Diagnosing constipation

Clinical history. It is essential to clearly understand the patient's discomfort, find out the duration of the symptoms and the general measures that the patient has taken to try and relieve this discomfort. The use of visual scales, such as the Bristol scale, may be useful in allowing the patient to describe the shape and consistency of their faeces. 

Physical examination. As part of a physical examination, a rectal inspection may provide a lot of information, as it allows anal diseases such as haemorrhoids, stenosis, fissures and rectocele (rectovaginal herniation) to be detected. Asymmetry in the anal opening may be due to a neurological disorder that affects the function of the sphincters. If the perineum does not descend when pushing, this suggests the presence of pelvic floor dysfunction. 

Blood analysis. There is no evidence that a general analysis is effective as a diagnostic tool, although it should be indicated in patients with alarm signs and in those with a clinical history that suggests a potential reason for the constipation. 

Single-view abdominal x-ray. This is indicated in patients who have been hospitalised due to acute constipation, or with significant worsening of acute constipation, above all when the physical examination suggests a possible obstruction. 

Colonoscopy. This is rarely useful in the initial diagnosis of constipation. It is carried out in patients who present alarm signs, including the onset of symptoms as of 50 years, or after initial measures with laxatives have failed. 

Anorectal manometry. This allows the function of the anal sphincter to be assessed at rest and during defecation, as well as the reflexive activation of the pelvic floor. 

Balloon expulsion test. This consists of introducing a balloon in the rectum. It is filled with 50 ml of water that the patient must evacuate. It allows doctors to determine how long it takes patients to expel the balloon in a squatting position. 

Determining colonic transit time (CTT). The patient ingests a plastic substance, generally made from polyethylene, which is used as a marker to then take a series of x-rays of the abdomen. Colonic transit time can be quantified in this way. 

Video defecography. It allows the anatomy and functional changes in the anus and rectum to be assessed. It is useful when there are anatomical causes of constipation such as enterocele (descent or collapse of the small intestine) or intussusception, and in patients with pelvic floor dysfunction. In this test, 150 ml of barium is inserted into the patient’s rectum. They are asked to perform Valsalva manoeuvres (coughing, pushing) and the elimination is monitored.