Postepy Hig Med Dosw. (online), 2012; 66: 838-842
Original Article
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Utility of transperineal and anal ultrasonography in the diagnostics of hidradenitis suppurativa and its differentiation from a rectal fistula
Użyteczność przezkroczowej i przezodbytniczej ultrasonografii w diagnostyce i różnicowaniu zapalenia gruczołów apokrynowych z przetoką odbytu
Małgorzata Kołodziejczak1  ABCDEF, Iwona Sudoł-Szopińska2  ABCDEF, Aleksandra Wilczyńska1  BCDEF, Jacek Bierca1  BCDEF
1Department of General Surgery and Proctology, Solec Hospital, Warsaw
2Department of Radiology, Institute of Rheumatology and Department of Diagnostic Imaging, Medical University of Warsaw, Warsaw
Corresponding author
Dr Małgorzata Kołodziejczak, Department of General Surgery and Proctology, Solec Hospital, ul. Solec 93, 00-382 Warszawa; e-mail:

Authors' Contribution:
A - Study Design, B - Data Collection, C - Statistical Analysis, D - Data Interpretation, E - Manuscript Preparation, F - Literature Search, G - Funds Collection

Received:  2012.01.02
Accepted:  2012.09.25
Published:  2012.11.14

Wstęp: Patogeneza zapalenia gruczołów apokrynowych nie jest dobrze poznana. Jest wiele teorii, w tym teorie mechaniczne, teorie podkreślające czynnik genetyczny, oraz teorie immunologiczne biorące pod uwagę dysfunkcje limfocytów. Klinicznie choroba często jest mylona z przetoką odbytu i w konsekwencji źle leczona.
Cel pracy: Określenie przydatności ultrasonografii przezkroczowej (TPUS-transperineal ultraso­und) oraz przezodbytniczej (AUS - anal ultrasound) w różnicowaniu zapalenia gruczołów apo­krynowych (HS-hidradenitis suppurativa) z przetoką odbytu i ropniem.
Materiał/Metody: Ocenie retrospektywnej poddano 51 pacjentów (5 kobiet, 46 mężczyzn) w wieku 20-71 lat (śred­nia wieku 47,5 lat) operowanych w latach 2006-2011 z powodu zapalenia gruczołów apokryno­wych okolicy odbytu i krocza, u których wykonano TPUS i AUS. Analizie poddano 67operacji, gdyż 11 pacjentów było operowanych więcej niż 1 raz z powodu nawrotu choroby.
Wyniki: U 66 z 67 pacjentów (98,5%) przedoperacyjne badanie TPUS I AUS było zgodne z obrazem śród­operacyjnym. Tylko u 1 pacjenta stwierdzono śródoperacyjnie torbiel włosową. U wszystkich 67 pacjentów obraz TPUS przedstawiał typowe zmiany płynowo-lite zajmujące podskórną tkankę tłuszczową. U 6 z 67 pacjentów z HS (8,9%) AUS przedstawiał przetokę odbytu współistniejącą z HS. W 2 przypadkach (2,9%)stwierdzono nowotwór skóry współistniejący z HS.
Wnioski: TPUS jest dostępną metodą obrazową, która potwierdza typową lokalizację zmian w przebiegu HS, umożliwiając ich pewne zróżnicowanie z przetoką lub ropniem odbytu.
Słowa kluczowe: zapalenie gruczołów apokrynowych • przetoka odbytu • przetoka włosowa • ultrasonografia transrektalna • rak odbytu

Introduction: The pathogenesis of hidradenitis suppurativa (HS) is not fully understood. There exist several theories, in which mechanical factors, genetic factors, as well as immunological dysfunction of lymphocytes are suspected. Clinically, this entity is frequently mistaken for anal fistula with con­sequently wrong treatment.
We aim to determine the utility of transperineal ultrasound (TPUS) and anal ultrasound (AUS) in the diagnosis of HS and its differentiation from an anal fistula.
Material/Methods: Retrospective analysis was performed on 51 patients (5 females, 46 males) aged 20-71 years (mean age 47.5), who were operated on in the years 2006-2011 for HS in the area of the anus and per­ineum, and pre-operatively had been imaged with TPUS and AUS. Sixty-seven operations were analyzed, as 11 patients were operated on more than once due to HS recurrence.
Results: In 66 out of 67 cases (98.5%), the pre-operative TPUS and AUS were in accordance with the in­traoperative findings. Only in 1 patient was a pilonidal cyst diagnosed intraoperatively. In all 67 patients, the TPUS showed typical fluid-solid changes localized in the subcutaneous adipose tis­sue. In 6 out of 67 cases of HS (8.9%) AUS showed an anal fistula coexisting with the HS. In 2 cases (2.9%) a skin malignancy coexisting with HS was found.
Discussion: TPUS is an accessible imaging method, which confirms the typical localization of changes of HS, and together with AUS it allows for the proper differentiation of HS from an anal fistula or an abscess.
Key words: hidradenitis suppurativa • anal fistula • pilonidal cyst • anal ultrasound • transperineal ultrasound • squamous cell carcinoma

