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EVALUATION OF THE KIDNEY & URINARY TRACT

HISTORY

When renal disease is suspected, the history should include the following:

  1. Preceding acute or chronic illnesses (eg, urinary tract infection [UTI], pharyngitis, systemic lupus erythematosus [SLE])

  2. Rashes or joint pain/swelling

  3. Growth delay or failure to thrive

  4. Polyuria, polydipsia, enuresis, urinary frequency, or dysuria

  5. Hematuria, proteinuria, or discolored urine

  6. Pain (abdominal, costovertebral angle, or flank)

  7. Sudden weight gain or loss or edema

  8. Drug or toxin exposure

  9. Perinatal history including prematurity, prenatal ultrasonographic studies, oligo- or polyhydramnios, birth asphyxia, dysmorphic features and other congenital anomalies, voiding patterns, and umbilical artery catheterization

  10. Family history of kidney disease, hypertension, deafness, dialysis, or kidney transplantation

PHYSICAL EXAMINATION

Important aspects of the physical examination include the height, weight, and growth percentiles. Blood pressure (BP) should be measured in a quiet setting with a manual cuff of the appropriate size in the right upper extremity, ideally with the child seated with feet flat on the ground and after 3–5 minutes of rest. The cuff should have a bladder length that is 80%–100% and a width that is 40% of the circumference of the upper arm. Peripheral pulses should be assessed, and presence of skin lesions (café au lait, ash leaf spots, purpura, or rash), pallor, edema, or skeletal deformities should be evaluated. Anomalies of the ears, eyes, or external genitalia may be associated with renal anomalies or disease. The abdomen should be palpated and auscultated, with attention to nephromegaly, abdominal masses, musculature, ascites, or bruits.

LABORATORY EVALUATION OF RENAL FUNCTION

Serum Analysis

The standard indicators of renal function are serum levels of blood urea nitrogen (BUN) and creatinine; their ratio is normally about 10:1. The BUN to creatinine ratio may increase when renal perfusion or urine flow is decreased, as in urinary tract obstruction or dehydration. Because serum BUN levels are more affected by these and other factors such as nitrogen intake, catabolism, and the use of corticosteroids, the serum creatinine is the more reliable single indicator of glomerular function. Normative values for serum creatinine relate to muscle mass, and the generation of creatinine may be affected by age, sex, malnutrition, chronic illness, and amputation. At birth, serum creatinine reflects the mother’s creatinine level and declines over the first 1–2 weeks to reach a normal level for age. Serum cystatin C, a cysteine protease inhibitor that is produced by all nucleated cells and released in the blood, is an additional indicator of glomerular function, and levels are not affected by sex, height, or muscle mass. Cystatin C assays are less reliable in certain clinical settings, such as with corticosteroid administration or thyroid disease. Less precise but nonetheless important indicators of possible renal disease are abnormalities of serum electrolytes, bicarbonate, pH, calcium, phosphorus, magnesium, albumin, or complement.

Glomerular Filtration ...

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