Greetings Ben / Ann.
I am sorry that your question was unanswered for long.
With your symptoms, before the colonoscopy (which I agree would be required in evaluation and you may need a biopsy of colon during the scopy), there are other investigations too, which should be done like stool exam, stool culture, blood work etc. The initial evaluation of diarrhea (and blood in bowel motion) is on these characteristic;
a) stool volume,
c) consistency, and
d) gross appearance.
with or without bleeding.
Stool volume can give an idea of disease location and underlying mechanism.
a) Large-volume stools (more than one liter per day) would point to small bowel disease and secretory diarrhea.
b) Small-volume stools (less than 300 ml per day) suggest large intestine diseases and functional gastrointestinal disorders like IBS.
Stool consistency can be varied ranging from formed to watery, and correlates with the rate of intestinal transit.
a) Secretory diarrheas are liquid.
b) Functional diarrheas are soft or semi-solid.
c) Stool floating will be indicative of if being filled with gas from fermentation of mal absorbed carbohydrates.
d) Mucus can point to both inflammatory and noninflammatory diarrheas, such as ulcerative colitis and IBS.
Stool appearance helps to classify diarrhea as;
a) Watery diarrhea is caused by carbohydrate malabsorption, medications, bile acid malabsorption, Crohn's disease, microscopic colitis, chronic mesenteric ischemia, post surgical diarrhea, hyperthyroidism, colonic adenomas and carcinomas, alcohol induced diarrhea, laxative abuse, and hormone-secreting tumors.
b) Steatorrhea or fatty diarrhea is greasy, oily, foul smelling, bulky, or voluminous stools that are often difficult to flush, might contain undigested food particles, and sometimes leaves an oily stain in the toilet bowl. These characteristics suggest pancreatic disease, short bowel syndrome, celiac disease, giardiasis, and small bowel bacterial overgrowth (SBBO).
c) Bloody diarrhea suggests Ulcerative colitis, Crohn's colitis, cancer and chronic infections.
Chronic diarrhea, is defined as the production of loose stools with or without increased stool frequency for more than 4 weeks. The main causes of the chronic diarrhea are following;
1) Irritable bowel syndrome; it is a sort of functional diarrhea in which no abnormality is found.
2) Inflammatory bowel disease (IBD); this is auto immune mediated type of diarrhea and it can involve other organs in the body. The biopsy of colon and small intestines need to be taken to establish the diagnosis with investigations like CRP, ANA, HLA B 27 etc. There are two type of IBD;
a) Crohn's disease
b) Ulcerative colitis
3) Microscopic colitis; Microscopic colitis is characterized by chronic watery (secretory) diarrhea without bleeding. It usually occurs in middle-aged patients. Two different types of microscopic colitis have been generally recognized:
a) Lymphocytic colitis
b) Collagenous colitis without lymphocytic infiltration of the surface epithelium
Collagenous and lymphocytic colitis produce a similar clinical picture characterized by non bloody chronic watery (secretory) diarrhea of up to two liters daily. So total amount of stools per day has to ascertained.
4) Malabsorption syndromes; The classic manifestations of malabsorption are pale, greasy, voluminous, foul-smelling stools and weight loss despite adequate food intake.
5) Chronic infections; Some persisting infections (C. difficile, Aeromonas, Plesiomonas, Camyplobacter, Giardia, Amebae, etc.) can be associated with chronic diarrhea.
You should be investigated for IBD, chronic infections or for secretory diarrhea (by estimating total amount of stools per 24 hours). Looking for the carcinoid tumor also may be considered. Gastrinoma and VIPoma also should be considered for prolonged secretory diarrhea and an high index of suspicion is required. Secretory diarrhea characteristically continues despite fasting, is associated with stool volumes more than 1 liter/day. Selective testing for plasma peptides such as gastrin, calcitonin, vasoactive intestinal polypeptide, and somatostatin, as well as urine excretion of 5-hydroxyindole acetic acid, metanephrine, or histamine and other tests of endocrine function, such as measurement of thyroid-stimulating hormone and serum thyroxine levels or an adrenocorticotropin-stimulation test for adrenal insufficiency, can be considered by your physician. An aspirate of small bowel contents for quantitative culture or breath tests with glucose or isotopically labeled xylose can be used to establish the presence of small bowel bacterial overgrowth.
A diarrhea with blood need to be ruled out for (especially in age group above 60);
2) ulcerative colitis
3) Crohn's disease
6) bleeding in intestine due to some oozing blood vessel (blood vessel abnormality).
So apart from colonoscopy mesenteric arteriography, stool culture would also be important. Gastro doctors may start with the colonoscopy in your age group but you may ask them to do the other tests first,
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
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