ABSTRACT. Solitary rectal ulcer syndrome (SRUS) is a rare condition that typically affects young adults and describes a spectrum of clinicopathological abnormalities. The diagnosis of SRUS is usually made on the basis of a combination of presenting symptoms and endoscopic and histological appearances. Characteristic radiological appearances have been described on transrectal and endoanal ultrasound, defecating proctography and barium enema. The radiological appearance of solitary rectal ulcer on MRI has not been previously described. MRI appearance of thickened ulcerated mucosa in the anterior rectal wall are non-specific and was indistinguishable from a malignant process. However, given that solitary rectal ulcer has a pre-disposition to occur in the anterior rectal wall, the presence on MRI of thickened rectal mucosa in this location could suggest solitary rectal ulcer in the correct clinical context. Case reportA 48-year-old man presented with a 6 week history of reduced bowel action and weight loss with episodes of rectal bleeding. Abdominal examination was unremarkable. Digital rectal examination identified a possible polypoid lesion approximately 5 cm from the anal margin. Colonoscopy revealed a broad-based lesion with an irregular surface measuring approximately 4 cm in diameter (Figure 1). This lesion was reported as a probable malignant ulcerating polyp; T 1 and T 2 weighted MRI of the rectum was performed for further evaluation.MRI demonstrated an area of focal thickening in the anterior rectal wall with a central area of ulceration confined to the mucosa. The muscularis propria was intact with no enlarged regional lymph nodes or fatty stranding (Figure 2). On the basis of these MRI features and the clinical history, a diagnosis of ulcerating rectal lesion with provisional staging of T1N0 was made. Carcinoembryonic antigen (CEA) levels were within normal limits at ,2.Histological analysis of biopsy specimens taken at the time of colonoscopy revealed features consistent with solitary rectal ulcer syndrome (SRUS): distortion of the crypts, splaying of the smooth muscle fibres of the muscularis mucosa, foci of hyperplasia in the crypts and the presence of muscle fibres and fibroblastic cells in the rectal mucosa; immunohistological staining excluded a neoplasm (Figure 3).On further questioning, the patient reported a history of obstructive defecation with digitation. Defecating proctography was performed. Digital rectal examination before the procedure revealed a fleshy mass at the 12 o'clock position. Rapid rectal evacuation was demonstrated with a significant small bowel enterocele and a degree of external rectal prolapse on defecation. There was no evidence of intussusception (Figure 4).