AUS - anal ultrasound; HS - hidradenitis suppurativa; TPUS - transperineal ultrasound.
Inflammation of apocrine glands around the anus (hidra­denitis suppurativa, HS) is a chronic condition that is dif­ficult to treat and often recurs. It most often appears after puberty, in the 2nd-3rd decade of life, three times more often in females than males. The changes may be of variable se­verity, meaning they can be single or multiple, and may be distributed in the axillary, groin, gluteal, perineal and other regions of the body where apocrine glands are loca­ted [14,17,21]. The entity was first described by Velpeau in 1839, in a patient with multiple suppurative changes in several locations. In 1854, based on a series of patients, Verneuil described inflammation of the apocrine glands in detail, and was the first to associate it with sweat glands; the disease is also known under his surname (Verneuil's disease). Only in 1922 did Schiefferdecker, through histo­pathology, confirm the possible association of the disease with apocrine glands [11,14,23].
The pathogenesis of HS is not fully understood [22]. There exist several theories, in which an infective factor is rarely mentioned. Most often mechanical factors are suspected, meaning occlusion of the hair follicle (much more rare­ly the apocrine gland, only in 5% of HS cases), with sub­sequent stasis of secretions and their infection [3,11,12].
There are also theories involving a genetic factor, which is found in up to 26% of cases [7,9,11,22]. An interesting hypothesis presented by Boer and Weltevreden states that due to an immunological dysfunction of lymphocytes, the inflammation spreads from the hair follicle to the apocri­ne glands, causing an inverse inflammation of the hair fol­licles (so-called acne inversa) [4,20].
HS accounts for approximately 5% of pustular changes of the anorectal area [15]. The anorectal localization of HS is more common in males, and the disease may be manifested by pain, swelling, purulent discharge, pruritus or bleeding and can mimic several common problems, such as furun­culosis, anal fistula, pilonidal disease, perianal abscess or Crohn's disease [14]. Due to the presence of external ope­nings to the skin, the inflammatory changes often resem­ble an anal fistula; thus patients are frequently referred for surgery with such a diagnosis (Fig. 1). Rarely, a fistu­la to the anal canal may coexist with HS; in such cases it extends only into the lower portion of the anal canal, be­low the dentate line [6,14].
Figure 1. Transperineal ultrasound: fluid-solid lesion within the subcutaneous tissue of the perianal area, which had developed within the course of HS (between arrows)

Aside from the proctological examination, anal ultraso­und (AUS) and transperineal ultrasound (TPUS) ima­ging play a decisive role in the preoperative diagnosis of HS [5,16]. AUS confirms the presence or absence of continuity between the inflammatory changes and the anal canal, while TRUS confirms the typical subcutaneous lo­cation of changes.
The aim of this study was to analyze, on the basis of a re­trospective review of own material, the utility of TPUS and AUS in the diagnosis of HS and its differentiation from anal fistula.
Materials and Methods
Retrospective analysis was performed on 51 patients (5 fe­males, 46 males) aged 20-71 years (mean age 47.5), who were operated on in the years 2006-2011 for HS of the anus and perineum, in a reference center dealing with diagnosis and treatment of proctological diseases. None of the pa­tients suffered from Crohn's disease. All patients had un­dergone a proctological examination, rectoscopy, TPUS and AUS imaging pre-operatively. The ultrasounds were performed using a BK Medical scanner, Profocus 2202, with a 8811 linear 6-12 MHz and 2050 type 3D mecha­nical volumetric endoprobe of 10-16 MHz frequency. On the basis of these 51 patients, 67 operations were analy­zed, as 11 patients were operated on more than once (9 pa­tients were operated on twice, one three, and one even se­ven times). The following procedures were performed in the above-listed patient group: deep excision of the changes to the depth of the fascia with wound closure and Redon drainage, excision of the lesions and wound closure using skin flaps, and multi-stage operations in cases of very wi­despread inflammatory changes. If there was co-existen­ce of an anal fistula, excision of the fistula was done con­comitantly, usually with fistulectomy, but in one patient using the Hippocratic technique. The pilonidal cyst was treated surgically through excision with wound closure and Redon drainage.
All patients gave their written informed consent with per­mission for publication of any of the material concer­ning them.
In all 67 surgical cases, TPUS showed typical fluid-so­lid changes localized in the subcutaneous adipose tissue (Fig. 1). In 1 out of 67 changes, such an ultrasonographic picture corresponded to a pilonidal cyst diagnosed intra­operatively confirmed through surgery and histopatholo­gy (Fig. 2).
Figure 2. TPUS showing a lesion with picture similar to HS, measuring 29×10 mm (between crosses) - histopathology showed the lesion to be a pilonidal cyst

