From Big Medical Encyclopedia

LENKA PHENOMENON (R. Lenk, Austrian radiologist, sort. in 1885) — 1) uniform decrease in transparency of the pulmonary field at X-ray inspection after transfer of the patient on trokhoskoy of vertical in horizontal position on spin that demonstrates existence in a pleural cavity of free liquid; it is caused by spreading of liquid along a back surface of a lung at horizontal position of investigated; 2) the radiological sign allowing to carry out with high probability topical differential diagnosis of a new growth, coming from mediastinum, or a tumor of a lung, closely adjacent to a mediastinum.

Schemes of roentgenograms of a thorax at a tumor of a lung (at the left) and tumors of a mediastinum (on the right): at a tumor of a lung — the ground mass of a tumor is projected in the pulmonary field (the shaded site of a circle); at a tumor of a mediastinum — the ground mass of a tumor is projected in a median shadow (not shaded site of a circle)

First L. t. it is for the first time found in 1924. It is observed at any character of liquid — serous, purulent, hemorrhagic. Time necessary for spreading of liquid — 2 — 3 min. This sign allows to judge with confidence availability of liquid in a pleural cavity in the absence of commissures, encystments and accumulation not less than 300 — 400 ml of liquid (see. Pleurisy ). Spreading of smaller amount of liquid does not bring to audible an eye to decrease in transparency of the pulmonary field and therefore identification of small pleural exudates is carried out at a lateroskopiya or a laterografiya in situation inspected on a sick side (see. Polyposition research ).

Second L. t. it is based on geometrical ideas of location of the center spherical patol. educations, to-ry at a tumor of a mediastinum it is located in a so-called median (cardiovascular) shadow, and at a tumor of a lung — out of it, in a projection of the pulmonary field (fig). This phenomenon deserves great attention since rentgenol, pictures of those and other tumors have strong likeness among themselves. However and during the use of L. t. differential and diagnostic difficulties are completely not excluded.

Bibliography: Kuznetsov I. D. and Rozenshtraukh L. S. Radiodiagnosis of tumors of a mediastinum, M., 1970; Rozenshtraukh L. S. and Vinner M. G. Radiodiagnosis of pleurisy, M., 1968, bibliogr.; Lenk R. Ront-genuntersuchungen zur Frage der Verschie-blichkeit von entziindlichen Ergiissen in der Pleura, Wien. klin. Wschr., S. 1206, 1924.

L. S. Rozenshtraukh.