Bile cast nephropathy: A systematic review of case reports and case series

Bile cast nephropathy (BCN) is suspected in the setting of liver disease and hyperbilirubinemia and is characterized by the formation of tubular bile casts and acute tubular injury. While postmortem studies reveal a high prevalence of BCN, little is known about this orphan acute kidney injury syndrome.

To address this knowledge gap, we performed a systematic review of case reports and case series of BCN, focusing on risk factors, diagnostic criteria, clinical presentation, kidney biopsy findings, severity, treatment approaches, and outcomes.

Electronic databases were searched to identify eligible studies of patients with possible, probable, or definite BCN, using pre-established criteria. Relevant variables were extracted and analyzed. We explored the impact of serum total bilirubin levels and alcoholic liver disease on BCN severity and outcomes by stratifying cases into total bilirubin tertiles and alcoholic vs non-alcoholic liver disease. Univariate and multivariable logistic regression analyses were used to examine factors associated with the composite outcome of dialysis requirement or death.

Sixty-seven case reports and six case series (involving 2 patients each) met the inclusion criteria, totaling 79 cases of BCN. The mean age was 48.3 years, and 83.5% were men. The most common cause of liver disease was drug-induced injury (30.4%), followed by infection (18.9%) and alcoholism (12.7%). BCN diagnosis was deemed definite, probable, and possible in 65.8%, 32.9%, and 1.3% of cases, respectively. Levels of serum creatinine, dialysis requirement, and renal recovery did not differ among the total bilirubin tertile groups. However, both initial and peak serum creatinine were significantly higher in the alcoholic liver disease group compared to the non-alcoholic group (P = 0.011 and P = 0.012, respectively). There was also a non-significant trend toward a higher incidence of dialysis requirement or death in the alcoholic liver disease group (80% vs 52%, P = 0.098). Finally, higher initial serum creatinine (per 1 mg/dL increase) was independently associated with dialysis requirement or death (adjusted odds ratio 1.291, 95% confidence interval: 1.032-1.615, P = 0.025).

BCN is a common and potentially serious cause of acute kidney injury in patients with liver disease. The degree of hyperbilirubinemia does not appear to correlate with BCN severity or outcomes. However, in alcoholic liver disease, BCN is associated with a greater rise in serum creatinine and a trend toward worse outcomes compared to non-alcoholic liver disease. Serum creatinine may be a valuable predictor of BCN prognosis. Further studies are needed to develop non-invasive diagnostic tools and establish effective treatments for BCN.