Hydrogel-Associated Ulcer Masquerading as Malignancy: A Rare Complication in a Prostate Cancer Patient

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Polyethylene-glycol hydrogel injection (SpaceOAR, Boston Medical, Boston MA) is a promising preventative strategy used in prostate cancer patients prior to radiotherapy, creating space between the prostate and anterior rectal wall, limiting rectal exposure to high-dose ionizing radiation.1 Although spacer administration is typically well-tolerated with a 99% technical success rate, adverse events from needle penetration of adjacent organs have been reported.1,2–9 We present a case of rectal ulcer associated with hydrogel insertion in a prostate cancer patient.

Case Presentation

A 74-year-old man presented to the emergency room with several episodes of painless hematochezia. He was hemodynamically stable with a hematocrit of 41. He was on warfarin for atrial fibrillation and had multiple colonic polyps on colonoscopy seven years prior. His warfarin was held, and he was referred for outpatient evaluation. He was scheduled to begin radiotherapy for prostate cancer. Physical examination revealed an anterior wall lobulated rectal mass and subsequent colonoscopy revealed a 5 cm ulcerated mass worrisome for malignancy (Figure 2a). Biopsies demonstrated granulation tissue consistent with an ulcer, multinucleated giant cells, and extracellular material—but no malignancy (Figure 1). The patient revealed that he had undergone hydrogel injection in preparation for radiotherapy. Subsequent sigmoidoscopies showed healing and re-epithelialization of the ulcer (Figure 2b and c).


Although complications of spacer administration have been described (rectourethral fistula, prostatic abscess, and rectal wall erosion), these cases have been primarily reported in the urology literature.2–9 Given the potential of hydrogel complications to mimic other (malignant) findings, endoscopists should be aware of patients being treating for prostate cancer receiving spacer gel prior to radiotherapy by eliciting a thorough medical history.


Though rare, hydrogel-associated complications in patients initiating radiotherapy for prostate cancer may mimic malignancy and should remain on the differential diagnosis for a rectal mass.


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