Table 3. Evidence-based summary of the utility of the diagnostic tests for chronic constipation(Modified from Ref (81).

Test	Clinical Utility		Evidence	Recommendation	Comment
	Strength	Weakness		(Grade)
Blood tests (thyroid, calcium, glucose, electrolytes)	Rule out metabolic disorder	Not cost-effective	No evidence	C	Not recommended routinely without alarm features
Imaging tests Plain abdominal X-Ray	Identify excessive amount of stool in the colon, simple, inexpensive, widely available	Lack of standardization and controlled studies	Poor	C	None
Barium enema	Identify megacolon, megarectum, stenosis, diverticulosis, masses	Lack of standardization, Radiation exposure. Lack of controlled studies	Poor	C	Not recommended for routine evaluation without alarm features
Defecography	Identify dyssynergia, rectocele, prolapse, excessive descent, megarectum, Hirschsprung disease	Radiation exposure, embarrassment, interobserver bias, inconsistent methodology	Fair	B3	Used as adjunct
Anorectal ultrasound	Visualization of the internal anal	Interobserver bias, availability.	Poor	C	Experimental
MRI	Simultaneously evaluate global pelvic floor anatomy, sphincter morphology and dynamic motion	Expensive, lack of standardization, availability	Fair	B3	Used as adjunct to anorectal manometry
Flexible sigmoidoscopy and colonoscopy	Visualization of mucosal disease	Invasive, risks of procedure and sedation	Poor	C	Lack of prospective study regarding efficacy
Physiologic testing Colonic transit with radiopaque markers	Evaluate colon transit, inexpensive and widely available	Inconsistent methodology	Good	B2	Useful to identify slow transit constipation
Colonic transit with scintigraphy	Evaluate slow, normal or rapid colonic transit.	Expensive, time consuming, availability, lack of standardization	Good	B2	Facilitates classification of pathophysiological subtypes
Wireless Motility Capsule	Standardized evaluation of slow, normal or rapid colonic and upper gastrointestinal transit No Radiation, Validated technique	Availability	Excellent	A1	Reliably identifies slow transit constipation and upper gut transit abnormalities
Anorectal Manometry	Identify dyssynergic defecation, rectal hyposensitivity, & hypersensitivity, impaired compliance,	Lack of standardization	Good	B2	Facilitates diagnoses of dyssynergic defecation, Rectal sensory problems and Hirschsprung's disease
Balloon expulsion test (BET)	Bedside assessment of dyssynergic defecation	Lack of standardization	Good	B2	Normal BET does not exclude dyssynergia.
Colonic manometry	Identify colonic myopathy, neuropathy Facilitates selection of patients for surgery Reproducible Clinically useful	Invasive, not widely available, lack of standardization	Good	B2	Adjunct to colorectal function tests

Grade A1: Excellent evidence in favor of the test based on high specificity, sensitivity, accuracy and positive predictive values

Grade B2: Good evidence in favor of the test with some evidence on specificity, sensitivity, accuracy, and predictive values

Grade B3: Fair evidence in favor of the test with some evidence on specificity, sensitivity, accuracy, and predictive values

Grade C: Poor evidence in favor of the test with some evidence on specificity, sensitivity, accuracy, and predictive values