Diagnosis of Medical Renal Disease
Medical renal diseases are those that involve principally the parenchyma of the kidneys. Hematuria, proteinuria, pyuria, oliguria, polyuria, pain, renal insufficiency with azotemia, acidosis, anemia, electrolyte abnormalities, and hypertension may occur in a wide variety of disorders affecting any portion of the parenchyma of the kidney, the blood vessels, or the excretory tract.
A complete medical history and physical examination, a thorough examination of the urine, and blood and urine chemistry examinations as indicated are essential initial steps in the workup of any patient.
History & Examination
A. FAMILY HISTORY
The family history may reveal disease of genetic origin, for example, tubular metabolic anomalies, polycystic kidneys, unusual types of nephritis, or vascular or coagulation defects that may be essential clues to the diagnosis.
B. PAST HISTORY
The past personal history should cover infections, injuries, and exposure to toxic agents, anticoagulants, or drugs that may produce toxic or sensitivity reactions. A history of diabetes, hypertensive disease, or autoimmune disease may be obtained. The inquiry may also elicit symptoms of uremia, debilitation, and the vascular complications of chronic renal disease, but often the patient is asymptomatic and presents with abnormal laboratory findings.
Proteinuria of any significant degree (2-4+) is suggestive of medical renal disease (parenchymal involvement). Formed elements present in the urine additionally establish the diagnosis. Significant proteinuria occurs in immune-mediated glomerular diseases or disorders with glomerular involvement such as diabetes mellitus, myeloma, or amyloidosis. Interstitial nephritis, polycystic kidneys, and other tubular disorders are not associated with significant proteinuria.
2. Erythrocyte casts-
Red blood cell casts point to glomerulonephritis. If red blood cell (erythrocyte) casts are not present, microscopic hematuria may or may not be of glomerular origin. Phase contrast microscope study may reveal dysmorphic changes in the erythrocytes present in the urine in patients with parenchymal renal disorders.
3. Fatty casts and oval fat bodies-
Tubular cells showing fatty changes occur in degenerative diseases of the kidney (nephrosis, glomerulonephritis, autoimmune disease, amyloidosis, and damage due to toxins such as lead or mercury).
4. Granular casts-
These types of casts result from degeneration of cellular casts. They are nondiagnostic of a specific renal disorder but do reflect an inflammatory condition in the kidneys.
B. OTHER FINDINGS
Abnormal urinary chemical constituents may be the only indication of a metabolic disorder involving the kidneys.
These disorders include diabetes mellitus, renal glycosuria, aminoacidurias (including cystinuria), oxaluria, gout, hyperparathyroidism, hemoglobinuria, and myoglobinuria.
Renal biopsy is a valuable diagnostic procedure. The technique has become well established, providing sufficient tissue for light and electron microscopy and for immunofluorescence examination. Contraindications for percutaneous kidney biopsy may include the anatomic presence of only 1 kidney, severe malfunction of one kidney even though function is adequate in the other, bleeding diathesis, and an uncooperative patient.
Clinical indications for renal biopsy, in addition to the necessity for establishing a diagnosis, include the need to determine prognosis, to follow progression of a lesion and response to treatment, to confirm the presence of a generalized disease (autoimmune disorder, amyloidosis, sarcoidosis), and to diagnose renal dysfunction in a transplanted kidney. Ultrasound or computed tomography (CT) guidance provides a more effective biopsy result. More recently, laparoscopic approach has been used by some urologists.
Flavio G. Vincenti, MD, & William J.C. Amend, Jr., MD