Etiologies and Outcome of Acute Renal Insufficiency in Older Adults
Etiologies and Outcome of Acute Renal Insufficiency in Older Adults
Abstract & Commentary
Synopsis: Renal biopsy is not only diagnostic in 90% of cases of ARF in older adults but also tells us that our clinical diagnosis is wrong in 34% of cases.
Source: Haas M, et al. Am J Kidney Dis 2000;35:433-447.
Acute renal failure (arf) is an increasingly common problem in older adults. A renal biopsy is often not needed for diagnosis of ARF in older patients because acute tubular necrosis (ATN) is a common cause and a clinical diagnosis may suffice. However, many studies have shown a striking disparity between the renal biopsy diagnosis and the prebiopsy clinical diagnosis. Haas and associates investigated the causes of ARF in patients 60 years of age and older who underwent a renal biopsy and studied the clinico-pathologic correlation with renal survival. Haas et al reviewed all native renal biopsy specimens from 1991 to 1998 at the University of Chicago Medical Center. During this seven-year study period, 1065 of 4264 (25%) of biopsy specimens received were from patients 60 years of age and older.
The most common indications for renal biopsy were nephrotic syndrome, ARF, and chronic/progressive renal insufficiency, each accounting for about one-fourth of the 1065 biopsies (see Table 1). Of the 259 cases with ARF, renal biopsy was diagnostic in 90% of cases. The common renal biopsy diagnoses are listed in Table 2. In addition to the etiology of ARF, renal biopsy also revealed nephrosclerosis in 55% of cases, suggestive of the aging effects on the kidney.
The renal biopsy diagnosis confirmed the clinical diagnosis in 33% of patients. In another 34% of patients, the biopsy diagnosis concurred with one of the differential diagnoses rather than the specific clinical diagnosis. For instance, the differential diagnosis could include diverse possibilities such as acute interstitial nephritis and vasculitis with crescentic glomerulonephritis (GN). Additionally, and very important, the clinical diagnosis was incorrect in one-third of the patients (34%). Commonly misdiagnosed diseases included post-infectious glomerulonephritis, ATN, acute interstitial nephritis, and atheroembolic disease. The distribution of diagnosis was similar when stratified by age groups 60-69, 70-79, and 80 and older, although younger age correlated with improved renal and patient survival.
| Table 1-Indications for Renal Biopsy in Adults Older than 60 (Total biopsies = 1065) | |
| Clinical Indication | Percent |
| Nephrotic syndrome | 25.7% |
| Acute renal insufficiency | 24.3% |
| Chronic/progressive renal insufficiency | 23.1% |
| Non-nephrotic proteinuria | 9.7% |
| Hematuria & proteinuria | 7.4% |
| Diabetic nephropathy, lupus nephritis, and hematuria alone were uncommon causes, less than 10% altogether. | |
The relative risk for development of end-stage renal disease (ESRD) was related to the specific renal diagnosis: light chain nephropathy (highest risk) > non-pauci-immune GN > atheroembolic, pauci-immune GN > tubulointerstitial diseases including ATN. The development of ESRD was highly correlated with decreased patient survival.
| Table 2-Common Renal Biopsy Diagnosis (%) in ARF in Older Adults | |
| Renal Biopsy Diagnosis | Percent |
| Glomerular diseases | 45.8% |
| Pauci-immune crescentic GN | 31.2% |
| Post-infectious GN | 5.5% |
| Anti-GBM nephritis | 4.0% |
| Tubulointerstitial diseases | 40.3% |
| Acute interstitial nephritis | 18.6% |
| ATN with and without nephrotic syndrome | 14.2% |
| Light chain nephropathy | 5.9% |
| Vascular diseases | 12.3% |
| Atheroembolic | 7.1% |
Comment by Kamaljit Sethi, MD, facp
The spectrum of renal diseases in older adults differs from younger adults. The four most common lesions in biopsied patients in this study were pauci-immune GN, acute interstitial nephritis, ATN, and atheroembolic disease. In clinical practice, however, the common causes of acute renal insufficiency in older adults include pre-renal azotemia due to hypovolemia, congestive heart failure, and obstructive uropathy, particularly in men secondary to prostatic disease. Renal biopsy is not indicated in these circumstances.
The questions in older adults with ARF are: When is renal biopsy indicated? Will it be of value in therapy? The indications for renal biopsy should include: proteinuria of 1 g or more, with or without nephrotic syndrome; nephritic urinary sediment with cells and casts, suggesting parenchymal disease; ARF without suspected ATN; and chronic progressive renal insufficiency with no other obvious etiology.
A renal biopsy offers both therapeutic and prognostic benefit. Early diagnosis of GN can improve prognosis. The often missed diagnosis of acute interstitial nephritis can help identify individuals with sensitivity to non-steroidal inflammatory agents and antibiotics, and thus be of value for future prevention of nephrotoxicity. Another important diagnosis that is frequently missed is atheroembolic disease. Contrast studies have higher risk for ATN in the elderly, but may also cause cholesterol embolization which may present with vasculitis, proteinuria, or just slowly progressive chronic renal insufficiency.
But first things first. Arising creatinine, either acutely or chronically (³ 20% of baseline value) should prompt a clinical search with ready exclusion of volume changes and urinary obstruction. Early nephrology consultation, with a biopsy if indicated, will permit early therapeutic intervention and may improve survival.
Based on this study, renal biopsy is not only diagnostic in 90% of cases of ARF in older adults but also tells us that our clinical diagnosis is wrong in 34% of cases! Renal biopsy should have the same priority in older adults as in younger individuals. The elders deserve no less.
Glomerulonephritis as a cause of acute renal insufficiency is most common in which age group?
a. Children younger than 10 years of age
b. Young adults 20-40 years old
c. Adults older than 60 years of age
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