Objective: To study the alterations in the expression pattern of alkaline phosphatase (ALP) in gallbladder mucosa in cases of cholelithiasis (cholesterol type) in order to find its role as an indicator of functional alteration in gall bladder mucosa in these cases.
Materials and methods: A prospective study was conducted over a period of 2 months started from July 1st 2010 to September 1st 2010 at the laparoscopic unit in Al-Jumhori Teaching Hospital, Mosul, Iraq, and the Laboratory of postgraduate studies at the Department of Anatomy, Histology and Embryology, College of Medicine, University of Mosul. Analysis of the sections which were obtained from twenty-two surgically resected gallbladder specimens using laparoscope was done. Mean age was 50.5±2.1 years (range 21-77), while the male:female ratio was 1:6. Clinical details were retrieved from the records. The cholecystectomy specimens that were received were fixed in 10% formalin. The findings on gross examination were noted, and the stones recovered from the gallbladder were analyzed by chemical examination. Multiple sections were taken from each cholesterol stone-containing gallbladder (body, neck, and fundus) for paraffin blocks and were examined after staining with hematoxylin and eosin (H&E). Microscopic examination was done to assess the type of histological changes. To evaluate the enzymatic activity of alkaline phosphatase, sections were stained using alkaline phosphatase stain (Gomori's method- Cobalt).
Results: Light microscopic examination using haematoxylin and eosin (H&E) revealed that 13 (59.09%) out of 22 cases were diagnosed as cholerterosis, while sections obtained from 3 (13.6%) out of 22 cases showed inflammation. Rokitansky-Aschoff sinuses were noticed in 6 (27.27%) out of 22 cases. Using alkaline phosphatase stain (Gomori's method- Cobalt), the amount of alkaline phosphatase activity varied considerably among the different areas in the same sections, and often among different areas of the same layer of gallbladder, thus making the assessment difficult. However, this study showed 14 (63.63 %) out of 22 cases with moderate reaction to ALP stain in the mucosa, while 8 (36.36%) cases showed weak to negative reaction to that stain.
Conclusion: The changes in ALP localization patterns may represent functional alterations either preceding or running concurrently with morphological damages in gallbladder with cholesterol stones. Futural studies will be recommended to localize ALP with different gallbladder disorders especially on ultrastructural, immunohistochemical, and biomolecular levels.

Keywords: Gallstones, histochemistry, alkaline phosphatase.