Acute abdomen in pregnancy revealing sigmoid colon carcinoma at caesarean section.

A primigravida at 32 weeks 6 days of gestation presented with abdominal pain and features of acute abdomen with suspected peritonitis of unclear aetiology. An emergency lower-segment caesarean section was performed resulting in delivery of a preterm neonate requiring neonatal intensive care. Intraoperatively, dense adhesions and a sealed perforation involving the sigmoid colon were identified, necessitating diversion colostomy and lymph node excision. Histopathology confirmed colorectal adenocarcinoma, and imaging revealed hepatic metastases. The patient was managed with a multidisciplinary approach and initiated on systemic chemotherapy with favourable maternal and neonatal outcomes. This case highlights the diagnostic challenges of acute abdomen during pregnancy and emphasises that both obstetric and non-obstetric causes, including rare conditions such as colorectal carcinoma, should be considered when the diagnosis remains uncertain. Careful intraoperative assessment may reveal unexpected pathology requiring multidisciplinary management.