From the Guidelines
Post-renal acute kidney injury (AKI) should be managed by promptly relieving the obstruction, which can be achieved through placement of nephrostomy tubes, ureteral stents, urethral catheterization, or suprapubic catheter placement, depending on the location and nature of the obstruction. According to the study published in the Journal of the American College of Radiology in 2021 1, postrenal AKI results from ureteral, bladder, or urethral obstruction, and identification of the specific cause of AKI is critical for appropriate intervention. The study highlights that renal and prerenal etiologies far outweigh obstruction as a cause of AKI, accounting for >97% of AKI, but prompt relief of the obstruction is essential to prevent permanent kidney damage.
Causes of Post-Renal AKI
- Kidney stones
- Enlarged prostate
- Urethral strictures
- Bladder tumors
- Blood clots blocking the urinary tract
Management of Post-Renal AKI
- Placement of nephrostomy tubes or ureteral stents for upper urinary tract obstruction
- Urethral catheterization or suprapubic catheter placement for lower tract obstructions
- Administration of intravenous fluids to avoid post-obstructive diuresis complications
- Monitoring of electrolytes, especially potassium, sodium, and phosphate, as rapid shifts can occur after obstruction relief
- Antibiotics if urinary tract infection is present
Prognosis and Post-Relief Care
The prognosis is generally favorable if the obstruction is relieved quickly, with kidney function typically recovering within days to weeks 1. However, prolonged obstruction can lead to permanent kidney damage. Post-relief care includes addressing the underlying cause, such as treating prostate hyperplasia, removing stones, or managing malignancies to prevent recurrence. As noted in the study, evaluation of the patient with AKI includes a thorough history, physical examination, and laboratory analysis of blood and urine, and renal biopsy may be indicated for differentiation of nephritic and nephrotic syndromes 1.
From the Research
Definition and Classification of Acute Kidney Injury
- Acute kidney injury (AKI) is defined as a sudden loss of excretory kidney function 2.
- AKI can be classified into three general categories: prerenal, intrarenal, and postrenal 3, 4, 5.
Post-Renal Acute Kidney Injury
- Post-renal acute kidney injury (PR-AKI) is caused by urinary tract obstruction 6.
- The pathophysiology of PR-AKI has been extensively studied in animal models, but clinical studies on this subject are limited 6.
- PR-AKI can lead to post-obstructive diuresis (POD), a potentially life-threatening polyuria that can develop after the release of obstruction 6.
- Predictors of POD occurrence include higher serum creatinine, higher serum bicarbonate, and urinary retention on admission 6.
Clinical Assessment and Management of Post-Renal Acute Kidney Injury
- Clinical assessment of a patient with PR-AKI involves a medical record review, thorough history and physical examination, urinary and blood tests, renal imaging, and, in some instances, renal biopsy 3.
- Management of PR-AKI involves the release of obstruction and supportive care, including fluid and electrolyte management 6.
- Appropriate treatment of PR-AKI patients also involves management of the underlying etiology, when possible, and use of nondialytic and dialytic therapies 3.
Complications and Long-Term Consequences of Post-Renal Acute Kidney Injury
- PR-AKI can result in many short- and long-term complications, including chronic kidney disease and end-stage renal disease 2, 3, 5.
- Even one episode of AKI increases the risk of cardiovascular disease, chronic kidney disease, and death 5.
- Early determination of etiology, management, and long-term follow-up of AKI are essential to prevent these complications 5.