Diagnostic considerations for detection of IBD include differential diagnosis for most conditions with profuse watery or bloody diarrhea, gastrointestinal bleeding and intestinal ulceration, as they are the sole strong indicator for bowel related abnormalities. Such conditions include Salmonellosis, Celiac disease, microscopic colitis, lactose intolerance, arteriovenous malformations, ischemic colitis, radiation induced colitis, irritable bowel syndrome, amebiasis, functional diarrhea and colorectal malignancy among others.
Weight loss, fatigue, loss of appetite and abdominal cramps could be indicators of a number of conditions including anorexia, IBS, IBD and bulimia, and hence need careful diagnosis to zero-in on IBD.
A series of laboratory tests including blood and stool tests and cultures, serologic studies, combined with radiography and imaging techniques are needed to diagnose the condition appropriately.
Complete blood count (CBC) and WBC counts along with detection of C-reactive protein (CRP) in blood and evaluation of the erythrocyte sedimentation rate (ESR) can help in evaluating the rates of inflammation and infection in the patient, though not very specific to IBD. Vitamin B12 levels and occasionally folate levels, could indicate gastrointestinal malabsorption and bowel disease. Fecal calciprotein has been denoted as a non-invasive marker of intestinal inflammation in patients with IBD, with a high sensitivity and specificity, and high success rates.
Serologic testing with Perinuclear antineutrophil cytoplasmic antibodies (pANCA) anti-Saccharomyces cerevisiae antibodies (ASCA) have been executed successfully in patients with Ulcerative Colitis and Crohn’s Disease. In patients with UC, a combination of a positive pANCA and negative ASCA (clumping only in case of pANCA) is seen, whereas the inverse is true, (clumping only in case of ASCA) for patients with CD. However, chances of false positives always remain in these tests and one needs to be careful not to judge on the basis of only these tests.
Stool samples need to be cultured to check for bacterial and protozoal infections which are another leading cause of profuse diarrhea. The main microbes to look out for include Entamoeba hystolytica, Clostridium difficile, Salmonella typhi, Yersinia enterolytica, and Cytomegalovirus.
Radiographic scans, computed tomography scans and magnetic resonance scans show abnormal views of the abdomen with fistulas, mucosal edema, abscesses and abnormal surface linings of the GI tract, with the regions of such abnormalities being the demarcating factor between UC and CD. If still not clear, high resolution CT scans or MRI scans accompanied with ingested contrasts (a technique known as CT or MR enterography) can be employed. Esophagogastroduodenoscopy (EGD) is used for the evaluation of upper gastrointestinal tract symptoms, particularly in patients with Crohn disease.
Barium enema imaging techniques are useful in detecting the minute intricacies if IBD when all other methods fail to provide concrete evidence in favor of any specific condition pertaining to IBD. A lead-pipe or stove-pipe appearance suggests chronic ulcerative colitis, rectal sparing suggests Crohn colitis in the presence of inflammatory changes in other portions of the colon, thumb printing indicates mucosal inflammation, and skip lesions suggest areas of inflammation alternating with normal-appearing areas, again suggesting Crohn colitis. Ultrasonography (USG) can also be used to detect Crohn’s disease with moderate to high sensitivity and specificity. The non invasive techniques of MRI, CT scanning and USG are preferred in younger patients.
Invasive techniques like histological examinations and biopsies of intestinal segments might be necessary in case of severe (fulminant) forms of the disease, with surgical procedures (more common in patients with CD) including removal of part or entire bowel or the colon or rectum, followed by anastomosis.