Blood tests
In someone suspected of having cholecystitis, blood tests are performed for markers of inflammation (e.g. complete blood count, C-reactive protein), as well as bilirubin levels in order to assess for bile duct blockage. Complete blood count typically shows an increased white blood count (12,000–15,000/mcL). C-reactive protein is usually elevated although not commonly measured in the United States. Bilirubin levels are often mildly elevated (1–4 mg/dL). If bilirubin levels are more significantly elevated, alternate or additional diagnoses should be considered such as gallstone blocking the common bile duct (common bile duct stone). Less commonly, blood aminotransferases are elevated. The degree of elevation of these laboratory values may depend on the degree of inflammation of the gallbladder. Imaging
Right upper quadrant abdominal ultrasound is most commonly used to diagnose cholecystitis. Ultrasound findings suggestive of acute cholecystitis include gallstones, pericholecystic fluid (fluid surrounding the gallbladder), gallbladder wall thickening (wall thickness over 3 mm), dilation of the bile duct, and sonographic Murphys sign. Given its higher sensitivity, hepatic iminodiacetic acid (HIDA) scan can be used if ultrasound is not diagnostic. CT scan may also be used if complications such as perforation or gangrene are suspected. Histopathology
Histopathology is indicated if preoperative imaging and/or gross examination gives a suspicion of gallbladder cancer. Differential diagnosis
Many other diagnoses can have similar symptoms as cholecystitis. Additionally the symptoms of chronic cholecystitis are commonly vague and can be mistaken for other diseases.
Also known as an ear pit or preauricular sinus. (Q26.6) Portal vein-hepatic artery fistula
(Q38.0) Congenital fistula of lip
(Q38.4) Congenital fistula of salivary gland
(Q42.0) Congenital absence, atresia and stenosis of rectum with fistula
(Q42.2) Congenital absence, atresia and stenosis of anus with fistula
(Q43.6) Congenital fistula of rectum and anus
(Q51.7) Congenital fistulae between uterus and digestive and urinary tracts
(Q52.2) Congenital rectovaginal fistula

T: External causes
(T14.5) Traumatic arteriovenous fistula
(T81.8) Persistent postoperative fistula

Causes
Disease: Infections including an anorectal abscess and inflammatory diseases including Crohns disease and ulcerative colitis can result in fistulas. Fistulas to the anus may occur in hidradenitis suppurativa. In women, fistulas can also occur following pelvic infection and inflammation. Surgical and medical treatment: Complications from gallbladder surgery can lead to biliary fistulas. As well as being congenital or resulting from trauma, arteriovenous fistulas are created purposefully for hemodialysis. Radiation therapy to the pelvis can lead to vesicovaginal fistulas. Persistent gastrocutenaous fistulas can develop after gastrostomy. Trauma: Prolonged childbirth can lead to fistulas in women, in whom abnormal connections may occur between the bladder and vagina, or the rectum and vagina. An obstetric fistula develops when blood supply to the tissues of the vagina and the bladder (and/or rectum) is cut off during prolonged obstructed labor. The tissues die and a hole forms through which urine and/or feces pass uncontrollably. Vesicovaginal and rectovaginal fistulas may also be caused by rape, in particular gang rape, and rape with foreign objects, as evidenced by the abnormally high number of women in conflict areas who have developed fistulae.