Webb J A
Br J Radiol. 1984 May;57(677):381-6. doi: 10.1259/0007-1285-57-677-381.
The concentrating mechanisms affecting contrast medium in the distal nephron have been studied using three contrast media of differing osmolality (monomer, dimer and non-ionic compounds) in antidiuretic dogs with three different basal solute excretion rates. Evidence has been obtained that, under conditions of contrast medium osmotic diuresis, the loop of Henle generates more free water. If the free water generated in response to the contrast medium solute load is reabsorbed in the collecting ducts, this can in part mask the different proximal tubular effects of contrast media of different osmolality. However, as basal solute excretion increases, the compensatory mechanism is overwhelmed and urine osmolality falls exponentially. At the higher basal solute excretion rates, different osmolar loads of contrast medium no longer produce different urine osmolalities and different urine contrast medium concentrations. It is therefore considered unlikely that contrast media of reduced osmolality will produce significant increases in urine contrast medium concentration under the conditions of solute diuresis which occur in renal failure.
利用三种不同渗透压的造影剂（单体、二聚体和非离子化合物），在具有三种不同基础溶质排泄率的抗利尿犬中，研究了影响远曲小管中造影剂的浓缩机制。已有证据表明，在造影剂渗透性利尿的情况下，亨利氏袢会产生更多的自由水。如果因造影剂溶质负荷而产生的自由水在集合管中被重吸收，这可能会部分掩盖不同渗透压造影剂对近端小管的不同影响。然而，随着基础溶质排泄增加，这种代偿机制会不堪重负，尿渗透压呈指数下降。在较高的基础溶质排泄率下，不同渗透压负荷的造影剂不再产生不同的尿渗透压和不同的尿造影剂浓度。因此，在肾衰竭时出现的溶质利尿条件下，渗透压降低的造影剂不太可能使尿造影剂浓度显著增加。
