ceftriaxone is one of the most commonly used 3rd generation parenteral cephalosporins because it has wide spectrum of anti - microbial activity , a long plasma half - life that allows once - daily administration and it can even penetrate the blood brain barrier . ceftriaxone could have potential complications and these are biliary sludge or biliary lithiasis , and even urinary tract precipitation , but these complication may be reversible upon discontinuation of ceftriaxone . we present here two cases of newly developed gallbladder ( gb ) stone after usage of ceftriaxone and the gb stone disappeared after discontinuation of the drug . a 21-year - old man who had no medical history was admitted to the hospital due to lower abdominal pain that he had for 1 day . physical examination revealed direct tenderness on the right lower quadrant without rebound tenderness . computed tomography ( ct ) showed cecal diverticulitis and there was no evidence of stone in the gb ( fig . q 24 hours ) was administered for controlling the diverticulitis , and consequently the pain was much improved . the follow - up ct , which was performed on the 8th hospital day , showed a newly developed huge gb stone without inflammation ( fig . 1b ) , and a 2.5  3.5 cm sized gb stone with an acoustic shadow was observed on ultrasonography ( fig . the patient had no symptoms to suspect cholecystitis , and the ceftriaxone had already been stopped , so we decided to observe this stone and the patient was discharged . follow - up ultrasonography that was performed one month later showed that there was no stones remained in the gb ( fig . a 22-year - old man visited the emergency department due to fever for two days with aggravated dyspnea . coarse breath sounds with rales were noted in both lungs , and a pneumonic infiltration was observed on the chest x - ray and chest ct . because the patient tolerated the antibiotics , he was not placed on bed rest and allowed to oral intake . the follow - up chest ct was performed on the 17th hospital day and it showed a newly developed stone in the gb ( fig . the ultrasonography that was performed on the 28th hospital day showed sustained gb sludge ( fig . 2c ) . the patient had no abdominal symptoms and the dyspnea and fever had resolved , so he was discharged on the 30th hospital day . the patient was readmitted to the hospital for follow - up and there was no more stone in the gb on the follow - up ct ( fig . a 21-year - old man who had no medical history was admitted to the hospital due to lower abdominal pain that he had for 1 day . physical examination revealed direct tenderness on the right lower quadrant without rebound tenderness . computed tomography ( ct ) showed cecal diverticulitis and there was no evidence of stone in the gb ( fig . q 24 hours ) was administered for controlling the diverticulitis , and consequently the pain was much improved . the follow - up ct , which was performed on the 8th hospital day , showed a newly developed huge gb stone without inflammation ( fig . 1b ) , and a 2.5  3.5 cm sized gb stone with an acoustic shadow was observed on ultrasonography ( fig . the patient had no symptoms to suspect cholecystitis , and the ceftriaxone had already been stopped , so we decided to observe this stone and the patient was discharged . follow - up ultrasonography that was performed one month later showed that there was no stones remained in the gb ( fig . a 22-year - old man visited the emergency department due to fever for two days with aggravated dyspnea . coarse breath sounds with rales were noted in both lungs , and a pneumonic infiltration was observed on the chest x - ray and chest ct . because the patient tolerated the antibiotics , he was not placed on bed rest and allowed to oral intake . the follow - up chest ct was performed on the 17th hospital day and it showed a newly developed stone in the gb ( fig . the ultrasonography that was performed on the 28th hospital day showed sustained gb sludge ( fig . 2c ) . the patient had no abdominal symptoms and the dyspnea and fever had resolved , so he was discharged on the 30th hospital day . the patient was readmitted to the hospital for follow - up and there was no more stone in the gb on the follow - up ct ( fig . after usage of ceftriaxone , 60% of the drug is excreted into the urine and 40% of the drug is excreted into the bile in patients with normal renal function . the mechanism of ceftriaxone associated gb sludge is as follows : the concentration of ceftriaxone in the gb can become 20 to 150 times greater than that in the serum , and excretion of ceftriaxone could disturb the excretion of the bile acids . the concentration of ionized calcium in the bile is elevated and ceftriaxone can precipitate with calcium , like what occurs with bilirubin , and so ceftriaxone - associated biliary sludge is mainly composed of a calcium - ceftriaxone complex . the incidence of ceftriaxone - associated sludge or pseudolithiasis has been reported in 15 to 46% of the patients treated with ceftriaxone   in korea , and the incidence was reported to be 30% ( 17 patients out of 57 ) of the pediatric patients who were treated with ceftriaxone . sludge can also occur in the urinary tract , but only a few of these patients suffer from symptoms . the main risk factors for ceftriaxone - associated gb sludge or stone was high daily dosages ( over 2 g daily ) and a long term duration of drug therapy . hypercalcemia , fasting and total parenteral nutrition , major surgery and dehydration can also cause this biliary sludge . in general , biliary sludge can be expected to take 3 to 22 days after beginning ceftriaxone therapy   and it may reversible upon discontinuation of the drug with a range of 2 to 63 days after the end of treatment . the sludge may serve as the nidus for gallstone pathogenesis , and the sludge commonly appears as a hypoechoic layer without acoustic shadowing . in our cases , we confirm that there was no gb stone initially , and gb stone was detected at 8th day and 17th day , respectively , after the ceftriaxone was started . the ceftriaxone - associated gb stone completely disappeared 1 month after discontinuation of the drug . there was gb sludge and no stone for the ultrasonographic findings of the 2nd case . this might be due to the interval between when this was first diagnosed via ct and the follow - up ultrasonography ; the ceftriaxone had already been discontinued , so the stone may have resolved and became sludge . in conclusion , gb stones can occur after ceftriaxone therapy and most of these resolved spontaneously after discontinuation of the drug . clinicians , and especially surgeons , should aware of this complication and they should avoid unnecessary surgical interventions .
ceftriaxone is a commonly used antibiotic due to some of its advantages . 
 reversible gallbladder ( gb ) sludge or stone has been reported after ceftriaxone therapy . 
 most of these patients have no symptom , but the gb sludge or stone can sometimes cause cholecystitis . 
 we experienced two patients who had newly developed gb stones after ceftriaxone therapy for diverticulitis and pneumonia , and this resolved spontaneously 1 month after discontinuation of the drug . 
 awareness of this complication could help to prevent unnecessary cholecystectomy .