Diagnostic relevance of urinary lactate dehydrogenase determination in nephroptosis and for the indication to nephropexy.

Previously reported experiments with animals suggested that reduced renal arterial flow might be the actual cause for the pathogenicity of nephroptosis. Clinical studies now give evidence that measurements of urinary LDH may be a criterion equal to the isotope nephrogram (ING) in considering this disease. Patients with a "mobile" kidney verified by i.v. pyelography were examined by an ING and a 1-day test for urinary LDH. In accordance with periodic kidney displacement total urinary LDH activities were measured in a 8-h urine volume in the supine position and a 8-h urine volume in the erect position of the patients. Evaluations were all expressed as percentage increase of LDH activity of the patient in the erect versus supine position and correlated with his ING-pattern. Among 45 nephroptotic individuals 34 showed, in accordance with a pathological ING, a mean LDH increase of more than a 100%. Eleven individuals had normal INGs and less than 20% increase equal to a group of 16 normal controls. We postulated a 30% increase as the upper limit between normal and pathological urinary LDH. The percentage distribution of isoenzymes was also altered within the pathological LDH range: LDH-I, which increases in normal controls, now decreased in nephroptotic patients. LDH-IV and V, which decrease in controls, now increased. Homomeric isoenzymes obviously show reciprocal behavior. The degree of kidney descent in cm does not correlate with percentage increase of urinary LDH, i.e. it is not a criterion for pathogenicity. Biopsies taken during nephropexy revealed that from an anamnestic duration of 50 weeks onwards the kidney is significantly affected and tissue damages become evident. If patients were re-investigated after nephropexy they showed normal i.v. pyelograms and normal LDH and no longer had clinical symptoms.