Bile cast nephropathy

Bile cast in renal tubule

Bile casts can sometime be seen in kidneys from autopsy of patients with marked jaundice. The significance of these casts regarding kidney function is not clear. The term cholemic nephrosis had been used in the past to describe functional and histologic abnormalities in the kidneys from jaundiced patients. However, the interest in medical community to study this entity has declined in recent time. Much interest has focused on hepatorenal syndrome which is purely functional in term of pathogenesis.
In order to study prevalence and characteristic of renal bile casts, van Slambrouck et al. looked into 41 autopsy and 3 renal biopsy cases with jaundice. They found that the presence of bile casts correlated with higher serum total and direct bilirubin level. A trend toward higher serum creatinine was noted, but not statistically significant. The amount of bile casts also correlated with the severity of acute tubular injury. Bile casts seems to be associated with poor prognosis, but this may be due to the fact that most of the cases were from autopsy. More study in biopsies is suggested to find out the clinical impact of bile casts in the kidneys.
The authors proposed the term bile cast nephropathy as a subset of patients with cholemic nephrosis or jaundice-related nephropathy. The patients with bile cast nephropathy have a more severe kidney injury. However, the criteria for dianosis was not mentioned in the article.
The mechanism of injury may be due to bilirubin toxicity and obstruction to tubules in similar fashion to myeloma cast nephropathy or rhabdomyolysis.

Myeloma kidney

Light chain casts surrounded by inflammatory cells in myeloma cast nephropathy

Stompor et al. reviewed renal involvement in multiple myeloma (MM). Renal abnormalities can be seen in 25-75% of patients with MM. The overall prognosis in these patients were poorer than those without renal lesions. Early detection and treatment of MM can improve long term renal outcome.

There are a number of factors determining the type and severity of renal involvement in MM: the amount and type of abnormal light chains (LCs), urine pH, calicinuria, amount of Tamm-Horsfall (TH) protein in distal nephron. The common renal diseases in MM are:

1. Myeloma cast nephropathy is most common form of renal involvement in MM and associated with poor renal and patient outcome. The interaction between the naturally-occurring Tamm-Horsfall protein and abnormal kappa LC is the basis of LC cast formation. Hypercalciuria and natriuresis enhance this process.
2. Amyloidosis of AL type is found in 15-35% of MM patients undergoing renal biopsy. Proteinuria is the leading renal abnormality. Lambda LC is found to be the precursor of amyloid protein in majority of the cases. Some of lambda LC amyloid cannot be identified by immunostaining due to change in immunologic fragments. Patients with AL amyloidosis have poor prognosis especially ones with extrarenal amyloid deposition.
3. Light chain deposition disease (LCDD) is found in 20-25% of MM patients undergoing renal biopsy. Abnormal light chain, mainly kappa, deposits in subendothelial space and mesangium causing proteinuria and extracellular matrix accumulation. Glomerular lesion is similar to diabetic nodular glomerulosclerosis.

Other rare form of renal diseases include proximal tubule disorder resembling Fanconi syndrome. These diseases can occur concurrently. Renal biopsy is advocated in most if not all patients with MM.