Effect of chronic bile duct obstruction on renal handling of salt and water.

Renal sodium reabsorption and the concentrating and diluting abilities of the kidney were evaluated in the same trained mongrel dogs before and after chronic common bile duct ligation (BDL). Glomerular filtration rate (GFR) and C(PAH) were not altered by BDL. The natriuretic response to a standardized infusion of 0.45% solution of NaCl was markedly blunted by BDL (P < 0.01); calculated distal sodium delivery was significantly less in experiments after BDL than in control studies. Furthermore, the fractional reabsorption of sodium at the diluting segment for any given rate of distal delivery was enhanced by BDL. Similarly, C(H2O)/100 ml GFR for a given sodium delivery was higher after BDL than control values. Maximal urinary concentration (Uosm-max) was lower after BDL, and the mean Uosm-max for the whole group of animals was 60% of the control value (P < 0.001). Mean maximal T(H2O)/100 ml GFR after BDL was not different from control values; however, T(c) (H2O)/100 ml GFR for a given Cosm/100 ml GFR was lower after BDL in three dogs only. The sodium content of the inner part of renal medulla after BDL was significantly lower than the values obtained in control animals. The excretion of an oral water load in the conscious state was impaired after BDL; although all animals excreted hypotonic urine, urinary osmolality was usually higher after BDL than in control studies. Maximal urinary concentration and the excretion of an oral water load were not affected by sham operation. These studies demonstrate that chronic, common bile duct ligation is associated with (a) enhanced sodium reabsorption both in the proximal and diluting segments of the nephron, (b) a defect in attaining maximal urinary concentration, (c) diminished sodium content in the renal papilla, and (d) impaired excretion of a water load. The results suggest that decreased distal delivery of sodium may underlie the abnormality in the concentrating mechanism and in the inability to normally excrete a water load. In addition, antidiuretic activity despite adequate hydration, may contribute to the impaired water diuresis. Chronic, common bile duct ligation appears to provide a readily available and reproducible model for the study of liver-kidney functional interrelationship.