Periureteral Abdominal Heterotopic Ossification Causing Hydronephrosis after Colonic Surgery: A Rare Postoperative Complication

Abstract

Abdominal heterotopic ossification (AHO) is a rare postoperative complication characterised by ectopic bone formation within soft tissues following surgical trauma. Although most commonly described in the abdominal wall or mesentery, involvement of retroperitoneal structures such as the ureter remains exceptional and may lead to significant functional impairment. We report the case of a 68-year-old female with a history of left-sided colonic adenocarcinoma complicated by postoperative peritonitis requiring multiple reoperations and stoma creation. During follow-up for metastatic disease, imaging revealed severe left ureterohydronephrosis associated with serpiginous hyperdense material adjacent to the ureter, as well as calcified tissue along the previous midline incision. The differential diagnosis included malignant obstruction and dystrophic calcification. An exploratory laparotomy was performed for colonic continuity restoration and etiological assessment of the ureteral obstruction. Intraoperatively, mature heterotopic ossification was identified in both the abdominal wall and periureteral region. While parietal ossification was successfully excised, periureteral dissection was deemed hazardous due to the risk of ureteral injury. This case highlights the diagnostic challenges and surgical implications of AHO, particularly in oncologic patients with complex postoperative courses. Chronic inflammation, repeated surgical trauma, and tumour-related molecular signalling pathways may contribute to ectopic bone formation. Awareness of this rare entity is essential to optimise preoperative planning and reduce operative morbidity.