system adds to
the classical anatomical description of fistulas, the identification of
complicances such as abscesses or secundary tracts. This system recognizes
six types:
• Grade 0 refers to a normal appearing anal canal.
• Grade 1 represents a simple intersphincteric fistula.
• Grade 2 represents an intersphincteric fistula with a secondary tract or abscess.
• Grade 3 fistula refers to simple transphincteric fistula.
• Grade 4 represents a more complicated transphincteric process with a secondary
tract or abscess.
• Grade 5 fistula represents a complicated abscess with a supra or translevator
component (Gage et al. 2013).
Another MRI score to assess the anatomical evolution of Crohn’s fistulas has
been described by van Assche et al. in 2003 (Van Assche et al. 2003)
MRI allows to execute a correct differential diagnosis among many conditions
that mimic perianal disease and that can occur in IBD and non-IBD patients.
• Pilonidal sinus: MRI is neither required or compulsory to make diagnosis.
However, when performed, it is typically shows inflammatory changes in the
superficial tissues around the coccyx and sacrum. The main feature to distinguish
pilonidal sinus from perianal fistula on imaging is the absence of intersphincteric
area envolvement.
• Rectovaginal/anovaginal fistulas and abscesses: fistulas are typically detected as
tiny hyperintense tracts on T2-weighted images. At the same way, abscess
cavities located in rectovaginal septum have typical hypointense signal on
T1-weighted images and hyperintense signal on T2-weighted images. Peri-
pheral mural enhancement is an important concomitant imaging feature of
abscesses.
• Anal fissures: usually visualised as small areas of increased signal intensity in the
midline posterior wall of anal canal on T2-weighted images.
• Hidradenitis suppurativa: cutaneous and subcutaneous envolvement is predomi-
nant around the perineum and the medial aspect of the thigh. As inflammation is
8 Clinical Assessment of Crohn Perianal Abscesses and Fistulas 123
the underlying mechanism, involved areas appear as hypointense on T1-weighted
images and hyperintense on T2-weighted and STIR images.
• Hypertrophic myopathy of internal anal sphincter: it is characterized by the
isolate finding of diffuse thickening of internal anal sphincter, without other
elements suggestive of inflammatory processes. Both CT and MRI are useful to
detect it, but MRI has shown to be superior to CT.
• Anal canal carcinoma: anal neoplastic lesions are typically seen as lesions with
intermediate or increased signal intensity on T2-weighted images (Balcı et al.
2019).
Contrast MRI sequences are generally acquired. In case the precontrast image
is not satisfyi ng or in case of first MRI evaluation of Crohn disease with
perianal involvement, gadolinium injection is performed in order to improve
the quality of imaging (Reginelli et al. 2020).
2.7.1 CT Scan
CT scan finds a limited role in the diagnosis and evaluation of perianal Crohn’s
disease, for a series of motivations. On the one hand, CT scan finds large use in the
diagnosis of abdominal abscesses, in Crohn disease as well. On the other side, it does
not present the same level of sensitivity and specificity in the detection of fistulas
compared to US, MRI, and EUA. Furthermore, since CT scan exposes the patient to
an elevate amount of ionizing radiations, it cannot be used in patients under therapy
(i.e., Infliximab) for follow-up (Ardizzone et al. 2007).
2.7.2 Fistulography
Contrast enhanced fistulography was historically the first imaging technique to be
used in the evaluation of fistulas. It consists in the insertion of a small catheter into
the external opening of a fistula.
It has been gradually withdrawn from the clinical practice because it presents
several disadvantages. In fact, it does not show the sphincters, so that the relationship
between the fistula and the sphincters can only be supposed or imagined. Compared
to MRI and US, this exam has shown bad results (Ardizzone et al. 2007).
2.7.3 Exploration Under Anesthesia
and Physician-Radiologist-Surgeon Dialogue
Evaluation of perianal disease in the operatory room (exploration under anesthesia,
EUA) has historically been considered as the diagnostic gold standard in the
diagnosis and characterization of perianal Crohn’s disease.
During examination under anesthesia, the surgeon drains any sepsis encountered
and probes the fistula tract with the intent of placing a noncutting seton. EUA is
especially important for patients who cannot tolerate digital rectal examination due
to perianal pain. In addition, rectosigmoid endoscopy is usually performed at the
time of EUA.
124 P. Puca et al.
A pivotal trial in 2001 evaluated the effectiveness of MRI, US, and EUA in
detecting perianal fistulas. Thirty-three patients were enrolled and each patient was
investigated with MRI, US, and EUA by an expert investigator who set the “correct
anatomy.” According to the diagnosis of the expert investigator, rectal US classified
correctly 91% of patients, MRI classified correctly 86% of patients; EUA classified
correctly 91% of patients. If each of three meth ods was superior to the threshold of
85%, they were found to be still more effective when combined. Combining two out
of three techniques, in fact, allowed to reach up to 100% accuracy whatever the
combination was.
The results of that study showed that the accuracy of the diagnostic evaluation of
patients with Crohn’s disease perianal fistulas can be improved from between 87%
and 91% up to 100% by combining any two of the diagnostic studies. This gives an
idea of the importance of the importance of dialogue and interplay between physician, surgeon, and radiologist when assessing perianal Crohn’s disease (Schwartz
et al. 2001)
2.8 Diagnostic Follow-up
No clear indication is given by guidelines about times and modalities of follow-up
throughout time in patients with perianal disease, especially after treatment. No
consensus has been defined about modalities and follow-up times for patients with
perianal disease both with confirmed or not confirmed undergoing Crohn disease.
Patients with surgical complications will be shortly followed up according to
surgical advice. Complex fistula requiring medical therapy (i.e., anti-TNF-α) should
be followed up with similar scheduling to assess colonic or small bowel Crohn’s
disease. In particular follow-up assessment should be planned following 6 months or
1 year after starting a medical therapy, or following optimization therapy or before
considering change of therapy. The techniques to be used depend on the availability
of the IBD center and also on diagnostic yield: ultrasonography could be the first
choice, MRI should be dedicated to patients for whom ultrasonography is not giving
good accuracy, and finally exploration under anesthesia to the minority of them.
Much more information is given about screening for malignancies instead. In
fact, according to ECCO statement, adenocarcinoma complicating long time standing perianal disease (especially fistulas) is rare though possible, especially in young
women. In particular, early disease onset, disease duration exceeding 10 years,
chronic colitis with high inflammatory activity, and persistence of chronic fistulas
and stenosis seem to be associated with malignant transformation. Regular surveillance for anorectal carcinoma should be requested for all patients with perianal
CD. It should include routine biopsy of any suspicious lesion and a biopsy under
anesthesia or curettage of fistula tracts when needed.
Though, the optimum frequency and modalities of surveillance are not known
(EL5) (Maaser et al. 2019).
8 Clinical Assessment of Crohn Perianal Abscesses and Fistulas 125
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