Does CCK Cause Voiding During Medical Imaging?
Yes, cholecystokinin (CCK) administration during cholescintigraphy causes gallbladder voiding (emptying/contraction), which is the intended physiological effect of the test. 1, 2
Mechanism of CCK-Induced Gallbladder Emptying
CCK is specifically administered during cholescintigraphy to stimulate gallbladder contraction and measure the gallbladder ejection fraction (GBEF). 1 The hormone binds to receptors in the gallbladder smooth muscle causing contraction, while simultaneously binding to receptors on inhibitory neurons innervating the sphincter of Oddi causing relaxation, which leads to increased bile flow into the intestine. 2 This coordinated mechanism makes CCK the principal hormone controlling gallbladder emptying. 2
Standardized Protocol for CCK Administration
The consensus recommendation is to infuse 0.02 μg/kg of sincalide (synthetic CCK) over 60 minutes during cholescintigraphy. 1, 3 This slow infusion protocol is critical because:
- Rapid CCK infusion (<30 minutes) should be avoided as it causes non-specific abdominal cramping and symptoms that confound interpretation. 3, 2
- The 60-minute infusion provides a physiologic, noninvasive, and accurate quantitative assessment of gallbladder contraction. 1
- Normal gallbladder ejection fraction is defined as ≥38% using this standardized protocol. 1, 3
Additional Effects During CCK Administration
Beyond gallbladder voiding, CCK administration can cause:
- Abdominal cramping when administered rapidly intravenously due to increased intestinal peristalsis. 2
- Recreation of the patient's typical symptoms during the test, though this symptom provocation does not have diagnostic value and does not necessarily reflect the presence of gallbladder disease. 1
- Some studies suggest symptom recreation may be clinically useful, though guidelines emphasize it should not be used diagnostically. 1, 4
Clinical Context
The entire purpose of CCK-cholescintigraphy is to measure how well the gallbladder empties (voids) in response to CCK stimulation. 1 A GBEF <38% indicates abnormal gallbladder contraction and may support a diagnosis of functional gallbladder disorder in appropriately selected patients with biliary-type pain. 1, 5