Our patient was a 65-year-old man who had ultra-low anterior resection and chemo-radiotherapy for rectal cancer. On follow-up computed tomography (CT) scan of the abdomen and pelvis a year later, he was found to have a bladder mass (Fig. 1). He subsequently underwent elective TURBT and received intravesical mitomycin C (40 mg diluted in 40 ml of saline 0.9%) within 6 h post-operatively. Histology revealed non-invasive, low-grade TCC. Three weeks later, a follow-up CT scan of the abdomen and pelvis was performed for routine follow-up of the rectal cancer; this scan incidentally detected calcification of the bladder wall at the surgical resection site (Fig. 1). He was asymptomatic. Cystoscopy and cystolitholapaxy was then performed for presumed bladder calculi, approximately three months after the TURBT. Extensive stone-like, whitish calcification of the bladder wall at the surgical resection site was found (Fig. 2), not merely slough or soft tissue material. These lesions were further resected down to the detrusor muscle layer as the material was not amenable to washout. Histology (Fig. 3) revealed chronic inflammation of urothelium and fragments of refractile, hard-edged material which was found to be made up of calcium phosphate. There were no features of malignancy. He had normal serum calcium and phosphate levels and no known history of exposure to tuberculosis or schistosomiasis or travel to Africa, Middle East or South East Asia. He had no symptoms of interstitial cystitis. Aside from the history of rectal cancer and associated therapy, he had no other relevant oncological history. He received intravenous fluorouracil, folinic acid and oxaliplatin adjuvant chemotherapy for rectal cancer with the final cycle administered more than 12 months prior to this diagnosis of bladder wall calcification. He never received any intravesical therapy prior to the single dose of mitomycin C administered after the initial TURBT. In view of the rapid onset and localized involvement of the resection site, the bladder wall calcification was most likely secondary to intravesical mitomycin C treatment. Since this episode, there was no further recurrence or long-term consequence. Thus, no further treatment was required aside from routine cystoscopy for follow-up of non-muscle invasive, low-grade bladder cancer.