As he was unkeen to trial other analgesic medication for his neuropathic perianal pain, a ganglion impar injection was planned. A diagnostic injection was performed using a fluoroscopic-guided transcoccygeal approach. Needle advancement was difficult necessitating injection at two distinct levels. This was attributed to tumour involvement. A 10ml mixture of 0.5% bupivacaine and 80mg methylprednisolone was injected (5ml at each level), with contrast confirming spread. As he had a temporary 60% improvement in his pain, a neurolytic block was performed.
During the neurolytic block, similar injection difficulties were noted. 3ml 0.5% bupivacaine was injected, followed by 7ml of 100% alcohol, split between two levels. The needles were flushed with lidocaine before removal.
Three days post-procedure, he developed new gluteal pain with a 5 x 5 cm skin discoloration indicative of necrosis, which was confirmed by plastic surgery review. After 1 month, the patient reported no improvement in his perianal pain and was continuing to take oral opioids. The gluteal skin necrosis had sloughed, revealing a foul-smelling ulcer with discharge, necessitating regular wound dressings. An MRI scan showed significant progression of the posterior rectal wall defect with a presacral collection extending to the gluteal ulcer. A CT scan revealed a dehiscent posterior low anterior resection anastomosis with a 3 cm supralevator fistula traversing to the gluteal skin, surrounded by inflammation.
After nine weeks, the patient’s perianal pain improved with oral medications. The gluteal ulcer was starting to heal with antibiotics and regular dressing changes. Subsequent MRI scans showed a persistent posterior perianal fistula but a smaller presacral abscess with the gluteal component almost collapsed. A CT scan showed partial improvement of the posterolateral perianal fistula.
