Assessment, Diagnosis, and Monitoring of the Patient with Kidney Disease
Assessment essentials
Begin with history, medications, comorbidities, volume status, blood pressure, weight trends, urine output, and access to care. Laboratory assessment includes creatinine and eGFR, BUN, electrolytes, bicarbonate, calcium, phosphorus, hemoglobin, and albuminuria. Urinalysis with microscopy helps distinguish glomerular, tubular, and infectious processes. Imaging and biopsy answer selected questions. CKD staging uses cause, GFR category, and albuminuria category; AKI diagnosis uses creatinine and urine-output criteria.
Monitoring and traps
Monitor trends, not isolated values. eGFR is less reliable in AKI and extremes of muscle mass. A normal creatinine does not exclude kidney injury in a frail or low-muscle patient. Watch potassium and ECG changes, fluid overload, anemia, and medication accumulation. For dialysis patients, track pre- and post-dialysis weights, blood pressure, access function, adequacy, and laboratory results. Traps include diagnosing AKI from one value, ignoring albuminuria, and failing to compare with baseline.
Worked example
A 70-kg patient produces 180 mL of urine over 6 hours. That is 0.43 mL/kg/hour, meeting the oliguria criterion of less than 0.5 mL/kg/hour for 6 hours. AKI also meets KDIGO criteria with a creatinine rise of at least 0.3 mg/dL within 48 hours or at least 1.5 times baseline within 7 days. Rule of thumb: trend creatinine, urine output, weight, and volume examination together; one number rarely tells the story.