Hæmorrhoidal Veins.—Mature worms, generally in copulâ, are usually found here, though young not fully grown females may also occur. The tissues of the rectal wall (or colon) show, as a rule, large quantities of lateral-spined eggs, though less often only terminal-spined eggs may be found.
Vesico-prostatic Plexus.—Worms in copulâ are found in the veins of the submucosa in the bladder, and the eggs in the mucosa, and those voided are usually terminal-spined, though lateral-spined eggs are not so rare as generally thought. The problem next arises as to how the eggs get to the lumen of the gut or bladder.
The female worm is 280 µ in diameter. Veins in the submucosa of the rectum less than 178 µ in diameter are not affected with endophlebitis. It is probable that the female even by stretching could not penetrate much beyond this. Eggs are probably then laid in the submucosa as near the muscularis mucosa as possible. Now if the eggs are laid in a vein of larger calibre than the worm fills, the eggs would be carried back to the inferior mesenteric vein, so that presumably the worm must succeed in blocking the vein already narrowed by endophlebitis, so that by the stasis which ensues the eggs may escape from the veins. How this occurs is not exactly known; it is not necessarily due to the spine, as the same escape into the tissues occurs in spineless eggs, such as those of Schistosoma japonicum. The eggs, then, pass as foreign bodies through the tissues. Another hypothesis is that the worms leave the veins in order to lay their eggs, but the evidence is against this.
Caval System.—Occasionally worms that have passed through the vesical plexus may be found in the iliac vein, inferior vena cava, and even the lungs. If the worms are young they contain a lateral-spined egg; if adult, numerous (50 to 100) terminal-spined eggs.
Lungs.—When the liver is strongly infected with (terminal-spined) eggs it is possible that by passive movements some may pass into the intralobular veins, and thence by the inferior vena cava to the lungs.
Gall-bladder.—Similarly terminal-spined eggs pass into the bile-capillaries and gall-bladder (where they may be abundant), and so into the fæces.
Detection of Eggs.—Occasionally eggs may be found in various other parts of the body. They are best detected by macerating pieces of the tissue in question in about 1/4 per cent. hydrochloric acid at 50 to 60°C. (Looss).
Pathological changes:—
Rectum.—These have been studied thoroughly by Letulle in the case of an apparently pure infection of the rectum.[274] They take the form of a chronic diffuse inflammation, which may result in—(1) ulceration, or (2) hyperplasia of the mucosa, producing adenomata.
Ulcerative Form.—The mucosa is transformed into a mass of vascular connective tissue. The connective tissue spaces next become invaded by numerous mononuclear cells. The tissue itself undergoes diffuse sclerosis, becoming hard and fibroid. Eventually ulcerative necrosis sets in. During these changes the Lieberkühn glands are destroyed. The process does not extend to the submucosa, in this respect differing from that in chronic dysentery.