Crohn病并发症瘘管。左边可见裂缝从黏膜延伸到黏膜下层、肌层，最终形成瘘管。瘘管可在肠袢间、膀胱和皮肤形成。累及结肠的直肠周瘘管常见。
One complication of Crohn's disease is fistula formation. Seen here is a fissure extending through mucosa at the left into the submucosa toward the muscular wall, which eventually will form a fistula. Fistulae can form between loops of bowel, bladder, and skin. With colonic involvement, perirectal fistulae are common.
