Cholescintigraphy: Normal Findings

 Normal Physiology of Liver:

• Liver –secretes  600 mL of bile/ day  (0.4 mL/min)
• 50%  enters  the  gallbladder (0.2  mL /min)
• Normal of GB capacity-50 mL
• Absorption of water –“concentration  function  of  the gallbladder”
• Mean basal pressure 
• Gallbladder lumen -10 cm of water
• CBD -12 cm of water 
• Sphincter of Oddi -15 cm of water 
• Absorption of water through the wall  is one  of two main  factors  that  facilitates hepatic bile entry  into the gallbladder
• Increase in  the  tone  of  the sphincter of Oddi

Gall Bladder Contraction and Emptying:

• Nervous 
• Endocrine 

• Nervous 

• Parasympathetic (vagus) -stimulate  contraction of  the  gallbladder
• Sympathetic (celiac ganglion)-relaxation of  the  gallbladder  
• Normal function of  the gallbladder -after its denervation
• Role of the  sympathetic and parasympathetic nervous system – very minimal 
• Primary regulator  of  gallbladder  emptying  is  the  hormone.

• Cholecystokinin (CCK)
• CCK-33 –by I cells of upper intestine- when food enters the duodenum
• Acts through CCK (A & B)receptors  in  the  smooth muscle 
• The biological action of the hormone  resides in its terminal eight  amino  acids

CCK

• Contracts gallbladder
• Relaxes the sphincter of Oddi 
• Threshold for sphincter of Oddi relaxation –is much lower
• May stay  relaxed  for  a  longer  period  of time
• The  commercially  available hormone -CCK-8
• Attach to  the  same  receptors  
• Degree of  gallbladder emptying relates directly to the number of CCK receptors

Radiopharmaceuticals:

• I 131 rose bengal
• Suboptimal imaging characteristics  
• Relatively high radiation dosimetry limited its clinical utility

• Tc -99m-iminodiacetic acid (99mTc-IDA) 

• Tc-99m-diosopropyl-IDA (DISIDA) or disofenin (Hepatolite)
• Tc-99m-bromotriethyl-IDA (BrIDA) or mebrofenin (Choletec)
• ^99mTc-IDA – follows same hepatocyte uptake, transport and excretion pathways as bilirubin
• Competitive inhibition
• Radiotracer transport into hepatocyte by high capacity carrier mediated anion clearance mechanism
• Tracer is transported into Bile canaliculi by an active membrane transport system similar to bilirubin
• Mebrofenin –Rp of choice in jaundice.
• Least bound to be involved by inhibition from bilirubin
• Mebrofenin is useful even at bilirubin of 20 -30 mg/dl

Normal HIDA Findings:

• Clearance of blood pool activity -5 min
• CBD is usually seen by 20 min
• Gall bladder – begins to fill by 10 min

In 90% normal individuals- GB is filled by 30-40 min

In 5% to7% normal individuals- GB is noted  late,  between 50 to 60 min

• Gut- is usually visualized by 60 min

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