MEDICAL RENAL DISEASE—OVERVIEW
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.
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. First-degree relatives of patients with diabetic renal disease have an enhanced risk of end-stage renal disease, inherited independently of diabetes mellitus. Another area of interest is the association of the nephrin (NPHS1) and podocin (NPHS2) genes in familial forms of focal segmental glomerulosclerosis (FSGS) and the newly recognized clinical significance of apolipoprotein L1 (APOL1) risk variants on the progression of chronic kidney disease (CKD) among African-American patients.
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. A history of illicit drug use may be relevant, given the recognition that contaminated sources of cocaine can induce antineutrophilic cytoplasmic antibody (ANCA) associated renal disease. The inquiry may also elicit symptoms of uremia, debilitation, and the vascular complications of chronic renal disease, but often, the patient is asymptomatic, and the diagnosis of renal disease is made incidentally on abnormal laboratory findings.
Pallor, edema, hypertension, retinopathy (either hypertensive or diabetic changes), or stigmata of congenital and hereditary disease may be detected.
Examination of the urine is the essential part of any investigation of renal disease.
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 seldom are associated with significant proteinuria. To better quantify the degree of proteinuria, one could either collect a 24-hour urine sample or use a spot urine protein: creatinine ratio (measured in milligrams of protein/mg creatinine) as a surrogate (see Figure 33–1).
This graph illustrates the relation between total 24-hour urinary protein excretion and the total protein-to-creatinine ratio ...