A case of colitis?

These linear lesions were found in a 50 yr old patient undergoing colonoscopy to investigate her loose stool. 
WHAT IS THE LIKELY DIAGNOSIS?

a) Crohn's disease

Does give linear ulcers but should be larger and deeper!

b) Ischaemic colitis

Also gives linear ulceration, often on the ante-mesenteric border.

c) Collagenous colitis

Absolutely!

d) Ulcerative colitis

Doesn't give linear ulceration and surrounding mucosa wouldn't be normal

e) Lymphocytic colitis

Perhaps one could develop into the other?

explanation

Actually, this patient had collagenous colitis! I suspect that the acute injury are linear tears in the mucosa which then granulate as in the images above. Finally, you are left with linear scars as in the image below. Pure speculation but seems logical ! 

At colonoscopy, the mucosa is often unremarkable but there may also be mild, patchy erythema or linear cracks. Histology reveals the typical thickening of the subepithelial collagen layer from the normal 3-6 μm to more than 10 μm as well as lymphocytic infiltration of the epithelium and the lamina propria. 

Rectal biopsies are not sufficient to make the diagnosis as normally the collagen layer is particularly thin here.  Samples from the rectum and sigmoid confirms the diagnosis is more than 90% of cases. 

Interestingly, patients with eosinophilic oesophagitis may also develop some fibrosis in the lamina propria which also 'cracks' in a spectacular way when a dilatation is carried out.