From the Guidelines
For patients with chronic constipation, fluoroscopy CCP or MR defecography is usually the most appropriate initial imaging modality when imaging is deemed necessary after clinical evaluation. This recommendation is based on the most recent guidelines from the American College of Radiology, as outlined in the 2022 study 1. The study emphasizes that these procedures are equivalent alternatives, and only one should be ordered to provide the necessary clinical information for effective patient management.
When considering imaging for chronic constipation, it's essential to evaluate the patient's symptoms and determine if imaging is necessary. The initial clinical evaluation should assess for signs of defecatory dysfunction, such as straining during defecation, difficulty initiating defecation, or incomplete evacuation. If imaging is required, fluoroscopy CCP or MR defecography can help identify pelvic floor disorders, such as rectocele or pelvic floor dyssynergia, which may be contributing to the patient's constipation.
In some cases, additional imaging modalities may be necessary. For example, a transrectal ultrasound of the pelvis may be used as a complementary test to fluoroscopic defecography or MR defecography in patients with suspected anal sphincter abnormalities, as noted in the study 1. However, the use of MRI pelvis dynamic maneuvers without defecation is not recommended due to insufficient medical literature supporting its benefits in this clinical scenario.
Key points to consider when ordering imaging for chronic constipation include:
- Fluoroscopy CCP or MR defecography as the initial imaging modality
- Transrectal ultrasound of the pelvis as a complementary test for suspected anal sphincter abnormalities
- Selective use of imaging after basic evaluation and initial management attempts
- Consideration of patient symptoms and clinical evaluation to determine the need for imaging.
From the Research
Imaging Options for Chronic Constipation
- Plain abdominal radiographs can be used to determine the level and cause of obstruction, such as sigmoid or cecal volvulus, and to show the extent of fecal impaction 2
- Barium enema radiographic examination or colonoscopy may be useful to detect the cause of obstruction 2
- Colonic transit time can be assessed on serial abdominal radiographs after the patient has ingested radiopaque markers 2
- Evacuation proctography can be used to diagnose a variety of functional disorders of the rectum and anus, such as rectocele, intussusception, and abnormal perineum floor descent 2
- Barium enema, measurement of colon transit time, and dynamic colpocystorectoviscerography are also useful radiological investigations 3
- Functional MR Imaging provides an objective, unifying diagnostic approach to the pelvic floor and the colon 3
- Wireless motility capsule test can be used to identify slow-transit constipation 4