116 C. Ratto, A. Parello, L. Donisi, F. Litta, G. Zaccone and G. B. Doglietto were not statistically different at 6 cm above (P = 0·674) or 1 cm below (P = 0·865) the ARJ, whereas differences between sectors were statistically signiﬁcant at 5, 4, 3 and 2 cm above the ARJ (P = 0·022, P = 0·020, P < 0·001 and P = 0·005 respectively). Discussion The pathogenesis of HD is unclear, but is probably multi- factorial. A number of elements have been claimed to be causative or predisposing factors. Disruption of supportive tissue surrounding haemorrhoids is considered to be an important factor in haemorrhoidal prolapse7 and a number of inﬂammatory mediators have also been cited8,9. A hyper- tonic internal anal sphincter has frequently been associated with HD and is regarded as a possible cause of haem- orrhoidal symptoms10. Haemorrhoidal vascularization appears to play a central role in the pathophysiology of HD. Hyperplasia of the arteriovenous network within the anorectal submucosa (corpus cavernosum recti, CCR) results in increased vascular pressure. Blood overﬂow to the CCR should also cause increased intravascular pres- sure, and is thus a signiﬁcant predisposing factor for HD11. Aigner and colleagues12 conﬁrmed the relationship between arterial overﬂow and HD. Using a transperineal Doppler probe to investigate haemorrhoidal arteries, they found a signiﬁcantly higher arterial calibre and ﬂow veloc- ity in patients with HD compared with controls. They then hypothesized that the coordinated ﬁlling and drainage of the anorectal vascular plexus is regulated by the intrinsic vascular sphincter mechanism, and that the morpholog- ical and functional failure of this vascular system may contribute to the development of HD13. A comprehensive understanding of anorectal vascular- ization should contribute to outlining the pathophysiology of HD. A recent study by Schuurman and co-workers14 highlighted how vascularization of the CCR is provided almost exclusively by branches of the superior rectal artery (SRA), a terminal branch of the inferior mesenteric artery. A previous study by Shaﬁk and Mostafa15 indicated that the lower half of the rectum is vascularized by the terminal branches of the SRA (two or three main branches), with plexiform patterns at the ends. The middle rectal artery has been reported in only 50 per cent of cadaver specimens15, and the functional role of this artery seems negligible in light of these anatomical inconsistencies. DiDio and colleagues16 also studied the middle rectal artery in 30 cadavers; it was present in 56·7 per cent of specimens, bilaterally (36·7 per cent) or unilaterally (20·0 per cent). The middle rectal artery arose from the internal puden- dal artery in 40 per cent of specimens, the inferior gluteal  2011 British Journal of Surgery Society Ltd Published by John Wiley & Sons Ltd artery in 26·7 per cent, and the internal iliac artery in 16·8 per cent. The consistent ﬁndings of the above stud- ies appear to demonstrate that the SRA branches play a predominant role in CCR vascularization. Therefore, it is particularly important to deﬁne the topography of these vessels within the rectal – perirectal area. Aigner et al.17 analysed ﬁve macroscopic preparations of human pelvis; they described the division of the SRA into left and right branches, then into three to ﬁve terminal branches pen- etrating the rectal wall in the middle and lower rectum. On examining microscopic preparations from 27 fetuses, they identiﬁed two to four terminal vessels penetrating the rectal wall and reaching the submucosa, especially in the posterolateral position (71 per cent of specimens)17. In the present study, the majority of arterial branches at the three highest levels (6, 5 and 4 cm from the ARJ) were located outside the rectal wall in the right lateral, right pos- terolateral, left posterolateral and left lateral sectors, where these vessels arise. In contrast, no haemorrhoidal arteries were detected in several sectors in the higher three levels; in particular, none was found in the right and left antero- lateral sectors. These ﬁndings suggest that the arterial pulses detected by Doppler ultrasonography in the ante- rior highest three levels of the low rectum during surgical procedures using this technology can be regarded as being generated by vessels that are not directed to haemorrhoids. In contrast, in the lower 2 cm, haemorrhoidal arteries were detected in 98 per cent of sectors; speciﬁcally, at 2 and 1 cm from the ARJ, arteries were identiﬁed in the submucosa in 96·6 per cent and 100 per cent of sectors respectively. These features can be conﬁrmed easily during Doppler- guided surgical procedures. Investigation of the position of the arteries in relation to rectal layers and levels showed that the mean arterial depth decreased signiﬁcantly from the highest to the lowest level, reaching the shallowest depth at the most distal 2 cm of the rectum where nearly all of the arteries were in the submucosa; this feature was invariably found regardless of the circumferential sector investigated. Both anatomical and physiological evidence obtained from the literature and the present study has implications for the various therapeutic approaches that are currently available. In this regard, the most innovative surgical techniques are SH (also known as Longo’s technique) and Doppler-guided ligation of haemorrhoidal arteries, including THD and DG-HAL techniques. The goal of the ﬁrst method is to treat haemorrhoidal prolapse by resecting the rectal mucosa approximately 3 – 4 cm above the den- tate line18; however, the level of anastomosis is frequently unpredictable as it is affected by the traction applied to the previously performed rectal purse-string. In fact, it has been established that, even though SH is performed according www.bjs.co.uk British Journal of Surgery 2012; 99: 112–118