Various causes are assigned for this displacement. It is stated to be usually congenital, but is not described as found post-mortem in children with at all the frequency that it occurs in adults; and it is certainly possible in adults to fix in many cases the beginning of the disease with a reasonable degree of certainty. That a certain amount of predisposition, or peculiarly favorable position of the kidney, or an unusual laxity of connective tissue, exists in a certain number of cases is undoubtedly true. The next most important factor is undoubtedly a laxity of the abdominal walls, affording a less firm and unyielding support to the contained viscera, and a deficiency, usually an acquired one, of the fat surrounding the kidney, which enables it in the normal condition to be supported by the layer of peritoneum passing across its front from the spinal column to the flank. This is seen in a certain set of cases where the trouble dates from an acute disease or a rapid emaciation. The well-known influence of repeated pregnancies is undoubtedly exerted in this way. Another set, especially those exceptional cases which occur in strongly-built and not thin persons, are referable to severe shocks received in gymnastic exercises, hard riding, or falls from a horse. One of the most frequent causes, and one which accounts for the fact of the affection being most prevalent among the working classes, is the use of a tight strap or cord to support the garments. Corsets, which exercise a more even pressure over a larger surface, do not have this effect. The right kidney, from the position of its superior extremity in front of the liver and its slightly higher place in the abdomen, appears to be more influenced by this pressure than the left. The movements of respiration, especially when reinforced by the forced inspiration and {23} compression of the abdominal viscera accompanying violent exertion, appear to assist in the dislodgment already favored by the pressure of the girdle. According to Müller Warnek,[3] who has laid especial stress on this method of causation, a slighter degree of displacement is possible in this way without or preceding the full development of wandering kidney. A pressure is exercised upon the descending duodenum with which the right kidney is brought into intimate relations behind, and bound down by, the peritoneum; which leads, as Bartels supposes, to a hindrance in the passage of food from the stomach, and consequent dyspeptic phenomena. In these cases, when the kidney has become a more freely movable one and has dropped farther down in the abdominal cavity, the pressure on the duodenum ceases, the consequent symptoms disappear, and give place to the dragging sensations and severe colicky attacks which are apt to characterize an older case. [Footnote 3: _Berl. klin. Woch._, 1877, 38.]