Avian renal disease may occur as a result of bacterial, viral, or parasitic infections; metabolic dysfunction; congenital deformity; toxic insults; or nutritional deficiencies or excesses. In an attempt to diagnose these maladies, a number of ancillary techniques have been advocated for use by the avian clinician. Serum or plasma biochemical parameters, such as uric acid, urea, creatinine, or creatine are either nondiagnostic or do not elevate until pathology has become substantial. Alterations in the urine, as noted in the urinalysis, further aid in the detection of renal disease, but are also typically nonspecific. Other noninvasive diagnostic imaging techniques, such as radiography, ultrasonography, computed tomographic (CT) scans, or magnetic resonance imaging, play limited roles as a result of their cost or inability to provide a definitive diagnosis in most cases. Rigid endoscopy with its inherent focal, directed illumination with magnification allows the clinician the opportunity to directly visualize the urinary system, as well as to collect biopsy specimens that may provide an etiopathogenic diagnosis.