Anatomical basis for impotence following haemorrhoid sclerotherapy

Impotence has been reported as a rare but important complication of sclerotherapy for haemorrhoids. The relationship between the anterior wall of the rectum and the periprostatic parasympathetic nerves responsible for penile erection was studied to investigate a potential anatomical explanation for this therapeutic complication. A tissue block containing the anal canal, rectum and prostate was removed from each of six male cadaveric subjects. The dimensions of the components of the rectal wall and the distance between the rectal lumen and parasympathetic nerves in the periprostatic plexus were measured in horizontal transverse histological sections of the tissue blocks at the level of the lower prostate gland (i.e. the correct level for sclerosant injection). The correct site of sclerosant in the submucosa was on average 0.6 mm (SD 0.3 mm) deep to the rectal mucosal surface and only 0.7 mm (SD 0.5 mm) in thickness. The nearest parasympathetic ganglion cells were a mean of only 8.1 mm (SD 2.0 mm) deep to the rectal lumen. The close proximity of the rectum to the periprostatic parasympathetic nerves defines an anatomical basis for impotence following sclerotherapy. This emphasises the need for all practitioners to be particularly careful when injecting in this area and for strict supervision of trainees.