acute cholecystitis is an inflammation of the gallbladder due to obstruction of the neck or cystic duct , primarily caused by gallstones . acute cholecystitis is characterized as a combination of local and systemic inflammation , and its treatment is dependent on the severity , although it is often treated conservatively with antibiotics . when acute cholecystitis becomes severe , it is treated surgically , while for some patients , percutaneous transhepatic gallbladder drainage ( ptgbd ) is an alternative to surgery . an accurate assessment of the severity is critical for the appropriate management of acute cholecystitis . abdominal ultrasonography ( us ) is useful for the diagnosis of diseases of the abdominal cavity . with abdominal us , however , this condition can be treated more appropriately if the severity is evaluated , using diagnostic imaging prior to the occurrence of organ failure or worsening of blood test variables . with regard to diagnostic imaging , wall thickening is representative of edema and correlates with the severity of acute cholecystitis , while inflammation is indicated by both edema and increased blood flow . if blood flow is assessed using abdominal us , it is possible to more accurately evaluate the severity of acute cholecystitis . superb microvascular imaging ( smi ) is based on color doppler imaging of abdominal us and enables the visualization of very slow blood flow without requiring contrast medium . it is composed of color - coded ( csmi ) and monochrome smi ( msmi ) , where csmi visualizes pulsatory signals such as color doppler images and msmi enhances the blood flow signal by suppressing background signaling . , we present the changes observed using csmi and msmi over the course of an acute cholecystitis in 1 patient . an 84-year - old man was admitted to the national hospital organization shimoshizu hospital with right upper abdominal pain that persisted for 3 days . white blood cell count ( wbc ) and c - reactive protein ( crp ) levels were 11.4  10/l and 15.3 mg / dl , respectively . total bilirubin , alkaline phosphatase , aspartate aminotransferase , alanine aminotransferase , and -glutamyl transpeptidase levels were 1.5 mg / dl , 206 iu / l , 20 iu / l , 10 iu / l , and 10 the possibility of obstructive jaundice was low . to clarify the cause of inflammation , computed tomography ( ct ) scans ( somatom emotion 16 ; siemens , munich , germany ) were performed , which showed slight thickening of the gallbladder wall ( fig . 1a ) . to confirm the results of the ct scans , the patient was subjected to abdominal us ( applio 400 ; toshiba medical , ohtawara , japan ) with a curved array transducer ( pvt-375bt ) at 3.75 mhz ( toshiba medical ) . the severity was classified as  mild as the patient showed no signs of organ failure . diagnostic imaging found no evidence of marked local inflammation such as pericholecystic or hepatic abscess . the patient was treated conservatively with antibiotics ( cefazolin sodium 3 g / day ) intravenously from the date of admission . after 2 days of treatment , right upper abdominal pain still persisted , and his body temperature rose to 38.7c . wbc and crp levels rose to 15.6  10/l and 19.6 mg / dl , respectively . these data indicated that the acute cholecystitis had worsened . to evaluate the acute cholecystitis morphologically , abdominal us showed that the wall thickness of the gallbladder had increased and a sonolucent area was visible ( fig . complications , such as liver abscess or peritonitis , were considered possible . to avoid complications and promote recovery , seven days after ptgbd , wbc and crp levels were 6.8  10/l and 1.2 mg / dl , respectively , also confirming recovery . , csmi showed a pulsatory signal on the wall of the gallbladder with the curved array transducer ( 2.0 cm / s ; pvt-375bt ) at 3.75 mhz ( fig . 2a ) , whereas no such signal was observed on the wall with msmi ( 2.2 cm / s ) ( fig . when his acute cholecystitis had worsened , this signal became more evident with csmi ( fig . after ptgbd , the gallbladder shrank due to drainage of the gall and the pulsatory signal was no longer visible with either csmi ( fig . abdominal us is recommended as a first - line diagnostic imaging tool for the diagnosis of acute cholecystitis ; however , false negatives are a known issue of this technique . in our case , a pulsatory signal was observed on the wall of the gallbladder on the day of admission , which suggested positive csmi , even when wall thickening was minimal . smi is expected to reduce the incidence of false negatives when diagnosing this condition . in the present case , the strength of the pulsatory signals correlated with the severity of the gallbladder inflammation , as illustrated using both csmi and msmi . the results suggest that the signal intensity of csmi and msmi is correlated with the severity of inflammation . our case shows that both csmi and msmi are useful for the diagnosis and evaluation of the severity of acute cholecystitis . contrast - enhanced abdominal us shows a strong enhancement that successfully differentiates acute cholecystitis from a healthy gallbladder and chronic cholecystitis . however , unlike contrast - enhanced abdominal us , smi does not require contrast medium and is therefore suitable for the management of acute cholecystitis . a primary limitation of the present study is that it is based on just 1 case of acute cholecystitis . in order to confirm the usefulness of smi for the evaluation of the severity of acute cholecystitis , more patients should be enrolled in larger studies and smi findings for acute and chronic cholecystitis compared . furthermore , signal intensity should be stratified against the severity of acute cholecystitis . in conclusion , a strong pulsatory signal correlated with the severity of acute cholecystitis with both csmi and msmi and may be suitable for the evaluation of the severity of this condition . this report was approved by the ethical committee of the national hospital organization of shimoshizu hospital . the study was considered an element of daily clinical practice as opposed to a clinical trial . written informed consent was obtained for the performance of contrast - enhanced ct and ptgbd . the patient 's records were anonymously and retrospectively analyzed , and written informed consent was obtained for their use in this report .
evaluation of the severity of acute cholecystitis is critical for the management of this condition . 
 superb microvascular imaging ( smi ) enables the assessment of slow blood flow of small vessels without any contrast medium . 
 an 84-year - old man visited our hospital with right upper abdominal pain . computed tomography and abdominal ultrasonography showed a slight thickening of the gallbladder . 
 white blood cell count and c - reactive protein levels were elevated . 
 he was diagnosed with acute cholecystitis and treated conservatively with antibiotics . 
 two days later , his condition worsened and percutaneous transhepatic gallbladder drainage ( ptgbd ) was performed . 
 the patient recovered and was discharged , and his drainage was withdrawn 7 days later . on admission , 
 color - coded smi ( csmi ) showed pulsatory signals on the slightly thickened gallbladder wall . on the day of ptgbd 
 , the intensity of the signal on csmi had increased . 
 once the patient was cured , no further signal was observed on the gallbladder wall with either csmi or msmi . in conclusion , the strong pulsatory signal correlated with the severity of acute cholecystitis observed with csmi and msmi . illustrating the signal intensity is useful for the evaluation of the severity of acute cholecystitis .