AKI Urine Microscopy

Order urinalysis with urine microscopy early in AKI when dipstick testing shows both blood and protein, when the creatinine trajectory is not explained by hemodynamics, medications, or obstruction, or when systemic findings raise concern for glomerulonephritis, vasculitis, or acute interstitial nephritis. Microscopy is particularly useful because an active sediment changes the next diagnostic branch: red cell casts support glomerular bleeding, granular casts support tubular injury, and crystals can identify a toxic-metabolic cause. BMJBMJAcute kidney injury - Diagnosis recommendations - BMJ Best Practice

Collect and examine urine as fresh as operationally feasible. Careful microscopy of a freshly collected, freshly spun specimen for red cell casts can confirm a glomerular source of hematuria. If this cannot be performed, hematuria without catheter trauma or urinary tract infection should still prompt concern for glomerular disease rather than reassurance from an incomplete sediment assessment. BMJBMJAcute kidney injury - Diagnosis recommendations - BMJ Best Practice

Do not allow a bland sediment to defer evaluation for common reversible causes. AKI is frequently associated with sepsis, cardiovascular collapse, heart failure, surgery, nephrotoxins, and urinary outflow obstruction; management remains directed at the precipitating illness, volume and electrolyte complications, nephrotoxin minimization, and obstruction relief. BMJBMJAcute kidney injury - Symptoms, diagnosis and treatment | BMJ Best Practice US

Red cell casts in AKI indicate glomerulonephritis or vasculitis, while dysmorphic red cells are particularly informative in systemic vasculitis, acute or rapidly progressive glomerulonephritis, and pulmonary-renal syndromes. The key decision is not to label this pattern as nonspecific hematuria: move from a generic AKI workup to a glomerular-disease pathway. BMJ+1BMJAcute kidney injury - Diagnosis recommendations - BMJ Best PracticeScienceDirectUrine Sediment - an overview | ScienceDirect Topics

Order targeted serologies according to the suspected syndrome. Listed tests for glomerulonephritis-oriented AKI evaluation include hepatitis B, C, and D testing, HIV testing, cryoglobulins, anti-streptolysin O titers, and assessment for complement abnormalities in hemolytic uremic syndrome; serum and urine testing for monoclonal light chains is appropriate when paraprotein-mediated disease is possible. BMJBMJAcute kidney injury - Diagnosis recommendations - BMJ Best Practice

Kidney biopsy may be required to diagnose glomerulonephritis or vasculitis and should be pursued through nephrology when histology will determine immunologic treatment. Do not delay urgent stabilization while arranging biopsy: recognize and treat hyperkalemia, acidosis, pulmonary edema, and uremia, and initiate renal replacement therapy when clinically required. BMJ+1BMJAcute kidney injury - Management recommendations | BMJ Best PracticeBMJAcute kidney injury - Symptoms, diagnosis and treatment | BMJ Best Practice US

Granular casts support acute tubular injury. Acute tubular necrosis is the major cause of intrinsic renal azotemia and follows ischemic or nephrotoxic kidney injury; correlate sediment findings with sepsis, cardiovascular collapse, major surgery, antibiotics, intravenous contrast, and other nephrotoxins. BMJ+2BMJAcute kidney injury - Diagnosis recommendations - BMJ Best PracticeBMJAcute kidney injury - Symptoms, diagnosis and treatment | BMJ Best Practice USThe LancetAcute renal failure

For granular-cast AKI, immediately stop or minimize nephrotoxic medications and address the driving illness. In suspected infection, perform an urgent septic screen and implement the local sepsis bundle within 1 hour. Continue close urine-output and electrolyte surveillance because more severe AKI is associated with greater mortality and a higher likelihood of renal replacement therapy. BMJ+1BMJAcute kidney injury - Management recommendations | BMJ Best PracticeBMJAcute kidney injury - Investigations | BMJ Best Practice

Oxalate crystalluria is an actionable exception: it suggests ethylene glycol poisoning. In a patient with compatible exposure or unexplained high-risk metabolic presentation, urgently shift from routine AKI management to toxicologic evaluation and treatment pathways while managing acidosis, electrolyte derangements, and dialysis-requiring complications. BMJ+1BMJAcute kidney injury - Diagnosis recommendations - BMJ Best PracticeBMJAcute kidney injury - Symptoms, diagnosis and treatment | BMJ Best Practice US

Relieve urinary tract obstruction promptly regardless of sediment findings. Urgent referral to urology and/or radiology is indicated for pyonephrosis, an obstructed solitary kidney, bilateral upper-tract obstruction, or AKI complications associated with obstruction. When bladder-neck obstruction is suspected and cannot be rapidly excluded by ultrasound, catheterization is indicated. BMJ+1BMJAcute kidney injury - Management recommendations | BMJ Best PracticeBMJAcute kidney injury - Investigations | BMJ Best Practice

A sediment pattern suggestive of intrinsic AKI does not exclude concurrent postrenal or hemodynamic injury. Continue to assess for obstruction, sepsis, cardiovascular collapse, heart failure, and nephrotoxic exposures while treating hyperkalemia, acidosis, pulmonary edema, or uremia as immediate threats. Dialysis may be required for these complications. BMJ+1BMJAcute kidney injury - Management recommendations | BMJ Best PracticeBMJAcute kidney injury - Symptoms, diagnosis and treatment | BMJ Best Practice US

After apparent recovery, reassess kidney trajectory rather than assuming resolution from a single improving creatinine. Transient AKI reverses within 48 hours; recovery within 2 to 7 days is termed persistent AKI, and failure to recover within 7 days is acute kidney disease. CKD represents kidney abnormalities persisting beyond 90 days. Nature+1NatureAcute kidney disease and renal recovery: consensus report of the ...Wolters KluwerDefining Early Recovery of Acute Kidney Injury : Clinical Journal of the American Society of Nephrology