The Echinococcus is of occasional occurrence, sometimes along with a simultaneous hydatid cyst of the liver. There is here, as in the liver, a large mother cyst surrounded by a distinct connective-tissue capsule, and containing the usual daughter cysts and brood-capsules.

Section of a stratified chitinous membrane from an old hydatid cyst of kidney, x 90.

Fig. 442. - Section of a stratified chitinous membrane from an old hydatid cyst of kidney, x 90.

The cyst not infrequently bursts into the pelvis of the kidney, and the daughter cysts and heads may be evacuated by the urine. Sometimes by obstructing the ureter they lead to hydronephrosis. Rupture also occurs into the pleura.

Sometimes the parasite dies, and the cyst comes to be occupied by a pultaceous material in which the remains of the laminated membrane are found (Fig. 442). The stratified character of this membrane is here, as in the case of the liver, of assistance in distinguishing the nature of the cyst, especially as all other trace of the parasite, even the hooklets, may have disappeared. The kidney tissue may be considerably opened up and pushed aside by this parasite.

The Filaria sanguinis occurs probably in the adult form in the lymphatic vessels of the kidney. The embryoes have been met with in the parenchyma of the kidney and in the Chylous urine,' which is the result of the presence of the parasite (see p. 409).

Literature

Romestau, Des Kystes hydatiques des reins, 1881; Barker, Cystic «ntozoa of human kidney, 1856; Manson, Filaria sang., 1883; Lewis, Memoirs, 1888.