A blood clot in a hemorrhoid can cause extreme pain. Caught early, it can be surgically evacuated. Once several days old, there is no advantage in doing so. Now it looks like an intrasphincteric injection of 0.6 ml of a solution containing 30 units botulinum toxin can give dramatic relief of pain within 24 hours.
Br J Surg. 2008 Oct 9;95(11):1339-1343.
Randomized clinical trial of botulinum toxin injection for pain relief in patients with thrombosed external haemorrhoids. Patti R, Arcara M, Bonventre S, Sammartano S, Sparacello M, Vitello G, Di Vita G. abstract
“A single injection of botulinum toxin into the anal sphincter seems to be effective in rapidly controlling the pain associated with thrombosed external haemorrhoids, and could represent an effective conservative treatment for this condition.”