What causes the ram’s horn sign on barium studies of the stomach?
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Answer:
The ram’s horn sign is a smooth, tapered, tubular narrowing of the gastric antrum with loss of the normal antral distensibility, so that the antrum curves like a ram’s horn as it approaches the pylorus. It is a described appearance of gastroduodenal Crohn disease, which is uncommon and almost always accompanies disease elsewhere in the gut, and it may be associated with the pseudo-Billroth I appearance, in which antral and duodenal bulb disease produces a tubular channel resembling a surgical gastroduodenostomy. Other findings of gastroduodenal Crohn disease are aphthous ulcers, cobblestoning, thickened folds and stricturing of the duodenum, and endoscopic biopsy showing non-caseating granulomas is confirmatory. The differential for a rigid, narrowed antrum is the important part of the report: scirrhous gastric carcinoma, the linitis plastica leather bottle stomach, which shows irregular, nodular narrowing with mucosal destruction and is the diagnosis that must never be missed; chronic peptic scarring; corrosive ingestion; gastric tuberculosis, syphilis and sarcoidosis; eosinophilic gastroenteritis; and amyloidosis. Cross-sectional imaging with CT or MR enterography assesses mural thickening, enhancement, extramural extension and the remainder of the bowel, and endoscopy with biopsy is required in every case because the appearances overlap.
Why is it called so?
The tapering, curved antrum resembles the spiral horn of a ram.
Pathophysiology
Transmural inflammation in Crohn disease involves the full thickness of the gastric wall, with lymphoid aggregates, granulomas and, in the chronic phase, fibrosis of the submucosa and muscularis. Fibrous contraction shortens and narrows the antrum in a smooth, symmetrical way, and the loss of distensibility means the segment retains a fixed narrowed shape regardless of gastric filling. This smooth tapering distinguishes it from scirrhous carcinoma, in which infiltration of the wall by desmoplastic tumour produces irregular narrowing with mucosal nodularity and ulceration. The pyloric and antral location reflects the tendency of gastroduodenal Crohn disease to involve the distal stomach and the first part of the duodenum contiguously.
Alternative names: Ram’s horn stomach; pseudo-Billroth I appearance when the duodenum is involved
Other associated named signs: Cobblestone appearance of the mucosa, the string sign of a Crohn stricture and the linitis plastica appearance of scirrhous carcinoma
References
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