LANCEREAUX as early as 1876 divided the large isolated cysts of the kidney into two classes-serous and haemorrhagic. The so-called serous variety is well known, and a large number of articles and case reports have recently appeared in the literature. Rarely, the contents of these cysts are bloodstained, but it is not this condition that is referred to in the term 'hzmorrhagic cyst'. Whatever the etiology of the latter may be, it seems to be undeniable that a group of cases have been reported from time to time with similar clinical symptoms and pathological appearances in the diseased kidney warranting the formation of a separate group.
Brin,l in his article on this subject, has reviewed eight cases selected by Souligoux and GougetZ from the whole of the previous literature as examples of true haemorrhagic cysts, and has added four subsequent cases, bringing the iiterature up to date. On a basis of these twelve cases the following description is given :- "The cysts are solitary, and their size as a rule is large. Their extirpation is difficult on account of adhesions to the surrounding organs. The cyst wall is whitish, and the contents consist of red or blackish fluid with old brownish clots. The latter may be black in colour, or they may be of white fibrin. The cavity of the cyst is received into the rest of the kidney substance as an egg into an egg-cup. Its waU is continuous with the outer surface of the kidney, without any obvious ridge of demarcation. The internal surface of the cyst wall is irregular and festooned with clots, of which the most superficial are of a dark-red or blackish colour, and the deepest, grey-white, formed of fibrin, and intimately adherent t o the fibrous lining of the cyst. The wall is always much thicker than in the case of the simple serous cysts, and may reach 5 mm. or even 1 cm. in width.
L L Microscopically three layers can be distinguished : (1) An inner layer of clots and fibrin : (2) A middle fibrous layer ; and (3) An outer layer formed by renal parenchyma atrophied and sclerosed.
" Both t h e part of the kidney containing the cyst and the rest of the organ are clothed in a fibrous capsule of normal thickness. There is rarely a communication with the kidney pelvis."
It is clear that this description refers to a condition totally different from the solitary cyst, which is thin-walled, projects from the surface of the kidney, and is clothed neither in compressed renal substance nor in fibrous capsule. Although full microscopic study was not made in each case, yet Brin is concerned in his series not to include cases of broken-down tumour forming cysts, or cases of haematonephroses and traumatic pararenal cysts, some of which have been reported under the caption of 'haemorrhagic cysts of the kidney '.