INTRODUCTION

Patients with kidney disease may have a variety of different clinical presentations. Some have symptoms or signs that are directly referable to the kidney (hematuria, flank pain) or to associated extrarenal manifestations (edema, hypertension, signs of uremia), but many patients are asymptomatic and are noted on routine examination to have an elevated serum creatinine concentration or an abnormal urinalysis (such as microscopic hematuria or proteinuria). Specific disorders are more likely to be either acute or chronic in duration, thereby narrowing the differential diagnosis among patients presenting with similar clinical findings related to the kidney.

An overview of the diagnostic approach to the patient with kidney disease is presented in this topic. There are two major components to this approach:

• Assessment of renal function by estimation of the glomerular filtration rate (GFR), initially by measurement of the serum creatinine concentration and, in patients with stable kidney function, the use of formulas that provide reasonable, but not precise, estimates of GFR. (See 'Assessment of kidney function' below.)
• Careful examination of the urine (by both qualitative chemical tests and microscopic examination), since the urinary findings narrow the differential (table 1). (See 'Urinary findings' below.)

The epidemiology of chronic kidney disease and indications for screening are discussed separately. (See "Epidemiology of chronic kidney disease" and "Screening for chronic kidney disease".)

TERMINOLOGY

In the past, the terms acute and chronic renal failure were commonly used. At present, acute renal failure has been replaced by acute kidney injury and chronic renal failure has been replaced by chronic kidney disease, in part because many patients have mild to moderate disease, not renal failure. (See "Definition of acute kidney injury (acute renal failure)" and "Definition and staging of chronic kidney disease", section on 'Definition of CKD'.)