Obstruction of the biliary tree and the inability to excrete bile into the intestine cause accumulation of substances, including bile salts and bilirubin, which have systemic toxic effects. Therefore, patients with obstructive jaundice have an increased incidence of renal dysfunction in various clinical settings, being particularly prone to renal failure. The association between renal dysfunction and obstructive jaundice has been recognized from early studies, but the exact incidence and the extent of the problem has yet to be determined.

In a large series of patients with obstructive jaundice due to cholangiocarcinoma, it appears that the patients with renal failure reach higher serum bilirubin levels and develop hyponatremia, hypokalemia, and hypotension more frequently than those without renal failure. Many reports have related renal function and obstructive jaundice in both humans and different animal species, but divergent and, in part, conflicting results have been reported in terms of species-specific effects or differences in the experimental design. For example, the early stage of obstructive jaundice in rabbits is characterized by reduced renal perfusion partly due to decreased cardiac output with a drop in creatinine clearance (Ccr) and increased liability to hemorrhagic hypotension. Also, Yarger found a decrease in plasma fluid volume and glomerular filtration rate (GFR) in rats after 4–7 days of bile duct ligation (BDL). Conversely, Better et al. observed no changes in GFR or in proximal tubular sodium reabsorption in rats 8–10 days after BDL. Although it has been recognized that an appreciation of the pathophysiology of obstruction of the extrahepatic bile duct is essential if morbidity and mortality are to be minimized in patients with obstructive jaundice, the mechanism whereby bile duct obstruction causes renal dysfunction remains to be determined. Several contributory factors have been put forward, including perioperative renal ischemia, bilirubin and bile salts toxicity endotoxemia, decreased reticuloendothelial activity, and myocardial depression.

At early stages of biliary obstruction, bacterial translocation has been reported. The large intestine provides the major source of Gram-negative bacteria in mammals and is implicated in the pathogenesis of systemic endotoxemia. Therefore, endotoxins absorbed from the intestine enter the systemic circulation and may contribute to the development of renal failure. Pathologic lesions of the kidney suggest that biliary obstruction causes systemic effects that decrease renal blood flow. In the past, attention concerning the contribution of vasoactive mediators was focused on the effects of the renin-angiotensin system and prostaglandin (PG) synthesis. More recent studies have indicated that atrial natriuretic peptide (ANP), nitric oxide, thromboxane and endothelin systems may play a role in the pathogenesis of impaired renal function in obstructive jaundice and their implications in the water-electrolyte changes accompanying this condition. In addition, the involvement of oxidative stress in renal functional alterations in extrahepatic cholestasis has been suggested as well as an enhanced renal susceptibility to ischemia-reperfusion injury and to nephrotoxic effect of gentamicin in jaundiced rats which served to assign a role of oxygen free radicals in this type of renal injury.

The aim of the present study was to assess the effects of bile duct ligation on the function and morphology of rat kidney, with special reference to renal handling of electrolytes and the activity of (Na + K)-ATPase.

A colony of adult male Wistar rats (Rattus norvegicus) weighing 200–240 g each was used. The animals were housed in individual cages under habitual conditions in a temperature-controlled room (22°C), with free access to food and water. At all times the animals received humane care in compliance with internationally accepted procedures.

The animals designated for bile duct ligation (BDL) were anesthetized with ethyl ether, and an abdominal midline incision was made in each animal. Muscle and peritoneal structures were dissected to expose the common bile duct, which was doubly ligated with a nonreabsorbable suture (4-0 silk) and carefully dissected between the two ligatures approximately 1 cm from the point of entry into the small intestine. At the end of the procedure, the abdomen was closed and the animals were allowed to recover. Surgery in the sham-operated group (sham) was performed with the same procedure, except that the bile duct was neither ligated nor dissected. The morphological and functional studies of kidney were carried out at 7, 14 and 21 days after BDL or sham operation was performed.

To ensure expansion of extracellular fluid volume, a salt loading was given the day before the experiment, by intragastric tubing, in a dose of 1.25 mmol NaCl/100 g body weight, in a 1-mL hypertonic solution. Thereafter, the animals were maintained for 17 h with free access to water and solid diet. Lithium chloride (0.12 mmol/100 g body weight) was given in a solution containing 60 mM LiCl and 5% glucose. One hour later, a water load (27 mL/kg) was administered by oral intubation to induce water diuresis. The rats were individually housed in metabolic cages and urine output (V) was collected between 30 and 60 min after giving the water load. Blood samples were obtained from the carotid artery through a PE-50 catheter, after an i.p. injection of sodium pentobarbital (50 mg/kg). Measurements of osmolality, concentration of bilirubin, electrolytes, urea, and creatinine were performed in urine and blood samples. Na⁺, K⁺ and Li⁺ were measured using a flame photometer (Eppendorf, Hamburg, Germany). Chloride determinations were carried out by a titrimetric method. Creatinine was determined using the Jaffé reaction, with Lloyd’s reagent to eliminate non-specific interferences. Total bilirubin was measured spectrophotometrically. Osmolar clearance (Cosm = Uosm × V/Posm) was established measuring plasma (Posm) and urine (Uosm) osmolalities with an Osmette osmometer (Precision System, Inc., Sudbury, MA, USA). Free water clearance (CH₂O) was calculated from the formula: CH₂O = V ? Cosm.

It is assumed that lithium and sodium are reabsorbable in the proximal tubule in the same proportion. Therefore, the lithium concentration at the end of the proximal tubule is equal to plasma lithium concentration. In addition, lithium will be non-reabsorbable in other segments of the nephron in the presence of sodium load35. C. Guerri, R. Wallace and S. Grisolía, The influence of prolonged ethanol intake on the levels and turnover of alcohol and aldehyde dehydrogenases and of brain (Na + K)-ATPase of rats. Eur J Biochem 86 (1978), p. 581. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (14). Lithium clearance (CLi) was calculated from the formula:

CLi = TPLi × Vprox/PLi

TPLi = Lithium concentration in proximal tubule fluid

PLi = Lithium concentration in plasma

Vprox = Tubular fluid volume at the end of proximal tubule

Because the isosmotic reabsorption in the proximal tubule does not modify the concentration of lithium in the tubular fluid, it can be assumed that:

TPLi = PLi, and therefore CLi ? Vprox.

Proximal and distal tubular reabsorption were determined according to formulae reported by Thomsen:

Proximal sodium reabsorption = (GFR ? CLi) × PNa

Distal sodium reabsorption = (CLi ? CNa) × PNa

GFR = Glomerular filtration rate

CNa = Sodium clearance

PNa = Sodium plasma concentration

The animals were exsanguinated to obtain blood samples and the kidneys were quickly removed. One kidney was placed in ice-cold saline to be used for enzyme analysis, and the other kidney was fixed in 10% neutral phosphate-buffered formalin for morphological studies.