An accurate history and careful examination will determine the sequence and spectrum of clinical investigations required to make a diagnosis or decide on prognosis or treatment for renal disease. Midstream urine (MSU) sample—this standard investigation requires consideration of (1) macroscopic appearance, (2) stick testing, and (3) microscopy. Quantification of proteinuria—this is important because the risk for progression of underlying kidney disease to endstage renal failure is related to the amount of protein in the urine. Low molecular weight proteinuria is caused by proximal tubular injury and can be detected with markers. Knowledge of the glomerular filtration rate (GFR) is of crucial importance in the management of patients, not only for detecting the presence of renal impairment, but also in the monitoring of all patients with or at risk of renal impairment, and in determining appropriate dosing of those drugs cleared by the kidney. Measurement of plasma creatinine remains the standard biochemical test used to assess renal function. The simplified Modification of Diet in Renal Disease (sMDRD) formula is explained, along with a revised version (CKD-EPI). Investigations of tubular function, including the proximal tubule, distal tubule, and renal-induced electrolyte and acid–base imbalances are discussed in this chapter. Renal imaging covered in this chapter includes ultrasonography, ultrafast multislice CT scanning, magnetic resonance imaging, nuclear medicine scanning, and fluorodeoxyglucose positron emission tomography. Invasive techniques including antegrade or retrograde ureteropyelography and angiography are discussed. A renal biopsy should be considered in any patient with disease affecting the kidney when the clinical information and other laboratory investigations have failed to establish a definitive diagnosis or prognosis, or when there is doubt as to the optimal therapy.
