Topography of haemorrhoidal arteries 113 signed an informed consent form regarding the procedures and purpose of the study. All patients had anal bleeding with or without haemorrhoidal prolapse. Before inclusion in the study, an accurate diagnostic assessment, includ- ing patient history, physical examination, anoproctoscopic and colonoscopic ﬁndings, if indicated, conﬁrmed HD. Patients with chronic bowel inﬂammatory disease, anal ﬁssures, anal ﬁstulas or abscesses, and a history of pelvic surgery and/or radiotherapy were excluded. The enrolled patients underwent endoanal – endorectal ultrasonography (ERUS) and colour duplex imaging per- formed by a single operator. An ultrasound system (Pro- Focus GreenTM ; BK Medical, Herlev, Denmark) ﬁtted with endoanal – endorectal probes (models 2052 and 8848; BK Medical) was used. Before ultrasound examinations, the patients were prepared with two enemas to ﬂush the rec- tum. During ERUS, the proximal edge of the puborectalis sling was identiﬁed to localize the anorectal junction (ARJ). The ARJ was regarded as the best reference point during anorectal ultrasonography. The anal dentate line cannot be identiﬁed using ultrasound techniques, and in patients with HD the anal pecten can frequently be displaced. The lower rectal circumference was subdivided into six sectors (left anterolateral, left lateral, left posterolateral, right postero- lateral, right lateral and right anterolateral) (Fig. 1). From the upper limit (6 cm above the ARJ), the same procedure was repeated every 1 cm until the lower limit was reached 6 cm 5 cm 4 cm 3 cm 2 cm 1 cm Anorectal junction Endorectal colour duplex imaging probe Fig. 1 Topographic schematic diagram showing different levels of the colour duplex imaging examination  2011 British Journal of Surgery Society Ltd Published by John Wiley & Sons Ltd (1 cm above the ARJ) (Fig. 1). A total of 300 sectors were studied for each of the six rectal levels. Using combined colour duplex imaging, the courses of arteries that reached haemorrhoidal piles were followed carefully. All perirectal arteries that were not directed to haemorrhoids (vaginal, prostatic, and seminal vesicle arteries) were excluded from the study. Arteries were classiﬁed according to their location in the rectal wall: running within the submucosa, between the submucosa and the rectal muscle, within the rectal muscle, between the rectal muscle and the perirectal fat, or outside the rectal wall. The distance between the centre of the arterial lumen and the ultrasound probe surface (deﬁned as ‘arterial depth’) was calculated. Close contact was maintained with the rectal mucosa, but care was taken to avoid applying excessive pressure to the rectal wall with the ultrasound probe to minimize any distortion of the ultrasonographic and Doppler signals owing to arterial occlusion or compression. For each sector investigated, at least one picture was obtained for review after the examination. Statistical analysis The mean(s.d.) value was calculated for each recorded parameter. One-way ANOVA was used to compare means. The Bonferroni method was used for multiple comparisons, when appropriate. P < 0·050 was considered statistically signiﬁcant. Results Fifty patients (36 men, 14 women) with a mean(s.d.) age of 47·1(13·1) years were studied. Five patients (10 per cent) had grade II, 41 (82 per cent) had grade III and four (8 per cent) had grade IV haemorrhoids. Signiﬁcantly fewer sectors in the upper part of the low rectum had an arterial supply directed to the haemorrhoids than in the lower part (64·3, 66·0 and 66·0 per cent at 6, 5 and 4 cm above the ARJ respectively versus 98·3, 99·3 and 99·7 per cent at 3, 2 and 1 cm respectively; P < 0·001). Fig. 2 shows colour duplex imaging samples of different artery locations in relation to the rectal wall layers. The distribution of haemorrhoidal arteries in relation to rectal layers and distance from the ARJ is shown in Table 1. In the majority of the upper sectors (97·9 per cent at 6 cm and 90·9 per cent at 5 cm from the ARJ), haemorrhoidal arteries were located in the perirectal fat, and only occasionally within the bowel wall. At 4 cm above the ARJ, a greater number of sectors had arteries located in the rectal muscle. At 3 cm, the arteries were shown to run into the www.bjs.co.uk British Journal of Surgery 2012; 99: 112–118