Gall-Stones: Subject Matter and Classification | Biochemistry

In this article we will discuss about the Subject Matter and Classification of Gall-Stones.

Subject Matter of Gall-Stones:

In the gall-bladder, cholesterol is solubilized by being held in micelles together with conjugated bile salts and phospholipids. The solubility depends on the ratio of cholesterol to bile salts plus phospholipids. The secretion of phospholipids into the bile depends on the availability of bile salts.

If bile salts content is decreased, the phospholipid content is also diminished and, hence, the solubil­ity of cholesterol is decreased causing crystalliza­tion. These crystals grow to form stones. Gall-stones are formed due to defects in the enterohepatic circulation and with the diseases of the terminal ileum as well as in patients with cir­rhosis. In these cases, there is reduction in the bile salt pool.

Infection of bile causes the de-conjugation of bile acids with a decrease in their solubility. This also results in the production of a phospholipase which converts lecithin to lysolecithin. This de­creases the stability of the micelles holding cho­lesterol in solution. Infection can give rise to calcium-bilirubinate stones which were frequent in Japan.

Chenodeoxycholic acid decreases the rate of secretion of cholesterol into the bile. Bile then be­comes unsaturated with respect to cholesterol and thus the cholesterol stone can be re-dissolved. Un­fortunately, bacterial action in the intestine con­verts chenodeoxycholic acids to lithocholic acid which is very hepatotoxic in Rhesus monkeys pro­ducing proliferation of bile ducts.

Classification of Gall-Stones:

Gall-stones are mainly of three types:

i. Cholesterol Stones:

(a) These stones may be single or multiple.

(b) They may be white or yellowish.

(c) They may be mulberry-shaped.

(d) They are not radio-opaque.

ii. Pigment Stones:

(a) These stones are formed by bile pigments, organic material and calcium.

(b) They are small multiple stones.

(c) They are hard, dark green or black.

(d) They are rarely radio-opaque.

iii. Mixed Gall-Stones:

(a) These are composed of a mixture of cho­lesterol, bile pigments, protein and calcium.

(b) They are faceted dark brown stones with a hard shell and soft centre.

(c) They may be radio-opaque.

(d) They are the commonest forms of gall­stones.