In 6 out of 67 HS-type changes (8.9%), the AUS study sho­wed co-existence of an anal fistula, with 1 patient having multiple fistulas (Fig. 3); all of these findings were confir­med intraoperatively. Four patients (5.9%) with intraope­ratively confirmed HS were initially referred for an ultra­sound study with suspicion of a fistula or anal abscess, from which 1 patient (1.5%) had been previously opera­ted on for an anal fistula. In this group of 4 patients, only 1 had a fistula found in AUS imaging (Fig. 4). In 2 patients (2.9%) with HS, the postoperative histopathological exa­mination revealed squamous cell carcinoma (SCC). On the basis of taken specimens recurrent HS was diagnosed in 11 patients (21.5%).
Figure 3. (A) Inflammatory changes typical of HS seen in TPUS to a depth of 21 mm (between crosses); (B) with a low, multiple anterior transsphincteric fistula in AUS (arrows)

Figure 4. (A) HS coexisting with an anal fistula; perianal changes in a HS patient and external outlets of a posterior anal fistula; (B) TPUS showing fluid-solid changes in the subcutaneous tissue measuring 43 mm (between the pluses) representing HS, (C) with a low posterior transsphincteric anal fistula with an internal orifice at the level of the distal end of the internal anal sphincter

Apocrine gland inflammation of the anal region requ­ires initial differentiation from an anal fistula, particu­larly due to the similar clinical picture of both entities. On one hand, the internal orifice of the fistula could clo­se, which will not allow for the exclusion of a fistula so­lely on the basis of a proctological examination. On the other hand, the external to the skin around the anus found in HS could imitate the external opening of a fistula (Fig. 5). TPUS is extremely helpful in this differentiation, and shows the superficial location of liquid/fluid-solid chan­ges in HS. Meanwhile, AUS can confirm the presence of a fistula running towards the anal canal and in many cases shows its internal orifice [5,16].
Figure 5. Inflammatory changes characteristic for HS in the perianal area with external openings suggestive of an anal fistula

The above presented data show the preoperative ultraso­nographic findings to be compatible with the intraopera­tive ones in 98.5% of cases. In one case, the lesion turned out to be a pilonidal cyst. It should be mentioned that the ultrasonographic examination can only evaluate the mor­phology and location of changes which are identical in the case of HS and a pilonidal cyst. Even the intraoperative as­sessment of low-grade HS changes could be ambiguous, especially in males with a hairy perianal area. In such ca­ses, the histopathological examination serves to differen­tiate the two, and carries certain consequences as the pa­tient must be moved from a lithotomy position to prone.
The co-existence of HS with an anal fistula occurs when inflammatory changes occupy the anal canal and lead to a secondary anal fistula, or the anal fistula could form inde­pendently of Verneuil's disease. In our study sample, the coexistence of HS and an anal fistula occurred in 8.9% of cases, among which the fistula was recognized in only 1 case through the proctological exam (the remaining 3 out of 4 clinical suspicions of a fistula turned out to be HS). The percentage of anal fistulas discovered in our patient group was surprisingly high, given that only individual cases of anal fistulas occurring due to HS have been pu­blished [1,13].
In 2 patients with a course of HS lasting several years (3% of patients) squamous cell carcinoma (SCC) of the skin was discovered (Fig. 6). This is in accordance with the fin­dings of other authors, who indicate an increased risk for the development of skin cancer in long-standing HS (mean length of 20 years) and emphasize the need for greater awa­reness that long-standing gluteal or perineal HS is a pre­malignant condition which should not be managed conse­rvatively [2,10,11,19].
Figure 6. Squamous cell cancer in the vicinity of the perianal inflammatory changes of HS

HS-type changes in the perianal area are particularly dif­ficult to treat. Patients are often misdiagnosed, reach a pecialist late in the disease course, and even if they appear early on, recurrence occurs despite proper treatment [11]. In our study, the recurrence rate was 21.6%. From the data of Ritz et al. [18], the rate of recurrence of HS after surgical treatment was 45%, broken down to 100% after drainage of abscesses, 42.8% after a partial excision and 25% after a radical excision of inflammatory changes. In contrast, the study of Harrison et al. [8] had 0% recurrence after peria­nal surgery and a high 37% rate after an inguinoperineal approach. In our patient group, 9 patients were operated on twice, 1 patient three times and 1 patient even seven ti­mes. The latter patient had very diffuse changes occupy­ing the groin, thighs, and buttocks. Additionally, he was initially treated with radiotherapy, to no effect.
In conclusion, TPUS is a simple and accessible imaging method, which confirms the typical localization of changes of HS. Together with AUS, it allows for the proper differen­tiation of HS from an anal fistula or abscess. Coexistence of HS with an anal fistula not evident on proctological exa­mination was found via AUS in 8.9% of cases, which was confirmed intraoperatively. AUS did not allow for diffe­rentiation between HS and a pilonidal cyst, which was po­ssible through the clinical, intraoperative and histopatho­logical examinations. In 3% of cases skin malignancy had developed within the course of HS.
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The authors have no potential conflicts of interest to declare.